Zeolite is an aluminosilicate mineral with a water framework structure and was first discovered in 1756. The Swedish mineralogist Cronstedt discovered that there is a type of natural aluminosilicate ore that boils when burned, and named it zeolite.
The concept of molecular sieve was proposed by McBain in 1932, which means a porous material that can sieve substances at the molecular level.
In other words, zeolite is a definition based on the physical and chemical properties of a substance, and molecular sieve is a definition based on the structure and function of the material. Zeolite can be used as a molecular sieve, even the most representative of molecular sieves, but strictly speaking, zeolite cannot be equated with molecular sieves; although many times it is often confused.
1. The chemical composition is different. The main chemical composition of natural zeolite is sodium aluminosilicate, while molecular sieves are crystalline silicates or aluminosilicates, which are formed by connecting silicon-oxygen tetrahedra or alumino-oxygen tetrahedra through oxygen bridges.
2. With different characteristics, zeolite has a glass-like luster and can re-absorb water or other liquids. Molecular sieves have the advantages of high adsorption capacity and strong thermal stability that other adsorbents do not have.
3. The molecular sieve is a powdery crystal with metallic luster, the hardness is 3 to 5, and the relative density is 2 to 2.8. Natural zeolite has color, synthetic zeolite is white, insoluble in water, thermal stability and acid resistance increase with the increase of SiO2/Al2O3 composition ratio.
The main difference between zeolite and molecular sieve is in their use. Zeolite is generally natural and has different pore sizes. As long as there is cavitation, it can prevent bumping. The functions of molecular sieves are much more advanced, such as screening molecules, as catalysts, slow-release catalysts, etc., so there are certain requirements for the pore size, and they are often artificially synthesized.
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