Sorption studies on dealuminated and decationated zeolites

Abstract

The sorption properties of a series of dealuminated and decationated zeolites prepared from Y-type zeolites in the sodium and ammonium forms have been studied as a function of cation concentration and silica : alumina ratio. As the aluminium content in the zeolite decreases, the sorption capacity increases due to an increase in the void volume. The volume modification is further substantiated by the higher sorption rates and equilibrium sorption capacities for benzene, cyclohexane, mesitylene (1,3,5-trimethylbenzene) and alcohol as compared with the sorption of water vapour on all the dealuminated zeolites studied. From the adsorption isotherms of cyclohexane and benzene on modified zeolites, isosteric heats of adsorption at various surface coverages were determined. The amount of adsorption and heat of adsorption of benzene on all zeolites are greater than the corresponding values for cyclohexane because of the specific interaction of the π bonds of benzene with the cations of the zeolites. The variation in the partial molar entropy elucidates the state of the adsorbed molecules.