Selective hydrogenation of phenylacetylene on Ni and Ni-Pd catalysts modified with heteropoly compounds of the Keggin type

It is established that unmodified Ni catalysts and Ni catalysts modified with Mo- and W-heteropoly compounds (HPC) of the Keggin type (6 wt %) along with catalyst containing 6% K 4 SiW 12 O 40 /Al 2 O 3 appear to be active in the reaction of phenylacetylene (PA) hydrogenation. At low temperatures (100–150°C), the selectivity of the process strongly depends on the nature of the modifier or second active metal (Pd). It is demonstrated that in the presence of 6% Ni-0.015% Pd/Al 2 O 3 modified by HPC K 4 SiMo 6 W 6 O 40 , the conversion of PA at 100°C was 87% at a styrene: ethylbenzene ratio of 1: 1. The acidity of HPC is found to influence the side reactions of alkylation and condensation. Transmission electron microscopy demonstrates that Ni in modified HPC 6% Ni/Al 2 O 3 is present in the form of the particles below 2 nm in size, and these particles of Ni become larger when affected by the reaction medium during PA hydrogenation.