Rezumat
CZU 621.762
The aim of this work is to study the solids obtained by pillaring Tunisian bentonite with zirconium polycations from the hydrolysis of zirconium tetrachloride. For comparative purposes, the pillaring of Wyoming montmorillonite, a reference clay, is also studied. Variations in the dialysis number, concentration of Zr solution, pH, temperature in the synthesis procedure as well as the pillaring method, affect the structure and properties of the pillared clay obtained. It has been verified that the structure of the pillared clays strongly depends on the method of preparation and the pH Zr solution in some cases, well ordered pillared clays (with basal spacings between 15 and 18.2A) have been obtained, while in several others noncrystalline solids yielded. Delamination of the clays seems to take place both when the intercalation solutions obtained from zirconium tetrachloride have pH > 2.8 and when they are subjected to a reflux treatment. Best results were obtained at pH = 2.8 [Zr4+] = 0.1M, at room temperature, and when using five dialysis, the direct method. The specific total surface area and micropore volume of the solids have reached the values up to 200 m2 g-1 and 0.06 cm3 g-1, respectively. Potentiometric titration and mass titration data suggest that pillared materials produce a shift of the point zero charge toward the point zero charge of the zirconium oxide. The amount of ZrO2 fixed have varied between 6 and 30% of the weight of the pillared samples. The activity of the zirconium pillared clay for 1,3-dioxolane synthesis has been investigated. The method of intercalation has been found to be the most suitable for this reaction.
Keywords: Zr-oligomer; pillared clay; point of zero charge; 1,3-dioxolane; acetalization.