Preparation and structure-property relationships of supported trimetallic PdAuAg catalysts for the selective hydrogenation of acetylene

- Trimetallic PdAuAg catalysts with two different morphologies are prepared by a co-reduction method.
- Both of the trimetallic catalysts exhibit higher selectivity than mono- and bimetallic catalysts.
- Compared with the cuboctahedral catalyst, the mesocrystal catalyst exhibits higher activity and selectivity.
- Enhanced activity could be ascribed to the high concentration of defect sites.
- Increase of facet (1 1 1)/(1 0 0) ratio and Pd-C phase contribute to the improved selectivity.

To simultaneously achieve thorough purification of acetylene and maximum ethene increment, a sea urchinlike trimetallic PdAuAg mesocrystal catalyst as targeting sample and cuboctahedral trimetallic PdAuAgx and bimetallic catalyst as control samples were prepared by a co-reduction method, immobilized on MgAl hydrotalcite. Compared with bimetallic PdAu and PdAg catalysts, trimetallic PdAuAgx catalyst gave prior selectivity due to the positive synergetic effect. Significantly, PdAuAg2 mesocrystal catalyst exhibited a turnover frequency of 0.063 s−1, 46.5% higher than that of cuboctahedral PdAuAg2 catalyst. A 76.2% ethene selectivity was achieved for the thorough purification of acetylene over PdAuAg mesocrystal catalyst with H2:C2H2 of 2:1. Further improving H2:C2H2 to 3, 76.5% yield can be maintained at 140 °C. Enhanced activity of the mesocrystal catalyst could be attributed to a high concentration of defect sites and a low activation barrier. Improved ethene selectivity could be ascribed to the increase in the (1 1 1)/(1 0 0) facets ratio and the formation of a Pd-C phase.

122