Semihydrogenation of Phenylacetylene Catalyzed by Palladium Nanoparticles Supported on Carbon Materials

Palladium catalysts were prepared supporting palladium colloids on three types of carbon supports: multiwall carbon nanotubes (NTs), carbon black (CB), and an activated carbon (AC). These catalysts were tested in a reaction of great industrial interest such as the partial hydrogenation of phenylacetylene. The liquid-phase hydrogenation reaction of phenylacetylene was performed under very mild conditions (323 K, flow of H2 of 30 mL/min, 1 bar of pressure). The catalytic activities are very close to that of the homogeneous catalyst. A total conversion was achieved in all the Pd/C catalysts and also with very high selectivity toward styrene (higher than 95%). The carbon support produces differences between the catalysts. The AC provokes a Pd particle agglomeration, and the catalyst has the lowest activity and selectivity. The highest selectivity is obtained for the Pd/NT sample. The ease of manipulation of the Pd/NT catalysts is noteworthy, facilitating its recovery by filtration and its subsequent reutilization. It was found that neither the catalytic activity nor the selectivity decreased appreciably throughout five consecutive cycles of the Pd/NT sample. Furthermore, no Pd leaching of the samples occurred during the catalytic reactions.