The holes and channels inside the zeolite crystal are uniform and fixed in size, and the diameter of the holes is generally 6~15A. Columnar activated carbon Shandong Only molecules with smaller diameter can enter the cavity through the zeolite channel and be adsorbed, while large molecules cannot enter the cavity and be adsorbed. Zeolite is also called molecular sieve because of its selective adsorption performance. However, silica gel, activated carbon and other adsorbents have no selective adsorption and screening performance due to their non uniformly fixed pore sizes and large changes. Shunyi zeolite filter material price. Because the silicon (aluminum) oxygen tetrahedron of natural zeolite crystal has many holes and channels, which occupy cations and water molecules. When some other goods are completely dehydrated after baking, the crystal skeleton is not damaged, but forms large holes on the inner surface, which can absorb and store a large number of molecules, so it has the characteristics of large adsorption capacity and high selectivity. Columnar activated carbon purchase In different zeolite minerals, the proportion of silicon and aluminum is different, and the different proportion will cause some characteristics of zeolite changes, such as ion exchange and acid resistance.

High silica zeolite type molecular sieves, this kind of zeolite has a series, and ZSM-5 is widely used, with ZSM-8 and ZSM-11 having the same structure; The other group is ZSM-21, ZSM-35 and ZSM-38. ZSM-5 is often called high silica zeolite, with the Si/Al ratio up to 50 and ZSM-8 up to 100. This group of molecular sieves also shows hydrophobic characteristics. Columnar activated carbon Direct selling Their structural units are similar to those of mordenite, consisting of pairs of five membered rings, with no cage like cavities and only channels. ZSM-5 has two sets of cross channels, one is straight through, the other is zigzag perpendicular to each other, both formed by ten yuan rings. The channel is oval and its window diameter is (0.55-0.60) nm. Columnar activated carbon purchase Zeolites belonging to the high silicon group also have silicalite-1 of all silicon type, which has the same structure as ZSM-5, and silicalite-2 is the same as ZSM-11.

Columnar activated carbon Shandong Because the aluminum oxide tetrahedron of zeolite has a negative charge, and the skeleton hole contains cations, a strong electric field is formed around the cations. Therefore, the adsorption force of zeolite not only has a strong dispersion force, but also has a large electrostatic force. It is precisely because of this electrostatic relationship that zeolites have preferential selective adsorption on polar, unsaturated and polarizable molecules. It can strongly adsorb molecules containing polar groups such as hydroxyl ion, ammonium ion and other polarizable groups, especially water, which can form hydrogen bonds with aluminum silicon skeleton, so zeolite has strong water absorption. It can still adsorb even under low relative humidity and concentration, and its water absorption is higher than that of silica gel and activated alumina. The main material of honeycomb zeolite adsorbent is natural zeolite. The manufacturer of zeolite is composed of silica Inorganic microporous material composed of al_2o_3 and alkaline metal or alkaline earth metal, with inner pore volume accounting for 40-50% of the total volume and specific surface area of 100-500 m2/g, is characterized by high temperature resistance, non flammability, good thermal stability and hydrothermal stability. It is an efficient molecular sieve carrier with good adsorption performance, no secondary pollution, and can be regenerated at high temperature. Compared with honeycomb activated carbon, its performance is about 25% of its efficiency, However, it is widely used in the fields of adsorption, separation, catalysis and environment due to its high temperature resistance and difficult ignition. It is more suitable for the treatment of organic waste gas with large air volume and low concentration.

Molecular sieve is a crystalline silicate or aluminosilicate, which is a pore and cavity system with molecular size (usually 0.3nm to 2.0nm) formed by connecting silicon oxygen tetrahedron or aluminum oxide tetrahedron through oxygen bridge bond, Columnar activated carbon Shandong Therefore, it has the characteristics of screening molecules. However, with the deepening of molecular sieve synthesis and application research, researchers have found phosphoaluminate molecular sieves, and the skeleton elements (silicon or aluminum or phosphorus) of molecular sieves can also be replaced by B, Ga, Fe, Cr, Ge, Ti, V, Mn, Co, Zn, Be and Cu, and the size of its pores and cavities can also reach more than 2 nm, Columnar activated carbon purchase Therefore, molecular sieves can be divided into silicon aluminum molecular sieves, phosphorus aluminum molecular sieves and skeleton heteroatom molecular sieves according to the composition of skeleton elements;

Because there are uniform small internal pores in the molecular sieve structure, Columnar activated carbon Shandong When the molecular linear degree of reactants and products is close to the pore size of the crystal, the selectivity of catalytic reaction often depends on the corresponding size of the molecule and pore size. This selectivity is called shape selective catalysis. There are two mechanisms leading to shape selectivity. One is caused by the difference of diffusion coefficient of molecules participating in the reaction in the pore cavity, which is called mass transfer selectivity; The other is caused by the space limitation of the transition state of the catalytic reaction, which is called transition state selectivity. Molecular sieve has clear pore cavity distribution, extremely high internal surface area (600m2/s), good thermal stability (1000 ℃), and adjustable acid site center. The acidity of molecular sieve mainly comes from three coordinated aluminum atoms and aluminum ions (AlO)+on the framework and in the pores. The OH based acid sensitive site center on the molecular sieve HY obtained by ion exchange, and the aluminum ion outside the framework will strengthen the acid site, forming the L acid site center. Polyvalent cations such as Ca2+, Mg2+and La3+can show the acid site center after exchange. The reduction of transition metal ions such as Cu2+and Ag+can also form acid site centers. In general, the higher the Al/Si ratio, the higher the specific activity of OH group. The modification of zeolite acidity can introduce protons through direct exchange of dilute hydrochloric acid. Columnar activated carbon purchase This method often leads to dealumination of molecular sieve framework. So NaY will become NH4Y and then HY.

Columnar activated carbon purchase Rely on its own unique void structure. The pore size of zeolite is uniform, the internal void structure is developed, the specific surface area is large, the adsorption capacity is strong, and contains a large number of invisible pore sizes. The pore size in 1g zeolite material can be expanded to the specific surface area of 500-1000m2, which is higher for special purposes. The mutual adsorption between molecules is also called "van der Waals gravity". Although molecular motion speed is affected by temperature, material and other factors, Columnar activated carbon Direct selling But it always keeps moving in the micro environment. Due to the mutual attraction force between molecules, when a molecule is trapped in the inner pore volume of zeolite, it will lead to more molecules being absorbed until the adsorption of zeolite is saturated.