To simultaneously achieve thorough purification of acetylene and maximum ethene increment, a sea urchinlike trimetallic PdAuAg mesocrystal catalyst as targeting sample and cuboctahedral trimetallic PdAuAg 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 H-2:C2H2 of 2:1. Further improving H-2:C2H2 to 3, 76.5% yield can be maintained at 140 degrees 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 (111)/(100) facets ratio and the formation of a Pd-C phase. (C) 2016 Elsevier Inc. All rights reserved.