Liquid-Phase Hydrogenation of Internal and Terminal Alkynes on Pd-Ag/Al2O3 Catalyst

The structure and catalytic properties of a bimetallic Pd-Ag/alpha-Al2O3 catalyst are studied in the liquid-phase hydrogenation of substituted internal and terminal alkynes using diphenylacetylene, phenylacetylene, 1-phenyl-1-propyne, and 1-phenyl-1-butyne as sample alkynes. IR spectroscopy of adsorbed CO, X-ray diffraction (XRD), and electron microscopy were used to show that the active sites on the Pd-Ag nanoparticle surface are Pd-1 sites. The synthesized Pd-Ag/alpha-Al2O3 catalyst shows a much higher selectivity in the hydrogenation of internal symmetric and asymmetric alkynes compared to the monometallic Pd/alpha-Al2O3 sample. Also, it was found in the hydrogenation of diphenylacetylene and 1-phenyl-1-propyne on Pd-Ag/alpha-Al2O3 that the rate of the stage of desired olefin hydrogenation substantially decreases, which favors the kinetic control of the process.