CROSS-LINKED SMECTITES .1. SYNTHESIS AND PROPERTIES OF HYDROXY-ALUMINUM-MONTMORILLONITE

A stable porous system consisting of montmorillonite cross-linked by Al-hydroxide oligomers was synthesized by reacting at room temperature an aqueous solution of such oligomers with a unit-layer dispersion of montmorillonite. The resulting cross-linked montmorillonite (Al-CLM) is a nonswelling material, showing basal spacings of 14. 4 to 18. 8 A after air drying, and between 14. 2 to 18. 0 A after treatment at 110 degree C. The basal spacing is found to depend on the age and OH/Al ratio of the Al-hydroxide solution, as well as on the relative amounts of the two reactants. A specific surface area of 160 m**2/g and a diffraction pattern with a dominant basal spacing of 17. 5 A is obtained by using Al-hydroxide with OH/Al equals 1. 85, aged for at least 5 days, and by applying an Al/montmorillonite ratio greater than 1. 5 in the cross-linking process. The basal spacing of Al-CLM remains essentially unchanged after heating at 220 degree C, while the specific surface area is not affected by heat treatment up to 480 degree C. Refs.