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

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/Al...