SINTERING OF MONTMORILLONITES PILLARED BY HYDROXY-ALUMINUM SPECIES

The sintering of montmorillonites pillared by hydroxy-Al species was investigated by several techniques. The change of the microporosity of the pillared interlayer clay with temperature shows that sintering was mainly due to the loss of microporosity. On calcination of the parent clay at 760 degree C, the X-ray powder diffraction pattern did not change; the 060 line shifted only slightly from 8. 988 to 9. 017 Angstrom. The infrared (IR) spectrum suggested some dehydroxylation, but the structure appears to have been preserved. On calcination of the pillared clay at greater than 700 degree C, the intensity of the 001 line decreased steadily, the 060 line broadened, and the b parameter decreased slightly from 8. 988 to 8. 928 Angstrom. Fe**3** plus ions apparently occupied only one site after calcination at 300 degree C and two sites after calcination at 700 degree C. The pillaring-induced decrease of thermal stability of the clay was likely due to the introduction of protons during the first step of the preparation.