Adsorption of benzene and cyclohexane on (lambda)-Al2O3 and Pd/(lambda)-Al2O3 at elevated temperature and pressure

Adsorption of benzene and cyclohexane on catalyst supports (lambda)-Al2O3 and catalyst pellets Pd/(lambda)-Al2O3 was studied from 393 to 453K 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/p0 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 (lambda)-Al2O3, a similar one was obtained on Pd/(lambda)- Al2O3 except that the hysteresis loop appeared a little bit earlier. As far as adsorption of benzene on (lambda)-Al2O3 was concerned, only physisorption was involved. But when it came to Pd/(lambda)-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.