THE LIQUID-PHASE HYDROGENATION OF PHENYL ACETYLENE AND STYRENE ON A PALLADIUM CARBON CATALYST/

The hydrogenation of phenyl acetylene and styrene have been studied ov er a palladium/carbon catalyst. The kinetics of the reactions were inv estigated and activation energies of 26 +/- 2 kJ mol(-1) and 41 +/- 8 kJ mol(-1) were obtained for phenyl acetylene hydrogenation and styren e hydrogenation, respectively. Both reactions were found to be zero or der concerning the alkyne or alkene. However the order in phenyl acety lene changed from zero order to first order at approximately 60% conve rsion. This change was due to the effect of styrene co-adsorption and not the concentration of phenyl acetylene. Competitive hydrogenation b etween the alkene and alkyne resulted in a dramatically reduced rate o f hydrogenation for both species. This reduced rate was explained by a reduction in the amount of surface hydrogen as well as the altered bo nding of the phenyl acetylene.