Unveiling the catalyst deactivation mechanism in the non-oxidative dehydrogenation of light alkanes on Rh(111): Density functional theory and kinetic Monte Carlo study

Abstract

Non-oxidative propane dehydrogenation (NOPDH) selectively converts propane to value-added propylene, and is therefore being evaluated as an industrial alternative to commercial propylene-production processes. Rh-based catalyst is being evaluated as a replacement for the state-of-the-art PtSn/Al2O3 catalyst. Rh has a high catalytic activity for C-H bond dissociation, but low NOPDH selectivity due to the side reactions including cracking reactions and deep-dehydrogenation. The present study uses density functional theory (DFT) calculations in conjunction with kinetic Monte Carlo (kMC) simulations to identify the key descriptors of NOPDH selectivity and mechanisms by which the Rh(111) surface can be deactivated. Ab-initio kMC simulations allow quantitative analysis of kinetic parameters in the operating conditions while explicitly considering lateral interactions, which cannot be done using only periodic DFT calculations. The kMC simulations consider all reaction elementary steps rigorously, so the overall reaction can be represented explicitly. Our theoretical analysis of the Rh(111) system suggests the deactivation mechanism and will provide design principles to achieve a highly active and selective Rh catalyst for NOPDH.