ADSORPTION OF METHANOL, AMMONIA AND WATER ON THE ZEOLITE-LIKE ALUMINOPHOSPHATES ALPO4-5, ALPO4-17, AND ALPO4-18

The heats of CH3OH and NH3 adsorption on zeolite-like aluminophosphate s AlPO4-5, AlPO4-17, and AlPO4-18 were measured calorimetrically. The isotherms of adsorption of CH3OH and H2O at different temperatures wer e determined for the same materials, The energetics of adsorption of p olar molecules shows that the electrostatic properties of zeolite-like AlPO4 are intermediate between those of zeolites and those of zeolite -like SiO2 modifications, The minima on the heat curves are observed a t coverages of about 0.5-1.0 mmol/g. The behavior of heats beyond the minima is explained in terms of complexation of Al atoms with adsorbed molecules and by interactions between them, Two types of adsorption i sotherms are found for AlPO4. The presence of vertical parts on the is otherms which are shifted to high pressures with increasing temperatur es corresponds to the formation of adsorption complexes with Al atoms. (C) 1996 Academic Press, Inc.