Mechanistic insights into the evolution of Cu active center in acetylene hydrochlorination

Abstract

Reserve–rich Cu–based catalysts are attractive for their favorable cost and sustainability and have exhibited extensive catalytic activities in the conversion of acetylene. However, the variable–valence and the presence of multi–species as well as the complexity of catalytic system pose challenges in deciphering the evolution process of Cu active center during working life–time. Herein, we investigated the evolution process of multivalent Cu–based species (Cu²⁺, Cu⁺ and Cu⁰) as model active centers for acetylene hydrochlorination. The reduction of Cu²⁺ driven by the activated carbon support and acetylene as well as oxidation of Cu⁰ induced by hydrogen chloride, have been clarified for these species, both of which with the terminated Cu⁺ species identified as the stable catalytic active center. Theoretical calculations have revealed the thermodynamics underlying the mechanism of species evolution determined by the covalent bond transition within Cu species, with comparisons of the differences in catalytic kinetics between sites. Moreover, a specific pathway for the catalytic decomposition of acetylene into coke deposits by Cu⁺ species was proposed. This knowledge provides mechanistic insights into the evolution process of Cu active centers in acetylene hydrochlorination, paving the way for understanding catalytic behavior and accurate catalyst design for new improved Cu–catalyzed ethynylation reactions.