Preparation of new silica sol-based pillared clays with high surface area and high thermal stability

A new microporous sol-pillared clay was prepared by the ion-exchange of the interlayer Na+ ions of montmorillonite with SiO2-Fe2O3 mixed oxide sol particles. The mixed oxide sol solution was prepared by titrating an Fe3+ aqueous solution with NaOH in the presence of silica sol particles. Upon pillaring with the iron-modified silica sol particles, the basal spacing of the clay was expanded to a value as large as 63 Angstrom and maintained at least up to 800 degrees C. More than 96% of the iron content was easily removed by acid washing, and the pillared clay was changed from brown to pale yellow in color, while the product retained the expanded basal spacing. On calcination at 400 degrees C, the SiO2-Fe2O3 mixed oxide pillared clay had an extremely large BET surface area of 720 m(2)/g. The acid-washed pillared clay had a larger surface area of 850 m(2)/g, and a considerable surface area of about 550 m(2)/g was retained even after calcination at 800 degrees C. Both pillared samples were characterized as microporous solids with weak acidic sites by an ammonia desorption measurement.