Supported Vanadium Catalysts for Selective Sulfur-Oxidative Dehydrogenation of Propane

The catalytic oxidative dehydrogenation of propane (ODHP) is a challenging reaction due to facile competing overoxidation to COx. The gaseous disulfur molecule, S-2, is isoelectronic with O-2 and has been shown to act as an alternative, "soft oxidant" for the analogous process (SODHP) over bulk metal sulfide catalysts. However, these bulk catalysts suffer from low surface areas and ill-defined active sites - issues that might be addressed with a supported catalyst. Here we investigate supported V/Al2O3 materials for SODHP. We show that these catalysts are highly selective for propylene, far surpassing the yields of the prior bulk systems. Isolated sulfided vanadium species are found to be more active and selective than crystalline vanadium sulfide. Additionally, we compare the S-2 and O-2 oxidants over sulfided and calcined V/Al2O3 materials, respectively, and find that the propylene selectivity is enhanced using S-2 as the oxidant. These results suggest that sulfur is a promising soft oxidant that can be used to achieve high propylene selectivities over supported metal sulfides.