Adsorption and ODH reaction of alkane on sol-gel synthesized TiO2-WO3 supported vanadium oxide catalysts: In situ DRIFT and structure-reactivity study

A titania-based mixed-oxide support containing 90 wt% TiO2, 90Ti-W, and several supported vanadium oxide (vanadia) catalysts, xV90Ti-W (x = 1-12.5 wt% vanadia), were synthesized and characterized. The anatase phase in the 90Ti-W support remained unaffected up to 1073 K. The presence of vanadia, however, leads to an appearance of the rutile phase and a decrease in the catalyst surface area. The xV90Ti-W catalysts possess surface vanadium and tungsten oxide dispersed species at moderate calcination temperatures. At high vanadia loadings, some interaction between the surface vanadium and tungsten oxide species may exist though bulk supported oxides were not detected. During ethane and propane adsorption, at relatively low adsorption temperatures, acetaldehyde and acetone species Were observed, which then oxidized to other adsorbed oxygenated species at higher temperatures. Propane oxidative dehydrogenation (ODH) reaction studies revealed that the propene yield measured at the same conversion increased with increasing loading up to 10 wt% vanadia and then decreased. Analysis of the kinetic parameters showed that the rate constant ratio of propene formation to propene combustion, k(1)/k(2), which represents the propene yield at the same conversion. also increased with vanadia loading. The 10V90Ti-W catalyst was the best amongst this series of catalysts for the propane ODH reaction in terms of activity and propene yield. (C) 2009 Published by Elsevier B.V.