Characterization of the porous structure of an alumina-pillared clay by means of nitrogen adsorption and immersion calorimetry

The characterization of the porous structure developed by the pillaring of a natural clay of the smectite class, a montmorillonite, with aluminum polycations using a relatively concentrated clay suspension ( 10 wt.%) is presented. Nitrogen adsorption data at 77 K and immersion calorimetry experiments with benzene, cyclohexane, tetraisopropyl o-titanate, and tri-2,4-xylylphosphate at 293 K have been considered for this purpose. Both slit-like and cylindrical pore models have been applied to the nitrogen adsorption results ( p/p(0) <= 0.2) to characterize the micropore region of the alumina-pillared clay. From the measured enthalpies of immersion into the various liquids, the presence of very narrow micropores or constrictions at the entry of the micropores in the alumina-pillared clay is suggested.