Supported catalysts based on Pd-In nanoparticles for the liquid- phase hydrogenation of terminal and internal alkynes: 2. catalytic properties

Pd-In/Al2O3 and Pd-In/MgAl2O4 catalysts prepared from dinuclear Pd-In acetate complexes were studied in the hydrogenation of alkyne compounds with different structures. The Pd-In catalysts demonstrate high selectivity in the hydrogenation of internal alkynes comparable with that of the Lindlar catalyst. Similar activity/selectivity characteristics are reached at a significantly lower Pd content. For terminal alkynes, the favorable effect of Indium introduction is considerably less pronounced. An analysis of the In effect on the selectivity and the ratio between the rates of the first and second hydrogenation steps suggests that the reaction selectivity is determined to a large extent by a thermodynamic factor (adsorption-desorption equilibrium between the reactants and the reaction products).