Synthesis of pillared clays assisted by microwaves

Microwave (MW) irradiation was used to synthesize aluminum-pillared clays ( MW-Al-PILCs) by replacing the conventional calcination of Al-PILCs pre curs ors (pre-Al-PILCs). X-ray diffraction (XRD) patterns acid nitrogen adsorpti on/desorption isotherms showed that the MW-irradiated pre-Al-PILCs gave a s eries of MW-Al-PILC materials exhibiting some characteristics comparable to Al-PILCs obtained by conventional heating. However, differential thermal a nalysis (DTA), thermogravimetric analysis (TGA), impedance spectroscopy, Al -27 MAS NMRI and intercalative adsorption of methylene blue (MB), indicated that the MW-Al-PILC samples were intermediate between Al-pre-PILCs and con ventional Al-PILCs, The Al-27 MAS NMR spectra showed that in MW-Al-PILCs ob tained after 18 min of MW irradiation, the Al-IV/Al-VI ratio was 1/9, which is comparable to that in Al-pre-PILCs (8% Al-IV; 92% Al-VI) and significan tly different from the typical values of conventional Al-PILCs (23% Al-IV; 77% Al-VI). It is assumed that the MW-induced calcination gives PILCs conta ining a fraction of residual, hydroxylated Al-polycations. The good thermal stability of the MW-Al-PILCs supports their possible use as acid catalysts , (C) 1999 Elsevier Science Ltd.