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PLATINUM METALS REVIEW A Quarterly Survey of Research on the Platinum Metals and of Developments in their Application in Industry www.platinummetalsreview.com

VOL. 49 APRIL 2005 NO. 2

Contents New Stirrer Technology for the Glass Industry

62

By Duncan R. Coupland and Paul Williams

Iridium/Carbon Films Prepared by MOCVD

70

By Changyi Hu, Jigao Wan and Jiaoyan Dai

Modern Palladium Catalysis

77

A book review by Mark Hooper

Potential Applications of Fission Platinoids in Industry

79

By Zdenek Kolarik and Edouard V. Renard

Ruthenium Catalyst for Treatment of Water Containing Concentrated Organic Waste

91

By YuanJin Lei, ShuDong Zhang, JingChuan He, JiangChun Wu and Yun Yang

Patents and Copyright for Scientists

98

By Ian Wishart

Abstracts

102

New Patents

106

Final Analysis: Thermocouples – Compensating Circuits

108

By Roger Wilkinson

Communications should be addressed to: The Editor, Susan V. Ashton, Platinum Metals Review, [email protected] Johnson Matthey Public Limited Company, Hatton Garden, London EC1N 8EE

DOI: 10.1595/147106705X45604

New Stirrer Technology for the Glass Industry LONG-TERM BENEFITS FROM THE ‘DIFFUSION CHOKE’ By Duncan R. Coupland* and Paul Williams Johnson Matthey Noble Metals, Orchard Road, Royston, Hertfordshire SG8 5HE, U.K.; *E-mail: [email protected]

The function of stirring in glass making is to create uniform, homogeneous glass. Stirring equipment operates at high temperatures and under high mechanical stresses, so stirring devices have to be robust and often involve large amounts of platinum or platinum alloys. The stirrers, stirrer bars, blenders, homogenisers, screw plungers and plunging stirrers currently used are generally effective in operation, reliable and with predictable lifetimes. Thus there has been no incentive to improve the technology, and stirrer designs have changed little in the last twenty or thirty years. However, the current economic climate in the glass industry demands lower costs, improved operational efficiency, and reduced platinum inventories – glass making uses large quantities of platinum, with stirring devices taking a large part of it. To help reduce these amounts work has been undertaken on stirrer technology. and recent developments have resulted in lower platinum requirements (in some cases by over 90 per cent) without jeopardising stirring effectiveness or stirrer longevity. Different types of glass stirrers are examined here and a new concept in stirrer design, a ‘diffusion choke’, is described.

Good quality glass has to be homogeneous. To achieve this, glass melting furnaces have been developed to give a high degree of mixing and capability to deliver uniform glass into the forehearth. However, the necessity to continuously condition (heat, cool, or de-gas, etc.) the glass flowing towards the working end can negate some of this design and can cause thermal and compositional inhomogeneities in the flowing glass. This could compromise the quality of the finished product. To produce homogeneous glass it is therefore necessary to stir the glass in the forehearth, and this is widely employed. However, the introduction of stirrers has repercussions; the function of stirring is of value, but the physical presence of the stirrer is a drawback. The choice of material for the stirrer helps to determine the optimum benefit, as the cost, effectiveness and durability need to be balanced. Each of these aspects depends on the final application of the glass and the nature of the molten glass, specifically, its viscosity, temperature, corrosivity, quality and value. Stirrers with their glass contact surfaces made in platinum or platinum alloys provide the best solution to this issue, but for many installation sites, such as container glass forehearths, where the

Platinum Metals Rev., 2005, 49, (2), 62–69

value of the product has traditionally been low, the cost of fabricated platinum stirrers has historically been too high. The introduction in 1994 of ACTTM platinumcoated ceramics changed this (1, 2). ACTTM technology provided great improvements in the resistance of ceramics to molten glass at relatively moderate cost by providing enhanced durability and longevity compared with prior used unprotected ceramic (3). For glasses of very high value, specifically optical glasses where quality and clarity are paramount, stirrers fabricated from platinum alloys have always been used, although they have limited durability in high viscosity glass, especially when the glass is used for large components. Stirrer cores made from molybdenum have been found (at least 15 years ago) to provide the strength that is required by platinum for parts used in high value glass making, such as in gobbing and high energy stirrers. Separation of the platinum and the molybdenum by an oxide diffusion barrier and evacuation of the resulting space are necessary to avoid the cores from volatilising at temperatures above ~ 400ºC. Other materials evaluated over the years for

62

Fig. 1 Three stirrers that were used together at the same time for the same time (approximately six months) in a colouring forehearth. The glass immersion line can be seen. The stirrers were identical except the one on the left has an ACTTM platinum coating. The stirrers rotate in the glass. They are ~ 1 m in length and made from an aluminosilicate ceramic

stirrer cores and similar applications in the glass industry have included platinum alloy coated, high strength oxide dispersion strengthened (ODS) superalloys, but without significant success. However, the recent development of ‘diffusion choke’ technology has overturned these failures and enabled the use of these superalloys. This paper looks at the background to the ‘diffusion choke’ development and the improvements that are now possible.

Recent Stirrer History ACTTM Platinum Coated Stirrers ACTTM platinum coating technology has been used in molten glass furnaces for more than ten years (1, 2). Some of the earliest applications were coated ceramic stirrers for application in the severest conditions, such as in opal and borosilicate

glass and colouring forehearths (where colour is added to glass). The objective was to prevent the ceramic from being eroded and to allow continuous efficient stirring. The effectiveness of the ACTTM technology can be seen by the uncorroded stirrer on the left in Figure 1; all three stirrers had experienced six months of continuous service. ACTTM technology is now being used to re-define the nature of stirrers and to give more advantages over conventional fabrications, see, for example Figure 2. In a recent application, co-planar ceramic stirrers with ACTTM platinum alloy coatings, see Figure 3, replaced helical stirrers fully fabricated from platinum alloy sheet. The improved performance they achieved in stirring molten TV panel glass has dramatically assisted in this economically difficult area. In one case, ACTTM-coated ceramic

Fig. 2 A conventional fabricated helical screw glass stirrer made of 10%Rh-Pt. This stirrer typically has a life of about 5 years. Such stirrers are used for all glass making that is inherently expensive due to the large amount of precious metal required. Welded joins on this stirrer are visible In a forehearth there may be from 2 to 16 such stirrers operating in banks of up to 4. They are mechanically operated in optimum stirring ‘patterns’, with the other end of the stirrer being fixed to a geared drive

Platinum Metals Rev., 2005, 49, (2)

63

Fig. 3 An ACTTM coated co-planar stirrer as used for homogenising and disturbing laminar flows of glass. These vanes will be fully immersed in the glass, with the glass surface being a few centimetres above the upper vane. The vanes operate in simple rotation but each pair of stirrers will be contra-rotated

stirrers replaced traditional fabricated platinum ones, and thus reduced the platinum that was being used from a total of 84 kg to only 8 kg. This reduction was partially accomplished by the superior design of the stirrer so that fewer were needed (from 10 to 4), and by the reduced thickness of the coating as compared to the prior fabricated stirrer. The design of an ACTTM coated stirrer is dictated by the ceramic and the requirements of the application. Many different configurations have been defined and utilised.

Platinum-Clad Base Metal Stirrers For many years molybdenum has been used as the material of choice for structural applications within the glass furnace as it performs well in molten glass. However, although it is used extensively as electrodes in electrically heated furnaces, if free oxygen impinges on its hot surface, it burns rapidly. This is a major limitation. To be effective the molybdenum must be protected if it is to function at any temperature > ~ 400ºC. Therefore in its major application of resistance-heating electrodes, it must be water-cooled to ensure that the zone not protected by immersion in molten glass is kept below this critical temperature. Platinum does not have this limitation and can be successfully used in such applications without water-cooling. It is assumed that using platinum would make an electrode too expensive, but this is not always the case and the introduction of ACTTM platinum coating technology has allowed electrode designs to be generated that have all the advantages of platinum without the disadvantages of


molybdenum. Indeed, in some applications where a solid electrode is required, iridium, which has unmatched stability in glasses that are especially aggressive when molten, and high environmental resistance, is now being considered as a viable alternative to molybdenum. In glass stirrer technology it is desirable to make use of the strength of molybdenum for applications where the shear strength requirements are very high and where unexpected failure would be expensive. Protecting the molybdenum is critical in achieving this. Platinum cladding has conventionally been utilised in a simple symbiosis: a platinum alloy cladding protects the strength-donating molybdenum. As in many symbiotic relationships there is a parasitic component, and the two materials can, under some circumstances, interact and form potentially detrimental intermetallic phases (4). The effect of this can be seen in Figure 4 which shows the weight losses observed for a series of molybdenum samples protected by platinum coatings of high thickness. The simple platinum layer can protect the substrate until interdiffusion and interaction promote failure of the platinum layer. Once this happens rapid oxidation of the molybdenum occurs with dramatic loss of weight. The addition of a ceramic barrier layer to keep the two metals apart was a natural progression. A ceramic barrier can control interdiffusion and oxygen removal from the inner space (the volume between the cladding and the molybdenum substrate) (5). This situation must be maintained for the duration of the service life of the component. These stirrer designs have been used to great

64

These molybdenum samples can be seen to lose weight even when coated with platinum

0.5

RELATIVE WEIGHT LOSS

Fig. 4 Results for test pieces of platinum covered molybdenum that have undergone air oxidation for 160 hours at 960ºC followed by 724 hours at 1300ºC.

0 -0.5 -1 -1.5 -2 -2.5 -3 -3.5 -4

0

50 100 150 50 100 150 200 250 300 350 400 450 500 550 600 650 700

TIME, h

success for several decades, and with care can have lives of more than five years. However, when the cladding fails either by mechanical damage, physical change or chemical attack, the introduction of oxygen onto the molybdenum can cause a dramatic and rapid failure. This failure can be anticipated and avoided, but if it is unexpected the damage to the forehearth and the resulting down-time can be extreme. Alternative core materials have been tested, and superalloys are most likely to be suited to this arduous task. These materials were developed specifically for the gas turbine industry and were designed to have excellent strength, and very good oxidation resistance up to temperatures of ~ 1100ºC. Oxide dispersion strengthened (ODS) alloys can, of course, be used to provide strength at temperatures up to 1300ºC. Some of these ODS alloys have considerable resistance to the harsh environment above molten glass and also when submerged in glass, but they tend to erode relatively rapidly at the glass line. This causes both

structural weakening and potential glass colouration problems. It would seem feasible to use a platinum cladding to negate this weakness, but work done a few years ago (6) showed that the tendency of the nickel in the ODS alloy and platinum to interdiffuse was too great for long term success. Figure 5 shows an example of a stirrer made from an ODS alloy of this type. It was ACTTM platinum coated and then laboratory tested in molten TV glass for 300 hours at 1150ºC. Approximately the top quarter of this component had platinum deposited directly onto the base metal substrate. Through-diffusion resulted in the development of surface oxide on top of the platinum. The lower three quarters of the sample had a ceramic interlayer which effectively blocked the diffusion, although there was slight colouration of the glass still attached to the sample surface. This indicates that iron, nickel or chromium migrated from the core alloy. Thus, while ACTTM coating technology offers improvement, a further technological advance is required to allow the effective

Fig. 5 A glass stirrer which has an ACTTM platinum coating on top of an oxide dispersion strengthened nickel-based superalloy which is very similar to PM 2000 alloy. Approximately the first quarter (on the right of this component) had platinum deposited directly onto the base metal substrate. On the remaining sample the platinum coating was separated from the nickel substrate by an oxide interlayer


65

Fig. 6 The typical structure of a knitted ‘diffusion choke’ gauze or mesh made from 10%Rh-Pt alloy. Here it is wrapped around the core of a stirrer

use of the ODS materials. Innovative technology has now been developed and patented (7), and the design and performance of a stirrer made using it is described below.

The ‘Diffusion Choke’ The process of melting glass and forming it into high quality shapes requires stirrers that can operate reliably for long periods in the temperature range 1000 to 1300ºC. Technical solutions do exist, but all have limitations either in performance or cost. These include the inherent limitations in design embodied in ACTTM-coated ceramic stirrers, or the cost and inherent potential for catastrophic failure of the extremely strong platinum-clad molybdenum stirrers. The ‘diffusion choke’ was designed as an alternative to the latter. Elimination of the risk of catastrophic failure can

allow for some potential reduction in the usual platinum cladding thickness, and hence some modest cost reduction. The technology was tested by a stirrer with a PM 2000 stirrer shaft and a 20%Rh-Pt sheet metal fabrication or cladding. A mesh or gauze of finely knitted 10%Rh-Pt alloy, the ‘diffusion choke’, was placed between the two materials, see Figure 6. Advantages of ‘diffusion choke’ technology are: • The ‘diffusion choke’ is designed to separate cladding from the substrate, and thus reduce the diffusion that arises from contact at high temperature causing the problems seen in Figure 5. • The ‘diffusion choke’ is designed to maintain an airway to the outside and ensure that adequate amounts of oxygen reach the surface of the core. This enables the inherent oxidation properties of the ODS alloy to develop and remain throughout

Fig. 7 Schematic diagram of a typical helical bladded stirrer. The position of a ‘diffusion choke’ in the form of knitted gauze is indicated in blue. This would then cover the stirrer core before being coated with platinum


66

Fig. 8 Preliminary sectioning of a stirrer core of PM 2000 with a 20%Rh-Pt sheet metal cladding between which was a gauze of finely knitted 10%Rh-Pt alloy. This stirrer was used in a hostile environment for 20 months. The numbers represent positions where analyses were performed.

1 2 3

Section A

4

5 6

Section B

13

7

8

The stirrer has been divided into four sections:

12

9 11

Section A is the top section linked up to the drive motor; Section B fits into Section A; Section C fits into Section B and to Section D; Section D is the stirrer blade end

10

Section C

Section D

prolonged operation at elevated temperatures. • The ‘diffusion choke’ restricts oxygen flow to the alloy surface, and ensures that excessive oxide thickness cannot develop. Under certain conditions this might otherwise give rise to an aggressive form of rapid oxidation. • An interesting further advantage results from the platinum of the ‘diffusion choke’ being in contact with the core alloy, which has a known effect of increasing oxide stability (8). A typical stirrer design is shown in Figure 7. This was tested in glass for TVs. The initial test

period was extended from 6 to 20 months, and though still performing well, the stirrer was removed for investigation. Initial visual examination indicated no surface degradation at any point along its length. Figure 8 shows sections of the stirrer prior to further dismantling. The discolouration at the upper end of the shaft in Section A was crusty and mineralised, indicative of deposition from the furnace vapours. At the glass line the platinum alloy was slightly brighter possibly indicating some minor surface interaction. A microfocus XRF unit examined the composition

Table I

Microfocus X-Ray Fluorescence Analysis of the Stirrer Surface Sample

Pt, %

Rh, %

1 2 3 4 5 6 7 8 9 10 11 12 13

27.4 14.5 77.2 77.9 79.7 80.2 80.4 80.1 80.1 80.3 80.4 80.9 80.7

19.7 27.7 17.6 18.8 19.3 19.2 19.6 19.5 19.9 19.7 19.6 19.1 19.3


Fe, %

0.2 1.1

Cr, %

K, %

0.7

44.1 5.2 3.4 2.5 1.0 0.6

Ca, %

Sb, %

As, %

7.5 31.0

0.6

21.3

Bi, %

Ba, %

0.1 0.7 0.7

0.3

67

was derived from the molten glass probably via condensation from the gas phase. This is, of XRF Results for the Inner Rh-Pt Tube Surface course, normal and expected. The rhodium contents of the alloy are exactly as the original alloy Sample Pt, % Rh, % Fe, % Cr, % specification, within the error expected for the 1i 79.8 20.2 analytical equipment. On the lower portion of the 2i 79.1 20.9 stirrer there were no ‘foreign’ elements detected on 3i 83.7 16.3 the alloy surface except for a trace of barium, a 4i 83.4 16.6 glass component, in the region of the glass line. 5i 83.4 16.6 6i 82.5 17.5 This lack of any surface impurities after immersion 8i 82.7 17.3 in molten glass indicates that the component had 9i 82.6 17.4 been quite well cleaned before being returned for 10i 82.4 17.6 investigation, and thus the lack of evidence of 11i 82.9 16.9 0.2 through-diffusion from the substrate was still unproven. Further disassembly of the stirrer was of the external surfaces, see Table I. therefore needed. Analysis of the upper region of the stirrer, posiThe cladding on Section A slid easily from the tions 1 to 6 showed that the yellowish encrustation base metal shaft. The ‘diffusion choke’ was retained within the 20%Rh-Pt tube, but further examination showed this was by very slight adhesion and minimal tenTable IIIa sion was required to remove the gauze. Analysis of the Outer Surface of the Diffusion Choke Gauze The same situation was found for the whole length of shaft (except, of Sample Pt, % Rh, % Fe, % Cr, % Y, % Ti, % course, where the fixing screws had 1g 88.3 11.7 been securely positioned to transfer 6g 87.8 12.2 8g 86.1 13.9 torque on the shaft to the cladding and 11g 85.8 14.1 0.1 hence to the stirrer blades themselves). Along most of the length of the shaft Table IIIb the gauze remained shiny and metallic, Analysis of the Inside Surface of the Diffusion Choke Gauze but in one region there was some greySample Pt, % Rh, % Fe, % Cr, % Y, % Ti, % ness and at the very top some gauze was yellow/brown. 1gi 89.6 10.4 6gi 87.7 11.2 0.3 0.1 0.7 Analyses of the inside of the tube 8gi 85.7 13.7 0.2 0.4 and of gauze samples at points corre11gi 85.9 13.0 0.2 0.5 0.3 sponding to the external analyses are given in Tables II and III, respectively. Analysis of the inner surfaces of the Table IV 20%Rh-Pt protective tubing showed Microfocus XRF Analysis of the Substrate Core Surface that no elements were present that Sample Pt, % Rh, % Fe, % Cr, % Y, % Ti, % would not have been present in the original alloy, with the possible excep14 1.0 0.1 79.1 17.8 0.8 1.1 tion of one sample below the glass line. 15 5.8 0.5 73.6 18.2 0.8 1.1 16a (light) 6.1 0.5 72.9 18.5 0.7 1.2 Interestingly, the rhodium level in the 16b (dark) 2.5 0.3 75.1 18.5 0.7 2.9 inside surface of the tube showed an 17 22.6 1.7 56.3 17.7 0.7 1.0 approximate 3% reduction from the 18 7.4 0.7 72.7 17.1 1.1 0.9 original bulk alloy composition, as did Table II


68

the average outer surface composition. Analysis of the ‘diffusion choke’ showed where the rhodium had gone. This showed a corresponding increase in rhodium content indicating that either a diffusion process or a vapour phase transfer process had been operating. In addition to an increased average rhodium content the ‘diffusion choke’ gave measurable levels of iron, chromium and titanium on the side in contact with the base metal substrate, but almost none on the side in contact with the Rh-Pt tube. The surface of the choke in contact with the core was slightly discoloured, and appeared to have physical contamination rather than a chemically-bonded contamination. PM 2000, the core of the stirrer, is an ironbased ODS alloy with major additions of chromium and aluminium plus various other minor ones. The key to its high strength at elevated temperature is the presence of yttria which, as a dispersed stable oxide, provides grain boundary strengthening. Table IV shows the results for microfocus XRF of the surface of the core PM 2000 alloy after service. The absence of values for aluminium is linked to the analytical technique, rather than being a mechanistic issue. Alternate analytical techniques can be used to confirm that aluminium has been retained. The presence of the occasional high values for platinum on the surface of the base metal core was due to very small adhered flecks of platinum. The nature of this tiny platinum-rich particulate has not been determined, so it is impossible to say whether they have been transported by a vapour phase mechanism or are simple physical artifacts. Visual observation, however, clearly indicated that a thin, protective surface oxide had been formed. This would be expected to change only slowly allowing protection to the substrate for a very long time.

Conclusions The ‘diffusion choke’ maintained an effective barrier to degradation of the stirrer for 20 months’ service. Indeed, the analyses suggests that the component would have maintained integrity for a much longer time perhaps comparable to the maximum life of clad molybdenum of 5 to 10 years. The in-service trial and subsequent destructive


analysis of the 20%Rh-Pt clad, ODS iron-based alloy stirrer reported here demonstrates that there is new technology to overcome many of the problems associated with traditional clad-molybdenum stirrers. The technology offers a breakthrough in stirrer design and thus additional help to the glassmaker when using stirrers for improving glass quality. In this trial the stirrer design was simple, with reliance on traditional fabrication skills in its construction. ‘Diffusion choke’ technology has potential for use in a wider range of stirrer types, and perhaps additional applications, where high strength, durability and longevity, without risk of catastrophic failure, are paramount.

References 1 2 3 4 5 6 7 8

D. R. Coupland, Platinum Metals Rev., 1993, 37, (2), 62 D. R. Coupland, R. B. McGrath, J. M. Evens and J. P. Hartley, Platinum Metals Rev., 1995, 39, (3), 98 D. R. Coupland, J. M. Evens and M. L. Doyle, Glass Technol., 1996, 37, (4), 108 G. L. Selman, Platinum Metals Rev., 1967, 11, (4), 132 A. S. Darling and G. L. Selman, Platinum Metals Rev., 1968, 12, (3), 92 Johnson Matthey Noble Metals, internal communication, 1991 Johnson Matthey PLC, World Appl. 03/059,826; 2003 C. W. Corti, D. R. Coupland and G. L. Selman, Platinum Metals Rev., 1980, 24, (1), 2

The Authors Duncan Coupland manages the Technology Team of Johnson Matthey Noble Metals in Royston. He is responsible for all technology aspects within the business unit. He was the originator of ACTTM technology, now extensively used in the glass industry. He is interested in all aspects of the metallurgical use of the platinum group metals and their utilisation in industrial and scientific applications. Dr Paul Williams has worked for Johnson Matthey Noble Metals since January 1997, as a development scientist then as a product specialist for ACT™ platinum coatings and fabricated products for the glass industry. He is now Johnson Matthey’s European Product Manager for medical products. He is interested in Nitinol shape memory alloys and platinum alloys for medical applications, including implantable medical devices.

69

DOI: 10.1595/147106705X45631

Iridium/Carbon Films Prepared by MOCVD OBSERVATIONS AND ELECTROCHEMICAL PROPERTIES RELATING TO OXYGEN ADDITIONS By Changyi Hu* and Jigao Wan Kunming Institute of Precious Metals, Kunming, Yunnan 650221, China; *E-mail: [email protected]

and Jiaoyan Dai Institute of Materials and Engineering, Central South University, Changsha, Hunan 410083, China

Iridium/carbon (Ir/C) films were prepared by MOCVD using iridium acetylacetonate as the precursor and some electrochemical properties were studied, in particular the effects of oxygen on the carbon content of the Ir/C films. Small additions of oxygen (4 ml min–1) to the source gas drastically decrease the carbon content of the films. Ir grains are formed, up to ~ 3 nm in diameter, in the amorphous carbon. It was found that Ir/C films with higher carbon content have better catalytic performance – for measuring the oxygen concentration – than Ir/C films with lower carbon content. The Ir/C films were used as electrodes in an oxygen concentration cell, and the sensitivity of the cell to oxygen was recorded. The Nernstian electromotive force of the cell is almost the same as that of a similar type of commercial oxygen concentration sensor from Bosch, but the response time is faster.

Noble metals are widely used as electrodes in gas sensors because of their unique physical and chemical properties, such as their inertness, good oxidation resistance, electrical conductivity and catalytic performance. However, due to sluggish charge transfer reactions at the sensing electrode interface at low temperature (less than 500ºC) (1), a gas sensor constructed with traditional Pt electrodes and ZrO2 electrolyte needs to be heated to a higher temperature to obtain sufficient voltage output and a shorter response time. In order to improve the properties of these sensors, Ir cluster films have been prepared by MOCVD (metalorganic chemical vapour deposition) and investigated (2–8). This paper reports on the composition, structure and electrochemical properties of some Ir/C films.

Experimental Procedure A schematic diagram of a horizontal hot-wall MOCVD apparatus is shown in Figure 1. The precursor for the Ir/C films was 500 mg of iridium tris-acetylacetonate, (CH3COCHCOCH3)3Ir, Ir(acac)3. Oxygen and argon were used as the reactant and transmission gases, respectively. The substrates were quartz (10 mm × 10 mm × 1 mm thick) and YSZ (yttria stabilised zirconia): 6 mol % Y2O3, (10 mm Φ × 2 mm thick). The temperature of the precursor (Tsor) was kept at 190ºC. The total gas pressure in the chamber was fixed at 500 Pa, with argon flow maintained at 50 ml min–1. The precursor was placed in a small quartz boat in the MOCVD apparatus. The deposition temperature (Tdep) was varied from 450 to 650ºC, for a deposition time of 60 minutes. The flow of oxygen (FO2)

Furnace

Furnace Manometer

Argon Oxygen

Precursor

Substrate

Vacuum pump

Fig. 1 Schematic diagram of chemical vapour deposition equipment used for the preparation of Ir/C films


70

Fig. 2 Schematic diagram of apparatus to measure e.m.f. values of an oxygen concentration cell. The cell has YSZ solid electrolyte and an Ir/C electrode

Volt-ohm-milliammeter

Furnace Thermocouple

Sample

Oxygen flowmeter

Oxygen gas

was varied from 0 to 10 ml min–1. The composition of the deposits was analysed by X-ray photoelectron spectroscopy (XPS). The exciting source of the XPS is Al (Kα), the sensitivity factors are 4.4, 0.25 and 0.66 for Ir, C and O, respectively. The film structures were also investigated by XRD and SEM. Figure 2 shows a schematic diagram of the measurement of the Nernstian electromotive force (e.m.f.) of the oxygen concentration cell having an Ir/C electrode attached to both sides of a YSZ solid electrolyte. Values of the e.m.f. were measured by changing the partial pressure of the oxygen at temperatures from 300 to 600ºC. A dynamic test apparatus (9) was used to assess the performance of the oxygen sensor. The air and

(a)

Ir4f

Ir4d 120000

INTENSITY, cps

O1s 90000

Argon gas

1#k

(b)

Ir4f Ir4d

240000

O1s

200000

C1s

Oxygen gas

fuel (natural gas) were adjusted to obtain the desired λ values (normalised air/fuel ratios). The exhaust gas was usually maintained in a rich condition, at λ = 0.95. A solenoid valve allowed additional air to the burner to switch the exhaust composition quickly to lean, when λ = 1.05, then cutting off the additional air and switching back to rich. The sensor voltage output was measured by a voltmeter having an input impedance of 107 Ω. The voltage switching response was determined using an oscilloscope, also with an input impedance of 107 Ω connected in parallel to the voltmeter. The response time was defined as the time taken for the output voltage, recorded on the oscilloscope, to sweep between 600 and 200 mV.

280000

Ir4p3

Oxygen flowmeter

Argon flowmeter

Ir4p3 C1s

160000

60000

120000

1#

6#k 80000

30000

40000

0

6#

0

600

500

400

300

B.E., eV

200

100

0

600

500

400

300

200

100

0

B.E., eV

Fig. 3 XPS spectra before argon sputtering (lower curves) and after argon sputtering (upper curves) for Ir/C films prepared: (a) without oxygen addition and (b) with oxygen addition. B.E. is the binding energy


71

Results Composition of Ir/C Films Figure 3 shows the XPS spectrum before and after argon sputtering (5 kV, 2 min) for Ir/C films prepared on quartz substrates with and without oxygen addition. Before argon sputtering, carbon was observed at the surface of the two samples. After sputtering, no observable signals from carbon were detected for the Ir/C films prepared with oxygen addition (trace 6#k), but signals of carbon were observed from films prepared without oxygen addition after sputtering (trace 1#k). The effects of oxygen and temperature on the contents inside Ir/C films prepared on quartz are shown in Table I. The addition of oxygen (from 0

to 4 ml min–1) is seen to decrease the carbon content and thus increase the iridium content. There is an increasing trend of carbon content inside the films prepared without oxygen addition with increasing deposition temperature. Films obtained with the addition of oxygen were smooth with silver-coloured surfaces: due to the oxygen reacting with carbon. The reaction products (carbon dioxide or carbon monoxide) are exhausted from the deposition chamber.

Structure of Ir/C Films Figure 4 shows the surface appearances and elemental maps of Ir/C films prepared without and with oxygen addition. Film prepared without oxy-

Fig. 4 Elemental maps of carbon for Ir/C films. Top map: Film prepared at 650ºC without oxygen addition. Bottom map: Film prepared at 600ºC with 4 ml min–1 oxygen addition


72

Table I

Composition of Ir/C Cluster Films Prepared under Different Deposition Conditions Tdep

500ºC

Ir, wt.% C, wt.% O, wt.%

550ºC

600ºC

650ºC

0

4

0

4

0

4

0

4

89.5 9.8 0.7

98.6 0 1.4

82.5 17.2 0.3

94.9 4.7 0.4

83.6 15.1 1.3

97.4 2.1 0.5

66.9 32.2 0.9

98.8 0.6 0.6

gen addition is seen to have a higher carbon content than film with 4 ml min–1 oxygen addition. The carbon is dispersed in the grain boundaries of the iridium. Figure 5 shows characteristic X-ray patterns of Ir wire and Ir/C film prepared under different oxygen flows. The height of the peak increases with increasing oxygen flow, indicating that the carbon content of the films is decreasing. The Xray peaks of Ir/C films are displaced in the same direction, comparable to the X-ray peak of the Ir wire. This indicates that the states of carbon deposited in these films are the same. The peaks in Figure 5 starting at the highest represent: standard Ir wire; Ir/C films prepared

with oxygen additions of 10, 8, 4, 0 ml min–1, respectively. Figure 6 shows characteristic XRD patterns of the Ir/C films prepared under different deposition conditions. The Ir/C film with higher carbon content has lower broader XRD peaks. Based on calculations from the half-width of the X-ray peaks, the Ir grains are ~ 3 nm in size, Fig. 6(a), consistent with direct observations by TEM (6).

(a) CPS

Flow O2, ml min

–1

8000

10.00

7000

50.00 2θ

100.00

6000

(b)

COUNTS

5000 4000

CPS

3000 2000 1000

10.00 6.0200 6.0400 WAVELENGTH, Å

6.0600

Fig. 5 Characteristic X-ray patterns of Ir wire and Ir/C films prepared in different oxygen flows. Peaks are: top: Ir wire, followed by Ir/C films prepared with oxygen additions of 10, 8, 4, 0 ml min–1


50.00 2θ

100.00

Fig. 6 Characteristics of the XRD patterns of Ir/C films prepared under different deposition conditions: (a) Film prepared at Tdep = 650ºC, FO2 = 0 ml min–1 (carbon content 32.2 wt.%) (b) Film prepared at Tdep = 550ºC, FO2 = 9 ml min–1 (carbon content 9.9 wt.%)

73

etched by argon sputtering, were identified by wavelength dispersive X-ray spectroscopy (WDS), see Figure 8 and 9. These figures show that the black and white granules (in Figure 7) represent carbon and iridium, respectively. The carbon exists as an amorphous structure determined from the WDS.

Properties of Ir/C Film Electrodes 7µm

SEI

Fig. 7 SEM of Ir/C film deposited without addition of oxygen (prepared at Tdep = 550ºC, FO2 = 0 ml min–1). The upper arrow indicates a black granule and the lower a white granule formed in the Ir/C films

An SEM surface observation of Ir/C film deposited without addition of oxygen is shown in Figure 7. The granules on the surface of the film,

COUNTS

100

carbon

The relationship between e.m.f. values at different temperatures and the ratio of the oxygen partial pressures (P1/P2) in the oxygen concentration cell is shown in Figure 10. The Ir/C film electrodes were deposited under various conditions. P1 is fixed at 0.1 MPa. The theoretical values are calculated from the Nernstian equation (10): e.m.f. = RT/4F ln P1/P2

where R is the gas constant, F is the Faraday constant and T is the absolute temperature.

100

80

80

60

60

40

40

20

20

0

carbon

0 43.000

44.000

45.000

46.000

43.000

100

45.000

iridium

80 COUNTS

44.000

46.000

WAVELENGTH, Å

WAVELENGTH, Å

iridium 10000

60 5000

40 20

0

0 6.255

6.260

6.265

6.270

WAVELENGTH, Å

Fig. 8 WDS of the black granules on the surface of the Ir/C film after argon sputtering


6.240

6.250

6.260

6.270

WAVELENGTH, Å

Fig. 9 WDS of the white granules on the surface of the Ir/C film after argon sputtering

74

30 25

35

(a)

¡ñ

¡ñ

e.m.f., mV

20

Measuring temperature

¡ø

30

¡ø

25

¡ö

(a)

Graph

(b)

!

¡ö

" 0 ml min

20

! 4 ml min

15

500ºC

(b) 600ºC

theoretical value –1

550ºC

650ºC

–1

550ºC

650ºC

15 10 10 5

5

1

1

2

2

ln P1/P2

Fig. 10 Relationship between e.m.f. values and the oxygen partial pressure ratio of the oxygen concentration cell

The difference between the experimental and the theoretical values may be caused by electrical leakage (11). The e.m.f. values of Ir/C films prepared without oxygen addition were found to be higher than those prepared with 4 ml min–1 oxygen addition. This means the catalytic response, to oxygen, of film with more carbon content (prepared without oxygen addition) is higher. Lastly, the response curves of the commercial sensor (BOSCH LSH6) and the oxygen concentration cell constructed with Ir/C film and YSZ are shown in Figure 11. The voltage outputs are almost identical, but the response time of the cell is shorter than that of the sensor.

Conclusions Ir/C films were prepared by MOCVD using iridium acetylacetonate as the precursor. Small additions of oxygen to the source gas greatly

decrease the carbon content of the films. Ir grains are formed up to ~ 3 nm in diameter by the amorphous carbon. Ir/C films with higher carbon content have better catalytic performance than Ir/C film of lower carbon content. The electrochemical properties of the oxygen concentration cell using Ir/C films as the electrodes is almost the same as that for a commercial sensor, but the response time is shorter. A research programme is currently being undertaken to use the Ir/C films as electrodes for commercial sensors.

Acknowledgements This project was supported by National Natural Science Foundation of China, Grant No. 50171031, and Yunnan Scientific Project (Program No. 2003 PY10). The authors would like to thank Mr Y. Wang and Senior J. M. Yang for their help with sample preparation and SEM observation, respectively.

e.m.f., mV

References 1000 800 600 400 200 0 1000

2000

3000

4000

5000

TIME, ms CVD Ir/C

Bosch

Fig. 11 Voltage-time response curves operating at 300ºC


1 T. Goto, R. Vargas and T. Hirai, Mater. Sci. Eng., 1996, A217–218, 223 2 T. Goto, R. Vargas and T. Hirai, J. Phys. IV, 1993, 3, 297 3 R. Vargas, T. Goto, W. Zhang and T. Hirai, Appl. Phys. Lett., 1994, 65, (9), 1094 4 B. S. Kwak, P. N. First, A. Erbil, B. J. Wilkens, J. D. Budai, M. F. Chisholm and L. A. Boatner, J. Appl. Phys., 1992, 72, (8), 3735 5 Y. M. Sun, J. P. Endle, K. Smith, S. Whaly, R. Mahaffy, J. G. Ekerdt, J. M. White and R. L. Hance, Thin Solid Films, 1999, 346, 100

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6 T. Goto, T. Hirai and T. Ono, Trans. Mater. Res. Soc. Jpn., 2000, 25, (1), 225 7 T. Goto, T. Ono and T. Hirai, Inorg. Mater., 1997, 33, (10), 1021 8 T. Goto, R. Vargas and T. Hirai, Mater. Trans., JIM, 1999, 40, (3), 209 9 C. T. Young and J. D. Bode, ‘Characteristics of ZrO2type oxygen sensors for automotive applications’, SAE Tech. Paper 790143, Int. Automotive Eng.

Congr. and Exposition, Detroit, Michigan, Feb., 1979 10 E. C. Sabbarao and H. S. Maiti, in “Science and Technology of Zirconia III, Advances in Ceramics”, Vol. 24B, eds. S. Somiya, N. Yamamoto and H. Yanagida, American. Ceramic Society, Westerville, OH, 1989, pp. 731–747 11 R. N. Blumenthal and M. A. Seitz, in “Electrical Conductivity in Ceramics and Glass”, Part A, ed. N. M. Tallan, Marcel Dekker, N.Y., 1974, pp. 35–178

The Authors Professor Changyi Hu is Professor of Materials Science at the Research and Development Center, Kunming Institute of Precious Metals, China. His major work is the preparations of films and coatings of precious metals and work pieces of refractory metals by MOCVD and CVD.

Dr Jiaoyan Dai is an engineer at the Institute of Materials and Engineering, Central South University, China. Her interests include CVD of precious metal films, catalysis of precious metals and electronic materials.

Jigao Wan is a Senior Researcher in the Functional Materials Division, Kunming Institute of Precious Metals, China. His current research is on oxygen gas sensors and other sensors.


76

DOI: 10.1595/147106705X46487

Modern Palladium Catalysis PALLADIUM REAGENTS AND CATALYSTS: NEW PERSPECTIVES FOR THE 21ST CENTURY BY J. TSUJI, John Wiley & Sons, Ltd., Chichester, 2004, 670 pages

ISBN (hardcover) 0-470-85032-9, £ 175.00, € 262.50; ISBN (paperback) 0-470-85033-7, £ 60.00, € 90.00

Reviewed by Mark Hooper Johnson Matthey Catalysts, Orchard Road, Royston, Hertfordshire SG8 5HE, U.K.; E-mail: [email protected]

This book is intended as an update to the original title “Palladium Reagents and Catalysts – Innovations in Organic Synthesis” written by the same author and published by Wiley in 1995 (1). It is to be used in conjunction with the original review to “cover the whole of organopalladium chemistry, from the past to the present” (mid2003). The book gives a detailed overview of the main recent advances in organopalladium chemistry from a synthetic organic chemist’s view point. The book is organised by types of organic reactions that are catalysed or effected by organopalladium reagents. The first chapter comprises a very concise and useful summary of the basic chemistry of organopalladium catalysis. This is followed by separate chapters on each type of synthetic reaction. The first types of reaction to be considered are oxidative reactions with Pd(II) compounds. As the author states in his introduction, ‘oxidative’ normally refers to a reaction of Pd where the oxidation state of the metal is increased. This chapter, however, refers to oxidation in the classical organic sense, for example, the conversion of an alkene to an aldehyde catalysed by a Pd(II) compound. The narrative begins with the first major example of this reaction, the Wacker process, and proceeds to more specific and recent examples. This chapter is detailed and includes some important chemistry contributed by the author himself. This is obviously an area close to his heart!

Pd(0)-Catalysed Reactions of Halides and Pseudohalides The third chapter considers Pd(0)-catalysed reactions of sp2 organic halides and pseudohalides. This is the main body of the book, comprising roughly half of the content (325 pages). It is a good


reflection of both the weight of academic research into this area of chemistry, and the increasing level of industrial interest and application. This field is often referred to as ‘cross-coupling’ reactions. The introduction to the chapter tries to make some sense of the many variations in this type of reaction, and each subsection describes a different type of coupling reaction. The chapter is organised in a systematic chemical manner based on the type of substrate reacted with the ‘aryl halide’. A useful addition, however, is the inclusion of the generic ‘names’ for each type of reaction in the titles and contents. This makes it easy for a synthetic chemist to find details on each ‘named reaction’, for example, Heck, Sonogashira, Suzuki, Stille, Negishi and Hiyama, which is often the way coupling reactions are referred to in practice. One important area that is included, but not named as such in this chapter, is the area often referred to as Hartwig-Buchwald amination. This reaction is listed as ‘arylation of nitrogen nucleophiles’ and included in the general group of C, N, O, S and P nucleophiles. This chapter reviews each type of coupling reaction well, with some mention of the historical development of the methodology and good details of the most recent, important contributions and methodologies. While it does not aim to provide details on the synthetic methods, the subject coverage is very thorough and the references provide ample leads for practical application of the chemistry. I believe I am reasonably well informed in some areas of coupling chemistry, and I was pleased to see all of the major recent contributions in the specific areas in the text. Based on this observation, it is clear that the author has provided a well-researched and comprehensive overview of this vast chosen field of palladium chemistry.

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Pd(0)-Catalysed Reactions of Allylic Compounds The next major area reviewed is that of the reactions of allylic compounds. This is a wellestablished area of chemistry and has both achiral and chiral synthetic utility. There is a useful general introduction to the various types of this reaction. This chapter covers chemistry from 1965 to the present, so there is a much to cover. It is well ordered in a logical, chemistry/reagent based system. Almost every reaction possible with an allylic substrate catalysed by Pd is mentioned, and the references provide a useful follow-up.

Other Pd-Catalysed Reactions The next three chapters cover reactions of 1,2and 1,3-dienes and methylenecyclopropanes; propargyl compounds; and alkynes and benzynes. These short chapters (of 20 to 30 pages) provide a good flavour of these less common areas of Pd chemistry and again most of the main issues and recent advances are covered. The final three chapters deal with alkenes, and miscellaneous reactions, and mention palladiumcatalysed reactions that the author sees as important but which do not fit in with the systematic subject order of the main chapters. This is useful and interesting to see glimpses of possible future

areas of important chemistry. There is also a useful set of tables detailing a long list of the ligands mentioned in the book. On perusal it appears that all of the major advances in ligand technology are there. In conclusion, this monograph is well written and a very well researched review of recent years in palladium chemistry. It provides the reader with a reliable starting point for learning about and even performing palladium-catalysed reactions. It is definitely worth the investment. The author has succeeded in completing his aim to cover the whole of organopalladium chemistry, in a systematic and logical manner. The book can act as a valuable learning tool and reference point to release the potential of the wealth of palladium chemistry that is now available. The only criticism, from my point of view, could be that the book does not try to compare various contributions to the fields of chemistry in terms of their actual usefulness to the practical or industrial chemist. However, the author is to be congratulated on taking on such a massive task and in his success in making some sense of the vast explosion in palladium-catalysed chemistry over recent years. Reference 1

M. V. Twigg, Platinum Metals Rev., 1996, 40, (3), 126

The Reviewer Mark Hooper is a Senior Development Chemist in the Catalyst Development Department, at Johnson Matthey in Royston, U.K. He holds a B.A. (Hons), chemistry, and a D.Phil., in organometallic chemistry from Oxford University. From 2000–2002 he held a post-doctoral position with Professor John Hartwig at Yale University, working on palladium catalysed amination. He joined Johnson Matthey in 2002. He is interested in novel homogeneous catalysts, especially Pd catalysts for coupling chemistry and anchored homogeneous catalysts and has worked with Smopex for the recovery/ separation of precious metals.


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DOI: 10.1595/147106705X35263

Potential Applications of Fission Platinoids in Industry By Zdenek Kolarik retired from Forschungszentrum Karlsruhe, POB 3640, 76021 Karlsruhe, Germany Present address: Kolberger Str. 9, 76139 Karlsruhe, Germany; E-mail: [email protected]

and Edouard V. Renard All-Russian Institute of Inorganic Materials, 123060 Moscow, Russia

Amounts of fission-generated platinoids, as recovered from high-level liquid radioactive wastes, could considerably supplement amounts of metals claimed from natural sources. Of particular interest are fission palladium and rhodium, which can be decontaminated from other fission products to a non-hazardous level. What remains is intrinsic radioactivity which is weak in fission palladium, and which in fission rhodium decays to an acceptable level after 30 years. The intrinsic radioactivity should not play a negative role when fission platinoids are applied to nuclear technology. Some non-nuclear applications of fission platinoids may be possible, if irradiation and contamination of personnel as well as uncontrolled release of the platinoids, are avoided.

The potential utilisation of fission-produced platinum metals (fission platinoids, FPs) as valuable products has attracted attention in the last few decades, as large amounts of spent nuclear fuel have accumulated worldwide. One metric ton of spent fuel, at a burn up of 33 GWd/t (gigawatt days per metric ton) contains > 1 kg palladium (Pd), > 400 g rhodium (Rh) and > 2 kg ruthenium (Ru) (1). Indeed, by 2030 spent nuclear fuel could supply up to 1000 t Pd and 340 t Rh. This would be a considerable addition to the yield from natural sources. FPs can be isolated from radioactive wastes that originate in the reprocessing of spent fuel by the Purex process. The FPs are contained mainly in the solid residue left after the dissolution of the fuel at an early processing stage, and in the aqueous waste stream emerging from the first process cycle (high-level liquid waste). Processes for the recovery of FPs from both fractions have been developed worldwide (2). The purification of FPs during recovery can be so effective that the radioactivity of the fission products left is compatible with safety regulations. However, there remains the intrinsic radioactivity


of the isolated FPs. Fission Pd contains 17 wt.% of the radioactive isotope 107Pd (half-life t½ = 7 × 106 years). Besides, fission Pd only contains stable isotopes with atomic masses 104 (17 wt.%), 105 (29 wt.%), 106 (21 wt.%), 108 (12 wt.%) and 110 (4 wt.%). 107Pd is a soft beta emitter (maximum energy, Emax = 0.035 MeV), but the radiation intensity at the surface of a foil of fission Pd metal (0.2 mg cm–2) is 520 Bq cm–2 (3) and this is higher than permitted by safety regulations in most countries. The specific beta radioactivity was compiled as 1.7 × 106 Bq g–1 (1), while 2.6 × 106 Bq g–1 was found experimentally (3). The intrinsic radioactivity of fission Rh and Ru may be a more serious problem. Fission Rh consists almost exclusively of the stable isotope 103Rh and trace mass fractions of the isotopes 102Rh (t½ = 2.9 years) and 102mRh (t½ = 207 days). Electron capture is the exclusive decay mode of 102Rh and it is the main decay mode of 102mRh, which also is a beta and positron emitter and undergoes an internal transition. The gamma radiation of the isotopes is rather energetic (0.47 to 1.1 MeV). Radioactive decay can reduce the radioactivity to an acceptable level after a suitable, indeed long storage time (≥ 30

79

years). The specific radioactivity of isolated Rh after a 5 year storage is ~ 107 Bq g–1 (1). Fission Ru exhibits higher intrinsic radioactivity than Rh, caused by the isotopes 103Ru (0.0036 wt.%, t½ = 39 days) and 106Ru (3.8 wt.%, t½ = 1.02 years). 103Ru emits beta particles with Emax = 0.76 MeV and little gamma radiation (0.05–0.61 MeV), and decays to stable 103Rh. 106Ru is a soft beta emitter (Emax = 0.039 MeV), which is in equilibrium with 106Rh (t½ = 30 seconds), a hard beta emitter (Emax = 3.54 MeV), also releasing some gamma radiation (0.51–0.62 MeV). The stable isotopes are 99 Ru (2.4 × 10–4 wt.%), 100Ru (4.2 wt.%), 101Ru and 102 Ru (both 34 wt.%), and 104Ru (24 wt.%). The specific radioactivity of isolated Ru after 5 year and 20 year storage has been compiled as 3 × 1011 and 1 × 107 Bq g–1, respectively (1). It is clear that intrinsic radioactivity restricts the applicability of isolated FPs. It has been suggested that the radioactive isotopes should be removed either by current methods of isotope separation or by special methods. Atomic vapour laser (4) and plasma (5) separation processes are applicable to all three FPs, laser separation to remove 107Pd from fission Pd (6) and electromagnetic separation to remove radioactive isotopes from fission Ru (7). However, all these operations would inevitably increase the price of isolated FPs which might not be acceptable by the market. In another approach (8), only stable isotopes of Pd and Rh would be obtained as final products if fission Ru was the exclusively separated platinoid, that is: beta decay of 106Ru via 106Rh would give stable 106Pd, while stable 103Rh would be formed from 103 Ru. However, this would, of course, essentially reduce the yield of FPs; large amounts of Pd and Rh would be left unexploited in the radioactive waste. Of the three FPs, Pd and Rh are most applicable. Fission Ru is too radioactive, due to the high 106 Ru content, while Ru obtained from natural sources has a lower commercial value than either Pd or Rh. The intrinsic radioactivity of FPs does not restrict their applications in fields in which it is not in conflict with safety regulations, for example, in nuclear engineering. In other fields, two require-

Platinum Metals Rev., 2005, 49, (2), bb–mm

ments must preferably be fulfilled: • Irradiation and contamination of personnel must be avoided and, • uncontrolled release of the FPs’ radioactivity must be suppressed to well below the legally permitted level. The first requirement is fulfilled without special precautions in using fission Pd; the major part of its soft beta radiation is self-absorbed in Pd itself or in its solid support. The range of the radiation in air is 0.2 cm, and is < 0.002 cm in tissue which is considerably shorter than the thickness of the horny layer of human skin. Fulfilling the second requirement differs from application to application. One precaution is inevitable both in nuclear and non-nuclear applications. Substances containing FPs would have to be treated as radioactive materials in common operations, such as fabrication, refabrication, regeneration and disposal. Such operations would have to be made in correspondingly licensed and equipped facilities and respect safety regulations. However, the impact of this on total productions costs would not necessarily be of great importance. This review outlines the potential for industrial and small scale applications of FPs. It shows that in some applications the intrinsic radioactivity would play no role, or a subordinate role. Elsewhere the use of FPs could be made compatible with safety regulations, but would not be always practicable. Due to the critical attitude of the public toward nuclear technology and applications, FPs could not be used in the production of consumer goods, even if their role in the production process was indirect and contamination of the final product excluded. On the other hand, the FPs may well be used in the fabrication of products for industrial use. Applications that are not acceptable are medical uses such as the production of bactericidal and antitumour pharmaceuticals, surgical implants, medical equipment and jewellery.

Nuclear Technology In any applications in this field the intrinsic radioactivity of FPs would play only a minor role. Possible applications are shown below, excluding

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“cold” nuclear fusion which, although having promised to be a revolutionary source of energy, turned out to be a misinterpretation of experimental results.

Structural and Special Materials Areas where platinoid additives improve the properties of structural materials: • In the Canadian deuterium-uranium reactor (CANDU), pressure tubes made from a Zr-Nb alloy are in contact with heavy water coolant (580 K, 11.1 MPa) on the inner side and with CO2 coolant on the outer side. Elemental deuterium formed in corrosion reactions diffuses towards the outer side of the tubes and weakens them due to hydrogen embrittlement. To inhibit this, the concentration of deuterium is suppressed by oxidation below the dissociation pressure of Zr hydride. Pd coating catalyses the oxidation, as shown in model experiments with pure Zr and hydrogen (9). Associated problems, such as oxygen corrosion of Zircaloy, catalyst deactivation, neutron absorption by Pd and radioactive waste production were shown to be manageable (10). • A Pd layer on nickel or cobalt-based alloys and stainless steels catalyses the reaction of hydrogen with oxygen or hydrogen peroxide in water at > 150ºC. This lowers the corrosion potential of these materials in pressurised water nuclear reactors (11). A platinoid catalyses the recombination of hydrogen and oxygen in a gas stream and, simultaneously, the decomposition of hydrogen peroxide in a water stream, when the streams are in counter-current contact (12). • Embrittlement of Zircaloy cladding of oxide fuel rods by fission product cadmium is prevented by Pd (0.25–2.0 g kg–1). The Pd can be blended with the bulk of the fuel, dispersed as coating on the oxide particles before or after their pressing to pellets, or applied as a coating on the inner side of the cladding tubes (13). • The oxidation resistance of the Zircaloy-4 cladding of fuel elements is increased by alloying its surface with Pd. For example, a Pd layer (2 µm) is electroplated onto the Zircaloy-4 surface and annealed at 950ºC and < 10–4 Pa (14). • 60Co-embedded oxide scales are formed on the


surface of stainless steel in boiling water reactors. The formation is reduced by a thin surface film of Pd, deposited either by vacuum evaporation or electrolysis (15). • Pd can be a component of shape memory alloys, that is, materials acquiring a prescribed form when heated to transformation temperature and restored to their initial shape on cooling. Such alloys may be TiNiPd, sputter-deposited as a thin amorphous film and crystallised at 700–750ºC (16) and Ti50Pd50–xNix, especially when improved by thermomechanical treatment (17). Shape memory alloys can be used in passive safety systems, thermocouplings for pipes and electric drives, equipment for repair and assembly of units, thermomechanical drivers, dampers, flow rate regulators, thermodetectors, self-operating emergency systems, units and elements in electrical transmission lines and electric contact devices (18). • The Ti-0.2Pd alloy is a prospective material for the construction of containers for solid high-level radioactive wastes, which are to be disposed in a rock salt depository. The passive layers of the material are adequately resistant to gamma radiation when it is in contact with salt brine (19).

Removal of Hydrogen Isotopes from Gases and Liquids Platinoid catalysed reactions can be of importance in gaseous, liquid and solid phases: • Tritium, free or bound in tritiated hydrocarbons, is removed from the off-gas stream of a fission reactor by conversion to tritiated water or its mixture with CO2. Catalysed by Pd, Rh or their mixture deposited on alumina or silica, the reaction proceeds at 90–500ºC and atmospheric pressure (20). • Tritium is removed from the aqueous effluents of a nuclear plant and directed into an aqueous concentrate in combining the electrolysis of tritiated water with the catalysed isotopic exchange reaction: HT(gas) + H2O(liquid) = H2(gas) + HTO(liquid)

Deposited on a styrene-divinylbenzene copolymer, Pd catalyses the exchange less efficiently than

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Pt, but it can be used in mixture with Pt (21, 22). The catalyst is prepared by agglomeration, crushing the agglomerate, pressing it into a cake and cutting catalyst particles from the cake (22). • Hydrogen in the primary cooling circuit of a gas-cooled nuclear power reactor is separated from radioactive impurities if it is passed through a Pd alloy film. The cooling gas must be pressurised and free from moisture and oxygen (23, 24). • To prepare a catalyst for hydrogen/oxygen recombination in a nuclear power plant, a platinoid is deposited on a porous metal, and heated at 400–850ºC, when it diffuses into the carrier surface where it forms an alloy layer (25). Alternatively, a ceramic granular material can be coated with Pd and used in a passive catalytic module, which is incorporated in a nuclear reactor for hydrogen mitigation during a core-melt accident (26, 27). • Alumina beads carrying 0.5% Pd catalyse the H2/O2 recombination to 99% at 25ºC in compacted solid radioactive waste stored in sealed packages. Hydrogen is formed if the waste is humid and swells as a result of the corrosion of aluminium, steel and zinc (28).

Hydrogen Isotope Diffusion, Trapping and Cleanup The utilisation of platinoids in the above operations finds broad application in non-nuclear industry (see later section on Hydrogen Production). Pure Pd metal, but not Pd alloys, exhibits considerable adsorption and permeation capacity for hydrogen; the capacity decreases in the order: Pd > Pd95Co5 > Pd90Co10 > Pd95U5 > Pd3U (300–600 K, ≤ 50 bar) (29). Hydrogen isotopes are separated from other components of the gas output of a fusion reactor by permeation through Pd-Ag (75/25 wt./wt.) membranes at 350–450ºC. The isotopic effects are H2/D2 = 1.72 and H2/DT = 2.06. The Pd-Ag alloy is poisoned by tritiated methane, but is regenerated by heating in air (30). Efficient devices have been constructed and tested in the U.S.A. (Savannah River Site) (31), Russia (32) and Japan (Japan Atomic Energy Research Institute) (33, 34). The dimension and operating conditions of a per-


meator can be calculated by mathematical modelling (35). Other materials used in permeation membranes are Pd alloys containing 10–40 wt.% Ag, 5–25 wt.% Au, 10–20 wt.% Pt or 5–10 wt.% Rh. Very promising materials are Pd-Ag or Pd-Au alloys with additions of Pt, Rh, Ru or Ir. Pd alloyed with 25 wt.% Ag, Au and Ru exhibits excellent hydrogen permeability and mechanical properties, and is also resistant to hydrogen embrittlement and swelling and fractures caused by helium bubble formation (36). Other applicable Pd alloys, developed for non-nuclear industry, contain 10–30% Ag, 0.5–5% Au, ≤ 2% Y, 0.2–2% Ru, ≤ 1% Pt and 0.01–0.5% Al (37). The methane poisoning is avoided in a doublefunction membrane reactor which incorporates a Pd-Ag tube packed in a Ni catalyst bed. After the bulk of HT in the inlet gas is oxidised to HTO over a Pt catalyst, He is added, and the gas is contacted with the Ni catalyst which converts the HTO and CH2T2 into HT, CO and CO2 at 310–600ºC. A HT product and a He + CO + CO2 waste stream are obtained (38–40). A mathematical model accounts for coupled effects of transportlimited permeation of H isotopes and various chemical reactions (41). Tritium can be separated from liquid Li in a thermonuclear power plant by transfer through a niobium “window” into a helium stream at 980ºC. The Nb “window” is protected from oxygen attack on the He side by an electrolytically deposited Pd layer (0.001 cm). Diffusion of Pd into Nb is prevented by an intermediate layer (250 nm) of yttrium which does not form solid solutions with Nb (42). Diffusion through a double-layer Zr-Pd window also separates tritium from liquid Li, and also from Li alloys (for example, Li17Pb83). Li or its alloy flows on the Zr side of the window, and a purge stream of argon and oxygen flows on the side of the Pd coating. At 450ºC tritium diffuses rapidly through the window and is recovered as T2O. Problems like reaction at the Pd surface and corrosion deserve attention (43). Hydrogen isotopes can be removed from fission and fusion liquid coolants by “pumping” against a partial-pressure drop. A gas containing H

82

isotopes as impurities is kept in a vacuum (10–8 Pa) or a reducing atmosphere on the lower concentration side, and H isotopes are permeated through a Pd or Pd-Ag (75/25) diaphragm (44) or a Pd-coated Zr membrane (45) into an oxidising atmosphere on the higher concentration side. There they are oxidised to water (600–700 K, upstream pressure 0.0007–0.03 Pa). The mechanism is discussed in (46). The behaviour of tritium on a Pd-Ag (75/25) cathodic membrane with and without a Pd black deposit, that is, the amount of diffused and trapped tritium, the retrodiffusion, diffusion coefficient, tritium concentrations in the alloy sublayer and the diffusion layer thickness, all depend upon the applied cathodic potential, temperature, Pd-Ag membrane thickness, presence of Pd black deposits and time. Without a Pd black deposit, the double layer capacitance is 40 µF cm–2 and the apparent diffusion coefficient is 3 × 10–7 cm2 s–1 at ~ 20ºC. A Pd black deposit increases the diffusion coefficient to 3 × 10–3 cm2 s–1 (47).

kieselguhr has been used in a pilot plant and a production facility constructed in the U.S.A. (Savannah River Plant) (56, 57). Pd can also be carried by a sulfonic acid cation exchanger (58). Problems arising from volume changes of Pd adsorbers are avoided if they are in the form of moulded granules containing a binder. The absorption rate is determined by surface reactions at –78ºC but mainly by hydrogen diffusion in pores of the adsorbent at 0ºC. Counter-current contact of the gas phase with the adsorber is preferably achieved by intermittent opening of independent column sections for the gas flow (see (48) and references therein). Adsorbers consisting of Pd or Rh on alumina, kieselguhr or other suitable oxide can be covered by a lipophilic layer (silicon resin, teflon, etc.), which is permeable to hydrogen gas and water vapour but not to liquid water. Then the isotope exchange reactions are (59): HD(gas) + H2O(vapour) = H2(gas) + HDO(vapour) HDO(vapour) + H2 O(liquid) = HDO(liquid) + H2O(vapour) 2

Separation of Hydrogen Isotopes This separation is based on isotope exchange reactions in Pd, such as: H2 + Pd-T → HT + Pd-H and D2 + Pd-T → DT + Pd-D.

The separation factors are: ln αHT = 284/T + 0.03 and ln αDT = 114/T + 0.002,

that is, at 296 K, αHT = 2.69 and αDT = 1.47 (48), while the ranges αHT = 2.68–4.16 and αDT = 1.47–1.54 are given elsewhere (49). Pelletised Pd black can be used at 0ºC, and the separation factors depend on the starting H2/D2, H2/T2, and D2/T2 ratios (50) and on the temperature (–80 to 100ºC) (50, 51) (see also (52)). Chromatography is currently used to separate H isotopes. The adsorbent can be Pd deposited on alumina (51, 53) and on carbon and other supports in frontal and displacement chromatography (51), and in twin-bed periodic counter-current flow (54). Alternatively, spongy Pd black is used in displacement chromatography (55) and Pd on


Other Nuclear Applications Dissolution of pulverised UO2 pellets in 8 M HNO3 at 80ºC (a modified head-end operation in the Purex process) is accelerated if they contain 0.1–1.0 wt.% Ru, Rh or Pd. The platinoid is added as RuO2, Rh2O3 or PdO to UO2 powder in the fabrication of the pellets, which are sintered at 1750ºC in hydrogen (60).

Hydrogen Production Platinoid-containing membranes are utilised in non-nuclear industry for the separation of hydrogen from other gases. Negligible amounts of FPs might be released to gaseous products from compact metallic or glassy materials. The stability of FPs dispersed as coatings on ceramic or oxide materials would have to be checked in each case. The mechanical properties and the plasticity of Pd-containing membranes can be improved when they are repeatedly loaded with hydrogen, and then unloaded (isobarically or isothermally) (61). Membranes made from Pd alloys containing 10–30 % Ag, 0.5–5% Au, ≤ 2% Y, 0.2–2% Ru, ≤

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1% Pt and 0.01–0.5% Al (B-X alloys) have been applied on industrial scale in the production of hydrogen from ammonia purge gas (37). Pd alloy membranes containing 6–8 wt.% In and 0.5–1.0 wt.% Ru can be used for purification of hydrogen at 400–900ºC and 5–10 atm (62). A Pd-Ag alloy can be spread on a thin film of γalumina, which is supported by a porous ceramic hollow fibre (63), or the alloy or Pd can be deposited electrochemically on a fine metal fabric (20–80 µm thread and 5–20 µm mesh) (64). A Pd/porousglass membrane (65) and a γ-alumina membrane impregnated with Pd in its bulk volume (66) separate hydrogen from nitrogen and carbon monoxide.

Catalysis In this much used application the platinoids are mostly contained in closed systems and, if FPs are used, the risk of personnel irradiation and contamination can be minimised. Release of the FPs to the product of the catalysed reaction can be minimised by the catalyst preparation, and minimum losses of the platinoid components are, in any case, strived for to achieve long catalyst lifetimes. Thus, in some systems the application of FPs could be quite acceptable. Incidentally, the use of an intrinsically radioactive element (technetium) has already been suggested: it strongly increases the catalytic activity of Pd (67). However, using FPs in automobile catalysts would not be acceptable. The release to the environment, even if minimised, would be worthy of consideration, due to the broad utilisation of such catalysts. Data on Pt concentrations in dust, soil and sediments, biological material and natural waters has been published (68). The following examples give a value to the possible extent of platinoid release from a catalyst, and also illustrate the extent of handling the weakly radioactive FPs if they are used as catalyst components. The lowest release of platinoids can be expected from compact metal bodies or layers. For example, Pd-Ru alloys (80–90/5–20 w/w) are used as foils covered on one or both sides by a porous copper layer (69). A Pd/Pt/Rh alloy is shaped to a composite wire, containing in its body a fibre of a


Rh/Y alloy; this is braided into a net (70). Another example is a package in which nets from two different alloys (Pd/Rh/Ru/Pt and Pd/Pt/Au) are alternately layered (71). A film of Pd can be supported by a layer of a siloxane polymer on a porous copper membrane (72). Catalysts of the type PdZnTe0.2, PdZn, or PdZn2 are prepared by reduction with formaldehyde or by metal displacement (73). A not-so-low release of platinoids might occur from catalysts in which platinoids are deposited on porous pretreated oxides: most frequently γ-Al2O3, less frequently TiO2, ZrO2, SiO2, V2O5 or MoO3. They are used either without mechanical support, or on a ceramic support such as cordierite. The pretreatment of γ-Al2O3 consists of calcining in air at 200ºC (74) or 550ºC (75, 76), after eventual ball milling in 0.5 M nitric acid (75), or contacting with an (NH4)2SeO3 solution and drying at 50ºC (76). Zr(IV) hydroxide can be converted to a superacid by treatment with an (NH4)2MoO4 solution, drying at 110ºC and calcining at 600ºC (77). The pretreated oxides (mentioned in the previous paragraph) are contacted with an aqueous solution of H2PdCl4, Pd(NO3)2 or RhCl3 at room temperature, dried at 50–120ºC and heated in air to 400ºC (74, 75, 77) or 540ºC (76). The Pd(II) is then reduced to metal by hydrogen at atmospheric pressure and 200ºC (77) or 400ºC (74), and the Rh(III) is reduced to metal at 0.1 MPa and 500ºC (75). In a wet sol-gel process, Al2O3 sol, for example, is formed by reacting Al isopropoxide with hexylene glycol at 120ºC. A Rh(III) solution hydrolyses the sol at 85ºC to a gel, which is then aged at 80ºC, dried at reduced pressure and heated to 600ºC in an atmosphere of air or nitrogen (78). Again calcination is the usual final step of the catalyst preparation if zeolites of various types and ionic forms (79, 80), mordenite (81) and silicon nitride (82) are used as carriers for platinoids. A non-calcined catalyst with encapsulated dicarbonyl rhodium(I) is prepared by introducing Rh(III) into zeolite Y by ion exchange with Na(I) and heating in a CO atmosphere at 120ºC and 1 MPa (83). On sulfide carriers, Pd or Rh in a valency state > 0 is bound to S atoms. For example, the reaction of bis(2-ethoxyethylxanthato)palladium(II) or

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tris(2-ethoxyethylxanthato)rhodium(III) with molybdenyl dithiocarbamate at 430ºC and 6.9 kPa in a hydrogen atmosphere results in the take up of Pd or Rh into highly dispersed molybdenum sulfide (84). Charcoal granules can be loaded with Rh(III) from an aqueous chloride solution, and the Rh(III) is converted to an oxide at 220ºC and reduced to a metal crystallite by humidified hydrogen at 325ºC (85). An iron/graphite carrier is loaded with Pd(II) from a solution of (π-C3H5PdCl)2 or πC3H5PdP(C6H5)3 in benzene and subsequently calcined in air at 750–850ºC (86). An organic carrier, the styrene-divinylbenzene copolymer HP20, is loaded with Pd from a Pd(II) acetate solution. The Pd(II) is reduced by hydrogen at 100ºC and the obtained catalyst is soaked with trichlorobenzene or trimethylbenzene (87). To prepare a silicon carrier, silica gel is treated with dimethylethoxysilane or triethoxy(2-ethyl-3pyridyl)silane and propylamine, or by (dimethylethoxysilylmethyl)diphenylphosphine. A silicon polymer is formed on the surface which, if contacted with an aqueous solution of PdCl2, incorporates Pd(II) bound to a nitrogen or a phosphorus donor atoms (88). A polymeric support can also be based on silane, silicone or carbon fluoride (89), and a porous material carrying a platinoid can be coated by a layer of a carbon fluoride polymer which is permeable only to gases (90).

Electrochemical Technology In this area the release of FPs and risks for personnel are reduced if the FPs are contained in compact and corrosion-resistant parts of the equipment involved. These FPs can be applied to the production of dimensionally stable anodes, cathodes for hydrogen evolution, platinised titanium electrodes as diffusion electrodes, three-dimensional electrodes (91), electrodes for fuel cells, monocrystalline electrodes and microelectrodes in microsensors for organics. Examples of electrode manufacturing show the extent of manipulation with FPs, and examples of the corrosion rate and the lifetimes give a figure for the FPs expected to be released.


Anodes for electrolytic reactions, made from amorphous alloys Rh-B (75/25), Rh-B-P (70/20/10) and Rh-B-Ti (60/20/20) are representative of compact electrodes. Their corrosion rate in chlorine evolution from aqueous chloride solutions is as low as 0.04–0.07 µm/year at 200 mA cm–2, 1.2 V vs. SCE and 60–80ºC (92). Electrodes made from amorphous alloys, such as Pd76–xPtxSi18Cu6, need no activation treatment (93).

Platinoid Layer/Ti Support Electrodes Electrodes consisting of a compact support carrying a platinoid-containing layer are more typical. In these cases Ti is often chosen as the support material. It is treated as follows: • It is electrolytically coated with the FeSn2 alloy, immersed in a nitrate solution of Pd, Fe and Cd, and heated to 600ºC. An active layer 0.04 cm thick is formed, containing 33–36% Pd. The lifetime of such an anode, used to electrodeposit Zn from a 1 M H2SO4 + 1 M ZnSO4 solution, is 255–287 days at 50 mA cm–2, 1.6 V and 35 ºC (94). • A pre-etched Ti coupon is repeatedly wetted with a solution of RuCl3, PdCl2, Ti(C4H9O)4 and HCl in butanol, dried at 120ºC and heated to 500ºC. This forms an active layer in which Pd oxide is finely dispersed in a solid solution of Ru and Ti oxides, containing 22–55 mol% Ru, 0.2–22 mol% Pd and 44–78 mol% Ti. The active layer can be top-coated with a porous layer of Ta2O5, formed by applying a solution of TaCl5 in pentanol and heating to 525ºC. The lifetime of the electrode is 140 hours in 1.5 M H2SO4 at 50ºC and the anode current density is 7.5 kA m–2. In a hypochlorite generator the electrode operated 24 days in diluted brine at a chloride current efficiency of 80–85% (95). • Ti is mechanically polished and etched by 0.2 M oxalic acid. Then it is repeatedly wetted with a solution of RuCl3, SnCl2 and HCl, then dried at 50ºC and heated to 350ºC (450ºC after the last cycle). A RuO2/SnO2 layer is formed, the composition of which is controlled by adjusting the concentration of the components in the applied solution. At a Ru content of 30 mass%, its maximum lifetime as an anode in 0.5 M H2SO4 at 500 mA cm–2 and 30ºC is ~12 h (96).

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Fuel Cell Catalyst Electrodes A catalyst electrode for a fuel cell is fabricated by forming a monoatomic layer of Pd or Rh on gold crystallites (5–10 nm in diameter) carried by carbon particles. The metals are underpotential deposited from 1–10 M NaOH or KOH containing 10–4–10–5 M Pd or Rh (97). Another catalytic electrode is prepared by depositing Pd onto a sputter-etched silicon surface. A 13.5 MHz radio frequency voltage can be used in an argon atmosphere (0.018 torr) both for the sputtering (500 W r.f. power input into the resulting Ar gas discharge, 30 s) and the Pd deposition (50 W, 5 s) (98).

Electrical Technology and Electronics The potential acceptability of FPs in this field is similar to that in the area of electrochemical technology. Examples of applications are: • Superconductivity is exhibited at < 2 K by CrRu alloys containing > 17 at.% Ru (99), and has been predicted to be a property of the compound LiPdHx (100). Ru, Pd and Rh not only enhance the superconducting transition temperature of high temperature superconductors but, for example, also shorten the synthesis of YBa2Cu3O7–δ from 60 to 10 hours, at a temperature of 880ºC instead of at 920–950ºC (101). • The compound Al2Ru is a semiconductor at low temperature, exhibiting rather anomalous direct current conductivities of ~ 10 and 0.21 Ω–1 cm–1 at 300 and 0.46 K, respectively (102). • The Pd-Ag alloy (70/30 w/w) does not react with the YBa2Cu3O7–δ superconductor at 980 and 1100ºC. A foil of the alloy can thus serve as a conductive barrier between the superconductor and a substrate (103). A non-porous, ductile and shiny coating of a Pd-Ag alloy can be deposited electrolytically from a solution containing PdCl2(NH3)2 or Pd(NO3)2(NH3)2, AgNO3, ammonium acetate or ammonium phosphate plus boric acid and mercaptosuccinic acid or mercaptopropionic acid plus succinic acid monoamide (104). • A Pd coating with increased microhardness can be deposited from a solution containing PdCl2(NH3)4, ammonium sulfate and a complex of ZnCl2 with


1,3,6,8-tetraazatricyclo(4,4,1,13,8)dodecane (105), or from a solution containing the salt (RH)2PdCl4 (R = tetramethylenediethylenetetramine) and ammonium sulfate (106). • Polypyridine complexes of Ru(NCS)2 and RuCl2 are used as sensitisers in solar energy conversion cells based on TiO2 mesoporous electrodes (107). Further special applications are molecular superconductors based on platinoid complexes with organic ligands, photoelectrochemical cells, microwave components, thin film resistors, thermocouples, multilayer structures and superthin wire for IC-chips, amorphous soft magnetic recording materials, magnetic and photorecording materials, antiferromagnetic corrosion-resistant films, and sandwich cermet capacitors.

Production of Corrosion Resistant Materials In this field as well, the FPs would be incorporated in a solid phase and control of their release should thus be possible. Uses may include: • Up to a few per cent of Pd improves or, depending upon the steel composition and type, causes deterioration to the corrosion resistance of stainless steels in diluted sulfuric acid (108, 109) and in solutions of hydrochloric acid or ferric chloride (110). Pd can suppress a particular form of hydrogen embrittlement (“flaking”) of even low alloy steels, and it can also improve mechanical properties (109). Platinoids enhance the corrosion resistance of alloys by modifying the cathodic reaction (“cathodically modified alloys”) (111). • Addition of ≤ 5% Pd enhances the resistance of chromium stainless steels to high-temperature water that contains hydrogen (112), to pressurised superheated steam at 1200ºC (109), to ≥ 90% sulfuric acid at ≤ 220ºC (113) and to air oxidation at 500ºC (114) and 900ºC (115). A content of ≤ 0.7 wt.% Rh improves the stability of chromium stainless steel toward sulfuric and nitric acids (116) and ≤ 0.3 wt.% Ru enhances the resistance of the ferritic Fe-40Cr alloy to diluted sulfuric acid (117). Laser surface alloying enhances the resistance to 0.5 M HCl by forming a surface layer of fine cellular dendrites containing 52 wt.% Ru (118). Passive films have been characterised in 0.5 M HCl at

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0–0.2 wt.% Pd (119), and in 0.5 M H2SO4 and 0.5 M HCl at 0.1–0.2 wt.% Ru (120). • Steel 316 containing 0.5 wt.% Pd is passivated to 1 N H2SO4 by a single cycle of hot pressing and sintering (121). A cathodic alloying additive of Pd (≤ 0.5%) improves the resistance of Cr and Ti alloys in non-oxidising acids or reducing media and also, depending on which components are present, improves the resistance of multicomponent stainless steels in aggressive environments (122). • Addition of 0.15% Pd or coating with PdO/TiO2 enhances the resistance of Ti in boiling non-acidic NaCl and MgCl2 solutions (123). MoCr alloys are resistant to inorganic and organic acids if they contain ≤ 10 wt.% Pd or Ru (124). Promising corrosion resistance in air is exhibited by alloys Al47Ru53, Al48Ru51Y, Al44.5Ru50.5Cr5 and Al44.3Ru50.2Cr5B0.5 at 1100ºC and by alloys Al46Ru52Sc2 and Al43Ru52Sc5 at 1350ºC (125). Ti metal or Ti-based alloys are resistant to acid chloride brines, if they contain 0.1% Ru (126). Surface alloying of a Pd plated Ti alloy is achieved by bombarding with Xe ions which disperse Pd homogeneously in the surface layer. This suppresses corrosion in boiling 1 N H2SO4 (127). The mechanism of the beneficial effect of Pd on the oxidation resistance of Mo-W-Cr alloys to air and oxygen at 1000–1250ºC is elucidated in (128).

Miscellaneous Applications A metallic and a carbon-containing material can be joined if a Pd/Si brazing material and an active metal (Ti, Zr, etc.) or hydride are placed between the surfaces and heated in vacuum (129). Pd can be a component of high temperature strain gauge alloys, such as Au-Pd-Cr, Au-Pd-Cr-Ni, Au-PdCr-Pt-Al or Au-Pd-Cr-Pt-Fe-Al-Y (130). Other potential applications are hydrogen getters in vacuum cryogenics, cryogenic temperature sensitive elements and crucible materials for growing crystals at superhigh temperatures.

barrier to their industrial use in particular cases. [2] A wide range of applications where the use of FPs might be possible has been identified. This includes applications in the nuclear industry, where the materials involved are themselves radioactive or become radioactive during operation, and other applications where the impact of the residual radioactivity could be satisfactorily controlled. [3] Any industrial utilisation of FPs must meet the following general criteria: • The cost of separating, processing and using the FPs should not exceed the costs of using naturally derived platinum group metals. • Irradiation and contamination of personnel as well as uncontrolled release of the FPs into the environment must be avoided. • It must be ensured that recycling of platinum group metals, which frequently occurs in industry, does not result in the contamination of the general stock of the metals by the weakly radioactive FPs. Especially, any risk of introducing the FPs into materials which later can be used in medicine or jewellery must be excluded. It has to be assessed whether this could be guaranteed by common safety regulations for the treatment of radioactive materials (which in many countries have become very strict in recent decades) or whether additional safeguards must be introduced by authorities and efficiently established by the industry.

References

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Conclusions

5 S. N. Suchard, Proc. Symp. Waste Management ’83, 27 Feb.–3 March 1983, Tucson, ANS/ASME, Arizona, U.S.A., Vol. II, p. 113

[1] Although fission platinoids (FPs) separated from high-level radioactive wastes will have residual radioactivity, this need not be an insuperable

6 H. Yamaguchi and N. Sasao, Proc. Int. Symp. Adv. Nucl. Energy Res. Near-Future Chemistry in Nucl. Energy Field, 15–16 Feb. 1989, Oarai, Ibaraki, JAERI, 1990, p. 129


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99 Y. Nishihara, Y. Yamaguchi, M. Tokumoto, K. Takeda and K. Fukamichi, Phys. Rev. B, 1986, 34, (5), 3446 100 D. Singh, R. E. Cohen and D. A. Papaconstantopoulos, Phys. Rev. B, 1990, 41, (1), 861 101 Yu. M. Shul’ga, E. N. Izakovich, V. I. Rubtsov and B. F. Shklyaruk, Platinum Metals Rev., 1993, 37, (2), 86 102 P. Volkov and S. J. Poon, Europhys. Lett., 1994, 28, (4), 271 103 J. L. Porter, T. K. Vethanayagam, R. L. Snyder and J. A. T. Taylor, J. Am. Ceram. Soc., 1990, 73, (6), 1760 104 W. C. Heraeus GmbH, German Patent 3,935,664; 1991 105 Moscow Inst. Fine Chem. Technol., Soviet Patent 1,705,417; 1992 106 Moscow Inst. Fine Chem. Technol., Soviet Patent 1,724,740; 1992 107 T. Renouard, R.-A. Fallahpour, Md. K. Nazeeruddin, R. Humphry-Baker, S. I. Gorelsky, A. B. P. Lever and M. Grätzel, Inorg. Chem., 2002, 41, (2), 367 108 I. R. McGill, Platinum Metals Rev., 1990, 34, (2), 85 109 I. R. McGill, Platinum Metals Rev., 1990, 34, (3), 144 110 B. E. Wilde, I. Chattoraj and T. A. Mozhi, Scr. Metall., 1987, 21, (10), 1369 111 H. Potgieter, Report M397, Mintek, Randberg, January 1990, 13 pp., ISBN 0-86999-876-5 112 General Electric Co., U.S. Patent 5,147,602; 1992 113 Mitsubishi Jukogyo K.K., U.S. Patent 5,151,248; 1992 114 S. C. Tjong and J. B. Malherbe, Appl. Surface Sci., 1990, 44, 179 115 S. C. Tjong and C. Y. Shih, Mater. Charact., 1991, 27, 175 116 Magnitogorsk Mining Metall. Inst., Soviet Patent 1,663,041; 1991 117 J. H. Potgieter and H. C. Brookes, Corr. Eng. (Houston), 1995, 51, (4), 312 118 S. C. Tjong, J. S. Ku and N. J. Ho, Surf. Coat. Technol., 1997, 90, 203 119 Sie Chin Tjong, Surf. Coat. Technol., 1989, 38, 325 120 A. Higginson, R. C. Newman and R. P. M. Procter, Corros. Sci., 1989, 29, (11/12), 1293 121 P. Peled and D. Itzhak, Corros. Sci., 1990, 30, (1), 59 122 J. H. Potgieter, J. Appl. Electrochem., 1991, 21, (6), 471 123 H. Satoh, K. Shimogori and F. Kamikubo, Platinum Metals Rev., 1987, 31, (3), 115 124 Tosoh Corp., European Appl. 0,446,009; 1991 125 R. L. Fleischer and D. W. McKee, Metall. Trans. A, 1993, 24A, 759 126 R. W. Schutz, Platinum Metals Rev., 1996, 40, (2), 54 127 Y. Chen, J. Jin, P. Wang, J. Chen and Y. Wang, Nucl. Instrum. Meth. Phys. Res., 1988, B34, (1), 47 128 D.-B. Lee and G. Simkovich, J. Less-Common Met., 1990, 163, 51 129 Nissan Motor Co., Japanese Patent Appl. 04-006,178; 1992 130 L. Tong and J. Guo, Platinum Metals Rev., 1994, 38, (3), 98

89

The Authors Zdenek Kolarik retired from the Forshungszentrum Karlsruhe in 1998. He was a member of the research staff in the Institute of Hot Chemistry, followed by the Institute of Nuclear Waste. His particular interest was separation chemistry, especially solvent extraction. He participated in work aimed to refine reprocessing of spent nuclear fuel by the Purex process and adapting the process to fast breeder fuel. He also participated in developing a process to separate actinides from radioactive high-level liquid wastes.

Edouard Renard is a group leader at the A. A. Bochvar All-Russian Institute of Inorganic Materials, Moscow. He works in separation chemistry, particularly with solvent extraction. His research work has been directed to further the development of the Purex process for reprocessing fast breeder fuel and recently to the development of a process for the recovery of fission platinoids from radioactive high-level liquid wastes.


90

DOI: 10.1595/147106705X45640

Ruthenium Catalyst for Treatment of Water Containing Concentrated Organic Waste By YuanJin Lei*, ShuDong Zhang, JingChuan He, JiangChun Wu and Yun Yang Kunming Institute of Precious Metals, Kunming, Yunnan 650221, China; *E-mail: [email protected]

The catalytic wet oxidation process (CWOP) is a promising technique for the treatment of highly concentrated organic wastewater that is difficult to degrade biochemically. This technique is based on the wet air oxidation (WAO) method of treating industrial effluent – in use for many years. WAO is a thermal liquid-phase process whereby organic substances in highly concentrated wastewater are oxidised by air at high temperatures and pressures, for long periods of time. Removal of ammonic nitrogen and cyanide is, however, difficult. The CWOP aims to improve on the disadvantages of the WAO method. Tests were conducted to find the best catalysts. Catalyst CWO-11 reduced the severity of the reaction required and improved the chemical oxygen demand and the total nitrogen conversion of organic wastewater.

With advancing industrial development in China, water pollution is becoming an increasingly serious problem. The chemical, petroleum, pharmaceutical, pesticide, electroplating and coke industries, paper manufacture and sugar refining all produce large quantities of organic wastewater. Efficient processing of wastewater is important to prevent water sources from becoming polluted. Processing highly concentrated organic wastewater is difficult, even by biochemical methods; direct burning is very expensive, and high temperature oxidation has a low conversion percentage and fails to eliminate ammonia. Other technologies have looked at destroying organic waste and cleaning ground water (1, 2). Wet air oxidation (WAO) is a thermal liquidphase process in which organic substances are oxidised in wastewater by air at high temperature and pressure for long treatment times (3–6). Ammonic nitrogen and cyanide, are difficult to remove. With WAO, the chemical oxygen demand (COD) conversion percentage of organic wastewater is 60 to 96%. The conversion of phenol and sulfur-containing organic compounds is nearly 99 %.

Catalytic Wet Oxidation Process The CWOP is a liquid-phase oxidation process using a solid catalyst in which organic compounds in aqueous solution are oxidised by oxygen or air at


elevated temperatures and pressures. Aqueousphase deep oxidation can be carried out at comparatively low temperatures and pressures (7). Various catalysts have been tested to reduce the severity of the reaction conditions and to improve the rate of the oxidation reactions of WAO (8, 9). Heterogeneous platinum group metal (pgm) catalysts are the ones generally selected. For successful implementation of CWOP technology it is necessary to use efficient and durable catalysts and to determine the optimal process conditions. Ruthenium was selected as it is strongly resistant to corrosion from both acidic and basic solution at comparatively high temperatures and pressures. Catalyst deactivation can be related to the dissolution of metal on the catalyst surface due to pH changes in the reaction solution; however, although the pH of wastewater changes, the performance of Ru-based catalysts remains steady. Alumina and titania were examined as catalyst support materials. Titania was favoured because of its chemical stability, and the strong metal-support interaction in Ru/TiO2 catalyst. Attention was also paid to the active components and manufacturing technology (10–14). In CWOP technology, both pgms and nonnoble metals are the active catalyst ingredients. Active ingredients are prone to run off the surface of non-noble catalysts due to changes in pH in the

91

Oxidation reactions typically taking place by catalysis in a CWOP reactor Hydrocarbon (HC) (phenol, benzene): O2 O2 O2 HC ⎯⎯→ aldehyde or alcohol ⎯⎯→ organic acid ⎯⎯→ CO2 + H2O

(i)

NH3, ammonic nitrogen, cyanide and N-containing organic compounds: 4NH3 + 3O2 ⎯⎯→ 2N2 + 6H2O

(ii)

H2S and S-containing organic compounds: H2S + 2O2 ⎯⎯→ H2SO4

(iii)

Scheme

reaction solution. However, pgm catalysts have a higher stability and activity. Tests were conducted to find the best catalyst. Activity tests were undertaken in a batch reactor operated at 250ºC, with a stirrer, using air as oxidant. Titania-supported catalyst was found to have higher activity than alumina-supported catalyst. Addition of a Group IIIB (rare earth) element to the pgm improved catalytic performance (15, 16). The rare earth element acted as an auxiliary catalyst. In the industrial tests the chemical oxygen demand (COD) and total nitrogen (TN) conversion percentage of organic wastewater by the catalysts approached 99%. A catalyst with good performance (CWO-11) was selected and compared with a commercial catalyst of the same type using industrial wastewater. CWO-11 was found to be efficient at converting organic compounds in industrial wastewater that are difficult to convert biochemically to CO2, N2 and H2O, see the Scheme. The CWOP equipment occupies less space than the biochemical method, and the energy produced during the oxidation can be recycled.

Experimental Work The carriers comprised mini-balls of 5 mm diameter TiO2 or Al2O3, of specific surface area 10–20 m2 g–1, prepared by mechanical means. The carriers were soaked with active components of platinum group metals and auxiliary components,

such as Ce, La, etc. The catalyst was then dried, calcined and reduced. All catalysts were prepared in this way. The organic wastewater used to evaluate the catalyst comprised: • Simulated organic wastewater composed of ammonium sulfate and oxalic acid in amounts 28.3 g l–1 and 7.4 g l–1, respectively, in distilled water. • Organic wastewater produced by a coke oven plant (in Kunming). The COD and TN (total nitrogen, including ammonic nitrogen, cyanide, and so on) are 4000 to 5000 mg l–1 and 2000 to 3000 mg l–1, respectively. This wastewater typically also contains hydrocarbons, benzene, phenol and its derivatives, cyanide, ammonic nitrogen, sulfurcontaining organic compounds, NH3 and H2S dissolved in aqueous phase.

Simulated Laboratory Evaluations The reaction conditions were kept constant throughout the tests. Temperature was at 250ºC. The reaction vessel was equipped with a mechanical stirrer with a fixed stirring rate of 1000 rpm. Organic wastewater was poured into the 500 ml flask. Catalyst (16 g) was then added, and air was introduced at a pressure of 28 kg cm–2. The reaction was free from external diffusion limitations. Diffusion is an indispensable procedure in a heterogeneous catalytic reaction. An improved flow rate for the reaction solution can eliminate the effect of external diffusion. If the reaction rate

COD of wastewater before reaction – COD of wastewater after reaction COD conversion, % = ⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯ ×100% COD of wastewater before reaction


(a)

92

Heater

Condenser Exhaust

Air compressor

Gas-liquid separator

Wastewater tank Pump

Reactor 1

Treated water

Reactor 3

Reactor 2

Fig. 1 Flow diagram of a simulated industrial test with three reactors where pH is measured at each reactor exit point

does not change along with the stirring rate (1000 rpm), the reaction is free from external diffusion limitations. Catalytic runs of 30 minutes’ duration were performed, after which the reaction was stopped by interrupting the air supply. The COD percentage conversion of organic wastewater was calculated according to Expression (a). Similarly, the TN content before and after the reaction can be used to give a conversion percentage.

Simulated Industrial Conditions in A Pilot Plant In this method 1 litre of solid catalyst was used in each of the three fixed-bed reactors; air and organic wastewater were continuously pumped in. The water flow used was 4 l h–1 (liquid hourly space velocity (LHSV) = 1.3 h–1) to treat the wastewater. A flow diagram of a simulated industrial test in the pilot plant is shown in Figure 1. The reactor is similar to one used for practical industrial operation. Four experiments were performed.

Table I shows that the COD conversion percentages in the two experiments were very close when the same equipment and conditions were used. This confirms that equipment and catalyst evaluation conditions were comparable.

Catalyst Evaluation by Batch Reactor The CWOP is usually carried out at high temperature and pressure in an oxidative medium, the pH of which can vary greatly. The pH of the reaction system in the batch reactor was measured before and after the reaction, at each reactor exit point. The pH of the reaction system varies, for example with the reactions: Hydrocarbon + O2 → aldehyde + O2 → organic acid + O2 → CO2 + H2O The catalysts tested for the purification of wastewater comprised carriers alumina or titania, and active components such as Pd, Ru and Group IIIB elements. Table II gives conversion data for wastewater from the coke oven plant. The catalyst

Results and Discussions Reproducibility of Conditions For consistent evaluation and to differentiate between catalysts it is important to select suitable equipment and good evaluation conditions. A 500 ml batch reactor was selected. Wastewater from the coke oven plant (carbonising water containing phenol, benzene, carbon dioxide and hydrocarbons) was evaluated twice using the same catalyst.


Table I

Repeated Runs Using Coke Oven Wastewater Number of runs

Catalyst

COD conversion, %

1 2

CWO-1* CWO-1

83.85 83.82

* CWO-1 is similar to catalyst CWO-11

93

Table II

Evaluation of Different Catalyst Systems Using Wastewater from a Coke Oven Plant Catalyst

Catalyst system

CWO-2 CWO-12 CWO-7 CWO-8 CWO-10 CWO-11 CWO-9

Pd/Al2O3 Ru/TiO2 Ru/TiO2 Ru-Group IIIB/TiO2 Ru-Group IIIB/TiO2 Ru-Group IIIB/TiO2 Ru-Pd-Group IIIB/TiO2

system CWO-2 Pd/Al2O3 is seen to be effective for COD conversion but not for TN conversion. Changing the active catalyst component to Ru and the support to TiO2, as in CWO-7 and CWO-12, increased the TN conversion percentage. More effective catalysis was obtained when a Ru-Group IIIB catalyst was used, as in CWO-8, CWO-10 and CWO-11. CWO-11 was the most effective. Both the COD percentage conversion and the TN percentage conversion of CWO-11 were very high. The catalyst system CWO-9, which contained Ru, Pd and a Group IIIB addition/TiO2 showed no advantage over the above catalysts.

Comparison with a Commercial Catalyst The performance of catalyst CWO-11 was compared in the batch reactor under identical reaction conditions with one of the best available commercial catalysts. This catalyst generally operates under similar conditions and with similar wastewaters. The results (Table III) show that the COD and TN percentage conversions of catalyst CWO-11 were higher than those of the commercial catalyst, with the difference for TN conversion being more pronounced.

COD conversion, % 79.8 77.1 78.3 80.4 74.9 85.2 76.8

TN conversion, % 5.6 53.6 43.8 44.8 33.5 66.5 48.7

Preliminary Examination of Changes in Catalyst Breaking Strength Knowing the breaking strength of a catalyst is important as catalysts in fixed-bed reactors need to bear high pressures, especially in the lower part of a reactor, where catalyst could be crushed, leading to a drift of active components from the catalyst surface, and reduced catalytic activity. The breaking strength of the catalyst is defined by the pressure applied by steel plate as the catalyst is being broken. Measurements of catalyst strength were taken by a hand crusher method, during which a steel plate slowly crushes the catalyst. The CWO-11 catalyst was tested under similar simulated conditions of reaction pressures: 90 × 2, 75, 60, 50 × 2 kg cm–2, and with large temperature increases and decreases. The processes were carried out one immediately after the other for 6 cycles for 58 hours (20 h for the reaction and 38 h for the temperature changes), see Figure 2. The breaking strengths of the catalysts before and after being used for 58 hours were measured. Ten samples of each kind of catalyst were randomly chosen for testing. Table IV shows the results. The data indicate that catalyst strength

Table III

Comparison of Catalysts Catalyst

COD conversion, %

TN conversion, %

CWO-11 (Kunming Precious Metals Institute)

85.2

66.5

Similar commercial catalyst (Osaka Gas Co. Ltd., Japan)

83.1

51.1


94

Table IV

Change in Catalyst Breaking Strength Before and After Use Sample number

1

2

3

4

New catalyst strength, kg

2.8

3.3

3.4

3.5

Average strength, kg Catalyst strength after 58 h, kg

5

6

7

8

9

10

3.5

3.5

3.5

3.7

3.8

4.0

3.5

3.5

3.6

3.6

4.1

3.5 2.6

3.3

3.3

3.4

Average strength, kg

3.4 3.4

8

6

STRENGTH, kg(k g ) S tr e n g th

Fig. 2 Test results of the breaking strength of new catalyst and the same catalyst after being used continuously for 58 hours

N e w C a ta ly s t C a ta ly s t u s e d fo r 5 8 h o u rs

4

2

0 0

2

4

6

8

10

SAMPLE N u m NUMBER ber

shows no obvious changes after testing over 6cycles, each lasting for 58 hours. The catalyst could thus be used for long periods without crumbling.

Results of Simulated Industrial Tests in a Pilot Plant on Catalyst CWO-11 As Table V shows, the COD percentage conversion for Reactor 3 exit point (R-3) is ~ 99.9%, (from 16,483.6 for raw wastewater down to 16.48)

and the TN percentage conversion has reached 100% (3528 for raw wastewater down to 0). The TN conversion percentage at Reactor 2 exit point (R-2) has also reached 100%. Table VI shows that the TN percentage conversion at Reactor 1 exit point (R-1) has reached 100%. The COD percentage conversion at Reactor 2 exit point (R-2) is up to 99.9%. In Table VII, the TN conversion percentage

Table V

Tests on CWO-11 with Simulated Industrial Wastewater Experimental conditions: air pressure: 70 kg m–2, temperature: 250ºC, water flow*: 4 l h–1 Wastewater sample

Raw wastewater R-1 exit point** R-2 exit point R-3 exit point

O2, %

pH

COD, mg l–1

TN, mg l–1

Flow rate, l h–1

Exhaust volume, l h–1

20.8 12.2 7.9 7.1

9.1 3.5 5.0 3.8

16,483.6 7905.4 414.44 16.48

3528 3.36 0 0

4.0 3.9 3.96

554.4 529.4 523.4

*Wastewater moves smoothly and continuously, and is not recirculated. **Exit points from Reactors 1, 2 and 3 are shown in Figure 1


95

Table VI

Tests on CWO-11 with Simulated Industrial Wastewater Experimental Conditions: air pressure: 90 kg m–2, temperature: 270ºC, water flow: 4 l h–1 Wastewater sample

Raw wastewater R-1 exit point R-2 exit point R-3 exit point

O2, %

pH

COD, mg l–1

TN, mg l–1

20.8 9.1 8.5 5.8

8.5 4.2 4.0 3.9

16,483.6 412.09 11.77 11.77

3640.0 0 0 0

can be seen, at R-3 to reach 100%. However, the COD conversion percentage at R-3 is only up to 68%. Table VIII shows, the COD percentage conversion at R-3 is up to 99.2%, while the TN percentage conversion reaches 99.9%. Thus, experimental conditions of 70 kg cm–2 and 250ºC and also of 90 kg cm–2 and 270ºC can meet the requirements for use in the conversion of wastewater using catalyst CWO-11. An air pressure of 70 kg cm–2 and reaction temperature of 250ºC would be economically more desirable.

Flow rate, l h–1 4.0 3.86 3.96

Exhaust volume l h–1 566.6 542.2 528

Conclusions We have obtained a new catalyst (CWO-11) for use in the catalytic wet oxidation process that is effective for converting organic compounds in simulated wastewater and wastewater from a coke oven plant into CO2, H2O and N2. CWO-11 has a higher activity for COD and TN conversions than a similar commercial catalyst. The COD and TN conversion percentages of organic wastewater are up to 99%. CWO-11 been used in scaled-up reactors, in a batch reactor in the laboratory and in a continuous

Table VII

Tests of CWO-11 with Simulated Industrial Wastewater

Experimental conditions: air pressure: 50 kg m–2, temperature: 230ºC, water flow: 4 l h–1 Wastewater sample

O2, %

pH

COD, mg l–1

TN, mg l–1

Flow rate, l h–1

Raw wastewater R-1 exit point R-2 exit point R-3 exit point

20.8 15.8 12.3 8.4

8.5 5.4 3.5 3.6

16,483.6 12,166.5 10,890.9 5214.2

3640.0 1372.0 2.160 0

3.96 3.92 4.0

Exhaust volume, l h–1 548 518.2 482.6

Table VIII

Tests on CWO-11 with Wastewater from a Coke Oven Plant Experimental conditions: air pressure: 70 kg m–2, temperature: 250ºC, water flow: 4 l h–1 Wastewater sample Raw wastewater R-3 exit point R-3 exit point Average value

Reaction time, min

O2, %

pH

COD, mg l–1

TN, mg l–1

Flow rate, l h–1

Exhaust volume, l h–1

0 45 45 45

20.8 15.5 15.0 15.2

8.9 5.4 2.5 4

3000.5 33.21 14.53 23.87

756.0 0 1.12 0.6

4.4 4.04 4.2

269.7 291.6 280.6


96

process in a pilot plant. This method of catalyst evaluation has effectively differentiated between catalysts of different performance.

It is planned to increase and improve the mechanical strength of the catalyst and to use CWO-11 in further industrial applications.

References 1 L. Davidson, Y. Quinn and D. F Steele, Platinum Metals Rev., 1998, 42, (3), 90 2 N. Korte, L. Liang, R. Muftikian, C. Grittini and Q. Fernando, Platinum Metals Rev., 1997, 41, (1), 2 3 V. S. Mishra, V. V. Mahajani and J. B. Joshi, Ind. Eng. Chem. Res., 1995, 34, (1), 2 4 D. Duprez, F. Delanoe, J. Barbier, P. Isnard and G. Blanchard, Catal. Today, 1996, 29, (1–4), 317 5 Jin Yi Song et al., “Environmental Catalytic Materials and Applications”, Chemical Industry Press, Beijing, 2002 (in Chinese) 6 N. M. Dobrynkin, M. V. Batygina and A. S. Noskov, Catal. Today, 1998, 45, (1–4), 257 7 St. G. Christoskova, M. Stoyanova and M. Georgieva, Appl. Catal. A: Gen., 2001, 208, (1–2), 243

8 F. Luck, Catal. Today, 1996, 27, (1–2), 195 9 J. Levec and A. Pintar, Catal. Today, 1995, 24, (1–2), 51 10 Wang Yong Yin et. al., Progr. Environ. Sci. (China), 1995, 3, (2), 35 11 U. S. Patent 4,115,264; 1978 12 J. Levec, Appl. Catal., 1990, 63, (1), L1 13 Jiang Yi et al., Environ. Sci. (China), 1990, 11, (5), 34 14 Japanese Patent 64-47,451; 1989 15 Japanese Patent 64-30,695; 1989 16 S. Imamura, in “Catalysis by Ceria and Related Materials”, ed. A. Trovarelli, Imperial College Press, London, 2002

The Authors YuanJin Lei is a Professor of Chemistry at Kunming Institute of Precious Metals, China. He has has been working in the area of catalytic materials for forty years. His main interests are the development of catalytic gas sensors, environmental catalysts, petrochemical catalysts, etc. ShuDong Zhang has a Master of Engineering Degree from Kunming Institute of Precious Metals. He has been working in the area of noble metal catalysts since 2002.

JiangChun Wu is a senior chemical engineer at Kunming Institute of Precious Metals. She has worked in analytical chemistry for the last ten years, and was involved in testing the performance of the catalytic gas sensor.

Yun Yang is a mechanical engineer at Kunming Institute of Precious Metals. She is interested in catalytic gas sensors.

JingChuan He is a senior chemical engineer at Kunming Institute of Precious Metals. His research interests include heterogeneous catalysis of noble metals and catalytic gas sensors.


97

DOI: 10.1595/147106705X45794

Patents and Copyright for Scientists INTELLECTUAL PROPERTY COVERS PATENTS, COPYRIGHT, TRADE MARKS, INDUSTRIAL DESIGNS AND RIGHTS IN CONFIDENTIAL INFORMATION By Ian Wishart Patents Department, Johnson Matthey Technology Centre, Blounts Court, Sonning Common, Reading RG4 9NH, U.K. E-mail: [email protected]

Intellectual property is an intangible asset, but it confers legal property rights similar to those of tangible assets (land, equipment, etc.). Thus, patents and copyright can be bought and sold, or leased (licensed) for money. A working scientist will frequently come across patents in the background research. In some areas of technology patents are by far the main type of technical publication, so it is important to understand these documents and their context, and not be unduly inhibited by their forbidding appearance. This article will give advice to practising scientists regarding patenting.

The Purpose of Patents A patent is a bargain between the State and an inventor. In return for the inventor describing the invention to the public – for the advancement of science and technology – the State rewards the inventor with a limited monopoly that will prevent unauthorised commercial use of the invention. The publication of a patent is intended to increase human knowledge, and the inventor has to describe to the skilled reader how to make the invention work. The inventor is granted a monopoly period, usually of 20 years, during which time the inventor can exploit the invention for financial reward. In most countries the monopoly will be for 20 years, but because of the delays in getting approval, for instance in medicine and agrochemicals, the time may be extended by up to 5 more years. Renewal fees must of course be paid for the patent to remain in force. In almost all countries, priority in patenting is granted to the first person to file the Application; (the first official description of the invention, and notice that a patent is being sought). However, in the U.S.A. priority is awarded to the first to invent.


This is a subtle difference that requires scientists in the U.S.A. to be good record keepers. The documents that people call “patents” are usually the published Applications. Patenting organisations publish Applications (the description of the patents) 18 months after the first application date (an important date also called the filing date or the priority date), so that researchers have early warning of what is being sought for patenting. When the patent is eventually granted it may have been amended by the patentees. Only then can the legal effect of the patent be determined.

Novelty and Inventiveness The invention to be patented has to meet standards of novelty and inventiveness, that is, it should not be already in the public domain nor be an obvious variant of something that is known. A patent (also called a specification) has two basic parts: • a description of the invention, possibly with drawings or graphs, and • the claims. While working examples of the invention are desirable, they are not generally required. The patenting process requires the Application to be lodged in a government patent office along with forms that name the owner of the patent and usually identify the inventor(s), and the patenting fee. The patent office will usually, but not always, carry out a search through prior documents in order to establish that there is novelty and also an inventive step in the patent.

Countries of Enforcement A patent only has effect in the country granting it. Thus, in order to protect an invention, it may be necessary to apply for a patent in a number of

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Advice for Inventors on Applying for Patents • It is not recommended that an inventor writes his own patents. This is because it is too easy to make the mistake of limiting the scope of the patent or include other fundamental errors. • An employer will normally have an in-house patent attorney or will use an outside patent attorney. • An individual should find a patent attorney, and websites or the government Patent Office can provide a list (lawyers do not generally have the technical background to adequately represent a client in patent drafting). A patent attorney needs to understand the invention, and will ask many questions. • The first Application is usually made in the inventor’s country of residence (for convenience). Overseas Applications, especially where translations are necessary, can be quite expensive, and an individual may be unable to fund this level of patenting.

countries. This is conventionally done within 12 months of the initial filing date (the priority date). Certain patent systems, such as PCT (Patent Cooperation Treaty) or European Applications, can cover a number of countries. Some patents can lead to confusion. For example, Japanese inventors apply for huge numbers of patents, but only about a quarter result in actual granted patents. Frequently, a scientist or businessman may be inhibited by the existence of such a “patent”, but closer inspection could show that the patent is only a Japanese Application, without legal status in countries outside Japan.

The Patent Claims The claims of a patent govern the legal effect of the patent, that is, the areas of technology that are to be monopolised. The accurate interpretation of patent claims is a skilled art, and an area in which patents professionals need to be consulted. However, a patent only protects against commercial activities, such as offering for sale, making, selling, etc., so this may not be necessary. Undertaking experimental work within the scope of the patent to prove, disprove or develop the patented invention is not prevented. Many scientists wrongly concentrate on the examples or specific description, just as they would carefully read the experimental sections of scientific papers. Generally it can be said that a feature is not protected unless that feature is claimed or covered by general language in the claims. Of course, an earli-


er patent may protect that feature. It may be an “infringement” of a patent to knowingly provide another person with the means to infringe a patent. This is not direct infringement but “contributory infringement”.

Monopoly Aspects of a Patent The monopoly granted by a patent is just one of many possible reasons for applying for a patent. The patent owner may in fact be interested in allowing others to operate within the patent, for example by having them pay a licence fee or royalty. A patent may also be used as a bargaining tool in negotiations, or it can act as a short-term barrier to allow the patent owner to establish a commercial lead. Sales personnel often wish to have a patent to show to customers, to establish that a particular product is novel. But above all the main reason for patenting for many companies is to establish “freedom to operate” and to make sure that a competitor cannot patent a particular development, and use it to prevent the company from commercialising an invention it was first to devise.

Challenging Patents If a patent is considered likely to prevent a company from proceeding with commercialising a new product or process, there are actions that can be taken. First, the new product or process should be carefully compared to the patent claims to establish if the process or product is the same as all the aspects of the claims. Care needs to be taken here,

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as courts may decide that a difference is insignificant. The legal status of the patent should be checked: that is: whether it exists in the relevant country, that all the renewal fees have been paid, and that the patent is not more than 20 years old. A discussion between the scientist or engineer and a patent attorney may identify a way around the patent claim(s). Finally, if all of the above are unsuccessful, a study of the validity of the patent will be required. Often, serious questions over the enforceability of the patent may arise from finding a prior document, or a prior commercial use that was not found during the patent examination process. This can be a time-consuming and expensive procedure, and may not always lead to a reliable conclusion.

Patent Owner It should be mentioned that the first owner of an invention is the inventor(s) unless the ownership is transferred by a contract, or the invention arose out of an employee’s duties. Most employed inventors will find that their contract of employment claims inventions as the property of the employer.

Patents Illustrate Technology Change As an example of the development of patenting, the field of the platinum group metals (pgms) has been analysed, see the block chart. This shows

25000 Os

20000

Ir

15000

Ru

10000

Rh

5000

Pd Pt

0 71/80

81/90

91/00

01/04

The number of Applications naming the six platinum group metals that were granted in the three decades before the millennium and for the current decade

the number of individual published Applications listing one of the six pgms in each recent decade. If two or more metals are listed, there are two or more counts, but duplications of the same invention have been eliminated. The current decade shows lower numbers since it is only part way through. As can be seen, each decade has resulted in more patents for each metal, with patents for platinum and palladium dominating. Thus, patents play an important part in commercial activities, protecting intellectual property and establishing legal rights. The information they contain and their effects are hugely important.

Glossary PCT (Patent Cooperation Treaty) can cover almost every country in the World (designated by the Applicant). European Applications/European Patents cover 30 “European” countries, including Turkey.

Important Patents in the Platinum Group Metals Field The following are the author’s personal selection of important pgms patents that have had a considerable effect on technology (1).

Early Catalysis In the early part of the 19th century, the first catalytic processes (although that term had only been coined by Berzelius in 1836) were being developed by Kuhlmann in France, represented by the platinum catalysed nitric acid and sulfuric acid processes in French Patents 11331 (Application filed 1838) and 11332, respectively. These concepts took some time to develop, until Ostwald (British


Patents 698 and 8300; 1902) and Kaiser (German Patent 271,517; 1909) established the bases of the huge ammonia oxidation industry using platinum gauze catalysts. The similar industrial process for making hydrogen cyanide was developed in the 1930s by Andrussow (German Patent 549,055; 1932).

Plating/Electroplating Plating of precious metals was of great interest in the first half of the 19th century, but effective methods of plating pgms were only slowly developed (in contrast to electroplating silver or gold).

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Two key patents from that time are H. B. Leeson’s British Patent 9374; 1842 and G. Howell’s British Patent 11,065; 1846.

Refining During the 1920s, with the discovery of the platinum-rich Merensky reef in South Africa, there was considerable research into refining methods Alan R. Powell and Ernest C. Deering, who both worked for Johnson Matthey, developed the matte process for smelting. This was patented as British Patent 316,063; 1929.

Homogeneous and Heterogeneous Catalysis In 1976 Geoffrey Wilkinson was awarded a patent (U.S. Patent 3,933,919) for the development of a rhodium-based homogeneous catalyst. This was a truly major step in chemical process technology. In heterogeneous catalysis, exhaust gas purification is a huge consumer of pgms. Once the increasingly detrimental effects of car exhaust gases on the environment was recognised as an

issue, patenting activity increased. For example, see Johnson Matthey’s 1975 patent British Patent 1,417,544. Johnson Matthey has also brought patented technology to the removal of soot from diesel exhausts (European Patent 341,832; 1989).

Biological Uses Finally, I mention the discovery of the biological activity of platinum complexes. This led to a new and effective way of treating cancers. The known compound cisplatin was patented in U.S. Patent 4,177,263; 1979, and the second generation compound carboplatin was patented in a number of countries (e.g. British Patent 1,380,228; 1975). Incidentally, the cisplatin patent was applied for before that for carboplatin, but granted afterwards. This was because of the difficulty in persuading the U.S. Patent Office that a platinum compound could be an active anticancer agent.

Reference 1

Donald McDonald and Leslie B. Hunt, “A History of Platinum and its Allied Metals”, Johnson Matthey, London, 1982

Other Intellectual Property Another area of intellectual property that scientists come across in day-to-day work is copyright. Copyright automatically applies to original literary or artistic work (regardless of merit) upon creation. Copyright is owned by the creator(s) unless the creator is an employee, in which case copyright is owned by the employer. Scientific authors will be asked to transfer or assign copyright to a publisher, to permit the publisher to print and publish a paper, otherwise this would technically be copyright infringement. The better copyright transfers permit the author some rights to re-use the material in the paper. Two important issues concerning copyright need to be mentioned. Recent changes in European copyright law allow copying of articles or parts of books only for research that is purely academic. A copyright fee is generally due for copying for commercial research, even when the researcher or employer already owns a copy. The other issue concerns electronic copies.


Scanning copies is regarded in the same light as photocopying. The Internet is another minefield for users. Because an article or image is available on the Internet does not mean that it can be freely copied, forwarded, stored in a database or used in another publication. The website concerned almost certainly will have a “small print” section with a copyright notice and conditions. As with patents, the complexities of copyright law warrant the use of a specialist where there is any case of doubt.

The Author Ian Wishart has the position of Corporate Patents & Licensing Director of Johnson Matthey PLC, where he has worked since 1987. After gaining a degree in Chemical Engineering from Edinburgh University, he trained in intellectual property, qualifying as a U.K. Patent Attorney in 1973. He has worked for Sandoz in Switzerland, and for the U.K.’s National Coal Board, where he became involved in licensing and other IP agreement work.

101

DOI: 10.1595/147106705X46496

ABSTRACTS

of current literature on the platinum metals and their alloys CHEMICAL COMPOUNDS

ELECTROCHEMISTRY

Dimeric Palladium Complexes with Bridging Aryl Groups: When Are They Stable?

Electrochemical Investigations of Platinum Phenylethynyl Complexes

A. C. ALBÉNIZ, P. ESPINET, O. LÓPEZ-CIMAS and B. MARTÍNRUIZ, Chem. Eur. J., 2005, 11, (1), 242–252

[Pd2(µ-R)2(η3-allyl)2] (R = haloaryl, mesityl) were prepared. The haloaryl complexes exchange between their cis and trans isomers (relative to the orientation of the two allyl groups in the dimer) by solvent-assisted associative bridge splitting. Stable aryl bridges are favoured by ancillary ligands of small size and lacking electron lone pairs, and aryl ligands reluctant to be involved in homo and hetero C–C coupling. Synthesis, Structure and Electrochemical Properties of Tris-picolinate Complexes of Rhodium and Iridium

S. BASU, S.-M. PENG, G.-H. LEE and Polyhedron, 2005, 24, (1), 157–163

S. BHATTACHARYA,

The pic ligands of [M(pic)3] (1) (M = Rh, Ir; Hpic = picolinic acid) are coordinated as bidentate N,Odonors. A water of crystallisation molecule is H bonded to the carboxylate fragments of two adjacent (1) and acts a bridge between the individual (1). (1) are diamagnetic and show intense MLCT transitions in the visible region. CV on (1) shows a M(III)–M(IV) oxidation and a ligand-centred reductive response.

L. KONDRACHOVA, K. E. PARIS, P. C. SANCHEZ, A. M. VEGA, R. PYATI and C. D. RITHNER, J. Electroanal. Chem., 2005, 576,

(2), 287–294

Pt phenylethynyl complexes exhibited irreversible oxidations in benzene/MeCN near +1.2 V vs. Ag|AgCl. However, trans-bis(tri-n-butylphosphine) bis(phenylethynyl)platinum(II) underwent reduction in THF at –2.786 V. Photophysical measurements established that as the phenylethynyl chain length increases, the absorbance wavelength increases. The emission wavelength shows a weak but similar trend. Controlled Growth of a Single Palladium Nanowire between Microfabricated Electrodes M. A. BANGAR, K. RAMANATHAN, M. YUN, C. LEE, C. HANGARTER and N. V. MYUNG, Chem. Mater., 2004, 16, (24),

4955–4959

Dimensionally controlled growth of a single Pd nanowire (1) between premicrofabricated Au electrodes was achieved using an electrochemical method. (1) of 100 nm, 500 nm, and 1 µm wide and 2.5 µm long channels (length-to-diameter ratio ~ 2.5–25) were grown. Current of –100 nA was used.

PHOTOCONVERSION

Iridium(I) and Rhodium(I) Cationic Complexes with Triphosphinocalix[6]arene Ligands: Dynamic Motion with Size-Selective Molecular Encapsulation

A Luminescent Pt(II) Complex with a TerpyridineLike Ligand Involving a Six-Membered Chelate Ring

Y. OBORA, Y. K. LIU, L. H. JIANG, K. TAKENAKA, M. TOKUNAGA and Y. TSUJI, Organometallics, 2005, 24, (1), 4–6

Y.-Z. HU, M. H. WILSON, R. ZONG, C. BONNEFOUS, D. R. Mc MILLIN and R. P. THUMMEL, Dalton Trans., 2005, (2),

The title complexes (1) exhibited dynamic behaviour with size-selective molecular encapsulation. Variable-temperature 31P{1H} NMR measurements were carried out in the presence of various molecules (1). (1) were divided into three groups, depending on the maximum projection area of the solvent-accessible surface, A: < 45 Å2, 45–68 Å2, and > 68 Å2. Molecules with A of 45–68 Å2 just fit in the cavity and slow the dynamic behaviour.

354–358

[Pt(1)Cl]+ (2) ((1) = 2-(8'-quinolinyl)-1,10-phenanthroline) was prepared. The six-membered chelate ring in (2) gives relief to the angle strain as well as some non-planarity in bound (1). In CH2Cl2 (2) exhibited higher energy charge-transfer absorption, but slightly lower energy emission than [Pt(3)Cl]+ ((3) = 2-(2'-pyridyl)-1,10-phenanthroline).

Synthesis and Derivatization of Iridium(I) and Iridium(III) Pentamethyl[60]fullerene Complexes

Electrochemical and Luminescent Properties of New Mononuclear Ruthenium(II) and Binuclear Iridium(III)-Ruthenium(II) Terpyridine Complexes

2005, 24, (1), 89–95

N. YOSHIKAWA, T. MATSUMURA-INOUE, N. KANEHISA, Y. KAI, H. TAKASHIMA and K. TSUKAHARA, Anal. Sci., 2004, 20, (12),

Y. MATSUO, A. IWASHITA and E. NAKAMURA,

Organometallics,

Ir(η5-C60Me5)(CO)2 (1) was obtained from the reaction of K(C60Me5) with [IrCl(CO)2]2 in MeCN/THF. Oxidation of the Ir atom of (1) by I2 gave an Ir(III) complex, Ir(η5-C60Me5)I2(CO) (2). The iodo and carbonyl ligands of (2) can be readily replaced by alkyl, alkynyl, phosphine, and isonitrile ligands. (2) may be used as catalysts for organic synthesis.


1639–1644

The title complexes include [RuII2Cl2(dpp)(terpy)2]2+ (1) and [IrIIIRuIICl2(dpp)(terpy)2]3+ (2) (dpp = 2,3bis(2-pyridyl)pyrazine). The absorption spectra of (1) and (2) exhibit ligand-centred bands in the UV region and MLCT bands in the visible region. The HOMO is based on Ru, and the LUMO is dpp-based.

102

Design of Novel Efficient Sensitizing Dye for Nanocrystalline TiO2 Solar Cell; Tripyridine-thiolato (4,4',4''-tricarboxy-2,2':6',2''-terpyridine) ruthenium(II) F. AIGA and T. TADA,

(3), 437–446

Sol. Energy Mater. Sol. Cells, 2005, 85,

The title Ru complex (1) was designed based on the DFT MO calculations with PBE0 functional. (1) is a modification of the Ru black dye (2), with the NCS ligands of (2) being replaced by C5H4NS ligands. (1) has a higher electron transfer rate from redox systems to oxidised dyes and higher absorption efficiency to the solar spectrum. A Highly Efficient Redox Chromophore for Simultaneous Application in a Photoelectrochemical Dye Sensitized Solar Cell and Electrochromic Devices A. F. NOGUEIRA, S. H. TOMA, M. VIDOTTI, A. L. B. FORMIGA, S. I. CÓRDOBA DE TORRESI and H. E. TOMA, New J. Chem., 2005,

29, (2), 320–324

Na6[{RuII(dicarboxybipyridine)2Cl}2(BPEB)] (1) (BPEB = trans-1,4-bis[2-(4-pyridyl)ethenyl]benzene) exhibits an electrochromic effect when reduced. The carboxylate groups of the bipyridine allow strong attachment to the surface of TiO2. This contributes to an efficient and reversible electron transfer from the oxide to the chromophoric ligand, colouring the oxide film blue. (1) also has a high photon-to-electron conversion efficiency when applied as a photoanode in a dye sensitised solar cell.

ELECTRODEPOSITION AND SURFACE COATINGS Characterizations of Pd–Ag Membrane Prepared by Sequential Electroless Deposition

W.-H. LIN and H.-F. CHANG, Surf. Coat. Technol., 2005, 194, (1), 157–166

Sequential electroless plating on porous stainless steel was used to prepare Pd-Ag membranes. AFM established that lower skin layer roughness and lower deposition rate were related. EDS confirmed the PdAg deposit over and inside of the porous substrate to be homogeneous. Preparation of Palladium and Silver Alloy Membrane on a Porous α-Alumina Tube via a Simultaneous Electroless Plating D. A. PACHECO TANAKA, M. A. LLOSA TANCO, S. NIWA, Y. WAKUI, F. MIZUKAMI, T. NAMBA and T. M. SUZUKI, J. Membrane

Sci., 2005, 247, (1–2), 21–27

For the title process, seeding of Pd nanoparticles (1) on an α-Al2O3 tube allowed codeposition of Pd and Ag. (1) were distributed by dip-coating with Pd acetate or [Pd(acac)2] in organic solvents followed by reduction with alkaline hydrazine solution. After simultaneous deposition, alloying of Pd and Ag was carried out at 500ºC for 4 h in H2.


Morphological Evolution of the Self-Assembled IrO2 One-Dimensional Nanocrystals

R.-S. CHEN, H.-M. CHANG, Y.-S. HUANG, D.-S. TSAI and K.-C. CHIU, Nanotechnology, 2005, 16, (1), 93–97

The morphological evolution of IrO2 1D nanocrystals (1) via MOCVD has been observed. (1) result from a decrease in the degree of interface instability. (1) occur from triangular/wedged nanorods via incomplete/scrolled nanotubes to square nanotubes and square nanorods. The polycrystalline films composed of continuous 3D grains belong to the most stable form as compared to the 1D nanocrystals. Thermophysical Properties and Deposition of B2 Structure Based Al–Ni–Ru–M Alloys

I. VJUNITSKY, P. P. BANDYOPADHYAY, St. SIEGMANN, M. DVORAK, E. SCHÖNFELD, T. KAISER, W. STEURER and V. SHKLOVER, Surf. Coat. Technol., 2005, 192, (2–3), 131–138

The normal value range for the thermal conductivity of the title alloys is 10–20 W m–1 K–1 at room temperature, but can be reduced to ~ 3.5 W m–1 K–1 by modifying the alloy composition. A fused and subsequently pulverised Al-Ni-Ru alloy was deposited on a Ni-based superalloy (modified CMSX-4) using vacuum and atmospheric plasma spraying. The coatings had favourable coating–substrate adhesion. A segregated intermetallic phase was detected at the Al50Ni40Ru10/modified CMSX-4 interface.

APPARATUS AND TECHNIQUE Fabrication and Characterisation of Ultra-Thin Tungsten–Carbon (W/C) and Platinum–Carbon (Pt/C) Multilayers for X-Ray Mirrors B. K. GAN, B. A. LATELLA and R. W. CHEARY,

2005, 239, (2), 237–245

Appl. Surf. Sci.,

Ultra-thin Pt/C and W/C multilayer films (1) were fabricated using DC magnetron sputtering. The bilayer period and the total number of layers were varied to ascertain the X-ray reflectance response. XPS established that a distinct intermixing layer develops in (1). (1) are mechanically reliable and have excellent adhesion. Hardness and Young’s modulus improved with increasing number of layers. (1) have potential as mirrors for high energy X-ray applications. Morphological Study of Supported Thin Pd and Pd–25Ag Membranes upon Hydrogen Permeation Y. ZHANG, M. KOMAKI and C. NISHIMURA,

2005, 246, (2), 173–180

J. Membrane Sci.,

H2 permeation of Pd and Pd-25Ag membranes supported by V-15Ni was investigated at 423–673 K. The Pd-25Ag membrane was more resistant to Hinduced cracking and grain growth. H permeation of the Pd-25Ag/V-15Ni membrane (1) was carried out at 573 and 673 K for 200 h. At 573 K, small amounts of oxide formed on the Pd-Ag surface. Whisker and fissure-oxide morphologies were dominant on the exit and entrance side of (1), respectively, along with severe metallic interdiffusion, at 673 K.

103

HETEROGENEOUS CATALYSIS

HOMOGENEOUS CATALYSIS

Preparation and Characterisation of Pt Containing NbMCM-41 Mesoporous Molecular Sieves Addressed to Catalytic NO Reduction by Hydrocarbons

Pd Nanoparticle Aging and Its Implications in the Suzuki Cross-Coupling Reaction

I. SOBCZAK, M. ZIOLEK and M. NOWACKA, Microporous Mesoporous Mater., 2005, 78, (2–3), 103–116

The title catalysts were prepared via impregnation of NbMCM-41 with Pt(NH3)4(NO3)2 or H2PtCl6 (1 wt.% of Pt). Smaller size Pt clusters were obtained with H2PtCl6. A FTIR study with NO + O2 + C3H6 indicated that Pt/NbMCM-41 has potential for the SCR process. The NbO– species enhance the oxidative activity in NO → NO2, whereas the Pt species is responsible for hydrocarbon activation. NbMCM-41 acts as storage for the nitrate/nitrite species. Flame-Made Pd/La2O3/Al2O3 Nanoparticles: Thermal Stability and Catalytic Behavior in Methane Combustion R. STROBEL, S. E. PRATSINIS and A. BAIKER,

2005, 15, (5), 605–610

J. Mater. Chem.,

Flame spray pyrolysis was used to prepare Pd nanoparticles (< 5 nm) supported on La-stabilised Al2O3 (1) with specific surface areas of 50–180 m2 g–1. (1) was tested for the catalytic combustion of CH4. (1) exhibited excellent thermal stability in terms of specific surface area up to 1200ºC and retarded γ- to α-Al2O3 transformation. (1) was tested as-prepared and after sintering at 1000ºC (Pd particles, 50–150 nm). All the materials exhibited similar catalytic performance after an initial conditioning cycle if the temperature was cycled several times (200–1000ºC).

J. HU and Y. LIU,

Langmuir, 2005, 21, (6), 2121–2123

The Pd nanoparticles (1) recovered from the N,Ndihexylcarbodiimide–Pd nanoparticle composite catalysts used in Suzuki cross-couplings, were found to transform from spherical-shape to larger needleshaped crystals. (1) aggregated into nanosized blackberry-like assemblies (100–200 nm) as a result of Ostwald ripening. In a second type of ripening, atomic rearrangement occurred and (1) transformed into needle-shaped nanocrystals. These observations will be important for the future design and optimisation of durable nanoparticle catalysts. Pd(II)-Biquinoline Catalyzed Aerobic Oxidation of Alcohols in Water

B. P. BUFFIN, J. P. CLARKSON, N. L. BELITZ and A. KUNDU, J. Mol. Catal. A: Chem., 2005, 225, (1), 111–116

Pd(OAc)2 stabilised by 2,2'-biquinoline-4,4'-dicarboxylic acid was used in the aerobic oxidation of primary and secondary alcohols. H2O was used as the reaction solvent, with air as the oxidant. Aliphatic primary alcohols were fully oxidised to carboxylic acid products. Secondary alcohols gave the corresponding ketones. The catalyst can be recycled. New Carbazole–Oxadiazole Dyads for Electroluminescent Devices: Influence of Acceptor Substituents on Luminescent and Thermal Properties

K. R. J. THOMAS, J. T. LIN, Y.-T. TAO and C.-H. CHUEN,

Mater., 2004, 16, (25), 5437–5444

Effect of the Promoter and Support on the Catalytic Activity of Pd–CeO2-Supported Catalysts for CH4 Combustion

G. PECCHI, P. REYES, R. ZAMORA, T. LÓPEZ and R. GÓMEZ, J. Chem. Technol. Biotechnol., 2005, 80, (3), 268–272

Pd-CeO2-supported catalysts, prepared by the solgel technique, were used for the catalytic combustion of CH4. The addition of CeO2 to Al2O3 gave a highly dispersed catalyst when compared with their ZrO2 counterparts. However, the catalytic activity of the Pd-CeO2-ZrO2 series is higher, due to the Pd having a larger particle size. The Oxidation of Water by Cerium(IV) Catalysed by Nanoparticulate RuO2 on Mesoporous Silica

N. C. KING, C. DICKINSON, W. ZHOU and D. W. BRUCE, Dalton

Trans., 2005, (6), 1027–1032

Mesoporous silicates were prepared by templating on the hexagonal mesophase of bis(2,2'-bipyridine)(4,4'-dinonadecyl-2,2'-bipyridine)ruthenium(II) dichloride using liquid-crystal templating. On calcination, the surfactant template was removed, except for the central Ru ion that was oxidised to RuO2 nanoparticles (1) within the pores. (1) were active in catalysing the oxidation of H2O by acidic CeIV.


Chem.

Oxadiazole-incorporated carbazoylylamines (1) were synthesised using Pd catalysed C–N coupling reactions with Pd(dba)2/P(t-Bu)3 catalyst and tBuONa base. The reactions were best carried out in toluene at 80ºC. Yields of (1) ranged from 75–95%. (1) were purified by reprecipitating twice from CH2Cl2/MeOH before application in the electroluminescent devices, such as OLEDs. Hydroformylation of 1-Hexene in Ionic Liquids Catalyzed by Highly Active Rhodium-Phosphine Complexes

H. ZHENG, M. LI, H. CHEN, R. LI and X. LI, Chin. J. Catal., 2005,

26, (1), 4–6

The hydroformylation of 1-hexene catalysed by HRh(CO)(TPPTS)3 complexes (1) (TPPTS = triphenylphosphine-m-trisulfonic acid trisodium salt) was carried out in 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim]BF4). The activity and selectivity of (1) in [bmim]BF4 were higher than those in other ionic liquids. The TOF of 1-hexene and selectivity for aldehyde were 1508 h–1 and 92%, respectively, under optimum conditions. The high activity of (1) is due to its higher solubility in [bmim]BF4 and to the absence of halide ions.

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Mononuclear Ruthenium Catalysts for the Direct Propargylation of Heterocycles with Propargyl Alcohols

E. BUSTELO and P. H. DIXNEUF, Adv. Synth. Catal., 2005, 347, (2–3), 393–397

While [(p-cymene)RuCl(PR3)][OTf] (PR3) (PR3 = PCy3, PPh3) catalyse the propargylation of furan or 2methylfuran by the alkynol HC≡CCH(OH)Ph in moderate yield, [(p-cymene)RuCl(CO)(PR3)][OTf] are more active. The stoichiometric reaction of [(pcymene)RuCl(PR3)][B(ArF)4] (ArF = 3,5-(CF3)2C6H3) and the alkynol resulted in the in situ formation, via allenylidene and hydroxycarbene intermediates, of [(p-cymene)RuCl(CO)(PR3)]B(ArF)4]. An Efficient Catalytic Asymmetric Route to 1-Aryl2-imidazol-1-yl-ethanols

I. C. LENNON and J. A. RAMSDEN, Org. Process Res. Dev., 2005, 9, (1), 110–112

Catalytic asymmetric transfer hydrogenation of 1aryl-2-imidazol-1-yl-ethanones with formic acid using [(R,R)-TsDPEN]Ru(Cymene)Cl gave homochiral 1aryl-2-imidazol-1-yl-ethanols. The hydrogenation was carried out under mild conditions at a molar substrate-to-catalyst ratio of 1000–2000. Bisphosphino Ru diamine complexes were found to be ineffective.

FUEL CELLS High-Temperature Polymer Electrolytes for PEM Fuel Cells: Study of the Oxygen Reduction Reaction (ORR) at a Pt–Polymer Electrolyte Interface Z. LIU, J. S. WAINRIGHT and R. F. SAVINELL,

2004, 59, (22–23), 4833–4838

Chem. Eng. Sci.,

A micro-band electrode cell was used to investigate the ORR for a Pt/polybenzimidazole–phosphoric acid system. The obtained Tafel plots were linear over four orders of magnitudes of kinetic current density. Both the kinetic parameters and the mass transport data were comparable to those of a Pt/phosphoric acid system. Effects of Preparation Conditions on Performance of Carbon-Supported Nanosize Pt-Co Catalysts for Methanol Electro-Oxidation under Acidic Conditions

J. ZENG and J. Y. LEE, J. Power Sources, 2005, 140, (2), 268–273

Pt/C and Pt-Co/C were prepared by NaBH4 reduction of metal precursors. Citric acid was used as the complexing agent. The largest Pt-Co particles (12 nm) were formed in alkaline solution and the smallest particles (3.7 nm) in unbuffered solution. XPS showed that Pt is in the metallic state, whereas most of the Co is oxidised. The performance of the PtCo/C catalysts in MeOH electrooxidation under acidic conditions showed improvements over the Pt/C catalyst in both activity and CO-tolerance due to the Co addition.


Catalytic Activity of Pt–Ru Alloys Synthesized by a Microemulsion Method in Direct Methanol Fuel Cells

L. XIONG and A. MANTHIRAM, Solid State Ionics, 2005, 176, (3–4), 385–392

A microemulsion method was used to prepare nanostructured Pt-Ru/C catalysts (1) with different particle sizes. The electrochemical performances of (1) were evaluated in half cells with a mixture of 1 M H2SO4 and 1 M MeOH and in single cell DMFCs. (1) prepared with a water to surfactant molar ratio (W) of 10 exhibited the maximum mass activity with the least charge transfer resistance at an optimum particle size of ~ 5.3 nm. The mass activity decreases and the charge transfer resistance increases as the value of W decreases or increases from 10. The Behavior of Palladium Catalysts in Direct Formic Acid Fuel Cells

Y. ZHU, Z. KHAN and R. I. MASEL, J. Power Sources, 2005, 139,

(1–2), 15–20

Pd-based anode catalysts were used in DFAFCs. Power densities of 255 to 230 mW cm–2 were achieved at relatively high voltages of 0.40 to 0.50 V in formic acid (3.0 to 15.0 M) at 20ºC. A MEA with a Pd catalyst gave some decay in fuel cell performance over several hours. However, the performance can be completely recovered by applying a positive potential at the anode.

ELECTRICAL AND ELECTRONIC ENGINEERING On the Perpendicular Anisotropy of Co/Pd Multilayers

J. I. HONG, S. SANKAR, A. E. BERKOWITZ and W. F. EGELHOFF,

J. Magn. Magn. Mater., 2005, 285, (3), 359–366

Co/Pd multilayers were deposited both at room temperature when thermally activated interfacial intermixing augmented the intentional alloying, and at 77 K. Stressed interfacial alloying is the dominant mechanism. Low temperature measurements indicated the presence of polarised Pd. The hard-axis magnetisation was modelled with a distribution of local perpendicular anisotropies which reflect local composition variations. Synthesis and Characterization of CaRuO3 and SrRuO3 for Resistor Paste Application

K. GURUNATHAN, N. VYAWAHARE and D. P. AMALNERKAR, J.

Mater. Sci.: Mater. Electron., 2005, 16, (1), 47–53

Ca and Sr ruthenates (1) were prepared by air heating admixtures of the respective carbonates of Ca/Sr and RuO2 at 500, 800 and 900ºC for 15 h. The solidstate reactions occurred at 700–800ºC. These powders still contained carbonate and hence were heated again at 900ºC for 15 h to eliminate the carbonate. The average particle size of (1) is ~ 200–400 nm. The resistor paste was formulated using (1) prepared at 800 or 900ºC and heat treated at 900ºC.

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NEW PATENTS METALS AND ALLOYS Alloys for High Temperature Applications

European Appl. 1,505,165 An alloy (1) for use in high temperature applications comprises (in at.%): ≥ ~ 50 Rh; ≥ ~ 5 of Pt and/or Pd; ~ 5–24 Ru; and ~ 1–40 Cr. (1) contains ≤ ~ 50% by vol. of an A3-structured phase which quantity is defined by: ([Cr] + 2[Ru]) is ~ 25–50%, and [Ru] and [Cr] are at.% of Ru and Cr, respectively. (1) is used for repairing articles, such as gas turbines, etc. GENERAL ELECTRIC CO

Hydrogen Occlusion Composites

Japanese Appl. 2004-261,739 A H occlusion material capable of occluding and releasing H at room temperature and atmospheric pressure comprises a C material with fine pores that are filled with a H occlusion alloy (1). The pore edges of the C support Pd and/or V, which have an occlusion pressure higher than that of (1). TOYOTA MOTOR CORP

HETEROGENEOUS CATALYSIS Diesel Particulate Filter

Modified High Strength Single Crystal Superalloy D. P. DeLUCA et al. U.S. Appl. 2005/016,641 A single crystal Ni base superalloy (1) contains (in wt.%): 3–12 Cr, ≤ 3 Mo, 3–10 W, ≤ 5 Re, 6–12 Ta, 4–7 Al, ≤ 15 Co, ≤ 0.05 C, ≤ 0.02 B, ≤ 0.1 Zr, ≤ 0.8 Hf, ≤ 2.0 Nb, ≤ 1.0 V, ≤ 0.7 Ti, ≤ 10 of Ru, Rh, Pd, Os, Ir, and/or Pt, with the balance being Ni. (1) is pore-free and eutectic γ-γ' free and has a γ' morphology with a bimodal γ' distribution.

European Appl. 1,493,484 Catalytic purification of exhaust gas from a diesel engine occurs by passing the exhaust gas through a wall flow filter containing a material (1) catalytically active in the reduction of NOx to N2 and the oxidation of carbonaceous compounds to CO2 and H2O. (1) comprises: Pd 0.25–1 g l–1 filter, Pt ≤ 2 g l–1 filter, V2O5 and WO3. The wall flow filter is made of sintered SiC particles having a surface layer of TiO2.

APPARATUS AND TECHNIQUE

Intermediates for Acetyl Cholinesterase Inhibitors HETERO DRUGS LTD World Appl. 2005/003,092 A simple and cost effective industrial process for preparing intermediates of acetyl cholinesterase inhibitors is provided. For example, 5,6-dimethoxy-2(4-pyridyl)methyl-1-indanone is hydrogenated using Pt oxide catalyst in the presence of HCl acid under 2 bars of pressure to give 4-[(5,6-dimethoxy-1indanon)-2-yl] methylpiperidine hydrochloride (1). Pd/C, Raney Ni or Ru oxide catalyst can also be used under 1–10 bars of H2. (1) is converted to donepezil hydrochloride, an acetyl cholinesterase inhibitor.

Pt-MOx for Dye-Sensitised Solar Cell

U.S. Appl. 2005/016,586 A counter electrode (1) for a dye-sensitised solar cell (2) is made by co-sputtering Pt and a metal oxide (MOx) as target materials to deposit nanocrystalline Pt and amorphous metal oxide on the substrate. MOx is selected from Ru, Ti, etc., with electrical conductivity ≥ 0.1 S m–1 and refractive index of ≥ 2. (1) exhibits improved performances as an electrocatalyst used in the reduction of I3– during operation of (2). KWANGJU INST. SCI. TECHNOL.

Plasma Display Panel and Device

HALDOR TOPSOE A/S

A plasma display panel has discharge cells formed between the front substrate and rear substrate, and electrodes (1) separated by partition walls (2). An electrode material (3) used to form (1) comprises: a conductive paste or sheet containing conductive particles of Pt, Pd, Ru, Ag, Au, etc., and glass borosilicate frit. (3) has sandblast resistance which is higher after baking than that of (2). (3) is capable of preventing damage to (1) caused by a sandblast process while (2) are formed.

Exhaust Gas Purification from a Lean Burn Engine World Appl. 2005/016,496 A catalyst structure for treating exhaust gas from a lean burn internal combustion engine comprises a substrate monolith of a lean NOx catalyst (LNC) composition associated with at least one partial oxidation catalyst (POC). The LNC composition is selected from: (a) Ag/Al2O3; and (b) metal(s) of Cu, Fe, Co and Ce supported on at least one zeolite. The POC is selected from: (i) a bulk oxide(s) of Mn, Fe, Ce and Pr; and (ii) Rh and/or Pd disposed on inorganic oxide support(s).

Organic Electroluminescent Element

High-Activity Isomerisation Catalyst

NEC CORP

DAINIPPON INK CHEM. INC

U.S. Appl. 2005/035,714

Japanese Appl. 2004-253,371

An organic electroluminescent element (1) comprises a luminous layer (2) between a positive electrode layer and a negative electrode layer formed on a transparent substrate. (2) contains a phosphorescent material made of an Ir(III) complex (3), and a partition wall layer. (3) contains a bidentate ligand, with a H atom or an alkoxyl group with 1–10 C atoms. (1) is made by wet film forming and has high luminous efficiency and high luminance.


JOHNSON MATTHEY PLC

U.S. Appl. 2005/027,154 A highly active isomerisation catalyst and process is disclosed for selective upgrade of a paraffinic feedstock to an isoparaffin-rich product for blending into gasoline. The catalyst support is a sulfated oxide or hydroxide of a Group IVB metal, with a first catalyst component of at least one lanthanide element or Y component, preferably Yb, and at least one Pt group metal component, preferably Pt, and a refractory oxide binder with dispersed Pt group metal(s). UOP LLC

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HOMOGENEOUS CATALYSIS

FUEL CELLS

Hydrogenation of Carboxylic Acids

A homogeneous process for the hydrogenation of carboxylic acids and/or their derivatives is carried out in the presence of a catalyst (1) comprising Ru, Rh, Os, Pd or Fe, and an organic phosphine, such as tris1,1,1-(diphenylphosphinomethyl)ethane, with ≥ 1 wt.% H2O. (1) can be regenerated in H2 and H2O. H2O acts as the solvent, so does not need removing from any reactant before the start of the reaction.

Fuel Cell Electrode with High Catalyst Utilisation TOYODA CHUO KENKYUSHO KK U.S. Appl. 2005/019,650 One side of a C paper electrode diffusion layer is soaked in a Teflon® dispersion solution and put into contact with a solution containing H2PtCl6 and aniline (1) and a graphite counter-electrode. Electrical current is applied; (1) is polymerised to a Pt-polyaniline (2) layer. The Pt is reduced to make an electrode. Two of these Pt electrodes are used to form a small fuel cell with (2) on the inside, next to Nafion®.

Production of Chlorotris(triphenylphosphine)Rh(I) W. C. HERAEUS GmbH World Appl. 2005/005,448 Chlorotris(triphenylphosphine)Rh(I) (1) is produced by reacting a RhCl3 solution with triphenylphosphine in mixtures of C2–C5 alcohols and H2O, followed by cooling and filtering of the resultant crystalline precipitate. The mixture of reactants is heated to ~ 75ºC and is then maintained at 80–110ºC. The method leads to increases in the yield and the quality of the resultant crystals of (1).

Organic Platinum Group Element of Fullerenol HONJO CHEMICAL CORP Japanese Appl. 2004-217,626 An organic Pt group element compound (1) is used as the catalyst in fuel cell electrodes. These comprise proton conductive C clusters of fullerenol (2) and/or fullerenol hydrogen sulfate ester (3) with Pt or Pd bonded to the C atoms. (1) is produced by reacting (2) and/or (3) with a zerovalent complex of a Pt group element, such as bis(dibenzylidene)Pt(0). (1) is a proton conductor; Pt/Pd is dispersed at the atomic level.

Carbonylation of Conjugated Dienes

ELECTRICAL AND ELECTRONIC ENGINEERING

DAVY PROCESS TECHNOL. LTD

European Appl. 1,499,573

World Appl. 2005/014,520 A continuous process for the carbonylation of butadiene proceeds by reacting the butadiene with CO and a hydroxyl group-containing compound in the presence of a Pd catalyst system (1) in a reaction zone to form a reaction mixture. (1) comprises: (a) a source of Pd cations; (b) a mono-, bi- or multidentate phosphine ligand containing P atom(s) directly bound to 2 or 3 aliphatic C atoms, as the process ligand (2), to give a Pd-phosphine ligand complex; and (c) a source of anions containing a carboxylic acid and halide ions. The process gives improved stability. (2) is fed continuously or periodically to the process. DSM IP ASSETS BV

Catalysts with N-Heterocyclic Carbene Ligands MERCK PATENT GmbH World Appl. 2005/016,522 Immobilisable Ru catalysts (1) have N-heterocyclic carbene (NHC) ligands comprising a SiR'n(OR')3–n carrying group on one of the two N atoms of the NHC ligand. (1) are used as homogeneous catalysts in C–C coupling reactions, especially in olefinic metathesis. The invention further relates to the use of these compounds as starting materials for producing analogue (1) catalysts having NHC ligands. Optically Active Amine Production

Japanese Appl. 2004-256,460 An optically active amine compound (1) is prepared in high yields and stereoselectivities by asymmetric hydrogenation of the corresponding amine in the presence of an Ir complex catalyst. The catalyst is [IrX(H)(Y)(L)]; X is Br or I; Y is an organic acid residue; and L is an optically active compound that can coordinate with the Ir atom, such as (S)-BINAP. The reaction proceeds without additives. (1) is useful as an intermediate for synthesising various compounds, particularly for pharmaceutical preparations. TAKASAGO INT. CORP


Palladium Complexes for Printing Circuits HEWLETT PACKARD DEV. CO World Appl. 2005/010,108 A stable ink-jettable composition includes a Pd aliphatic amine complex (1) solvated in a liquid vehicle. (1) is used in electronic devices by jetting onto a variety of substrates in a predetermined pattern. A second composition contains a reducing agent, such as formic acid, and is also applied to the substrate by ink-jet printing. It reduces (1) to Pd metal on heating. Current Perpendicular to the Planes Sensor HITACHI GLOB. STORAGE TECHNOL. U.S. Appl. 2005/024,790 A magnetic read head has a current perpendicular to the planes (CPP) sensor with a highly conductive top cap layer of Ru or Rh, or a top cap layer structure which includes a first Ta layer only, a second layer of Ru, Rh or Au with the first layer located between a spacer layer and the second layer. The CPP sensor further comprises: a ferromagnetic pinned layer structure and a free layer structure, with a nonmagnetic spacer layer located between. Weak Inversion Mode MOS Decoupling Capacitor INTEL CORP U.S. Patent 6,849,909 A method and apparatus for a weak inversion mode MOS decoupling capacitor is described, embodied by an enhancement-mode p-channel MOS transistor (1). The gate material of (1) is PtSi or Ta nitrate, Ir, Ni and As, with work function < –0.56 V. The threshold voltage of (1) is changed by modifying the substrate dopant levels. The flat band magnitude of (1) is shifted by the changed materials. When (1) is connected with the gate lead connected to the positive voltage, the other leads are connected to the negative voltage an improved decoupling capacitor results.

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FINAL ANALYSIS

Thermocouples – Compensating Circuits This is the final article in a short series examining ways of looking after thermocouples (1–3). A thermocouple converts a temperature difference into a voltage which is converted into a reading by a temperature indicator. The voltage is generated by the lengths of wire in the temperature gradient between the hot junction in the furnace and the cold junction at the indicator. In practice, the temperatures between the indicator and the furnace wall are low and the gradients are small. To reduce costs these lengths of thermocouple wire are replaced by base metal ‘compensating wire’, connected at the thermocouple ‘head’. Compensating wires should generate the same voltage as the thermocouple wires they replace. (The indicating instrument corrects for the difference between its terminal temperature and the standard cold junction temperature of 0ºC.) Users can choose wire grades A or B (4) to replace thermocouple wire Types R (Pt versus 13RhPt) and S (Pt versus 10RhPt). Grade A has an error of ≤ 30 µV (equivalent to ≤ 2.6ºC at 1000ºC), with a maximum operating temperature of 100ºC. Grade B has a maximum permitted error of ± 60 µV but has suitable insulation for use up to an operating temperature of 200ºC. The compensating wires used for Types R or S are very similar: pure copper for the positive limb and 0.6%NiCu for the negative one. The international standard for insulation colour coding specifies orange for the outer insulation, orange for the positive and white for the negative. (The superseded U.K. standard (5) specified a green lead with white to code for the positive wire. Green is now used for Type K leads.) Thermocouple Types R and S, made to either the International Practical Temperature Scale of 1968 (IPTS-68) or the International Temperature Scale of 1990 (ITS-90), can use the same compensating wire, as their voltage outputs differ by only 2 µV at 100ºC and 28 µV at 200ºC. Type B (6RhPt versus 30RhPt) thermocouples require only connecting, rather than compensating,

Platinum Metals Rev., 2005, 49, (2), 108

leads because the output is low at low temperatures. Using copper lead, with the thermocouple head at 80ºC, reduces the output by 17 µV, equivalent to an error of only –1.9ºC when measuring 1000ºC. However, the error will increase to –10ºC if the head is at 150ºC. The connecting wires should be colour coded grey and white (to lessen risk of connection to a mains voltage supply). To check a Type R or S compensating circuit, link the limbs at the thermocouple head – the indicator should then show the head temperature; this can be independently verified. Alternatively, disconnect the lead from the head, twist the compensating wires together to form a ‘hot’ junction and place in boiling water, the indicator should show close to 100ºC. Potential errors, when the head is at 80ºC, the indicator terminals at 30ºC and the hot junction at 1000ºC are: (a) Type R used with copper cable under-reads by –330 µV (–25ºC). (b) Type R used with compensating lead with the polarity reversed under-reads by –660 µV (–50ºC). (c) Type R used with Type K cable reads high by +1734 µV (+130ºC). (d) Type B used with Type R/S compensating lead reads high by +311 µV (+34ºC). Minimising the head temperature by careful location, radiation shields or forced cooling, will keep the compensating wires within their operating range. Correctly used, compensating leads offer significant cost saving with only a small impact on measurement accuracy. 1 2 3 4 5

References

R. Wilkinson, Platinum Metals Rev., 2004, 48, (2), 88 R. Wilkinson, Platinum Metals Rev., 2004, 48, (3), 145 R. Wilkinson, Platinum Metals Rev., 2005, 49, (1), 60 IEC 60584-3 Ed. 1.0 b.,1989-08-15 BS 1843:1952

The Author Roger Wilkinson is a Principal Metallurgist at Johnson Matthey Noble Metals in Royston, U.K. He has worked with platinum thermocouples since 1987 in manufacturing, calibration and customer technical support.

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