ABSTRACT
This chapter describes the preparation of clay-supported reagents and their use as heterogeneous catalysts for various organic conversions. The smectite group of layer silicates, especially the commercially available K10 montmorillonite, has widely served as support materials. Supported reagents include metal salts, metal oxides and metal sulfides, (zero-valent) metal nanoparticles, organic/metal-organic complexes, and heteropoly acids. The clay mineral is said to be impregnated or doped by the reagent in question, while the reagent may be adsorbed, entrapped, immobilized, or intercalated by the host mineral. For example, K10-supported ZnCl2 (clayzic) and its commercial counterpart, Envirocat EPZ10, can efficiently catalyze the Friedel−Crafts and other organic reactions. K10-supported ferric nitrate (clayfen), cupric nitrate (claycop), and ammonium nitrate (clayan) are similarly useful for organic catalysis. The types of organic conversions catalyzed by clay-supported metal nanoparticles, metal-Schiff base complexes, and heteropoly acids are summarized in a series of tables.
