Abstract
The greenhouse gas CO2 is a promising soft oxidant for the oxidative dehydrogenation of light alkanes. However, the occurrence of side reactions including cracking, hydrogenolysis, and reforming results in lower olefin yields compared with direct dehydrogenation. We report that Pt-M (M = Sn/In/Zn) bimetallic catalysts on non-redox-active silica support can break the equilibrium limit of direct propane dehydrogenation using CO2 as a co-reactant to consume the hydrogen formed in propane dehydrogenation. Unlike the commonly postulated direct CO2-assisted dehydrogenation mechanism, we confirm that CO2-oxidative dehydrogenation of propane (ODHP) proceeds in two tandem steps on these bimetallic catalysts, i.e., propane dehydrogenation and reverse water-gas shift, with the latter being the rate-determining step. In situ X-ray absorption studies and density functional theory calculations suggest that the PtmMn-MOx (e.g., Pt3Sn-SnOx) interfaces are likely active sites.
