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

• Published in: Journal of catalysis 2017-04, Vol.348, p.135-145
• Main Authors: Liu, Yanan, Zhao, Jiaying, He, Yufei, Feng, Junting, Wu, Tian, Li, Dianqing
• Format: Article
• Language: English
• Subjects: Acid-base sites; Hydrogen spillover; Reducible Mg-Ti mixed oxide; Selective hydrogenation of acetylene
• ISSN: 0021-9517; 1090-2694
• DOI: 10.1016/j.jcat.2017.02.020

[Display omitted] •MgxTi1−xOy with tunable acidity/basicity is prepared as new supports for acetylene hydrogenation.•PdAg/Mg0.5Ti0.5Oy shows excellent performance with 83.8% selectivity at >99% conversion.•Moderate acidity promotes hydrogen-spillover effect, which favors hydrogen dissociation.•Negatively-charged Pd caused by basic sites and Ti3+ favors desorption of ethene.•High alloying degree of PdAg/Mg0.5Ti0.5Oy also contributes to the improved selectivity. 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/MgxTi1−xOy varied with Mg/Ti ratio increasing as volcano curve, which corresponded well with amount of medium acid and weak basic sites. PdAg/Mg0.5Ti0.5Oy 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 Mg0.5Ti0.5Oy 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 Ti3+ species of Mg0.5Ti0.5Oy support also contributed to the improvement of selectivity.