The skeleton composition of molecular sieve

The skeleton composition of molecular sieve

Molecular sieve is a kind of aluminosilicate inorganic compound, can withstand high temperature, has good thermal stability, provides convenience for regeneration, and can be reused many times. The skeleton is not decomposed by microorganisms or the like. The main components of the framework part of the molecular sieve are silicon-oxygen tetrahedron and aluminum-oxygen tetrahedron. Because the valence of aluminum is 3, the valence of one oxygen atom in the aluminum-oxygen tetrahedron AlO4 is not balanced, so that the entire aluminum-oxygen tetrahedron is banded. There is a negative charge. In order to maintain electrical neutrality, there must be positively charged metal ions in the vicinity of the aluminum oxide tetrahedron to offset its negative charge. A strong electric field is generated between the positively charged metal ions and the negatively charged molecular sieve framework, which has a huge impact on the adsorption performance of the molecular sieve. The adsorption capacity of molecular sieves for polar substances is much stronger than that for non-polar substances. At the same time, due to the strong electric field, it also has considerable adsorption capacity for substances containing double bonds or large π bonds by inducing polarization. Generally, the more the charge of the cation, the smaller the ion radius, the stronger the electric field generated, the greater the induction effect on the double bond, and the greater the adsorption capacity for such substances. For example, 5A molecular sieve can adsorb a large amount of olefins and alkynes such as ethylene and propylene.