Abstract--By ion exchanging expandable clay minerals with large, cationic oxyaluminum polymers, "pillars" were introduced that permanently prop open the clay layers. On the basis of thermal, infrared spectroscopic, adsorption, and X-ray powder diffraction (XRD) analysis, the interlayering of commercial sodium bentonite with aluminum chlorohydroxide, lAI1304(OH)24(HzO)12] +7, polymers appears to have produced an expanded clay with a surface area of 200-300 m2/g. The pillared product contained both Br6nsted and Lewis acid sites. XRD and differential scanning calorimetry measurements indicated that the micropore structure of this interlayered clay is stable to 540~ Between 540 ~ and 760~ the pillared day collapsed with a corresponding decrease in surface area (to 55 m2/g) and catalytic cracking activity for a Kuwait gas oil having a 260~176 boiling range.