(245b) Computational Study of Dehydrogenation of Light Alkanes over Pt and Pt/Sn Alloys

The effect of platinum tin alloy structure and composition on the kinetics and thermodynamics of dehydrogenation and coke formation pathways during light alkane dehydrogenation have been studied using density functional theory. Light alkane dehydrogenation to olefins can add significant value to hydrocarbon processes that generate ethane and propane by converting low value commodity fuels to high-value chemical and polymer precursors. Supported Pt catalysts are known to be active for ethane and propane dehydrogenation, but the high temperatures required by these endothermic reactions leads to significant coke formation and deactivation. Alloying Pt with Sn and other main group elements has been shown to decrease the amount of coke formed and leads to more stable catalysts. We apply periodic density functional theory to understand how the structure and composition of these alloys affect their ability to suppress coke formation. We investigate the potential energy surfaces from ethane and propane along the desired pathway to their corresponding alkenes, and along the undesired pathways towards surface carbon/coke. The effect of catalyst composition (e.g. Pt/Sn ratio) and surface geometry is investigated. As compared to pure Pt, C-H bond scission is more difficult on the alloys, and dihydrogen desorption is more facile.