Complementary approach to the volume filling theory of adsorption in zeolites

In the present paper are discussed some important features related with the standard theory of volume filling, i.e., definitions and terminology, adsorption energetic and the osmotic and Dubinin adsorption isotherm equations. Afterwards, is carried out an exposition of a complementary approach to the theory of adsorption in zeolites based in the theory of volume filling. In this analysis are included some remarks about the Thermodynamic theory of adsorption, a model description of the sorbent-sorbate interactions and the deduction of Langmuir and Fowler-Guggenheim type adsorption isotherm equations, describing adsorption in zeolites not as surface coverage but as volume filling. Finally, in order to test the proposed procedures for the evaluation of adsorption data, the following were experimentally studied: the calorimetry of adsorption of NH3 in a FAPO-5 molecular sieve, the adsorption of Ar and N-2 in Na-X, Na-Y, H-ZSM-5, and H-mordenite zeolites and NH3 in natural clinoptilolite, mordenite and erionite. The proposed methodology for the analysis of the experimental adsorption data allow the determination of the zeolite micropore volume, the different heats of adsorption and its relation with adsorption interactions and confer a physical meaning to the calculated parameters. (C) 2000 Elsevier Science B.V. All rights reserved.