Temperature-programmed sulfiding of vanadium oxides and alumina-supported vanadium oxide catalysts
- Univ. of Amsterdam (Netherlands)
Sulfiding of bulk and alumina-supported vanadium oxides has been studied using temperature-programmed sulfiding and reduction techniques. Bulk compounds (V{sub 2}O{sub 5}, V{sub 2}O{sub 3}) and V/Al{sub 2}O{sub 3} catalysts are sulfided via a similar mechanism. For bulk V{sub 2}O{sub 5}, two major sulfiding steps have been identified. At temperatures up to 673K, V{sub 2}O{sub 5} is reduced to V{sub 2}O{sub 3} by O-S exchange and subsequent rupture of V-S bonds where H{sub 2}S acts as reducing agent. Sulfiding to V{sub 2}S{sub 3} takes place above 673K. The catalysts are sulfided more easily than the bulk oxides due to the higher dispersion of the vanadium species. In catalysts sulfided at 673K which are still partially oxidic, four types of sulfur have been observed, viz. adsorbed H{sub 2}S, stoichiometric sulfur, S-H groups, and nonstoichiometric (excess) sulfur (S{sub x}). There are indications that (isothermal) room temperature H{sub 2}S adsorption can be used to determine the dispersion of the supported microcrystallites at higher vanadium loadings. From the present results it is inferred that alumina-supported vanadium-based catalysts, when sulfided at temperatures commonly applied in hydrotreating operations, essentially consist of an oxide, the outer surface of which is sulfided. 22 refs., 6 figs., 4 tabs.
- OSTI ID:
- 98971
- Journal Information:
- Journal of Catalysis, Vol. 154, Issue 1; Other Information: PBD: Jun 1995
- Country of Publication:
- United States
- Language:
- English
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