ZSM-5 Molecular Sieves

Product Detail

Introduction of ZSM-5 zeolite:

1. ZSM-5 zeolite contains ten-membered rings, and its basic structural unit is composed of eight five-membered rings. Its crystal structure belongs to the orthorhombic system, space group Pnma, lattice constant a = 20.1, B = 19.9, C = 13.4.

2. ZSM-5 zeolite has a special structure without cages like zeolite A, X and Y. Its pore is its cavity. The skeleton consists of two kinds of intersecting channel systems. The straight cylindrical channel is elliptical, the long axis is 5.7-5.8, and the short axis is 5.1-5.2.

3. The other type of ZSM-5 zeolite is Z-shaped transverse channel with a cross-section approaching circular and a pore diameter of 5.4+0.2. It belongs to mesoporous zeolite. The zigzag channel has an angle of 110 degrees. Sodium ions are located on the symmetrical surface of the 10-membered annular channel. Its anionic skeleton density is about 1.79 g/cm 3, and the crystal structure of ZSM-5 zeolite is very stable.

4. The chemical composition of ZSM-5 zeolite can be expressed by oxides as follows: Al2O3/SiO 2/NaO 2/H 2; ZSM-5 zeolite has a high Si/Al ratio, and can synthesize molecular sieves with different Si/Al ratios according to need and can vary in the range of 10 to 3000.

5. ZSM-5 zeolite has good acid resistance, it can resist all kinds of acids except hydrofluoric acid.

6. ZSM-5 has high Si/Al ratio and low surface charge density. Water is a highly polar molecule, so it is not easily adsorbed by ZSM-5. Although the diameter of water molecule is smaller than that of n-hexane, the adsorption capacity of ZSM-5 to n-hexane is generally larger than that of water.

7. ZSM-5 zeolite is used as catalyst. Only molecules with smaller pore size can enter and exit. The catalytic reaction is controlled by the pore size of zeolite. Zeolite catalyst shows great selectivity to the size and shape of reactants and product molecules. The pore system of ZSM-5 zeolite with 10-membered ring has medium and small aperture diameter, which makes it have good shape selectivity. Therefore, ZSM-5 molecular sieve is usually called shape-selective molecular sieve.

Application of ZSM-5 zeolite:

1. ZSM-5 zeolite has high thermal stability. This is due to the structural stability of the five-membered ring in the skeleton and the high ratio of silicon to aluminium. So far, ZSM-5 is one of the highest thermo-qualitative zeolites known. Therefore, it is particularly suitable for high temperature processes.

2. ZSM-5 can be used as catalyst to increase the production of aromatics and the octane number of reformed gasoline by adopting a process similar to selective reforming, and the concentration of aromatics in liquid products can reach 90%.

3. ZSM-5 zeolite has high hydrothermal stability, high specific surface area, excellent shape-selective catalytic effect, wide range of Si/Al ratio, unique surface acidity and low carbon deposition. Based on the above advantages, ZSM-5 zeolite has been widely used in oil refining industry, fine chemical industry and environmental protection.

4. Diglycol was synthesized into 1,4-dioxane in liquid phase using ZSM-5 zeolite as catalyst at 205-225 C.

5. The famous processes based on ZSM-5 zeolite are: Mobil middle distillate oil dewaxing process, namely MDDW process; lubricant dewaxing process, namely MLDW process; M-reforming process; Mobil-Badger synthesis of ethylbenzene; xylene isomerization process; toluene disproportionation process; methanol to gasoline process, etc.

6. OCC process, Propylur process, Superflex process and MOI process have made progress in increasing propylene production. The key technology is to modify ZSM-5 as the main catalyst. The unique acidity and selectivity of ZSM-5 can make olefins transform internally through oligomerization, cracking and disproportionation reactions, increase the production of low-carbon olefins such as propylene, alleviate market demand and make rational use of C4 and C5. It's very useful.