Effect of R-SO2-R′ ligands on the gold-based catalysts for acetylene hydrochlorination: A DFT study

Gold-based mercury-free catalysts have great potential in the industrial production of vinyl chloride. In order to further understand the factors affecting the catalytic activity, the catalytic reaction mechanisms of five kinds of sulfur-containing ligand gold-based catalysts are studied by DFT calculation at the PBE0/def2-TZVP level, and dispersion-corrected DFT-D3 is performed. The results show that the rate control step in the reaction path is the transfer of proton hydrogen. With the increase of Mulliken charges of Au and S atoms in the catalyst, the energy barrier of acetylene hydrochlorination decreases. The catalyst formed by methanesulfonic acid and AuCl3 has the lowest energy barrier of acetylene hydrochlorination (23.18 kcal/mol). Compared to AuCl3 catalyst, adding ligands can significantly reduce the products desorption energy. When the ligand has an electron-withdrawing group, the corresponding acetylene self-polymerization barrier is lower. These results provide valuable theoretical guidance for preparation of efficient sulfur-containing ligand gold-based catalysts in future.