Highly dispersed bimetallic Pd-In catalysts on Al2O3 were prepared by a simple impregnation method. In comparison with the unsupported intermetallic catalyst, the supported Pd-In catalyst exhibited several magnitudes higher activity and similar selectivity for selective acetylene hydrogenation. Moreover, the activity, selectivity, and anticoking performance of the Pd-In catalyst were superior to those of the monometallic Pd catalyst. The electron transferred from indium weakened the adsorption of ethylene on the negatively charged Pd sites and hence improved the selectivity of Pd-In/Al2O3. The inhibited formation of hydride due to the presence of indium also contributed to the higher selectivity. The promoted activation of hydrogen, owing to the weak adsorption of acetylene on Pd-In/Al2O3, and decreased particle size jointly contributed to the enhanced activity of Pd-In/Al2O3. In addition, green oil formation on Pd-In/Al2O3 was retarded by the presence of indium, contributing to the enhanced stability of the catalyst. The bimetallic Pd-In catalysts showed a strongly composition dependent performance, which resulted from the different extent of electronic and/or geometric modification of Pd active sites.

acetylene hydrogenation; Pd; Al2O3; hydride; indium; green oil

East China University of Science and Technology