Investigation of the active species in the carbon-supported gold catalyst for acetylene hydrochlorination

• Published in: Catalysis science & technology 2016-01, Vol.6 (13), p.5144-5153
• Main Authors: Liu, Xi, Conte, Marco, Elias, David, Lu, Li, Morgan, David J, Freakley, Simon J, Johnston, Peter, Kiely, Christopher J, Hutchings, Graham J
• Format: Article
• Language: English
• Subjects: Acetylene; Activation; Catalysts; Cations; Chloroauric acid; Gold; Hydrochlorination; Monomers
• ISSN: 2044-4753; 2044-4761
• DOI: 10.1039/c6cy00090h

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. The active site for a Au/C catalysts for acetylene hydrochlorination involves a Au + -Au 3+ couple.