Highly efficient PdAg catalyst using a reducible Mg-Ti mixed oxide for selective hydrogenation of acetylene: Role of acidic and basic sites.

A series of reducible Mg-Ti mixed oxides supported PdAg catalysts with tunable acidity/basicity were synthesized for selective acetylene hydrogenation, to investigate the implications of acid-base property on the nature of active component. Catalytic performance of PdAg/Mg x Ti 1− x O y varied with Mg/Ti ratio increasing as volcano curve, which corresponded well with amount of medium acid and weak basic sites. PdAg/Mg 0.5 Ti 0.5 O y exhibited >99% conversion and 83.8% selectivity at 70 °C. Enhanced activity was attributed to the promoted hydrogen-spillover effect by moderate acidic sites of Mg 0.5 Ti 0.5 O y support, which facilitated hydrogen activation/dissociation. Preferred selectivity was reasonably owing to the significant geometric effect resulting from high alloying degree of Pd-Ag, which increased the number of Pd linearly coordinated sites, and therefore facilitated the desorption of ethene. Additionally, the increased Pd electronic density caused by the electron transfer from the basic sites and Ti 3+ species of Mg 0.5 Ti 0.5 O y support also contributed to the improvement of selectivity. [ABSTRACT FROM AUTHOR]