Synthesis of silica-supported palladium nanocatalysts for selective phenylacetylene hydrogenation

摘要

Silica-supported palladium materials containing 4.0 and 9.1 wt % Pd have been synthesized. It has been demonstrated by electron microscopy that these materials are nanosized systems, with a Pd particle size of 1.70 0.72 and 1.30 0.64 nm, respectively. The effects of Pd content and precursor (palladium(II) acetate) reduction conditions on the catalytic properties of Pd/SiO_2 in the selective hydrogenation of phenylacetylene into styrene at 25C have been investigated. Increasing the palladium content from 4.0 to 9.1% and raising the reduction temperature from 50 to 120C do not cause any significant coarsening of the Pd particles and, accordingly, exert only a weak effect on the rate and selectivity of phenylacetylene hydrogenation. The nanosized Pd/SiO_2 systems have been demonstrated to be efficient catalysts for phenylacetylene hydrogenation, an industrially important process. They afford a high styrene selectivity of 96.75 and 90.3% at conversions of about 50 and 100%, respectively, which is well above the maximum selectivity that was earlier attained in alkyne hydrogenation (at most 75% at ~100% conversion).