Selective Phenylacetylene Hydrogenation on a Polymer-Supported Palladium Catalyst Monitored by FTIR Spectroscopy

The progress of phenylacetylene hydrogenation (at room temperature) on palladium nanoparticles supported on the porous polymer poly(4-ethylstyrene-co-divinylbenzene) is monitored by in situ FTIR spectroscopy. Results clearly show that, when the hydrogen excess is not too large, very close to 100% selectivity for C C triple bond hydrogenation, converting phenylacetylene to styrene, can be attained. Nevertheless, this selectivity declines when the ratio of hydrogen to phenylacetylene is greatly increased. The reproducibility of the results is tested by repeated catalytic runs, which also indicates that the catalytically active sites are not significantly altered during the phenylacetylene to styrene hydrogenation process. These studies are made possible by the chosen polymer support, which combines a high surface area and an organic nature and favors condensation of reactants and reaction products, so that the reaction occurs in a liquid-like phase. Moreover, the high transparency of the polymer in the infrared region facilitates monitoring of the relevant IR absorption bands