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The pillaring of smectites (two saponites and a montmorillonite) with various Ti precursors was studied. The minerals were intercalated with ‘classical ’ Ti precursors, such as titanium tetrachloride and titanium tetraethoxide, and also with new precursors, such as solutions of titanium tetraisopropoxide in acetic acid, or titanium (bis (ethylacetoacetato) diisopropoxide) in acetone. A complete characterization of the intercalated solids was carried out and a comparison of the properties of the solids as a function of the precursors used in the intercalation established. The influence of the severe conditions in which the intercalation with Ti oligomers is usually carried out (low pH and/or high temperature) on the properties of the intercalated solids was analysed. Intercalation with TiCl4 and Ti(EtO)4 strongly affected the structure of the clays, not by acid attack on the octahedral sheet, but mainly by disaggregation of particles. Ti(isop)4 was found to be less aggressive for the clays, while Ti(etacet)2(isop)2 did not form pillared solids but organo-clays, and therefore was of no use as a pillaring agent. The solids were thermally stable up to 300°C, showing a high specific surface area.

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Saponite, a magnesic trioctahedral smectite, from Yunclillos (Toledo, Spain) was intercalated and pillared with aluminum-chromium solutions. Seven intercalating solutions, containing different Al 3+ /Cr 3+ ratios and partially hydrolyzed with OHsolutions, were used. Al 3+ always polymerizes to form [Al 13 O 4 (OH) 24 (H 2 O) 12 ] 7+ polycation, while Cr 3+ forms the trimer [Cr 3 (OH) 4 (H 2 O) 9 ] 5+ , the dimer [Cr 2 (OH) 2 (H 2 O) 8 ] 4+ , or does not polymerize, depending on the Al 3+ /Cr 3+ ratio in the solution considered. When chromium oligomers were used as the intercalating polycations, the pillared solid obtained had a basal spacing of 19 Å and was not thermally stable at temperatures higher than 200 °C. When aluminum Al 13 oligomer was used, pillared compounds with a basal spacing of 18 Å and thermal stability up to 600 °C were obtained. The addition of aluminum to the chromium intercalating solutions improved the thermal stability of chromium pillared solids.