Adsorption of benzene and cyclohexane on γ-Al2O3 and Pd/γ-Al2O3 at elevated temperature and pressure

Adsorption of benzene and cyclohexane on catalyst supports gamma-Al2O3 and catalyst pellets Pd/gamma-Al2O3 was studied from 393 to 453 K over an adsorbate relative pressure range of 0.2-1.0. The corresponding adsorption isotherms, which were experimentally measured in the range of the relative pressure p/p(0) larger than 0.2, were considered to be type IV, and can be simulated by a simple adsorption model. The adsorption isotherm of benzene was similar to that of cyclohexane. Compared with the adsorption isotherm of benzene on gamma-Al2O3, a similar one was obtained on Pd/gamma Al2O3 except that the hysteresis loop appeared a little bit earlier. As far as adsorption of benzene on gamma-Al2O3 was concerned, only physisorption was involved. But when it came to Pd/gamma-Al2O3, both chemisorption and physisorption occurred, and the chemisorption process facilitated the formation of monolayer, multilayer and capillary condensation in spite of the lower metal loading of the catalyst. (C) 2007 Elsevier B.V. All rights reserved.