Development of Au/C catalysts by the microwave-assisted method for the selective hydrochlorination of acetylene

Abstract

The comparison of microwave-assisted catalyst preparation techniques with conventional impregnation (CI sample) and the effect of drying condition for Au/C catalysts have been studied using XPS, XRD, and STEM methods. The catalytic activity for vinyl chloride monomer (VCM) production via acetylene hydrochlorination is the highest for catalysts using optimal conditions of microwave drying. Drying times affect both initial and pseudo-steady state activities; microwave drying for 0.5 min gave an optimum balance of residual surface Au3+ species and the smallest Au particle sizes. For all catalysts, the selectivity to VCM was >99.5 %, with 1,2-dichloroethane being the only by-product. Acetylene conversions for MW_S (0.5 min) and MW_L (2.0 min) samples are greater than that of the CI sample. The initial activity (0–2 h) for acetylene conversion was the highest for the CI sample and is related to the amount of Au3+ on the surface (XPS results) in the following order: CI > MW_S > MW_L. The amount of Au3+ on the surface catalyst affects only the initial activity whilst the pseudo-steady state conversions are promoted by the higher concentrations of active gold species obtained for the smaller Au particles, and follows the trend MW_S > MW_L > CI. The reasons for catalytic deactivations of this reaction appear to be linked to both the reduction of active Au sites to Au0 and the subsequent gold aggregation.