Oxidative Dehydrogenation of Propane over Vanadate Catalysts Supported on Calcium and Strontium Hydroxyapatites

Abstract

The oxidative dehydrogenation of propane to propylene was investigated over vanadate catalysts supported on calcium and strontium hydroxyapatites (VO_x/CaHAp and VO_x/SrHAp, respectively). Catalytic activities were improved by both CaHAp and SrHAp supports, but the improvement was greater for VO_x/SrHAp than for VO_x/CaHAp. The maximum yield of propylene observed for 5% VO_x/SrHAp was comparable to that of Mg₂V₂O₇, which is one of the most active catalysts for the oxidative dehydrogenation of propane. The combination of active sites for loading (VO_x) and the OH groups of the support (CaHAp and SrHAp) resulted in the enhanced catalytic activity. Furthermore, the redox nature of the loading directly contributed to the enhancement of VO_x/SrHAp activity. The effect of catalyst weight (5% VO_x/SrHAp) relative to the feedstock flow rate on selectivities to propylene and CO_x suggested that oxidative dehydrogenation proceeded through a consecutive mechanism in which propylene was formed from the oxidative dehydrogenation of propane, followed by deep oxidation from propylene to CO_x, rather than the direct oxidation of propane.