Al-hydroxy intercalated clays (ALHICs) obtained from different parent clays were used to investigate the interactions between oligomers and clay surface layers.

The thermal stability of ALHICs obtained from natural, Cs-, Ca-, Ba-, Fe-, Cu- or Ce-montmorillonites has been investigated by studying the relationship between basal spacing and calcination temperature. X-ray diffraction has shown that the basal spacing of ALHICs obtained from Cu-montmorillonite calcined at 550°C is 13.4 Å, different from basal spacings of ALHICs obtained from Fe-montmorillonite (16.0 Å) and other parent clays (16.7 Å). Thermograms for AlHICs obtained from natural, Fe- and Ce-montmorillonites displayed distinct steps at 225 and 650°C, attributed to the dehydration of Al13 oligomers, and the dehydroxylation of the surface layer, respectively. By contrast, thermograms of ALHICs obtained from Cu-montmorillonite displayed one step between 250 and 700°C for both dehydration and dehydroxylation. Mössbauer parameters showed that Fe3+ octahedra in octahedral sheets are distorted in pillared interlayered clay (PILC) obtained from Cu-montmorillonite and undistorted in that obtained from Fe-montmorillonite. The difference in thermal stability for the various ALHICs is attributed to the retention of some of the original cations after intercalation with Al13 oligomers, which induces several interactions between the oligomers and the clay surface layers.

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.