Investigation of the active species in the carbon-supported gold catalyst for acetylene hydrochlorination. Issue 13 (23rd March 2016) - Liu, Xi
Abstract : The active site for a Au/C catalysts for acetylene hydrochlorination involves a Au + –Au 3+ couple. Abstract : The nature of the active species in carbon-supported gold catalysts used for synthesis of vinyl chloride monomer from acetylene hydrochlorination has been investigated using X-ray photoelectron spectroscopy and electron microscopy. Catalysts prepared by impregnation of chloroauric acid dissolved in aqua regia are initially inactive. During the initial reaction they show a pronounced induction period and we have used this opportunity to examine the evolution of the active catalyst as it is transformed during acetylene hydrochlorination. The fresh catalyst comprises a Au(iii ) surface film which on reaction with acetylene and HCl transforms to a mixture of Au(i )/Au(iii ). Experiments in which the catalyst is exposed sequentially to HCl and acetylene show that high activity is associated with a catalyst containing significant amounts of cations with both oxidation states and that the Au(i ) and Au(iii ) oxidation cycle is important in the activation of both molecules. These findings are discussed in relation to the nature of the active species.