Particle size effect in liquid-phase hydrogenation of phenylacetylene over Pd catalysts: Experimental data and theoretical analysis

The liquid-phase hydrogenation of phenylacetylene (PA) over 1 wt% Pd/Al2O3 catalysts with the mean palladium cluster size varying from 1.5 to 22 nm was studied at 5 bar H2 pressure and 25 degrees C. Turnover frequency in hydrogenation of the triple and double bonds displayed a significant increase with an increase of the cluster size, which was more pronounced for the former case. The effect of Pd nanoparticle size on the hydrogenation kinetics was analyzed and discussed using an approach based on a continuous distribution of edges and terraces exhibiting different reactivity. A quantitative description of the concentration dependences with incorporation of Pd particle size in the rate equations demonstrated an excellent correspondence between theory and experiments.