Molecular Sieve Types and Structures

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Ⅰ. There are two types of molecular sieves: natural zeolite and synthetic zeolite.

1. Most natural zeolites are formed by the reaction of volcanic tuff and tuffaceous sedimentary rocks in marine or lacustrine environments. At present, more than 1,000 kinds of zeolite minerals have been discovered, of which 35 are more important. The common ones are clinoptilolite, mordenite, erionite and chabazite.

2. Because natural zeolite is limited by resources, people later use synthetic zeolite in large quantities. Commercial molecular sieves often use prefix numbers to classify molecular sieves with different crystal structures, such as type 3A, type 4A, and 5a molecular sieve.

Ⅱ. The structure of molecular sieve

A microporous sieve-like structure formed by winding proteoglycan polymers tortuously is called a molecular sieve. Molecular sieve only allows substances smaller than its micropores to pass through, and has a barrier effect on macromolecular substances and bacteria larger than its micropores. Its pores are uniform in diameter and can adsorb molecules smaller than their diameter into the cavities. Therefore, it can separate molecules with different degrees of accessibility, degree of saturation, molecular size and boiling point, and have the function of "sieving" molecules.