(581d) Computational Design of Alloy Catalysts for Propane Conversion

Propane dehydrogenation is a major process involved in the production of petrochemicals via the selective dehydrogenation of propane to propylene. This reaction, and other propane conversion reactions, requires a catalytic material that can activate propane while mitigating coking on the surface and cracking of hydrocarbons. While past work indicates that single-atom alloys (which consist of one metal doped as single atoms into the surface of another metal) can meet both of these criteria, single-atom alloys with higher performance are needed to improve the overall process efficiency; further, these improved single-atom alloys could be effective catalysts for other challenging alkane conversion reactions. Because experimental screening of catalysts is generally expensive and time-consuming, we used density functional theory (DFT) to computationally examine the behavior of different single-atom alloy catalyst for propane conversion. The IrAg single-atom alloy is predicted to be effective for propane conversion, but is not predicted to be stable. To address this stability issue, we found that trimetallic Ag-based surfaces can stabilize the Ir single-atom site while maintaining similar energetics as IrAg. This strategy of using bimetallic hosts to stabilize single-atom sites greatly opens up the space of useable single-atom alloys. We also found that a TiCu single-atom alloy surface is predicted to be effective for propane dehydrogenation, partly due to agostic (i.e., C-H-M) interactions. Thus, this work identifies promising catalytic surfaces for alkane conversion, with possible applications in more delicate and selective reactions such as alkane coupling, and also develops new strategies for designing stable single-atom sites with desired reactivity.