PILLARING OF A SAPONITE WITH ALUMINUM-CHROMIUM OLIGOMERS - CHARACTERIZATION OF THE SOLIDS OBTAINED

Saponite, a magnesic trioctahedral smectite, from Yunclillos (Toledo, Spain) was intercalated and pillared with aluminum-chromium solutions. Seven intercalating solutions, containing different Al3+/Cr3+ ratios and partially hydrolyzed with OH- solutions, were used. Al3+ always po lymerizes to form [Al13O4(OH)(24)(H2O)(12)](7+) polycation, while Cr3 forms the trimer [Cr-3(OH)(4)(H2O)(9)](5+), the dimer [Cr-2(OH)(2)(H2 O)(8)](4+), Or does not polymerize, depending on the Al3+/Cr3+ ratio i n the solution considered. When chromium oligomers were used as the in tercalating polycations, the pillared solid obtained had a basal spaci ng of 19 Angstrom and was not thermally stable at temperatures higher than 200 degrees C. When aluminum Al-13 oligomer was used, pillared co mpounds with a basal spacing of 18 Angstrom and thermal stability up t o 600 degrees C were obtained. The addition of aluminum to the chromiu m intercalating solutions improved the thermal stability of chromium p illared solids.