In the mid-nineteenth century, scientists discovered a stone that resembles a sponge in weight and shape. It is formed by melting and boiling of some mineral rocks in the case of volcanic eruptions, which was then called "focal zeolite".
From 1930 to 1950, scientists systematically studied the chemical and physical properties of zeolites, and applied the properties of their classified particulate matter to industrial production. The natural zeolite mineral resources are very scarce, far from meeting modern industrial production. The large-scale needs, so people began to artificially synthesize it, and its imitations were renamed molecular sieves.
Molecular sieves are made of alkali (sodium oxide, potassium oxide, calcium oxide, etc.), aluminum sulfate (or gibbsite, aluminum trichloride, etc.), silica (or silicon chloride, silicic acid, etc.) and water. A crystal having a skeleton structure synthesized by the steps of compounding, gelation, heating, crystallization, ion exchange, molding, activation, etc., and then dehydrating treatment, exhibits extremely strong adsorption performance.
China began the research and production of molecular sieves in 1959, and has successfully developed various types of molecular sieves. There are many kinds of molecular sieves, which are classified into A type 9 [potassium A (3A), sodium A (4A), calcium A (5A)], X type [calcium X (10X), sodium X (13X) in terms of pore size structure and size. )], Y type [sodium Y, calcium Y] and mordenite type; from the aspect of appearance, there are spherical, flake, strip and particulate. There is also a molecular sieve that can change color, which is usually blue, and becomes white or pink after adsorbing water. This product is easy to observe and monitor, and is favored by molecular sieve desiccant manufacturers and users.
The range of applications of different molecular sieves is also different.
Type 3A molecular sieve desiccant:
It is mainly used for the drying of petroleum cracking gas, olefins, gas refineries and oilfield gas. It is an industrial desiccant for chemical, pharmaceutical and insulating glass.
Chemical formula: 2/3K2O·1/3Na22O·AI2O3·2SiO2·.9/2H2O
Main uses: 1. Drying of liquids (such as ethanol)
2, air drying in insulating glass
3. Drying of nitrogen-hydrogen mixed gas
4, the drying of the refrigerant
Type 4A molecular sieve desiccant:
It is mainly used for the drying of natural gas and various chemical gases and liquids, refrigerants, pharmaceuticals, electronic materials and volatile substances, argon purification, separation of methane and ethane propane.
Chemical formula: Na2O·Al2O3·2SiO2·9/2H2O
Main uses: 1. Deep drying of gases and liquids such as air, natural gas, hydrocarbon, and refrigerant;
2. Preparation and purification of argon gas;
3. Static drying of electronic components and moisture-sensitive substances;
4, as a dehydrating agent in paints, polyesters, dyes and coatings.
Type 5A molecular sieve desiccant:
Chemical formula: 3/4CaO·1/4Na2O·Al2O3·2SiO2·9/2H2O
Main uses: 1. Natural gas drying, desulfurization, decarbonation;
2. Nitrogen and oxygen separation, separation of nitrogen and hydrogen, and preparation of oxygen, nitrogen and hydrogen;
3. Dewaxing petroleum, separating normal hydrocarbons from branched hydrocarbons and cyclic hydrocarbons.
The large specific surface area and polar adsorption of the 5A molecular sieve achieves deep adsorption of water and residual ammonia. The decomposed nitrogen-hydrogen mixture enters the dryer to remove residual moisture and other impurities. The purification device adopts a double adsorption tower process, one adsorbing dry ammonia decomposition gas, and the other one desorbs the water and residual ammonia in a heated state (generally at 300-350 ° C), thereby achieving the purpose of regeneration.
13XAPG molecular sieve desiccant:
It is mainly used for the purification of raw material gas in large and medium-sized air separation plants.
Special molecular sieve series for insulating glass:
Simultaneously adsorbing moisture and residual organic matter in the insulating glass, so that the insulating glass remains smooth and transparent even at very low temperatures, and fully reduces the strong internal and external pressure difference of the insulating glass due to seasonal and day-night temperature difference, completely solving the problem of ordinary insulating glass drying. The agent easily causes the problem of twisting and breaking caused by expansion or contraction of the ordinary insulating glass, and fully prolongs the service life of the insulating glass.
Molecular sieve activated powder series:
It is a molecular sieve obtained by dehydrating the original fraction of molecular sieves. It has a certain degree of dispersion and a fast adsorption speed. Mainly used as additives for coatings, paints, resins and related adhesives.