Au/C catalysts are effective materials for the gas phase hydrochlorination of acetylene to vinyl chloride monomer, and to date, the most effective catalyst preparation protocol make use of impregnation using aqua regia. In the present study, the effect of this solvent is evaluated and discussed in detail by modifying the ratio of HCl and HNO 3 and the temperature of the impregnation step. These factors are observed to affect the Au 3+ /Au 0 ratio of the final catalyst, in addition to the modification of the functional groups of the carbon used as support. The results can be rationalized by the oxidation effect of HNO 3 on both the gold nanoparticles and the functional groups on the carbon surface, as well as a nucleation effect of HCl towards gold over the carbon support. Kinetic parameters for the reduction of Au 3+ to Au 0 were also determined and these support the existence of a redox cycle between Au 3+ /Au 0 that could explain the overall catalytic activity.

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The effect of the gold oxidation state and carbon structure on the activity of Au/C catalysts 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 on the presence of Au 3+ species in 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 a subset of Au nanoclusters which do not take part in the reaction, as well as changes in the textural properties of the carbon that can affect its long term reusability.

Exposure of MTA, BA and ERRM to PBS resulted in precipitation of apatite crystalline structures that increased over time. This suggests that the tested materials are bioactive.

The oxidation of methane, the main component of natural gas, to selectively form oxygenated chemical feedstocks using molecular oxygen has been a long-standing grand challenge in catalysis. Here, using gold nanoparticles supported on the zeolite ZSM-5 we introduce a method to oxidise methane to methanol and acetic acid in water at temperatures between 120-240 °C using molecular oxygen in the absence of any added co-reductant. Electron microscopy reveals that the catalyst does not contain gold atoms or clusters, but rather gold nanoparticles are the active component while a mechanism involving surface adsorbed species is proposed in which methanol and acetic acid are formed via parallel pathways.

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