PROCESSES OF AMMONIA ADSORPTION IN GALLIUM ZEOLITES AS STUDIED BY MICROCALORIMETRY

Tn adsorption calorimetric studies, it is necessary to analyse the obt ained calorimetric and volumetric data in relation to coverage or numb er of sites. For this purpose, procedures have been developed to relat e quantitative measurements of heat Liberation to the different proces ses which are taking place as the amount of adsorbed ammonia increases , due to reversible and irreversible adsorption. In order to describe the relative contributions of these two phenomena (physical and chemic al adsorption) to volumetric isotherms as well as to calorimetric ther mograms, they have been modeled and chemisorption was separated from p hysisorption. Calorimetric and volumetric measurements performed on H- [Ga]-BEA and H-[Ga]-MFI zeolites have provided experimental data to va lidate the theoretical models. The acidity of the gallium samples has been compared with that of the corresponding aluminum samples. (C) 199 8 Elsevier Science B.V.