A study of intercalated clay metal complexes

Abstract

This thesis contanins five chapterswhich include review of the sub-ject and details of the research methodology adopted, experimental details, results and discussion and conclusion. CHAPTER-I The first chapter contains the review of clay minerals and its applica-tion in catalysis. The review consists of the defination of clay, classification of clay, structure, surface area, composition and chemistry of clay. Clay are composed extremely fine crystals or particles, often colloidal in size and usually platy in shape. Clay consists of a silicate SiO4-4 tetraherdral layer (T) and a octahedral gibbsite (Al2OH6) or brucite (Mg3OH6) layer (O). The structure are either with alternate tetrahedral and octahedral sheet i.e.- OT or 1:1; or octahedral layer sandwich between two tetrahedra TOT or 2:1 as in smectite. Isomorphous replacement of Si4+by Al3+ions results in nega-tively charged layer. To balance this charge, possitively charged ions are intercalated. This give rise to cation exchange property to the clays. This cations are hydrated which results in expansion of the anion sheet of the clay. The surface of smectite represents both external and internal surface area which is accessible to water or other polar molecules. The large sur-face area of smectite in comparison to alumina and silica makes it attractive support for catalysis. Clay minerals shows both Bronsted and Lewis acidity. Bronsted acidity is derives from the dissocion of water mol-ecules in the hydration sphere of the intercalated cations. The Lewis acidity is normally associated with exposed Al3+ and Fe3+ ions at the broken crys-talline edges. Bronsted acidity can be increase by heating the clay to above 3000C. Acid treatment of clay by strong mineral acid results in breakdown of the platelates and increase dissolution of cations which exposes metal sites, therefore surface area, adsorption property and catalytic activity of the clay increases. The last part of the Chapter-1 deals with the different types of reactions that is carried out with clay- i)...