Effects of preadsorption of organic amine on Al-PILCs structures

Abstract

Al-pillared clays were prepared by a reaction of Na-ghassoulite (Na-Gh) with base-hydrolyzed solutions of Al 3+ salts and a subsequent thermal conversion of the intercalated polycations. These pillared clays have relatively low micropore volumes. By preadsorption of amines between the clay layers prior to pillaring with aluminium precursor, it was possible to increase the microporosity of the obtained material. This improvement can be explained by the decrease of the Al-pillars density between the clay sheets. This explanation was proved by the decrease of the aluminium amounts in the treated samples determined by chemical analyses. The amount of amine was successively 1/4, 1/2 and 3/4 of the cation exchange capacity of the clay mineral. As a result, the pillar density decreases because a part of the interlayer space is occupied by the amine and during the calcination, the pillaring precursors are converted into rigid aluminum oxide pillars and the organic compounds are removed reflecting an improvement in the orientation of the clay layers. The surface area of this product increase to reach 624 m 2 g −1 and the micropore volume becomes three times higher than that prepared without preadsorption of diethylamine.