Transition-metal oxide pillared clays .2. A comparative study of textural and acidic properties of manganese(III) pillared montmorillonite and pillared acid-activated montmorillonite

Abstract

Manganese(III) pillared montmorillonite samples have been prepared by intercalating the trinuclear manganese(III) acetate complex {[Mn3O(COOCH3)(6)(H2O)(3)](CH3COOO-)-C-+} between the silicate layers of both Na-exchanged (NaMont) and acid-activated montmorillonite (HMont), and characterised by different techniques. As far as the intercalation is concerned, 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 which decomposes at 300 degrees C. Materials prepared from both clays are thermally stable up to 500 degrees C, with basal spacings of 17.1 and 16.9 Angstrom and surface areas of 280 and 268 m(2) g(-1), (NaMont, HMont respectively). Although the acid-activated pillared montmorillonite shows low uptake of the complex and low surface area, the resultant material has higher pore volume and acidity in comparison to the product from the Na-exchanged material. Samples prepared from acid-activated clays possess both micropores and mesopores (average pore diameter 41 Angstrom) while those prepared from Na-exchanged clays show predominately uniform small pores with an average pore diameter of 33 Angstrom.