Dependence of concentration of montmorillonite and boehmite sol on the properties of Al-PILC

Abstract

Al-pillared montmorillonite has been prepared by the intercalation of boehmite (A1OOH) sol by a novel method involving refluxing the montmorillonite-boehmite mixtures. Al/g montmorillonite ratio in the range 0.25 to 20 has been used for the preparation of a variety of pillared compounds. Results indicate that a minimum amount of A1 is required (> 5 m mol Al/g montmorillonite) for obtaining thermally stable pillared montmorillonite. Specific surface area values in the range of 212-180 m 2/g and basal spacing 20.6–16.4 Å after calcination of the intercalated species at 700°C over a period of 4 h was obtained in the various experiments. The possibility of obtaining desired pillar population with different Al/montmorillonite ratio is also highlighted. Further, changing the concentration of montmorillonite suspension in the range 1–40 wt% in the intercalation reactions while keeping the intercalant concentration constant, it was possible to obtain a range of properties with respect to the surface area and thermal stability. The reflux method of intercalation adopted in the present work could achieved specific surface area as high as 146 m 2/g at 700°C in the reaction containing a concentrated suspension of montmorillonite as high as 40 wt%. Samples were characterised by X-ray diffraction, N 2 adsorption BET method and chemical analysis. These results are novel since the earlier studies on intercalation have shown very low solid content in the precursor mixtures. The combined effect of delamination of montmorillonite and intercalation at the interlayers are expected to contribute better properties in reflux method.