Effect of thermal treatment on microporous accessibility in aluminium pillared clays

Abstract

The effect of thermal treatment on the microporous accessibility of an aluminium pillared clay has been investigated. When the calcination temperature was increased up to 673 K, the specific total (or micropore) surface areas increased, but a further increase in the calcination temperature produced a decrease in the specific surface areas. Similar behaviour was observed for the specific pore volumes. Nitrogen adsorption data obtained from very low relative pressures was used to obtain a thorough characterisation of the microporosity of the solids. The Dubinin–Radushkevich formalism was used to describe the volume filling of micropores and the energetic heterogeneity of microporous solids. The adsorption potential distributions and the Horvath–Kawazoe model confirmed the existence of two sizes of micropores. The thermal treatment determined the microporous properties of the aluminium pillared clay. The results obtained were related to the dehydroxylation of the pillar up to 673 K and with the sintering of the pillars and the dehydroxylation of the clay sheet surface, for higher temperatures.