Improvement of catalytic functions of binary V-Sb oxide catalysts for oxidative conversion of isobutane to isobutene

Dehydrogenation of isobutane in the presence of oxygen-industrially prospective process for isobutene production-has been studied over vanadium-antimony oxide catalysts. Their catalytic behaviour was compared with the sample characterisation data by specific surface area (SSA), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Substantial improvement of the catalytic performance has been achieved as a result of proper spreading of active V-containing component onto an appropriate support. Optimisation of the composition and loading of the active component, the chemical nature and morphology of support material, as well as the preparation procedure allowed to further improve the yield of isobutene. Microspheric gamma-alumina with moderate SSA and large average pore diameter was found to be the best support for the efficient catalyst. The loading of vanadia corresponding to 1-1.5 formal monolayer coverage and doping with antimony (V-to-Sb atomic ratio 8.8) were found to be optimal. The use of "citrate" preparation technique showed an advantage in comparison with ordinary impregnation method, giving the catalyst with well dispersed (amorphous) and homogeneously distributed supported V-Sb-O-component. The optimised catalyst demonstrated improved stability, high activity and olefin selectivity (70% at 36% conversion), producing yields of isobutene (up to 26% per pass) among the best reported in the literature. (C) 2003 Elsevier Science B.V. All rights reserved