On the structural changes of a saponite intercalated with various polycations upon thermal treatments Original Research Article

A comparative study of the evolution of the structures of Al-, Cr-, Al/Cr-, Zr-, and Ti-intercalated saponites when heated under oxidant or inert atmospheres to give the final pillared solids is presented. The study has been carried out mainly employing DTA–TGA–DTGA, X-ray diffraction and nitrogen adsorption techniques. Significant differences are observed between the thermal behavior of the precursors depending both on the nature of the metallic intercalating oligomers and on the thermal treatment atmosphere. Textural analyzes from nitrogen adsorption data at 77 K are also considered. These results indicate that all the intercalated clays show important modifications of their structural characteristics on heating at 300 or 500°C, a fact which has been related to the pillar distribution and to the presence of organic moieties in some of the intercalating species. This behavior has to be taken into account in order to establish reliably the catalytic applications of these materials.