Construction of Cu(DMF)₂Cl Active Sites for Gas-Solid Acetylene Dimerization: Effects of DMF Ligand and Catalytic Mechanism

Dimerization of acetylene to monovinylacetylene (MVA) is a vital process for producing chloroprene rubber in the industry and is highly attractive and challenging. To study the influence of ligands on the catalytic performance of the Cu-based catalyst and the catalytic mechanism in the gas-solid acetylene dimerization reaction, the Cu-based catalyst modified with N,N-dimethylformamide (DMF) ligands was prepared via an incipient wetness method, which increased the average MVA yield by 50% compared to Cu/AC catalysts. X-ray photoelectron spectroscopy, X-ray absorption fine structure spectroscopy, hydrogen temperature-programmed reduction, and transmission electron microscopy results revealed that the Cu-15DMF/AC catalyst formed a Cu-O coordination structure during the process of preparation, which thus changed the electronic environment, enhanced the reducibility of Cu-(II) species, and improved the dispersion of active metals. Furthermore, the gas-solid acetylene dimerization reaction in the catalytic mechanism of Cu/AC and Cu-DMF/AC catalysts was comprehensively elucidated through the DFT calculation. It is demonstrated that the rate-determining step for the Cu/AC catalyst was Cu-(II) reduction with Cl dissociation (Ts1), whereas the Cu-DMF/AC catalyst was acetylene addition (Ts2). The coordination of DMF and Cu species reduced the energy barrier of the dimerization of acetylene to form MVA and raised the energy barrier of the side reaction. This study provides valuable insights into designing efficient and reusable Cu-based catalysts for gas-solid acetylene dimerization.