Competitive hydrogenation in binary diene systems on a palladium catalyst  

Summary

Hydrogenations of individual C₅ dienic substrates (1,3-cyclopentadiene, isoprene, 1,4-pentadiene, cis-1,3-pentadiene, trans-1,3-pentadiene) and their binary mixtures on a heterogeneous palladium catalyst were studied in cyclohexane at 25°C and 2 MPa. Selectivities of the competitive hydrogenations were determined and the substrates relative adsorption coefficients calculated. Effects of the diene structure on their reactivity and the stability of the surface complex are discussed. It was found that differences in selectivity of the competitive hydrogenations of C₅ dienes are caused by the difference both in adsorptivity values and in reactivity of adsorbed molecules. The presence of a five-membered ring in the C₅ dienes leads, , in significant reduction of surface complex stability as compared with acyclic structures of C₅ dienes. On the other hand, it has a very positive effect on the rate of surface reaction.