Computational investigation of acetylene hydrogenation to ethylene over transition metal–exchanged chabazite zeolites: mechanistic insights and descriptor-based predictions

Abstract

The selective hydrogenation of acetylene to ethylene is a key reaction for producing polymer-grade ethylene in industrial processes. We study the efficiency of transition metals (Fe, Co, Ni, Cu, and Zn) confined in a chabazite (CHA) zeolite for the selective hydrogenation of acetylene to ethylene using density functional theory (DFT) calculations with the M06-L functional. The proposed reaction mechanism involves H₂ dissociation, followed by the formation of an ethenyl intermediate and its subsequent conversion to ethylene. We find that Cu-CHA exhibits the highest catalytic activity among the studied catalysts and shows high selectivity for the hydrogenation of acetylene to ethylene based on the calculated overall reaction barrier and its selectivity parameter. The zeolite frameworks are found to stabilize all the species formed along the reaction pathway, but particularly at the transition states, thereby lowering all the activation barriers. We also find that the zeolite's dipole moment and metal charge are moderately accurate descriptors for predicting the overall activation barrier of the reaction. We use the sure-independence screening and sparsifying operator (SISSO) method to identify optimal nonlinear combinations of DFT-based descriptors,enabling accurate predictions without time-consuming reaction pathway calculations.