AL-PILLARED MONTMORILLONITE OBTAINED IN CONCENTRATED MEDIA. EFFECT OF THE ANIONS (NITRATE, SULFATE AND CHLORIDE) ASSOCIATED WITH THE AL SPECIES

Abstract

Basic Al chloride, sulfate and nitrate were prepared by hydrolysis of Al chloride followed by precipitation with a Na sulfate solution, then re-dissolution in a Ba nitrate solution. The three laboratory-synthesized oligomers and solid, commercial chlorhydrol were characterized by X-ray diffraction, 27Al nuclear magnetic resonance and scanning electron microscopy coupled with energy dispersion spectroscopy analysis. The results showed that basic Al chloride contained unknown crystalline Keggin species. In commercial chlorhydrol, Al13 species were present in small amounts aside from the monomeric species. Basic Al nitrate or sulfate contained exclusively Al13 species. Pillaring a raw montmorillonite with different Al complexes in very concentrated media using both the clay and the oligomer in the solid state led to different pillared structures. Characterization by transmission electron microscopy, nitrogen adsorption, and thermogravimetric analysis of the materials obtained shows that pillaring with sulfate or chloride oligomers gave very heterogeneous pillared clays. Although basic Al nitrate and commercial chlorhydrol give better ordered and well organized pillared clays, the stacking obtained with chlorhydrol is greater.