A new thermally stable SiO2–Cr2O3 sol pillared montmorillonite with high surface area Original Research Article

A new sol pillared clay is prepared by ion-exchange of Na+ ions in montmorillonite with SiO2–Cr2O3 mixed oxide sol particles, which are prepared by titrating a Cr3+ aqueous solution with NaOH in the presence of silica sol particles. Upon pillaring of oxide sols, the basal spacing of montmorillonite is expanded up to 47 Å and the porous textures of pillared compounds are retained at least up to 700°C. In spite of large interlayer separation, the pillared clay exhibits characteristic adsorption behavior of microporous solid with a large BET surface area of 420 m2/g. The temperature-programmed-desorption spectra of ammonia revealed that the sample calcined at 400°C has both strong Brönsted and weak Lewis acid sites, whereas the sample heated at 600°C shows significant Lewis acidity due to the formation of a new Si–O–Cr linkage.