The effect of benzonitrile on the hydrogenation of phenylacetylene and 1-phenyl-1-propyne over a palladium/carbon catalyst

Characterization of Activated Carbon Using X-ray Photoelectron Spectroscopy and Inelastic Neutron Scattering Spectroscopy

“…An additional point that arises from these adsorption studies is that when carbons such as the Sutcliffe DCL 230 are used as catalyst support materials and applied to liquid-phase hydrogenation reactions involving substituted aromatic molecules, , then one needs to be aware that substantial amounts of reagents can be retained by the carbon. Moreover, as a consequence of the number and distribution of adsorption sites present on these carbons, one reagent could be preferentially adsorbed which could affect the supply of reagents to the active site (the metal) and possibly affect selectivity profiles.…”

“…Previous work by Jackson et al has examined alkyne and alkene hydrogenation in the liquid phase using carbon-supported palladium catalysts. 12,13 Addition of modifiers such as benzonitrile was found to have a marked effect on the activity/selectivity characteristics of the systems studied. For example, in the hydrogenation of phenylacetylene, the addition of benzonitrile shifted the main hydrogenated product from being styrene in the absence of the modifier to ethylbenzene when the benzonitrile was present.…”

“…For example, in the hydrogenation of phenylacetylene, the addition of benzonitrile shifted the main hydrogenated product from being styrene in the absence of the modifier to ethylbenzene when the benzonitrile was present. 12 observation was rationalized in terms of the benzonitrile acting as an efficient hydrogen transfer agent that opened up an additional hydrogenation pathway to that already available on the metal. 12 These studies by Jackson et al demonstrate how modifiers can be successfully used to affect rates and product distributions in metal-catalyzed reactions.…”

“…12 observation was rationalized in terms of the benzonitrile acting as an efficient hydrogen transfer agent that opened up an additional hydrogenation pathway to that already available on the metal. 12 These studies by Jackson et al demonstrate how modifiers can be successfully used to affect rates and product distributions in metal-catalyzed reactions. However, we note that the carbons selected for use in such liquid phase hydrogenations tend to have large surface areas (ca.…”

C-5 alkene hydrogenation: Effect of competitive reactions on activity and selectivity

“…A number of recent studies have investigated competitive hydrogenation reactions, such as phenyl acetylene and styrene on Pd/C [5], benzonitrile on higher alkynes [6], 1-pentyne and 2-pentyne [7,8] and competitive reactions of C6 and C8 species over palladium and platinum catalysts [9]. Various effects have been demonstrated in these studies, from rate depression of one or more of the competing reactants, to a rate enhancement of both reacting species.…”