Using high-valent Au(iii) catalysis is highly desirable in many reactions; however it is plagued by the poor stability of Au(iii) complexes.

Commercialization of acetylene hydrochlorination using AuCl 3 catalysts has been impeded by its poor stability. We have been studying CsCl as a promoter, which can improve acetylene hydrochlorination activity as well as have resistance to catalytic deactivation. In III -added to the Au-Cs I /AC catalysts worked as efficient catalysts for the hydrochlorination of acetylene to vinyl chloride. A 10 series of trimetallic catalysts (1AuxIn III 4Cs I /AC with x = 0.5, 1, 2, 3) were prepared and assessed for their ability to promote hydrochlorination of acetylene. The enhancement of stability observed for Au/In III /Cs I weight ratio of 1:1:4 was particularly remarkable. It delivered a stable performance within the conversion of acetylene, reaching more than 92.8% and there was only 3.7% C 2 H 2 conversion loss after 50 h running under the reaction conditions of temperature 180 °C and C 2 H 2 hourly space velocity of 1480 h -1 . 15 Moreover, the 1Au1In III 4Cs I /AC catalyst delivered a stable performance with an estimated lifetime exceeding 6520 h at C 2 H 2 hourly space velocity of 50 h -1 . H 2 -TPR, TEM, HCl-TPD, C 2 H 2 -TPD, XPS and TGA techniques were further applied to reveal the structural information on the Au-In III -Cs I /AC catalysts. The results reveal that the addition of InCl 3 increased the electron density of Au 3+ species via electron transfer from In atoms to Au 3+ center can increase the adsorption of hydrogen chloride and therefore 20 improve the catalytic stability. These results demonstrate that the addition of metal additives CsCl and InCl 3 results in a synergistic effect to enhance the activity and the stability of Au-based catalysts. The excellent catalytic performance of the 1Au1In III 4Cs I /AC catalyst demonstrated its potential as an alternative to mercury chloride catalysts for acetylene hydrochlorination.