Highly Active Bimetallic Single-Atom Alloy PdAg Catalysts on Cerium-Containing Supports in the Hydrogenation of Alkynes to Alkenes

Abstract

A study of a series of single-atom-alloy catalysts Pd1Ag3/Al2O3, Pd1Ag3/CeO2–Al2O3, and Pd1Ag3/CeO2–ZrO2 in the selective hydrogenation of diphenylacetylene (DPA) showed a significant (five-fold) increase in activity for the PdAg3/CeO2–ZrO2 sample in comparison with that of Pd1Ag3/Al2O3. It was especially noted that the increase in activity was not accompanied by a decrease in the selectivity for the target product. This catalytic behavior can be explained by two factors: (1) a more than twofold increase in the dispersity of the PdAg3/CeO2–ZrO2 catalyst and (2) a change in the electronic state of the nanoparticles, as determined from the results of an IR-spectroscopic study of adsorbed CO. The retention of the high selectivity of the synthesized catalysts indicated the stability of the structure of Pd1 monoatomic sites in the catalysts prepared by deposition on Ce-containing supports, which was also confirmed by the IR spectroscopy of adsorbed CO. The experimental results indicate that Ce-containing supports are promising for the synthesis of catalysts for the selective hydrogenation of substituted alkynes.

Unraveling Hydrogenation Kinetic Behavior of Transition Metal Oxides via Decoupling Dihydrogen Dissociation and Substrate Activation

“…The semihydrogenation of alkynes to alkenes is widely used in the industrial production of polymers and pharmaceutical intermediates. − Transition metal oxide (e.g., TiO 2 , CeO 2 , and ZrO 2 )-supported noble metals (e.g., Pd and Pt) are conventional catalysts applied in the semihydrogenation of alkynes, in which both noble metal sites and oxide support have been identified as active sites. Specifically, Pd and Pt species can efficiently activate hydrogen, but undesired overhydrogenation products are commonly attained because alkenes are not easily desorbed on the noble metal ensembles.…”