Zeolites

Zeolites are hydrated, crystalline microporous aluminosilicates, whose structures enclose channels and/or cavities of molecular dimensions (0.3–1.5nm diameter). Zeolites are present in our everyday life, being widely employed as sorbents, as ion exchangers in detergents, or as catalysts in industrial processes, and as diverse as oil refining or petrochemistry and chemicals and fine chemicals. Many different zeolite structures have been described, leading to a wide versatility in terms of their pore dimensions, channel systems' dimensionality, or composition. In the following sections, we try to evidence the importance of zeolites, not only because of their functionality, but also according to their environmentally ‘green’ character, due to their nontoxicity and safe operation. With that in mind, zeolites are first defined and their possible structures described. Then, zeolite synthesis procedures are revised, highlighting the main factors which influence the crystallization of a final structure, as well as the main new trends that are being followed today. In a final section, the principal properties of zeolites are related with their main applications in different fields.