Thermal stability of hydroxy groups in dealuminated mordenites

Abstract

Results obtained by proton magnetic resonance and derivatographic measurements permitted the following conclusions regarding the thermal stability of OH groups in the framework of dealuminated mordenites: 1. (1) after vacuum pretreatment at room temperature, the adsorbed water molecules are removed. OH groups exist either in completely filled OH nests at the sites of aluminium vacancies, or as structural and terminal OH groups; 2. (2) the thermal stability of the OH nests is low, for after pretreatment at about 500 K, such nests could be detected neither with n.m.r., nor with derivatographic methods.