IngentaConnect Structure and Reactivity of a V2O5/Al2O3 Catalyst Modified with C...

Abstract:

The oxidative dehydrogenation (ODH) of cyclohexane with air was studied on a 10 w/w% V₂O₅/Al₂O₃ catalyst modified by different weight percentage (wt%) cerium loadings. The catalysts employed were characterized by N₂ adsorption, O₂ chemisorption, TEM, XRD and FT-IR spectroscopy. Benzene and cyclohexene were the main components of the products, with the benzene and cyclohexene selectivities depending on the wt% cerium loading, the order of cerium and vanadium impregnation, and the reaction temperature. The best cyclohexane conversion and good benzene selectivity were obtained at 500°C using a vanadium catalyst modified by 10 wt% cerium. The same catalyst exhibited a maximum selectivity for cyclohexene at 300°C.

Different types of vanadyl species present in the system were identified by IR measurements. Thus, vanadium–oxygen clusters were detected in the V₂O₅/Al₂O₃ material, although such clusters were not found in the cerium–vanadium catalysts. Polymeric CeVO₄ species were detected in cerium-modified V₂O₅/Al₂O₃ catalysts by XRD. The concentration of these species depended on the wt% cerium loading and the order of cerium and vanadium impregnation on alumina. The selectivity of cerium-modified V₂O₅/Al₂O₃ catalysts towards cyclohexene was attributed mainly to the presence of such polymeric CeVO₄ species. Oxygen chemisorption and electronic microscopic studies attributed the marked improvement in cyclohexane conversion of the cerium–vanadium samples to the presence of relatively high-dispersed vanadium species.

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Structure and Reactivity of a V2O5/Al2O3 Catalyst Modified with Cerium in the Oxidative Dehydrogenation of Cyclohexane

Structure and Reactivity of a V₂O₅/Al₂O₃ Catalyst Modified with Cerium in the Oxidative Dehydrogenation of Cyclohexane