Gold chlorides markedly poison gold catalysis for acetylene hydrochlorination

Active Au species are fundamental issues in Au-catalyzed acetylene hydrochlorination (AH). As classical AH catalyst is prepared by impregnation with HAuCl4 aqua regia solution, various AuClx species are frequently regarded as the active Au species. Here, we reveal that “Au-Cl bond” free Au is highly active. It even shows noticeable room-temperature activity that fully vanishes when just a small fraction of Au binds to Cl. The mechanism is also well elucidated by combining experimental and elaborate theoretical studies. The gained knowledge can help to develop efficient catalysts or mild process, e.g., lowering process or light-off temperature to inhibit hotspots in reactor, catalyst sintering, or equipment corrosion by the corrosive reactant HCl. This is vital to industrial application, as AH is a strongly exothermic reaction; however, usually ≥180 °C is required owing to the inactivity of catalysts below ~180 °C. AuClx species are frequently regarded as the active Au species among the AuClx and Au(0) species present in Au catalysts for acetylene hydrochlorination. Here, the authors show that Au sites free of chloride bonding act as highly active sites even at room temperature, with low-temperature activity vanishing when a small fraction of Au binds to chloride.