Abstract: Pillared synthetic dioctahedral clays (designated SMM) are prepared by introducing hydrox-yl Al oligomer and hydrolysis material of CH₃CH₂CH₂NH₂Si(OCH₂CH₃)₃ into SMM layers respectively. X-ray diffraction results show that the basal spacing of Si pillared SMM is larger than that of Al pillared SMM slightly. The Si and Al pillar's length are 0. 86 and 0. 83 nm respectively. According to the value of Si-O bond length, the Si pillar may be the tripolymer of silica.In the studies of DTA, IR, it is found that the dehydroxylation of octahedral hydroxyl group is easier at high temperature calcination because of pillaring. These indicate that bonding between the pillar and the layers may occur.The surface acidities of Si-CLM and Al-CLM determined by pyridine adsorbtion and NH₈-TPD show some differences, there are more weak Bronsted acid sites on the former, however, more strong Lewis acid sites on the latter. The total surface acid amounts of the sampales are almost the same.Pillared SMM has a higher activity for cumene cracking and a lower delay rate compared with NH₄-SMM. The initial activities of the catalysts are mainly related to the strong acid sites, however, the delay rates seem to be affected by strong Lewis acid sites.

Key words: Pillared mica-montmorillonite, Acidity, Cracking activity