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 clays were monitored as a function of temperature, and it was found that the beidellites were usually more thermally stable than the corresponding pillared montmorillonites. Al-27 MAS NMR spectra were obtained in an effort to understand the structural changes taking place in the pillars and in the clay layers upon calcination; the signal from tetrahedral 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.