TRANSITION-METAL OXIDE PILLARED CLAYS .2. A COMPARATIVE-STUDY OF TEXTURAL AND ACIDIC PROPERTIES OF MANGANESE(III) PILLARED MONTMORILLONITE AND PILLARED ACID-ACTIVATED MONTMORILLONITE

Manganese(III) pillared montmorillonite samples have been prepared by intercalating the trinuclear manganese(III) acetate complex {[Mn3O(COO CH3)(6)(H2O)(3)](CH3COOO-)-C-+} between the silicate layers of both Na -exchanged (NaMont) and acid-activated montmorillonite (HMont), and ch aracterised by different techniques. As far as the intercalation is co ncerned, the multistep ion-exchange process gave better loading of the complex in comparison to the single-step process. FTIR analysis shows the presence of a bidentate acetate group inside the silicate layer w hich decomposes at 300 degrees C. Materials prepared from both clays a re thermally stable up to 500 degrees C, with basal spacings of 17.1 a nd 16.9 Angstrom and surface areas of 280 and 268 m(2) g(-1), (NaMont, HMont respectively). Although the acid-activated pillared montmorillo nite shows low uptake of the complex and low surface area, the resulta nt material has higher pore volume and acidity in comparison to the pr oduct from the Na-exchanged material. Samples prepared from acid-activ ated clays possess both micropores and mesopores (average pore diamete r 41 Angstrom) while those prepared from Na-exchanged clays show predo minately uniform small pores with an average pore diameter of 33 Angst rom.