Deactivation and Oxidative Regeneration of Modern Catalysts for

ISSN 1070-4272, Russian Journal of Applied Chemistry, 2011, Vol. 84, No. 1, pp. 95−102. © Pleiades Publishing, Ltd., 2011. Original Russian Text © S.V. Budukva, O.V. Klimov, G.S. Litvak, Yu.A. Chesalov, I.P. Prosvirin, T.V. Larina, A.S. Noskov, 2011, published in Zhurnal Prikladnoi Khimii, 2011, Vol. 84, No. 1, pp. 95−102.

ORGANIC SYNTHESIS AND INDUSTRIAL ORGANIC CHEMISTRY

Deactivation and Oxidative Regeneration of Modern Catalysts for Deep Hydropurification of Diesel Fuel: Oxidative Regeneration of IK-GO-1 Catalyst S. V. Budukva, O. V. Klimov, G. S. Litvak, Yu. A. Chesalov, I. P. Prosvirin, T. V. Larina, and A. S. Noskov Boreskov Institute of Catalysis, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia Received January 21, 2010

Abstract—Oxidative regeneration of a deactivated IK-GO-1 catalyst was studied in removal of carbonaceous deposits and sulfur from the catalyst composition. Elemental analysis data, texture characteristics, and catalytic activities of fresh and regenerated samples were compared. Raman spectroscopy, X-ray phase analysis, electronic diffuse reflectance spectroscopy, and X-ray photoelectron spectroscopy were used to examine the structure of cobalt and molybdenum compounds entering into the composition of the catalysts. DOI: 10.1134/S1070427211010162

Previously, properties of an IK-GO-1 catalyst deactivated on a laboratory installation have been described and it was shown that its activity in hydropurification of diesel fuel decreases because the active component is blocked by carbonaceous deposits [1]. The characteristics of carbonaceous deposits obtained in model deactivation (their amount, chemical composition, particle size, layer thickness, apparent density, localization in the catalyst) are typical of hydropurification catalysts deactivated under industrial conditions, described in the literature. In the industry, hydropurification catalysts are mostly regenerated by in-reactor burning-out of carbonaceous deposits in a flow of an oxygen-containing gas at a temperature not exceeding 550°C [2–4]. To preclude local overheatings caused by coke combustion, the regeneration is performed either in inclined rotating furnaces with an agitated catalyst bed or by transporting a thin layer of the catalyst on a perforated band through a tunnel furnace. As a rule, the hydropurification activity of regenerated catalysts is markedly inferior to that of fresh samples. In the case of a complete removal of carbonaceous deposits, the following four main reasons

for the decrease in the activity of a regenerated catalyst, compared with a fresh sample, can be distinguished [2–4]. (1) Deposition on the catalyst surface of compounds of metals that are brought with raw materials and cannot be removed by calcination. (2) Decrease in the content of active metals. (3) Change in texture characteristics of the catalysts. (4) Formation, in the course of regeneration, of oxygen-containing compounds of molybdenum and cobalt, which are not converted into an active component of hydropurification reactions in further sulfation. The goal of our study was to compare the activity of catalysts regenerated in laboratory and under industrial conditions with that of fresh samples. EXPERIMENTAL We used an industrial catalyst for deep hydropurification of diesel fuel, IK-GO-1, manufactured by Industrial Catalysts private company (Ryazan). We examined four samples: no. 1, fresh IK-GO-1 catalyst; 95

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no. 2, sulfated sample no. 1; no. 3, sample no. 1 calcined in air at 550°C for 2 h; and no. 4, deactivated sample described in [1], upon regeneration. All the catalyst samples were used in the form of a 0.50–0.25-mm fraction. Prior to being tested in hydropurification, all the catalysts were sulfided in a flow of hydrogen sulfide. The conditions of sulfidation, testing of the catalysts in hydropurification of diesel fuel, and their deactivation have been described in detail previously [1]. A deactivated catalyst was regenerated by its calcination in a muffle furnace in air under the following conditions: heating of the catalyst from room temperature to 550°C in the course of 2 h, calcination at 550°C for 2 h, and cooling to room temperature in the course of 2 h. To compare texture characteristics and elemental analysis data, the fresh catalyst was calcined under the same conditions. To minimize local overheatings, the thickness of the catalyst layer being calcined did not exceed 5 mm. The methods and apparatus for determining the concentrations of C, H, N, and S in the catalysts and their texture characteristics and recording Raman spectra were described in [1]. A thermal analysis of preliminarily dried samples was made with a Shimadzu DTG-60H instrument. TGA–DSC curves were recorded in the range from room temperature to 1000°C in a flow of air at a heating rate of 10 deg min–1. For analysis, a 10-mg portion of a sample was charged into a platinum crucible having no cover. Electronic diffuse reflectance spectra (EDRSs) were recorded with a Shimadzu UV-2501 PC spectrophotometer with an ISR-240 A diffuse reflectance attachment. Samples in the form of a powder were placed in an optical cuvette with an optical path length of 2 mm. The spectra were recorded relative to a reflection reference, BaSO4, in the spectral range 11000–53000 cm–1. The EDRS data obtained are plotted

in the coordinates of the Kubelka–Munk function F(R)– wave number. The X-ray phase analysis (XPA) was performed with an HCG 4-C diffractometer (Freiberger Prдzisionsmechanik, Germany) with a copper anode (CuKα radiation with a wavelength of 1.54 Å). X-ray photoelectron spectra (XPS) were measured with a SPECS photoelectron spectrometer with a PHOIBOS-150 MCD-9 half-sphere analyzer (AlKα radiation, hν = 1486.6 eV). The scale of binding energies Eb was preliminarily calibrated against peaks of core levels Au4f7/2 (84.0 eV) and Cu2p3/2 (932.67 eV). Samples were deposited onto a double-side conducting adhesive tape. As the internal standard for calibration of the resulting photoelectron spectra was used the line C1s (284.8 eV) of carbon present on the catalyst surface. In the fabrication technique of IK-GO-1, there is no stage of high-temperature calcination, and, as a result, the catalyst contains organic ligands, which are further removed in the stage of sulfidation [5, 6]. In addition, in storage of the catalyst in air, water molecules may be physically adsorbed on the support surface or coordinated with the supported bimetallic complex. For a catalyst of this kind, the elemental composition cannot be precisely determined or its characteristic measured. Therefore, the texture characteristics and chemical composition of the regenerated catalyst were compared with the data obtained for a fresh catalyst, or for a catalyst calcined in air at 550°C, or for that sulfided in hydrogen sulfide at 400°C. The elemental analyses and texture characteristics of the catalysts are listed in Table 1. As a result of deactivation and subsequent regeneration, the concentrations of Na, Fe, and Si in the catalyst remained unchanged and those of Ni, V, and As, which may be present in catalysts deactivated by diesel fuel according to [2–4], were below the detection limit for these elements, 0.001 wt %. Situations have been reported in the literature in

Table 1. Texture characteristics and contents of elements in the catalysts Pore Average volume, pore cm3 g–1 diameter, Å

Sample no.

Ssp, m2 g–1

2

192

0.53

3

191

4

189

Content, wt % С

H

N

S

Co

Mo

Na

Fe

Si

111

0.11

0.49

0.01

7.73

3.25

10.95

0.01

0.01

0.05

0.54

113

0.06

0.57

0.01

0.01

3.40

11.00

0.01

0.01

0.05

0.55

119

0.07

0.50

0.01

0.40

3.35

11.12

0.01

0.01

0.05

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T, °C

TGA, mg

τ, min Fig. 1. (1) TG, (2) DTG, (3) DTA, and (4) T curves for a deactivated catalyst. (T) Temperature and (τ) time.

which the concentration of cobalt and molybdenum in catalysts markedly decreases upon their regeneration, although reasons for such a behavior have not been discussed in detail [7, 8]. Possibly, combustion of coke in catalyst pores yields carbon oxides and water, which can react with cobalt and molybdenum to give volatile carbonyls and hydroxy complexes, with cobalt and molybdenum compounds thereby lost from the catalyst composition [4, 9]. For the catalysts studied, differences in the metal concentrations fall within the accuracy of the analysis, and, consequently, no noticeable loss of cobalt and molybdenum by the catalyst occurs in its regeneration. The concentrations of all other elements in the regenerated catalyst, except sulfur, almost coincide with those obtained for a fresh calcined catalyst. The residual content of sulfur (0.4%) is in rather good agreement with the reports [10, 11], in which catalysts regenerated at various temperatures contained 0.4–0.9% sulfur. Removal of sulfur and carbon from deactivated Co–Mo catalysts begins at a regeneration temperature of 150°C [2, 10]. Further, with increasing temperature, the content of sulfur and carbon in the catalyst decreases; however, the temperature dependences of the concentrations of these elements are different. For carbon, the concentration sharply falls in the range 300–450°C, after which, as the temperature increases further, the residual content of carbon in the catalyst remains nearly unchanged (0.1–0.3%). It should be noted that a fuller removal of carbonaceous deposits, compared with that reported in [10], could be achieved. The main amount of sulfur is removed from the catalyst on its being heated to 250°C. Further, with increasing

temperature, the decrease in the concentration of sulfur becomes steady and continues to 800°C. The results of a thermogravimetric analysis of a deactivated catalyst described in [1] are shown in Fig. 1. As the sample is heated to 150°C, a steady decrease in its mass is observed, accompanied by a minor endothermic effect. Apparently, adsorbed water is removed from the catalyst in this stage. Further, in the temperature range 150–350°C, a strong exothermic effect peaked at 280°C is observed; however, no noticeable changes in mass are seen in this case in the DTG curve. In agreement with the results of [2, 10], according to which most of sulfur is removed in this temperature range, the DTA and DTG curves indicate that sulfide species of the active component are oxidized. Because a molar ratio Co : Mo : S = 1 : 2 : 4 is characteristic of a sulfided catalyst [1], the oxidation can be described by a simplified scheme CoMo2S4 + 7.5 O2 → CoMoO4 + MoO3 + 4 SO2.

(1)

Further, oxidation of a part of the resulting SO2 to SO3 [3, 11] and its interaction with hydroxy groups of the support are possible, to give surface sulfates by the scheme 2[>Al–OH] + SO3 → [>Al–O]2SO2 + H2O.

(2)

The overall occurrence of reactions (1) and (2) gives rise to the exothermic effect in the DTA curve at a temperature of 280°C, which is not accompanied by any change in the mass of the sample in the DTG curve. As the sample is heated further, the main part of

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carbonaceous deposits burns out, which is manifested as an exothermic effect peaked at 402°C and a loss-of-mass peak in the DTG curve. The total loss of mass by the sample on its being heated to 500°C is, with 2.0% water that is adsorbed in storage and sample preparation in air taken into account, 21.3%. This value is in rather good agreement with elemental analysis data [1], according to which the total content of carbonaceous deposits and sulfur in a deactivated catalyst was 18.85%. A minor exothermic effect at 500–550°C is a consequence of removal of surface hydroxy groups from Al2O3 [12]. The subsequent heating leads to a steady loss of mass in the TG curve, which apparently occurs via decomposition of surface sulfates. It should be noted that an additional exothermic peak at 800– 900°C is present in the temperature range under study. This peak can be attributed to melting of MoO3, phase transitions of Al2O3, or decomposition of surface sulfates [8]. On the whole, thermogravimetric studies of a catalyst deactivated under model conditions revealed heat effects and changes in mass that are typical of catalysts deactivated in industrial installations [2, 10]. The texture characteristics of the regenerated catalyst differ only slightly from those obtained for a fresh sulfided or calcined catalyst (Table 1). The isotherms of nitrogen adsorption–desorption on regenerated and fresh calcined catalysts, shown in Fig. 2, are nearly identical. It should be noted that the hysteresis loop of the regenerated catalyst has no fragment at pressure ratios in the range P/P0 = 0.3–0.6. This confirms the

previous conclusion [1] that narrow pores with an average diameter of less than 40 Å, which appear in the deactivated catalyst, are channels between coke particles. As carbonaceous deposits are burnt-out, these pores disappear and, accordingly, so do the abovementioned fragment of the hysteresis loop. A small increase in the volume and average diameter of pores at an insignificant decrease in the specific surface area upon the regeneration points to a minimum caking of the catalyst. Results obtained in tests of the catalysts in hydropurification of diesel fuel are listed in Table 2. The residual content of sulfur in the hydrogenizate on the regenerated sample is approximately the same as that on a fresh catalyst calcined at 550°C (Table 2). Both samples subjected to calcination are strongly inferior in activity to the fresh catalyst. For modern European hydropurification catalysts intended for manufacture of ultra-low-sulfur diesel fuel. the decrease in the specific surface area as a result of regeneration does not exceed 10%, with the relative activity of a regenerated catalyst constituting 80–100% of the activity of the fresh catalyst [2]. The 11% decrease in the relative activity can be compensated for by a 3° increase in the starting temperature of hydropurification on a regenerated catalyst, compared with that in the fresh state. The dependence of the relative activity of the catalyst on the starting temperature of the process from the report [2], in which precise conditions of the hydropurification process and properties of the raw material were not specified, cannot be directly compared with the results obtained in our study. It should be noted, however, that, to reach a 50-ppm residual content of sulfur on catalysts calcined at 550°C, it was necessary to raise the hydropurification temperature by 11–12°, compared

V, cm3 g–1

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Table 2. Catalyst activity in the hydropurification of diesel fuel

Fig. 2. Isotherms of nitrogen adsorption–desorption on regenerated and fresh calcined catalysts. (V) Adsorbed volume of nitrogen and (P/P0) relative pressure. Sample (1, 2) no. 3 and (3, 4) no. 4. (1, 3) Adsorption and (2, 4) desorption.

a

Sulfur content,a ppm 340°С

360°С

Temperature when residual content of sulfur (50 ppm) reaching, °С

2

50

10

340

3

152

35

351

4

163

34

352

Sample no.

We reported averaged data by the residual content of sulfur in hydropurified diesel fuel for 12 h at 340°С and for 8 h at 360°С.

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with the fresh catalyst (Table 2). All the three catalysts under study have very close texture characteristics, contain equal amounts of active metals, and were sulfided under the same conditions before the tests. Therefore, it is apparent that the strong difference in activity between the uncalcined and calcined catalysts in hydropurification can only be attributed to differences in the structure of cobalt and molybdenum compounds in the catalysts before the sulfidation stage. It has been shown previously that the content of sulfur in the diesel fuel depends on the temperature of the preliminary drying of the fresh catalyst in air [13, 14]. The fresh catalyst dried at temperatures of up to 220°C contains cobalt and molybdenum only in the form of a bimetallic compound Co2[Mo4(C6H5O7)2O11]·xH2O, which was used as a starting component for fabrication of the catalyst. Sulfidation of a sample of this kind makes it possible to obtain the highest activity catalysts. At a higher drying temperature, the bimetallic complex decomposes to give various compounds of cobalt and molybdenum. In the least active catalyst dried at 400°C, β-CoMoO4 has been identified by Raman spectroscopy [5, 13, 14]. In further sulfidation, this compound is not selectively converted into the most active component of hydropurification catalysts, Co–Mo–S phase [15]. Raman data for the catalysts studied are presented in Fig. 3. The spectrum of the fresh catalyst contains a set of bands related to the bimetallic compound Co2[Mo4(C6H5O7)2O11]·xH2O [13, 14]. Seven main bands in the spectrum of the regenerated catalyst are fully identical to those described [15] for an industrial Co– Mo catalyst. The bands at 950, 940, 823, and 335 cm–1 are attributed to β-CoMoO4, and those at 568, 361, and 220 cm–1 correspond to surface aluminomolybdates AlMo6 with the Andersen structure. The spectrum of a fresh catalyst calcined at 550°C also contains these bands, with, however, a number of additional peaks not present in the spectrum of sample no. 4. These are rather intense peaks at 980 and 818 cm–1, attributed to orthorhombic α-MoO3 [16], and a peak at 1006 cm–1, assigned to Al2(MoO4)3 [17]. In addition, a large number of low-intensity peaks, which can be attributed to various forms of CoMoO4 and MoO3, and also to Co3O4, are present in the range 800–100 cm–1 [17]. Figure 4 shows EDRS spectra of the starting Co–Mo sample no. 1 and catalyst nos. 3 and 4. Mo6+ cations in the tetrahedral and octahedral oxygen coordinations, contained in various monomeric and polymeric

99

ν, cm–1 Fig. 3. Raman spectra of the catalysts. (I) Signal intensity and (ν) wave number. Digits at curves, sample numbers; the same for Figs. 4 and 5.

ν, cm–1 Fig. 4. Electronic diffuse reflectance spectra of the catalysts. [F(R)] Kubelka–Munk function and (ν) wave number.

compounds, appear in EDRS spectra as a characteristic set of peaks in the range 25 000–50 000 cm–1 [18, 19]. In the absorption range, ligand–metal charge-transfer bands of Co2+ cations in tetrahedral and octahedral oxygen coordinations may also be observed above 42 500 cm–1. Therefore, the electronic state of cobalt in Co–Mo catalysts was only analyzed on the basis of absorption bands that appear in the visible range of the ERDS spectra and are due to d–d transitions of Co2+ cations in tetrahedral and octahedral oxygen coordinations. In the EDRS spectra of sample nos. 3 and 4, there appear an absorption band at 17 100 cm–1 and two shoulders at 15 800 and 18 300 cm–1 due to the d–d transition of Co2+ cations in the tetrahedral oxygen coordination, with a multiplet structure of the absorption band, which may enter into the composition of a poorly catalytically active CoAl2O4 phase with a spinel structure. At the same time, absorption bands of β-CoMoO4 lie in the same range of EDRS spectra [23, 24]. It is noteworthy that no absorption bands related to Co3+ cations stabilized in the form of the oxide Co3O4

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Table 3. Binding energies of elements, found from XPS spectra Sample no.

Eb, eV Mo3d

Co2p

C1s

Al2p

O1s

S2p

1

232.3

782.0

284.8 288.7

74.7

531.6

–

3

232.8

782.0

284.8

74.8

531.7

–

4

232.7

782.0

284.8

74.7

531.6

169.3

[25] are observed in our spectra of calcined catalysts. Thus, it follows from the EDRS data that Co2+ cations in catalyst sample nos. 3 and 4 are mostly in the tetrahedral oxygen coordination and enter into the composition of CoAl2O4 and/or β-CoMoO4 phase. The EDRS spectrum of a fresh uncalcined catalyst no. 1 contains in its visible range only a single absorption band peaked at 18 000 cm–1, related to Co2+ cations in the octahedral oxygen coordination [22, 25]. It should, however, be noted that the small shift of the absorption band at 19 000 (18 900) cm–1, characteristic of hexa-aqua complexes of Co2+, to a lower energy of the d–d transition of Co2+ cations in the octahedral oxygen coordination may be due to replacement of water molecules by oxygen-containing ligands from the second coordination sphere [26]. Previously, it has been demonstrated by using a large number of physicochemical methods that cobalt enters in this form into the composition of the bimetallic compound Co2[Mo4(C6H5O7)2O11]·xH2O [14]. XPA data for the three catalyst samples under study and an Al2O3 sample used to fabricate IKGO-1 are presented in Fig. 5. The X-ray diffraction

2θ, deg Fig. 5. XPA data for the catalysts. (2θ) Bragg angle.

pattern of a fresh catalyst contains a set of peaks that fully coincides with that obtained for the starting support, and, consequently, all cobalt and molybdenum compounds in the fresh catalyst are X-ray-amorphous. In the X-ray diffraction patterns of sample nos. 3 and 4, we can distinguish, in addition to the peaks attributed to β-CoMoO4 (2θ 23.4, 26.5, and 33.7°) [27], also peaks associated with the spinels CoAl2O4 (31.2, 36.8, 55.5, 59.2, and 65.1°) and Al2(MoO4)3 (22.1, 23.5, 25.5, 26.3, 28.0, and 30.8°), with the highest intensity observed for the peaks associated with β-CoMoO4. The binding energies Eb of elements, found from XPS spectra, are listed in Table 3. For sample nos. 3 and 4, the electron binding energies at the Mo3d5/2 level are almost the same and well coincide with the data of [30], where CoMo/Al2O3 catalysts calcined at 550°C, with the same content of metals as that in the given samples, are described. The value Eb = 232.7– 232.8 eV corresponds to molybdenum in the oxidation state +6 and is close to the values reported in [31, 32] for MoO3, Al2(MoO4)3, and CoMoO4. In the fresh catalyst, the binding energy for Mo3d5/2 is 232.3 eV, which also corresponds to Mo6+. Because the fresh catalyst contains molybdenum only in the form of the bimetallic compound Co2[Mo4(C6H5O7)2O11]·xH2O [5, 6, 13, 14], the 0.4–0.5 eV difference in Eb, compared with calcined catalysts, is in all probability due to the donor-acceptor effect of citrate ligands coordinated to molybdenum [31]. The presence of citrate ligands in the fresh catalyst is confirmed by the fact that the spectrum contains a C1s peak with Eb = 288.7 eV, characteristic of carbon in the composition of carboxy groups [31]. The value Eb = 232.3 eV we obtained is typical of molybdenum in catalysts prepared using polybasic organic acids exhibiting a higher activity in hydrodesulfuration, compared with catalysts fabricated without chelate agents [33]. The value of Eb for electrons at the Co2p3/2 level is

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the same for all the catalysts (782.0 eV), which markedly differs from the data [30, 31, 34] for Co3O4, CoO, and CoAl2O4. The value obtained for Eb falls within the range 781.9–782.4 eV, typical of calcined CoMo/Al2O3 catalysts [11, 34, 35], and corresponds to Co2+ in the form of CoMoO4 [30] or binary cobalt and molybdenum oxides [36]. The S2p spectrum of sample no. 4 contains a peak with Eb = 169.3 eV, typical of regenerated hydropurification catalysts [11, 35]. This peak has been attributed to sulfate ions, which are in all probability bound to aluminum because a close value Eb = 169.0 eV corresponds to Al2(SO4)3 [31]. The whole body of data furnished by physical methods of study indicates that calcined catalysts contain a set of diverse compounds of cobalt and molybdenum. Some of these compounds are undesirable because of not being converted into the most active component of hydropurification catalysts, Co–Mo–S phase of type II [37, 38], upon sulfidation at temperatures of up to 400°C. A compound of this kind is β-CoMoO4, which is not converted into the Co–Mo–S phase [15], apparently because of specific features of its structure. Compounds with a Mo–O–Al chemical bond, such as surface aluminum molybdates Al2(MoO4)3 and aluminomolybdates AlMo6 with the Andersen structure, are converted into a comparatively catalytically lowactive oxygen-containing Co–Mo–S phase of type I [37, 38]. The CoAl2O4 spinel is a chemically stable material and is not sulfided, either, under the conditions specified. CONCLUSIONS (1) It was found that calcination at 550°C fully removes carbonaceous deposits and most part of sulfur from a deactivated IK-GO-1 catalyst. (2) The general pattern of removal of carbonaceous deposits and sulfur from a catalyst deactivated under model conditions in industrial hydropurification installations was confirmed. (3) It was shown that the texture characteristics of regenerated, fresh sulfided, and fresh calcined catalysts are nearly the same. (4) It was demonstrated that regenerated and fresh calcined catalysts have comparable activities in hydropurification of diesel fuel, which a markedly inferior to the activity of a fresh uncalcined catalyst. (5) It was found that calcined samples contain various cobalt and molybdenum compounds, among which are

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noticeable β-CoMoO4, surface aluminum molybdates, and CoAl2O4, undesirable components of the catalysts. ACKNOWLEDGMENTS The authors are grateful to T. Ya. Efimenko for assistance in a study of texture characteristics of the catalysts, D.G. Aksenov for elemental analyses, and S.V. Bogdanov for X-ray phase analyses. REFERENCES 1. Budukva, S.V., Klimov, O.V., Pashigreva, A.V., et al., Zh. Prikl. Khim., 2010, vol. 83, no. 12, pp. 2017–2024. 2. Dufresne, P., Appl. Catal. A: General, 2007, vol. 322, pp. 67–75. 3. Nefedov, B.K., Radchenko, E.D., and Aliev, R.R., Katalizatory protsessov uglublennoi pererabotki nefti (Catalysts for Deep Processing of Oil), Moscow: Khimiya, 1992. 4. Furimsky, E. and Massoth, F.E., Catal. Today, 1993, vol. 17, no. 4, pp. 537–660. 5. Bukhtiyarova, G.A., Klimov, O.V., Kochubey, D.I., et al., Nucl. Instruments Methods Phys. Research, Section A: Accelerators, Spectrometers, Detectors Associated Equipment, 2009, vol. 603, nos. 1–2, pp. 119–121. 6. Pashigreva, A.V., Bukhtiyarova, G.A., Klimov, O.V., et al., Kinet. Kataliz, 2008, vol. 49, no. 6, pp. 855–865. 7. Ramasvamy, A.V., Sharma, L.D., Singh, A., et al., Appl. Catal., 1985, vol. 13, no. 2, pp. 311–319. 8. Walendziewski, J., Appl. Catal., 1989, vol. 52, no. 3, pp. 181–192. 9. Leyrer, J., Mey, D., and Knцzinger, H., J. Catal., 1990, vol. 124, no. 2, pp. 349–356. 10. Dufresne, P., Valeri, F., and Abotteen, Dr.S., Stud. Surf. Sci. Catal., 1996, vol. 100, pp. 253–262. 11. Arteaga, A., Fierro, J.L.G., Delannay, F., and Delmon, B., Appl. Catal., 1986, vol. 26, pp. 227–249. 12. Ratnasamy, P., Mehrotra, R.P., and Ramaswamy, A.V., J. Catal., 1974, vol. 32, no. 1, pp. 63–71. 13. Pashigreva, A.V., Bukhtiyarova, G.A., Klimov, O.V., et al., Catal. Today, 2010, vol. 149, nos. 1–2, pp. 19–27. 14. Pashigreva, A.V., Co–Mo Catalysts for Deep Hydropurifi cation of the Diesel Fraction, Prepared via the Stage of Synthesis of Bimetallic Compounds, Cand. Sci. Dissertation, Novosibirsk, 2009. 15. Mazoyer, P., Geantet, C., Diehl, F., et al., Catal. Today, 2008, vol. 130, no. 1, pp. 75–79. 16. Mestl, G., J., Mol. Catal. A: Chemical, 2000, vol. 158,

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