CHARACTERIZATION OF SYNTHETIC MICROPOROUS PILLARED BEIDELLITES OF HIGH THERMAL-STABILITY

The clay mineral beidellite was synthesized and pillared, separately, with the three different tridecameric cations AlO4Al12(OH)(24)(H2O)(12 )(7+), GaO4Al12(OH)(24)(H2O)(12)(7+), and GaO4Ga12(OH)(24)(H2O)(12)(7). The basal spacings and surface areas of the resulting pillared clay s were monitored as a function of temperature, and it was found that t he beidellites were usually more thermally stable than the correspondi ng pillared montmorillonites. Al-27 MAS NMR spectra were obtained in a n effort to understand the structural changes taking place in the pill ars and in the clay layers upon calcination; the signal from tetrahedr al aluminum diminished considerably after calcination at 500 degrees C , The argon adsorption isotherms were measured, and the pillared clays were found to have a bimodal micropore size distribution, with maxima at 0.6 and 0.8 nm.