MODIFICATION OF PETROCHEMICAL FLUID CATALYTIC CRACKING CATALYST WASTE PROPERTIES BY TREATMENT IN HIGH TEMPERATURE Valentin Antonovič1, Pranas Baltrėnas2 , Marius Aleknevičius1, Ina Pundienė1, Rimvydas Stonys1 Vilniaus Gediminas Technical University Institute of Thermal Insulation, Linkmenų str.28, LT-08217, Vilnius, Lithuania. E-mail:
[email protected] 2 Vilniaus Gediminas Technical University Department of Environmental Protection, Saulėtekio ave. 11, LT-10223 Vilnius, Lithuania. E-mail:
[email protected] 1
Abstract. Approximately 400 000 tons of waste catalysts are produced by petrochemical industry in fluidized bed catalytic cracking (FCC) process annually. In Lithuania (Mažeikiai Oil Refinery) the waste amounts up to about 200 tons/year. As FCC catalyst is an inorganic alumosilica zeolite material, the properties of it are important for refractory concrete. This work investigated properties of the waste fired at temperature of 800-1300 o C. It was established that at temperatures higher than 1050o C, in the waste FCC catalyst the physical and structural changes take place, the zeolitic structure is destroyed and the mineralogical composition undergoes changes, as well as porosity and size of particles. In case of reuse of catalyst waste in refractory concrete, these changes of material can negatively influenced on properties of refractory concrete. One of the promising directions for reuse of waste in refractory material is its modification at temperature of approximate 1000 oC when the porosity of particles changes and, supposedly, the germs of mullite crystals are forming, irrespective of the still dominating zeolitic structure. Keywords: FCC catalyst waste, zeolite, thermal treatment, refractory concrete.
als such as vanadium and nickel, occurring on the parts per million levels (Pacewska et al. 2002). Hence, Ni and V in the catalyst probably come from crude oil. Moreover, the waste catalysts may contain residues of sulphur and carbon compounds, which have not burnt off during the process of catalyst’s regeneration.
1. Waste Fluid catalytic cracking catalyst Approximately 400 000 tons of waste catalysts are produced by the petrochemical industry in fluidized bed catalytic cracking (FCC) process annually (Furimsky 1996). In Lithuania (Mažeikiai Oil Refinery) the waste amounts up to about 200 tons/year. As the oil industries are growing very fast, the generation of waste catalyst unavoidably increases. The fluid catalytic cracking produces high octane gasoline, C3/C4 olefins and isobutene by catalytic cracking of heavy gas oil. FCC catalyst is used in the FCC unit to cause hydrocarbon molecules to break into two or more smaller molecules (Wu et al. 2003). The FCC unit consists of a reactor, a stripper and a regenerator (Fig.1). During the catalytic operation in the reactor at temperature of ~550 °C, some cracked products or coke will deposit on the catalyst particles. They are removed or burned off (at 700 °C) either in the stripper or in the regenerator. The waste FCC is eroded catalyst debris from the cracking unit, which is collected by an electrostatic precipitator. It is mainly composed of Al2O3 and SiO2 and slightly contaminated with metals, including heavy met-
reaktor
regenerator stripper
Fig 1. Scheme of thermal equipment of FCC unit
In the European Waste Catalogue (Commission Decision 94/3/EEC), the spent fluid catalytic cracking 6
rials with required properties obtained due to the additive of waste catalyst could give great economical benefit. FCC catalyst, as a fine additive, was tested in a refractory castable with liquid glass binder (Goberis et al. 1996). However, it was established that along with increase in amount of FCC additive in a castable, the demand for liquid glass needed to produce the castable increases considerably as well. This factor affects negatively the thermal and strength properties of such castable at high temperatures. The efforts were made to use milled FCC catalyst in refractory concretes with alumina cement (Antonovič et al. 2005). In comparison with the mentioned above study (Goberis et al. 1996), the polycarboxylate plasticizer were used for reduction of liquid phase in concrete. In this way the positive effect of waste catalyst on strength after hardening of concretes could manifest itself. Yet, at high temperatures the cold crushing strength and thermal shock resistance of concrete was lower than the concrete’s without catalyst. The method to modify the properties of waste FCC catalyst, which can more effectively appear in the refractory materials, is heat treatment at temperatures higher than operational temperature of catalyst (700 oC). It is known that the particularities of structure of zeolites (such as waste catalyst) predetermine such properties as low density and big volume (after firing at temperature of >500 oC), stability of dehydrated crystalline zeolitic structures, properties of ion exchange, existence of one-type channels with diameters of molecule size in dehydrated crystals, electric conductivity, gas and vapor adsorption, catalytic properties (Breck et. al. 1976). The temperature modification of zeolitic structure in waste catalyst would enable to change (or to adjust as appropriate) their properties, thus extending the possibilities to develop advantage refractory material. In study (Tseng et al. 2005) it was showed that pozzolanic activity of FCC catalyst in Portland cement composition could be improved by heat treatment at 450850°C. Authors indicated that particle size of the fired catalyst in the temperature range of 25-1000 °C was found almost the same as that of the untreated, while specific surface area drastically decreased after heat treatment at 850 °C. The goal of this work is to investigate the properties of waste catalytic cracking catalyst received from the joint stock company AB Mažeikių Nafta (Lithuania) before and after treatment at temperatures of 800-1300 C and to evaluate the possibilities of modified material to be used as an additive for refractory concrete.
catalysts (code 16 08 04) are classified as non-hazardous. In 2006 the European Cracking Catalysts Producers Association (ECCPA) identified the potential reuses of waste catalyst, which include constructional work, cement, insulation materials and metal casting industry. In some countries the waste catalyst was partly utilized in the rotary furnaces during production of Portland cement clinker (Schreiber et al. 1993), as a filler in asphalt concrete mixes (Lin et al. 1995) or a substitute for kaolin in the industry of ceramic frits (Escardino et al. 1995). Later investigations showed that the waste catalyst can be used as a fine additive in grouts for various purposes, in concrete and in other cementitious compositions (Su et al. 2000; Hsu et al. 2001; Pacewska et al. 1998; Paya et al. 1999). It is established that FCC catalyst reacts with Ca(OH)2 (the product of cement hydration) as a pozzolanic material (Pacewska et. al. 2002, Paya et. al. 2003) and increases the compressive strength and other properties of the compositions with Portland cement (Paya et. al. 2001, Wu et. al. 2003, Bukowska et. al. 2004). The pozzolanic properties of of FCC waste may be activated, simultaneously improving the strength of cementitious materials by means of waste milling (Pacewska et. al. 2004). It should be noted that the scientists, who investigate the building materials with waste catalyst, face certain difficulties. In some applications of lime binders the pozzolanic activity of FCC catalyst was not sufficient (Paya et. al. 2004). J. Dweck found (Dweck et. al. 2008), that beside the pozzolanic activity which occurs in Portland cement composition, in some cases the compressive strength of pastes containing spent catalyst was lower then that of pastes formed with only cement and water. Supposedly, some elements, like nickel, which is present in the spent catalyst composition, may have limited the pozzolanic activity. Larger amounts of waste in cement compositions require larger water and cement ratio to assure good workability. With a lesser amount of water, only super plasticizers are essential to obtain proper workability of cement paste (Zornoza et. al. 2007). Generally, it can be stated, that despite the investigations of last 15 years, the problem of utilization and reuse of waste catalyst in building materials is still live. Why? The generated amount of waste catalyst is very small in comparison with production volume of building materials, therefore, the manufacturers of building materials are not interested in amendment of their production technologies. Besides, depending on the FCC unit and operating conditions, in some cases the concentration of Ni increases up to >2000 mg/kg (Bayraktar 2005). Then, bioleaching can be used for mobilization of nickel from catalyst particles. This means that the reuse of waste catalyst in broad-used building materials must be very careful. The situation may change in case of the reuse of waste in materials dedicated for industrial purposes, such as refractory materials. These materials are very expensive. So, development of new advantage refractory mate-
2. Experimental The microstructure of FCC waste particles was observed by a SEM (EVO50, JEOL JSM-7600F) and their size was measured by a coulter laser size analyzer (Analysete 22, Fritch Germany). The X-ray phase analyses were carried out using a DRON-7 diffractometer (anticathode – cooper, anode voltage 30 kV, anode current 8 mA). The phase composition was identified using reference data from ICDD database. For thermoanalytical 7
studies of FCC catalyst, a STA PT-1600 (Linseis Germany) thermoanalyser was used, operating at temperatures ranging up to 1400 °C in air, at heating rate of 10°C min-1, sample mass of 10 mg. The TG, DSC, curves were registered. In order to investigate fired FCC waste, it was kept for 5 hours and fired in an electronic controller furnace at temperatures of 750, 800, 850, 900, 950, 1000, 1050, 1100, 1150, 1200 °C. For calorimetric measurements, a differential calorimeter (produced in VGTU Thermal Insulation Institute) was used. The mixes (0,5 g distilled water and 1 g of solid substance) were studied at the starting temperature of 25°C and the heat evolution curves were registered. pH and electrical conductivity of suspensions (distilled water and FCC waste at ratio of 10:1) was measured with a Mettler-Toledo (electrode InLab 410, measurement accuracy for pH 0.01 and an electrode InLab 730 for electrical conductivity with measurement range of 0-1000µS/cm).
a
3. Results The chemical composition of waste FCC catalyst was determined to be as follows [mass-%]: Al2O3 – 39.4, SiO2 – 50.1, Fe2O3 – 1.3, SOx –2.3, CaO – 0.5, MgO – 0.49, Na2O – 0.2, K2O – 0.07, Mn2O3 – 0.06; ignition loss –5.4 % (Antonovič et al. 2005). Fig 2 a shows the scanning electron micrograph (SEM) of FCC waste, indicating that catalyst particles are spherical. In the waste one can observe a certain amount of destroyed spheres. These are particles of irregular shape (Fig 2 b). The specific surface of FCC catalyst is very large (about 100 m2 g-1) (Pacewska et. al. 2004). The picture of inner structure of a particle is provided in Fig 2 c. Though the waste FCC catalyst is not allocated to the group of harmful waste, nevertheless, the waste generated in the joint stock company AB Mažeikių Nafta was evaluated from ecological point of view. By method of atomic absorption spectrophotometry, the concentrations of heavy metals (Ni, Fe, Cr, Pb, Zn) were determined in the waste (Table 1). We can see that except for Fe, the concentration of other metals is very low.
b
c Fig 2. SEM micrograph of waste FCC catalyst particles (a) and structure of destroyed particles (b, c) Table 2. Ni amount in waste FCC catalyst (periodical testing)
Table 1. Results of analysis of heavy metals in waste FCC catalyst N/N
Metal
1
Ni
2
Fe
3 4 5
Cr Pb Zn
Concentration detected in mg/kg 43,59; 44,62; 46,15 4839,51; 5333,33; 5777,78 76,92; 71,79; 72,82 31,74; 28,97; 33,33 28; 40; 48
Average concentration in mg/kg 44,79 5316,87 73,85 31,65 38,67
Serial number of analysis
Ni in ppm
1
187
2
205
3
227
4
322
5
110
The investigation of distribution of particles in the waste FCC catalyst fired at various temperatures showed (Fig.3) that at firing FCC waste catalyst up to 1000 oC, the diameters of particles remain the same, and the average diameter of particles is ~42 μm. Only after firing at temperature of 1200 oC, one can observe that the diameter of particles decreased to the medium size, ~38 μm.
The systematic annual control of Ni concentration in the joint stock company AB Mažeikių Nafta also shows that the concentration of this harmful element in the waste is stably low (Table 2).
8
Average diameter, m
gram (Fig 6) one can see endothermal effect (87 oC) and two exothermal effects (973 oC, 1280 oC).
45
a
μ 40
M
K
M M M MM K M
0
1200 C
0
35
1150 C 700
800
850
900
950
1000
1050
1100
1150
1200
Temperature, ºC
0
1100 C 18
Volume, %
16
non treatment 0 1200 C
38 μm
b
42 μm
0
1050 C
14 12
M
M
10 8
0
1000 C
M M M MM
Y YY
6
Y YY Y Y
0
950 C
4 2 0
20 40 Diameters of particles, μm60
80
0
900 C
100
Fig 3. Average diameter of FCC catalyst particles depending on firing temperature (a) and the character of distribution of particles by diameter (b)
0
850 C
0
800 C
By tests of porosity, it was established that the structure of catalyst pores undergoes changes after thermal treatment at temperature of 950 oC (Fig 4). The biggest decrease of porosity of catalyst waste occur after thermal treatment at temperature of 1200 oC
0
750 C 1000
Y YY 0
10
Y YY Y Y 20
non-treated 30
40
50
60
70
Fig 5. X—ray diffraction of waste FCC catalyst fired at various temperatures. Y – y zeolite, M – mullite, K – cristobalite 1.0
0.5
2Θ
0.5 0.0
0
973 C
-0.5
0.0 0
1280 C
-0.5
-1.0
-2.0
-1.5
DSC,
-2.5 -2.0
-3.0 -3.5
Fig 4. Pore size distribution for non-treated and treated at different temperature waste catalyst
TG, %
-1.0
-1.5
-2.5
-4.0 -3.0
-4.5 -5.0
-3.5
-5.5
By X-ray phase analyses (Fig 5), it was established that in waste FCC catalyst, the structure typical to Y zeolite does not change after firing temperatures of 750– 900 oC. After firing at temperature of 950 oC the size of main peaks of Y zeolite slightly changes (Fig.5 a) and a transforms into mullite (1000–1150 oC) and cristobalite (1200 oC). The more precise information about the changes going in the structure of waste FCC catalyst is shown by thermographic tests (Aleknevičius et. al. 2009). Namely, during the firing process, in the curve DSC of thermo-
0
87 C
-6.0 0
-4.0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400
Temperature, °C
Fig 6. DSC and TG curves of waste FCC catalyst
The endothermal effect at temperature of 87 oC may be explained by desorption of water from catalyst pores and channels (Dweck at. al. 2008) (the losses in the mass reach ~4 %). First exothermal effect at temperature near 1000 oC occurs due to crystallization of mullite, the 9
second exothermal effect occurs at 1280 oC due to crystallization of cristobalite (Fig.6). Although the mineralogical changes in structure of catalyst are determinated after treatment at temperature of 1000o C, the sharp changes in surface of catalyst particles are observable only after treatment at temperature of 1200o C when the surface of waste particles changes considerably (Fig.7).
The decrease of electric conductivity in suspensions of waste treated at temperature 850–1200 °C versus that of non-treated waste suspension means that at this temperature the ion exchange is less activated (Fig 8). We can see that the maximum of heat release rate, which describe the sorption properties of the catalyst, also decreased, when material was treated at temperature >850 °C (Fig.8).
a Fig.8. Dependence of electric conductivity (1) and maximum of heat release rate (2) in suspension with waste FCC catalyst and water (FCC/water=2/1)
Eelectric conductivity and maximum of heat release rate are lowest in suspension with material fired at 1200 oC. Analyze of results of investigation show, that after treatment at temperature of 950 °C, the zeolitic structure still dominates (X-ray phase analysis), however, at temperature of 973 °C the germs of mullite crystals are forming as well the porosity of substance changes, electric conductivity decreases and sorption properties worsen. After treatment at 1200 °C when the zeolitic structure is destroyed, the properties of sorption and electric conductivity are equal to those of certain traditional additives of concrete.
b Fig 7. SEM photos of waste FCC catalyst surface after firing at temperature: a) of 1100 ºC , b) of 1200 ºC
Conclusions
We can see (Fig.7) that after firing at temperature of 1200 ºC the surface of catalyst particles is coated richly by new formations generated. These are crystals of mullite, 50–100 nm wide and 100–400 nm long, and crystals of cristobalite of irregular shape. The performed investigations showed that at temperature higher than 950 °C in waste FCC catalyst phaseand structural changes occur, the zeolitic structure is destroyed and the mineralogical composition, as well as porosity undergoes changes. However, the particle size and surface of catalyst changes considerably only after treatment at temperature of 1200 °C. At planning to use the FCC catalyst waste as an additive in cementitious materials (refractory mortars and concretes), it is of importance to evaluate the properties of the waste in water suspension, since the characteristics of sorption and electric conductivity have a great influence on hydration of cementitious material.
1. It was established by spectrophotometry that the concentration of heavy metals (Ni, Fe, Cr, Pb, Zn) in waste FCC catalyst is very low (from 31 to 74 mg/kg), except for Fe, the content of which amounts to 5317 mg/kg. 2. By X-ray phase analyses, it was established that the zeolite Y structure in waste FCC catalyst does not change after firing at temperature of 750–900 °C. The phase conversion of zeolitic structure into mullite at temperature of 1000 °C and into cristobalite at temperature 1200 °C is accompanied by endothermal effects and reduced porosity, while the changes on surface of catalyst particles in shape of new formations sized 50–100 nm (crystals of mullite and cristobalite minerals) are observable after firing at 1200 °C. After firing of waste at 1200 °C, the average diameter of particles decreased from 42 µm to ~38 µm. 10
complex binder consisting of high-alumina cement, liquid glass and metallurgical slag, Cement and concrete research 34: 1939–1941. doi:10.1016/j.cemconres.2004.01.004
3. The investigations of electric conductivity and heat release rate of water suspension of waste FCC catalyst fired at different temperatures show that these characteristics may be controlled by treatment of waste at an appropriate temperature. The control of these properties (utilization of modified waste) would enable to extend the line of concretes for various purposes.
Goberis, S.; Stuopys, A. 1996. Utilization of Waste Catalyst in Refractory Concrete, Interceram 45 (1): 16–20. Hsu, K.-C.; Tseng, J.-S.; Ku, F.-F.; Su N. 2001. Oil cracking waste catalyst as an active pozzolanic material for superplasticized mortars, Cement and Concrete Research 31 (12): 1815–1820. doi:10.1016/S0008-8846(01)00693-7
Acknowledgments The scientific investigations, results of which are presented in this work, were financed by the Lithuanian State Science and Studies Foundation (Project NanoCSM)
Lin, J., Tarn, J., Yu, D., Hsiao, L. 1995. Utilization of ROC spent catalyst on asphalt concrete, Proceedings of the international conference on industrial waste minimization, National Central University Taiwan, 667–674.
References
Pacewska, B.; Bukowska, M.; Wilińska, I.; Swat, M. 2002. Modification of the properties of concrete by new pozzolan – A waste catalyst from the catalytic process in a fluized bed, Cement and Concrete Research 32 (1): 145– 152. doi:10.1016/S0008-8846(01)00646-9
Aleknevičius, M.; Antonovič, V. 2009. Calorimetric investigations of high aluminate cement hydration in the presence of waste oil-cracking latalyst, Cheminė technologija 2(51): 33–38.
Pacewska, B.; Wilinska, I.; Bukowska, M.; Blonkowski, G.; Nocun-Wczelik, W. 2004. An attempt to improve the pozzolanic activity of waste aluminosilicate catalyst. Journal of Thermal Analysis and Calorimetry 77: 133–142. doi:10.1023/B:JTAN.0000033196.30760.af
Antonovič, V.; Goberis, S.; Pundiene, I.; Stonis, R. 2005. The effect of waste oil-cracking catalyst on the properties of refractory castable. Ceramika (Polski biuletyn ceramiczny) 88: 143–150. Baltrėnas, P.; Kvasauskas, M. 2008. Experimental investigationa of biogas production using fatty waste, Journal of Environmental Engineering and Landscape Management 16(4): 178–187. doi:10.3846/1648-6897.2008.16.178-187
Pacewska, B.; Wilinska, I.; Bukowska, M.; Nocun-Wczelik, W. 2002. Effect of waste aluminosilicate material on cement hydration and properties of cement mortars, Cement and Concrete Research 32 (11): 1823–1830. doi:10.1016/S0008-8846(02)00873-6
Baltrėnas, P.; Zagorskis, A. 2008. Investigation of cleaning efficiency of biological air-treatment device with activated charge of different origin, Journal of Environmental Engineering and Landscape Management 16(3): 113–120. doi:10.3846/1648-6897.2008.16.113-120
Pacewska, B.; Wilinska, I.; Kubissa, J. 1998. Use of spent catalyst from catalytic cracking in fluidized bed as a new concrete additive. Thermochim Acta 322 (2): 175–181. doi:10.1016/S0040-6031(98)00498-5
Bayraktar, O. 2005. Bioleaching of nickel from equilibrium fluid catalytic cracking catalysts, World Journal of Microbiologu and Biotechnology 21: 661–665. doi:10.1007/s11274-004-3573-6
Paya, J.; Monzo, J.; Borrachero, M. 1999. Fluid Cracking residue (F3CR): an excellent mineral by-product for improving early-strength development of cement mixtures, Cement and Concrete Research 29 (11): 1773–1779. doi:10.1016/S0008-8846(99)00164-7
Breck, D. 1976. Цеолитовые молекулярные сита [Zeolite Molecular Sieves]. Maskva: Mir. 781 p.
Paya, J.; Monzo, J.; Borrachero, M. V. 2001. Physical, chemical and mechanical properties of fluid catalytic cracking residue (F3CR) cements, Cement and Concrete Research 31 (1): p. 57–61. doi:10.1016/S0008-8846(00)00432-4
Bukowska, M.; Pocewska, B.; Wilińska, I. 2004. Influence of spent catalyst used for catalytic cracking in fluidized bed on sulphate corrosion of cement mortars, Cement and Concrete Research 34(5): 759–767. doi:10.1016/j.cemconres.2003.08.007
Paya, J.; Monzo, J.; Borrachero, M.V.; Velazques, S. 2004. Chemical activation of pozzolanic reaction of fluid catalytic cracking catalyst residue in lime pastes;thermal anglysis, Advances in cement researcg 16(3): 123–130.
Dweck, J.; Pinto, C.A.; Buchler, P.M. 2008. Study of a Brasilian spent catalyst as cement aggregate by thermal and mechanical anglysis, Journal of Thermal Analysis and Calorimetry 92: 121-127. doi:10.1007/s10973-007-8750-z
Paya, J.; Monzo, J.; Borrachero, M. V.; Velazques, S. 2003. Evaluation of the pozzolanic activity of fluid catalytic cracking catalyst residue. Thermogravimetric analysis studies on FC3R-portland cement pastes, Cement and Concrete Research 33(4): 603–609. doi:10.1016/S00088846(02)01026-8
Escardino, A.; Amoros, J.; Moreno, A.; Sanchez, E. 1995. Utilizing the used catalyst from refinery FCC units as a substitute for kaolin in formulating ceramic frits, Waste Management and Research 13: 569–578 Furimsky, E. 1996. Spent refinery catalysts: environment, safety and utilization, Catal Today 30 (4): 223–286. doi:10.1016/0920-5861(96)00094-6
Pundiene, I.; Goberis, S.; Antonovich, V.; Stonis, R. 2006. Study of the applicability of waste catalyst in heatresistant concrete, Refractories and Industrial Ceramics 47(5): 330- 334. doi:10.1007/s11148-006-0119-5
Goberis, S.; Antonovič, V. 2004. Influence of sodium silicate amount on the setting time and EXO temperature of a
11
mortars, Cement and Concrete Research 33: 245–253. doi:10.1016/S0008-8846(02)01006-2
Schreiber, R.; Yonley, G. 1993. The use of spent catalyst as a raw material substitute in cement manufacturing, Journal of American chemical Society 38 (1): 97–99.
Zornoza, E.; Garces, P.; Monzo, J.; Borrachero, M.V.; Paya, J. 2007. Compatibility of fluid catalytic cracking catalyst residue (FC3R) with various types of cement, Advances in Cement Research 19(3): 117–124. doi:10.1680/adcr.2007.19.3.117
Stonis, R.; Pundiene, I.; Antonovič, V.; Goberis, S.; Aleknevičius M. 2008. The effect of Waste Oil-Cracking Catalyst on the Properties of MCC-Type Castable, Materials Science: Medžiagotyra 14(1): 59–62.
Zvironaite, J.; Gaiducis, S.; Kaminskas, A.; Maciulaitis, R. 2008. Hydration and Hardening of Composite Binder Containing Mechanically Activated Hemihydrate Phosphogypsum. 17th International Conference on Materials Engineering, Materials Science: Medžiagotyra 14 (4): 356–360.
Su, N,; Fang, H.; Chen, Z.; Liu, F. 2000. Reuse of waste catalysts from petrochemical industries for cement substitution, Cement and Concrete Researc. 30 (11): 1773–1783. doi:10.1016/S0008-8846(00)00401-4 Wu, I.; Wu, W.; Hsu, K. 2003. The effect of waste oil-cracking catalyst on the compressive strength of cement pastes and
12
