Efficient and stable N-heterocyclic ketone–Cu complex catalysts for acetylene hydrochlorination: the promotion effect of ligands revealed from DFT calculations

Abstract

Cu-based catalysts are a promising alternative to toxic mercury catalysts for acetylene hydrochlorination, but their effectiveness is limited due to the poor dispersion and deactivation caused by reduction, agglomeration, and carbon deposition. In this study, the activity and stability of carbon-supported CuCl₂ catalysts were largely improved by introducing N-heterocyclic ketones. Remarkably, N-methyl-2-pyridone (NM2P) coordinated Cu-based catalysts exhibited over 95% acetylene conversion with better stability under the reaction conditions of T = 180 °C, GHSV (C₂H₂) of 80 h⁻¹, and V_HCl/V_C2H2 = 1.2. The combined results of characterization and exhaustive density functional theory (DFT) calculations revealed that the O–Cu coordination between the NM2P ligand and Cu cation strengthened the combination of reactants and Cu active sites, lowering the key reaction energy barrier, thereby leading to high activity. Meanwhile, the addition of the NM2P ligand significantly inhibited the reduction of Cu²⁺ to Cu⁺/Cu⁰, avoiding the formation of CuCl aggregates and the coking caused by Cu⁰, enhancing the catalytic stability. Overall, our study provides important insights into the design and optimization of Cu-based catalysts for acetylene hydrochlorination.