|Place of Origin:||China|
|Minimum Order Quantity:||1 tons|
|Delivery Time:||1 week|
|Payment Terms:||T/T, L/C, Western Union|
|Supply Ability:||5000 tons/month|
|Usages:||Drying, Detergent, Additive,etc||Color:||White|
Molecular sieves are a class of adsorbents or thin-film materials with uniform micropores, mainly composed of silicon, aluminum, oxygen and some other metal cations, which are used to screen various fluid molecules according to their effective pore size. Zeolite molecular sieves refer to those natural and synthetic aluminosilicates with molecular sieve action . Due to its unique structure and properties, zeolite molecular sieves have been used in petrochemical, environmental bioengineering, food industry, pharmaceutical and chemical industries. With the development of various industries in the national economy, the application prospects of zeolite molecular sieves are increasingly broad.
Structure of zeolite molecular sieve
Zeolite is a general term for zeolite family minerals. It is an aqueous alkali or alkaline earth metal aluminosilicate mineral. After heating and dehydration, the zeolite crystal pores can adsorb material molecules smaller than the pores and repel material molecules larger than the pore diameter. The mixture of different molecular sizes is separated to function as a sieve.
The zeolite molecular sieve is a crystal of a three-dimensional aluminosilicate metal structure formed by a silicon-aluminum tetrahedron, and is a strong polar adsorbent having a uniform pore size. Zeolites or zeolite molecular sieves modified by different metal cations or modified by other methods have high selective adsorption separation ability. The most commonly used synthetic molecular sieves in the industry are only Type A, Type X, Type Y, mordenite and ZSM series zeolites. The chemical composition of zeolite molecular sieves is: [M2(I)M(II)]O•Al2O3•nSiO2•mH2O, where M2(I) and M(II) are monovalent and divalent metals, respectively. The ions are mostly nano and calcium, n is called the silica-alumina ratio of zeolite, silicon is mainly derived from sodium silicate and silica gel, and aluminum is derived from sodium aluminate and aluminum hydroxide, etc., which are prepared by reacting with sodium hydroxide aqueous solution. The colloid is dried to form a zeolite.
The most basic structure of zeolite molecular sieve is silicon tetrahedron and aluminoxy tetrahedron. The tetrahedron is connected to each other into a multi-ring and has a three-dimensional polyhedron, which constitutes the skeleton structure of the zeolite. Because of the hollow cage in the skeleton structure, it is often called For cages, there are many kinds of cages, such as α cage, β cage, γ cage, etc. These cages are connected to each other to form A type, X type, and Y type molecular sieves.
Application of zeolite molecular sieve
Air drying can be carried out by using the polar hydrophilicity of a zeolite molecular sieve having a low silicon to aluminum ratio (e.g., type A, type X, etc.). In recent years, the incorporation of ethanol into gasoline to replace part of gasoline has received extensive attention. The ethanol content as a fuel requires less than 0.8% of water, and due to the azeotropy of ethanol and water, only 95% of ethanol can be obtained by rectification. For the dehydration of ethanol with lower water content, adsorption and dehydration of zeolite molecular sieve is the best choice. The zeolite molecular sieve used in this method is type A, on the one hand because of the polarity of type A molecular sieve and on the other hand because of the pore of type A molecular sieve. With a diameter of about 0.3 nm, water molecules can enter freely, while ethanol molecules larger than 0.3 nm in diameter cannot enter the pores of zeolite molecular sieves .
2. Separation of mixed xylene
There are many separation methods for mixed xylene, such as rectification precision rectification, pressure crystallization cryogenic crystallization, etc., which are traditional separation methods, but their common disadvantages are high energy consumption, large equipment, high operational requirements, and adsorption. Separation method is a highly efficient separation method. The key is the preparation of adsorbent. Due to the special structure and variety of zeolite molecular sieve, it is a good application prospect to separate the mixed xylene with zeolite molecular sieve as adsorbent. The process of adsorption, elution, rectification and eluent can be used to separate and purify p-xylene with good yield and purity. This method was first used to separate para-xylene, the representative process UOP Parex process and Japan Toray's Aromax process. Now UOP develops a Sorbex process for adsorption separation of meta-xylene, in which Parex and Aromax processes are liquid phase adsorption. The Sorbex process separates high-purity meta-xylene from the raffinate by multi-column adsorption in a low-pressure gas phase .
3. Separation of N2/O2
In the pressure swing adsorption (PSA) method, the zeolite molecular sieve utilizes the difference in equilibrium adsorption of N2/O2 gas on its surface, selectively adsorbing N2, because the polarizability of N2 is large, and thus the cation in N2 and zeolite molecular sieve Its polar surface action is stronger than O2. LiA zeolite molecular sieve has higher N2/O2 selectivity and N2 adsorption capacity, but its thermal stability is poor. Therefore, the A-type zeolite molecular sieve after lithium ion mixed with alkaline earth metal has higher N2/O2 selective separation. Coefficient, N2 adsorption capacity and high thermal stability. For the X-type zeolite molecular sieve with low silicon-to-aluminum ratio, after ion exchange, the N2/O2 separation selectivity is high and the stability is good. For example, the low-silicon X-type zeolite has a separation coefficient of 3.15 for nitrogen and oxygen in the air, which is higher than 2.33 for 5A molecular sieves and 2.36 for 13X molecular sieves .
4. Applications in the field of catalysis
Zeolite molecular sieves have a complex structure and a unique pore system, and are excellent catalysts. The addition of zeolite molecular sieves to the hydrocracking technology can provide an acid center. As a cracking catalyst, it provides a support for a metal having a hydrogenation function. This bifunctional catalyst greatly reduces the operating pressure of the hydrocracking unit. Extending the operating cycle of the device significantly improves production flexibility and economy, and also improves the desulfurization and denitrification effects of hydrorefining . In the hydrogen depressing technology, the unique pore structure of the molecular sieve can be utilized, so that the cracked small molecules enter the pores, and the macromolecules cannot enter the pores, so that the alkane having a high freezing point is cleaved into small molecular hydrocarbons, and is separated from the oil. , reducing the freezing point of the oil.
|mgCaC03/g dry 4A zeolite|
|Particle distribution %||≤10um||≥99||≥99||≥99|
|PH (1% ,25℃ burning loss)||≤11.0||≤11.0||≤11.3|