Dissecting the role of Bi and Ba in the catalytic efficiency of VSbBiBa/Al2O3 catalysts in oxidative dehydrogenation and oxidation of propane

Abstract

The oxidative dehydrogenation of propane into propene could be a way to produce propylene as an alternative to steam cracking or fluid catalytic cracking, if efficient catalysts were discovered and developed. VSbBiBaO/Al₂O₃ catalysts, which have been proposed for the reaction, have the advantage of being operational at a relatively low temperature allowing their further use in combination with propene oxidation catalysts to produce acrolein. This study reports a deep characterization of the catalysts by various techniques, before or after catalytic testing, in order to determine the respective roles of the constitutive elements as well as those of the dopant and the support. The results show that the active phase corresponds to a vanadium antimonate with a rutile-type structure with antimony partially substituted by bismuth. Bismuth increases the surface content of V⁵⁺ which are the active sites for the first step of propane dehydrogenation and thus increases the intrinsic activity of the catalysts since this step is the rate limiting step. Barium added as a surface dopant was shown to decrease the catalyst's acidity which avoids total oxidation and creates basic sites both on the rutile-type phase and the support that contributes to the desorption of propene.