IMPROVED SYNTHESIS OF ALUMINA-PILLARED MONTMORILLONITE BY SURFACTANT MODIFICATION

An improved synthesis of alumina-pillared montmorillonite has been achieved by incorporating a nonionic surfactant of general formula C12-14H25-29O(CH2CH2O)5 (abbreviated C-12-14E5) into the Al13O4(OH)24(H2o)127+ pillaring reagent. The co-intercalation of Al13 oligomer (0.086 mol) and C-12-14E5 (0.42 mol) per 020(OH)4 unit cell formula resulted in an X-ray scattering domain size of 256 A along the layer stacking direction, as compared to 81 angstrom in the absence of surfactant. The enhanced crystallographic ordering was manifested in a substantially narrower micropore distribution for the alumina pillared montmorillonite formed by calcination of the Al13 intercalate at 500-degrees-C. Also, the presence of the surfactant greatly improved the hydrolytic stability of the intercalated Al13 oligomer. Normally, uncalcined Al13-Montmorillonite hydrolyzes to a chlorite-like phase within a few weeks of aging under ambient conditions. However, no hydrolysis was noted for the surfactant-modified product after 8 months of aging. The calcined alumina-pillared product obtained by surfactant-modified synthesis exhibits a more uniform micropore distribution than the material produced without surfactant modification. Thus, the use of surfactant provides an effective means of mediating the pore structure and, potentially, the shape-selective catalytic and adsorption properties of pillared clays. Finally, the use Of C-12-14E5 surfactant during synthesis facilitates clay platelet flocculation and reduces greatly the amount of water needed for product processing. This latter property can be important for the large-scale production of pillared clay materials.