Characterization by Physisorption of a New Class of Microporous Adsorbents: Pillared Clays

In this study, adsorption data were used for characterizing the microporosity of five pillared clays pillared by oxides of Zr, Al, Cr, Fe, and Ti), a new class of adsorbents for gas separation. The results show that these pillared clays (PILCs) are highly microporous and possess pores of width no greater than 2 nm. A theoretical approach for calculating the micropore size distribution of pillared clays is outlined, and the calculated micropore size distributions are compared with the results obtained from probe molecule sorption data. A close agreement between the calculated micropore size distribution with those obtained from molecular probing was found, indicating that the theoretical approach is sound. It was found that, in all PILCs, the pore sizes were limited by the interpillar spacing, not by the interlayer spacing obtained by X-ray diffraction. In addition, these materials were further characterized using thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), and inductively coupled argon plasma atomic emission spectroscopy (ICAP-AES).