Water adsorption in aluminium pillared clays and zeolites

Abstract

Adsorption of water at 298 K has been studied in aluminium pillared clays (PILCs) and in zeolite types A, Y and ZSM-20, and kinetic and equilibrium results obtained. PILCs were prepared by two methods, which differ only in the OH/Al ratio of the oligomer solution, and by using three different parent clay materials. These methods led to PILCs that, when calcined at 623 K, present BET areas ranging from 250 to 350 m ² g ^-1 and basal spacings from 1.6 to 1.8 nm. For Y and ZSM-20 zeolites, the sodium and protonated forms were studied. The equilibrium results were compared with literature data corresponding to an ideal isotherm for use in dehumidification and discussed in terms of textural and chemical properties, namely the Si/Al ratio of zeolites and PILCs. For these latter materials an effect of the parent clay on water adsorption was studied, which seems to be related to the degree of substitution in the tetrahedral sheets.