Abstract
To clarify the adsorption amounts and adsorption sites of organic species during benzene hydrogenation, adsorption measurements of benzene and cyclohexane on Pd-Al2O3 catalysts were made at 108-175°C by using an electrobalance. It was found that reversible adsorption on the alumina support is predominant and the amount of adsorption on palladium atoms is negligibly small under a hydrogen atmosphere where hydrogenaton of benzene proceeds. On the other hand, there exist reversible adsorption on palladium atoms and irreversible adsorption in addition to reversible adsorption on the support under a hydrogen-free condition. Comparing these facts with the reaction rate data, the hydrogenation of benzene seems to occur between hydrogen adsorbed on the metal atoms and benzene adsorbed reversibly on the alumina support situated near the metal-support boundary.
