Gold nanoclusters supported on different materials as catalysts for the selective alkyne semihydrogenation

Catalysts based on gold nanoclusters supported by different materials have been used for the selective semihydrogenation of phenylacetylene to styrene. The most active species were formed by catalyst thermal activation in a reductive atmosphere. It is shown that the activity and selectivity of these catalysts is mainly controlled by the interaction of the gold nanoclusters with the support, as demonstrated by using materials with high surface area and different acidity/basicity, i.e. MgO, AlO and Mg/Al hydrotalcite. There is an important influence of the acid/base properties of the support on the selectivity. Higher activity is obtained for gold supported on basic materials (MgO and hydrotalcite) and the best results are obtained with the Au catalyst supported on the MgAl hydrotalcite exhibiting high activity and the best selectivity to the alkene. This was explained by the intermediate basicity of the support that favors the heterolytic cleavage of H while avoiding the overreduction of the alkynes to alkanes.