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The development history of molecular sieves

2022-04-19 09:24:18
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The origin of molecular sieves can be traced back to 1756, when natural microporous aluminosilicates, namely natural zeolites, were first discovered in the pores of basalt. In 1840, it was found that natural zeolite has the properties of reversible water absorption and dehydration, and its transparency and crystal shape do not change during heating. Therefore, the microporosity of natural zeolite and its performance in adsorption and ion exchange have attracted the attention of researchers. In 1858, according to the performance of zeolite dehydration crystals that can separate molecules of different sizes, the separation of isoparaffins and n-paraffins was successfully achieved. In 1925, it was found that chabazite can rapidly absorb water, ethanol and formic acid vapor, but basically does not absorb acetone, ether and benzene, which once again confirmed the molecular sieve effect of zeolite. Thus, the name zeolite molecular sieve, which not only represents its composition, but also its function, was born. Researchers initially mainly used zeolite molecular sieves as adsorbents and desiccants in fluid drying and purification processes, and later for fluid separation.


The mid-1950s to the early 1980s was the heyday of molecular sieve research, application and industrial development. In 1960, the concept of shape-selective catalysis of the regular structure of molecular sieve was proposed. In 1962, the X-type zeolite molecular sieve was first used in the catalytic cracking process. At this stage, the low and medium silicon-aluminum ratio (SiO2/Al2O3≤10) type A and type X were found. , Y type, mordenite, etc. are called the first generation molecular sieves.


In the 1970s, the new structure zeolite molecular sieve with high silicon three-dimensional cross straight channel, represented by ZSM-5, developed by the Mobil Petroleum Division of the United States is called the second-generation molecular sieve. Such as ZSM-5, ZSM-11, ZSM-12, etc. These high-silicon molecular sieves have high hydrothermal stability, lipophilic and hydrophobic, and most of the pore sizes are around 0.6 nm. They have good activity options for methanol and hydrocarbon conversion reactions. The development of such molecular sieves has promoted the research on the structure and properties of molecular sieves and microporous compounds, and also greatly promoted the research on the application of molecular sieves.


In the 1980s, United Carbon Company developed phosphorus-aluminum molecular sieves with non-silicon and aluminum skeletons, which represent the third generation of molecular sieves. Structure of zeolite molecular sieves. As of 2003, 30 elements have been found that can be used as the framework constituent elements of this phosphorus-aluminum series molecular sieve. Due to the variety of molecular sieve framework elements and pore structures of this molecular sieve and its derivatives, the applications of molecular sieves in adsorption separation, catalysis and new materials are expanded.


In 1983, a new type of titanium-silicon molecular sieve with super oxidizing property, TS molecular sieve, was reported. In the presence of hydrogen peroxide, this molecular sieve is mainly used to catalyze the oxidation of alkanes, epoxidation of alkenes, and the oxidation of alcohols. Hydroxylation of benzene and phenol, ammoxidation of cyclohexanone, etc., some of the reactions have been industrialized.


With the increasing development of molecular sieve research work, the International Zeolite Association came into being, and in 1967, the first International Zeolite Conference was held in London, England. IZA has established two Breck Prizes to reward scientists who have contributed to the field of zeolite research. In 1988, China established the Molecular Sieve Research, Production and Application Collaborative Committee, referred to as the China Molecular Sieve Association, which mainly conducts exchanges and discussions on molecular sieve research, production technology, and application technology.

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