Synthesis and Characterization of the Microporosity of Ion-Exchanged Al2O3-Pillared Clays

Abstract

We have studied the effects of postsynthesis ion exchange on the microporous properties of Al2O3-pillared clays. These changes were effected by incorporating differently-sized charge-compensating cations from the alkali and alkaline earth series into the pillared clay by standard ion-exchange techniques. The resulting materials were characterized with respect to their surface area, interlayer spacing, and micropore size distribution. The micropore size distributions were determined from their N2 adsorption isotherms at 77 K using the slit-pore model of the Horvath−Kawazoe equation (and applying the Cheng−Yang correction). The results showed a bimodal micropore size distribution for the unaltered pillared clay and for all of the ion-exchanged pillared clays. In every case, the micropore volume for those pores in the lower distribution (<0.45 nm) increased with increasing ionic radius of the charge-compensating cations used in the ion exchange. In each case, the micropore volume for those pores in the upper...