Montmorillonite clay: Introduction and evaluation of its applications in different organic syntheses as catalyst: A review

Microscopic crystals with soft phyllosilicate group of minerals which formed through precipitation of water solution, are called montmorillonite (MMT). It is concentrated and transformed by natural weathering in environment caves and left aluminosilicates which were contained in the bedrock. By the adding water, montmorillonite swells and expanded considerably more than other clays. The amount of expansion is depended on the type of exchangeable cation contained in the sample. The presence of sodium as the predominant exchangeable cation, is increased the swelling several times rather original volume. Hence, Na-MMT used as the major constituent in nonexplosive agents for splitting rock in natural stone quarries. Advantageous properties of montmorillonite made it appropriate for many applications such as use in oil drilling industry as a component of drilling mud, soil additive, component of foundry sand, desiccant to remove moisture from air and gases, catalyst and various medicinal and pharmacological applications. This review article consists the various synthetic methods for preparation of catalysts based on MMT for organic syntheses and assessing their catalytic activities.