Nature of the active phase in hydrodesulfurization: molybdenum carbide supported on activated carbon
Resumen
This paper studies the effect of the presulfiding agent and the synthesis method on the catalytic activity of thiophene hydrodesulfurization (HDS), using activated carbon supported molybdenum carbides. The catalytic precursor was prepared by co-impregnation of the support with the ammonium heptamolybdate solution. The conventional carbiding consists of a temperature-programmed treatment under a CH4/H2 atmosphere at 1073 K (MC), while the carbothermal method employs pure H2 at 973 K (MCH). The passivated carbides were characterized by X-ray Diffraction (XRD), surface area calculated by the Brunauer–Emmett–Teller multipoint method (BET) and X-ray Photoelectron Spectroscopy (XPS). XRD confirmed the presence of -Mo2C for both methods of synthesis, while specific area were in the order of 400 m2/g. XPS showed the presence at the surface of Moo+ (0 ≤ o ≤ 2), Mo4+ and Mo6+, whose abundance was influenced by used synthesis method with greater proportion of high oxidation states in MCH. Prior to catalytic testing, the passivated carbides were presulfided in situ. HDS tests showed that regardless of the presulfiding agent (H2S or CS2), the carbides obtained by MCH had higher activity than those obtained using the conventional method. The B-Mo2C presulfiding suggests that the carbides with sulfided surfaces or carbo-sulfide mixtures could be the active phase in HDS.
Referencias bibliográficas
https://doi.org/10.1006/jcat.1996.0367
Al-Megren, H. A., Xiao, T., González-Cortés, S. L., Al-Khowaiter, S. H. & Green, M. L. H. (2005). Comparison of bulk CoMo bimetallic carbide, oxide, nitride and sulfide catalysts for pyridine hydrodenitrogenation. J. Mol. Catal. A: Chem., 225(2), 143-148.
https://doi.org/10.1016/j.molcata.2004.08.041
Callant, M., Grange, P., Holder, K. A., Viehe, H. G. & Delmon, B. (1993). Secondary effects in catalytic tests for hydrodenitrogenation reactions due to side reactions with sulfur compounds. J. Catal., 142(2), 725-728.
https://doi.org/10.1006/jcat.1993.1245
Chianelli, R. R. & Berhault, G. (1999). Symmetrical synergism and the role of carbon in transition metal sulfide catalytic materials. Catal. Today, 53(3), 357-366.
https://doi.org/10.1016/S0920-5861(99)00130-3
Da Costa, P., Manoli, J. M., Potvin, C. & Djéga-Mariadassou, G. (2005). Deep HDS on doped molybdenum carbides: from probe molecules to real feedstocks. Catal. Today, 107-108: 520-530.
https://doi.org/10.1016/j.cattod.2005.07.166
Da Costa, P., Potvin, C., Manoli, J. M., Genin, B. & Djéga-Mariadassou, G. (2004). Deep hydrodesulphurization and hydrogenation of diesel fuels on alumina-supported and bulk molybdenum carbide catalysts. Fuel, 83(13), 1717- 1726.
https://doi.org/10.1016/j.fuel.2004.03.007
Delannoy, L., Giraudon, J. M., Granger, P., Leclercq, L. & Leclercq, G. (2000). Group VI transition metal carbides as alternatives in the hydrodechlorination of chlorofluorocar- bons. Catal. Today, 59(3-4), 231-240.
https://doi.org/10.1016/S0920-5861(00)00289-3
Dhandapani, B., Clair, T. St. & Oyama, S. T. (1998). Simultaneous hydrodesulfurization, hydrodeoxygenation, and hydrogenation with molybdenum carbide. Appl. Catal. A: Gen., 168(2), 219-228.
https://doi.org/10.1016/S0926-860X(97)00342-6
Djéga-Mariadassou, G., Boudart, M., Bugli, G. & Sayag, C. (1995). Modification of the surface composition of mo- lybdenum oxynitride during hydrocarbon catalysis. Catal. Lett., 31(4), 411-420.
https://doi.org/10.1007/BF00808605
Dufresne, P., Brahma, N., Labruyère, F., Lacroix, M. & Breysse, M. (1996). Activation of off site presulfided cobalt-molybdenum catalysts. Catal. Today, 29(1-4), 251-254.
https://doi.org/10.1016/0920-5861(95)00280-4
Iglesia, E., Baumgartner, J. E., Ribeiro, F. H. & Boudart, M. (1991). Bifunctional reactions of alkanes on tungsten carbides modified by chemisorbed oxygen. J. Catal. 131(2), 523-544.
https://doi.org/10.1016/0021-9517(91)90284-B
Kelty, S. P., Berhault, G. & Chianelli, R. R. (2007). The role of carbon in catalytically stabilized transition metal sulfides. Appl. Catal. A: Gen., 322: 9-15.
https://doi.org/10.1016/j.apcata.2007.01.017
Laine, J., Labady, M., Severino, F. & Yunes, S. (1997). Sink effect in activated carbon-supported hydrodesulfurization catalysts. J. Catal., 166(2), 384-387.
https://doi.org/10.1006/jcat.1997.1507
Leary, K. J., Michaels, J. N. & Stacy, A. M. (1986). Carbon and oxygen atom mobility during activation of Mo2C catalysts. J. Catal., 101(2), 301-313.
https://doi.org/10.1016/0021-9517(86)90257-5
Ledoux, M. J., Pram Huu, C., Guille, J. & Dunlop, H. (1992). Compared activities of platinum and high specific surface area Mo2C and WC catalysts for reforming reactions: I. Catalyst activation and stabilization: Reaction of n- hexane. J. Catal., 134(2), 383-398.
https://doi.org/10.1016/0021-9517(92)90329-G
Lee, J. S. & Boudart, M. (1985). Hydrodesulfurization of thiophene over unsupported molybdenum carbide. Appl. Catal., 19(1), 207-210.
https://doi.org/10.1016/S0166-9834(00)82682-2
Lee, J. S., Volpe, L., Ribeiro, H. & Boudart, M. (1988). Molybdenum carbide catalysts: II. Topotactic synthesis of unsupported powders. J. Catal., 112(1), 44-53.
https://doi.org/10.1016/0021-9517(88)90119-4
Liu, P., Rodríguez, J. A. & Muckerman, J. T. (2004). The Ti8C12 Metcar: A new model catalyst for hydrodesulfurization. J. Phys. Chem. B., 108(49), 18796-18798.
https://doi.org/10.1021/jp045460j
Liu, P., Rodríguez, J. A. & Muckerman, J. T. (2005). Sulfur adsorption and sulfidation of transition metal carbides as hydrotreating catalysts. J. Mol. Cat. A: Chem., 239(1- 2), 116-124.
https://doi.org/10.1016/j.molcata.2005.06.002
Mangnus, P., Bos, A. & Moulijn, J. (1994). Temperature- programmed reduction of oxidic and sulfidic alumina- supported NiO, WO3, and NiO-WO3 catalysts. J. Catal., 146(2), 437-448.
https://doi.org/10.1006/jcat.1994.1081
Mangnus P., de Beer, V. H. J. & Moulijn, J. (1990). Influence of phosphorus on the structure and the catalytic activity of sulfided carbon-supported Co-Mo catalysts. Appl. Catal., 67(1), 119-139.
https://doi.org/10.1016/S0166-9834(00)84436-X
Manoli, J. M., Da Costa, P., Brun, M., Vrinat, M., Maugé, F. & Potvin, C. (2004). Hydrodesulfurization of 4,6-dimethyldibenzothiophene over promoted (Ni,P) alumina- supported molybdenum carbide catalysts: activity and characterization of active sites. J. Catal., 221(2), 365-377.
https://doi.org/10.1016/j.jcat.2003.08.011
McCrea, K. R., Logan, J. W., Tarbuck, T. L., Heiser, J. L. & Bussell, M. E. (1997). Thiophene hydrodesulfurization over alumina-supported molybdenum carbide and nitride catalysts: Effect of Mo loading and phase. J. Catal., 171(1), 255-267.
https://doi.org/10.1006/jcat.1997.1805
Mordenti, D., Brodzki, D. & Djéga-Mariadassou, G. (1998). New synthesis of Mo2C 14 nm in average size supported on a high specific surface area carbon material. J. Sol. St. Chem., 141(1), 114-120.
https://doi.org/10.1006/jssc.1998.7925
Penning, R. T. (2001). Petroleum refining: a look at the future. Hydrocarb. Process., 80(2), 45-46.
Portela, L., Grange, P. & Delmon, B. (1995). XPS and NO adsorption studies on alumina-supported Co-Mo catalysts sulfided by different procedures. J. Catal., 156(2), 243-254.
https://doi.org/10.1006/jcat.1995.1251
Power Diffraction File. (1995). International Center for Diffraction Data. Newtown Square, Philadelphia.
Puello-Polo, E. & Brito, J. L. (2008). Effect of the type of precursor and the synthesis method on thiophene hydrodesulfurization activity of activated carbon supported Fe-Mo, Co-Mo and Ni-Mo carbides. J. Mol. Catal. A: Chem., 281(1-2), 85-92.
https://doi.org/10.1016/j.molcata.2007.09.015
Puello-Polo, E. & Brito, J. L. (2010). Effect of the activation process on thiophene hydrodesulfurization activity of activated carbon supported bimetallic carbides. Catal. Today, 149(3-4), 316-320.
https://doi.org/10.1016/j.cattod.2009.05.025
Puello-Polo, E., Gutiérrez-Alejandre, A., González, G. & Brito, J. L. (2010). Relationship between sulfidation and HDS catalytic activity of activated carbon supported Mo, Fe-Mo, Co-Mo and Ni-Mo carbides. Catal. Lett., 135(3-4), 212-218.
https://doi.org/10.1007/s10562-010-0303-6
Ramanathan, S. & Oyama, S. T. (1995). New catalysts for hydroprocessing: Transition metal carbides and nitrides. J. Phys. Chem., 99(44), 16365-16372.
https://doi.org/10.1021/j100044a025
Rueda, N., Bacaud, R. & Vrinat, M. (1997). Highly dispersed, nonsupported molybdenum sulfides. J. Catal., 169(1), 404-406.
https://doi.org/10.1006/jcat.1997.1669
Sajkowski, D. J. & Oyama, S. T. (1996). Catalytic hydrotreating by molybdenum carbide and nitride: Unsupported Mo2N and Mo2C/Al2O3. Appl. Catal. A: Gen.,134(2), 339-349.
https://doi.org/10.1016/0926-860X(95)00202-2
Scheffer, B., Dekker, N., Mangnus, P. & Moulijn, J. (1990). A temperature-programmed reduction study of sulfided CoMo/Al2O3 hydrodesulfurization catalysts. J. Catal., 121(1), 31-46.
https://doi.org/10.1016/0021-9517(90)90214-5
Solymosi, F., Cserényi, J., Szöke, A., Bánsági, T. & Oszkó, A. (1997). Aromatization of methane over supported and unsupported Mo-based catalysts. J. Catal., 165(2), 150-161.
https://doi.org/10.1006/jcat.1997.1478
Szymańska-Kolasa, A., Lewandowski, M., Sayag, C. & Djéga-Mariadassou, G. (2007). Comparison of molybdenum carbide and tungsten carbide for the hydrodesulfurization of dibenzothiophene. Catal. Today, 119(1-4), 7-12.
https://doi.org/10.1016/j.cattod.2006.08.021
Szymańska-Kolasa, A., Lewandowski, M., Sayag, C., Brodzki, D. & Djéga-Mariadassou, G. (2007). Compari- son between tungsten carbide and molybdenum carbide for the hydrodenitrogenation of carbazole. Catal. Today, 119(1-4), 35-38.
https://doi.org/10.1016/j.cattod.2006.08.039
Vangestel, J., Leglise, J. & Duchet, J. C. (1994). Catalytic properties of a CoMo/Al2O3 catalyst presulfided with alkyl polysulfides: Comparison with conventional sulfi- ding. J. Catal., 145(2), 429-436.
https://doi.org/10.1006/jcat.1994.1053
York, A. P. E., Claridge, J. B., Brungs, A. J., Tsang, S. C. & Green, M. L. H. (1997). Molybdenum and tungsten carbides as catalysts for the conversion of methane to synthesis gas using stoichiometric feedstocks. Chem. Commun., 1: 39-40.
https://doi.org/10.1039/a605693h