Modifications of the metal and support during the deactivation and regeneration of Au/C catalysts for the hydrochlorination of acetylene

The effect of gold oxidation state and carbon structure on the activity of Au/C catalyst for the hydrochlorination of acetylene was investigated by a combined approach using TPR, XPS and porosimetry determinations. The activity of the catalyst in the synthesis of vinyl chloride monomer was found to be dependent from the presence of Au 3+ species into the catalyst. However, by preparing catalysts with different Au 3+ content it was possible to determine the existence of a threshold Au 3+ amount, beyond which the excess of Au 3+ was not active for the reaction. This was explained by the existence of active sites at the Au/C interface, and not just by the presence of Au 3+ species on top of Au nanoparticles, as explained by current models for these catalysts. It was also possible to determine the existence of subset of Au nanoclusters which are not taking part to the reaction, as well as changes in the textural properties of the carbon that can affects its long term reusability.