Desiccant materials for use in gas fired cooling and dehumidification

Abstract

The present invention provides for a process of reducing the polarity on the internal surfaces of various zeolites having a SiO.sub.2 to Al.sub.2 O.sub.3 ratio of at least about 3 and an average pore diameter size within the range of from about 4 to about 10 angstroms. The modified zeolites in accordance with the present invention are prepared by heating the starting zeolite in an aqueous medium also containing an acid or a source of ammonium ions to at least partially dealuminize the zeolite and thereby increase the ratio of silicon to aluminum present in the tetrahedral structure. At the same time, the process provides for hydrogen ion exchange with respect to those zeolites which contain significant amounts of metallic cation in the structure thereby replacing the bulky metallic cations with less bulky hydrogen ions and thereby increasing the water adsorptive capacity of the zeolite. Achievement of the appropriate equilibrium between reduced surface polarity on the one hand and increased sorptive capacity of the zeolite on the other hand gives rise to zeolite materials having an isotherm with a separation factor within the range of from about 0.07 to about 0.1 which renders the modified zeolite an ideal desiccant for gas fired air conditioning and dehumidification equipment.