By Lzh | 08 February 2023 | 0 Comments
Why molecular sieves have acidity and selectivity for molecular size?
What is molecular sieve?
Molecular sieve is a kind of synthetic hydrated aluminosilicate (foamed zeolite) or natural zeolite that has the function of screening molecules. Its chemical formula is (M ′ 2M) O · Al2O3 · xSiO2 · yH2O, M ′, and M are monovalent and divalent cations, such as K+, Na+, Ca2+, Ba2+, etc. It has several pores with uniform pore size and well-arranged pores in structure. Molecular sieves with different pore size separate molecules of different sizes and shapes. According to the different molecular ratios of SiO2 and Al2O3, Molecular sieves with different pore sizes are obtained. Their models include 3A (potassium A type), 4A (sodium A type), 5A (calcium A type), 10Z (calcium Z type), 13Z (sodium Z type), Y (sodium Y type), sodium mordenite type, etc. Its adsorption capacity is high, selectivity is strong, and high-temperature resistance. It is widely used in organic and petrochemical industries and is an excellent adsorbent for gas dehydration. It is also increasingly valued in waste gas purification.
Effect of Si-Al ratio molecular sieve on the synthesis of molecular sieve
The initial silica-alumina ratio of the reactant greatly influences the final reaction product, but there is no corresponding relationship between the two. Generally speaking, LTA molecular sieves with low silica-alumina ratio, SOD molecular sieves, FAU molecular sieves, etc., are crystallized from the original feeding system with low silica-alumina ratio and high alkalinity. High-silicon zeolites such as ZSM-5 and Beta are often obtained from the original feeding system with a high silica-alumina ratio and low alkalinity. Increasing the Si-Al ratio of the feed can often increase the Si-Al ratio of the product within a certain range. Still, not all molecular sieves can synthesize products with high or low silicon by adjusting the Si-Al ratio of the raw material, such as high-silicon LTA molecular sieves, low-silicon ZSM-5 molecular sieves, and other products beyond the normal Si-Al ratio range are difficult to synthesize. In addition, the Si-Al ratio obtained in the final product is often lower than the Si-Al ratio of the original feed because OH - preferentially dissolves the silicon species; almost all aluminum species enter the skeleton, leaving excess soluble silicon in the mother liquor.
Structure of molecular sieve
Because the AlO4 tetrahedron has a negative charge, it can combine with sodium plasma and become electrically neutral. In an aqueous solution, Na is easily exchanged with other cations. Most molecular sieve catalysts are multivalent metal cations or H exchange compounds. A molecular sieve has acidity and selectivity for molecular size and can be used as a catalyst or carrier. High silica zeolites show a high affinity for organic groups.
In contrast, Low-silica zeolites exhibit hydrophilicity due to their Lewis and Bronsted acid properties. Silicon and aluminum atoms form oxygen rings through oxygen. The size of the oxygen ring determines the pore size of the zeolite/the number of oxygen atoms in each oxygen ring is 4 to 12. Generally, there are eight-membered rings (0.4 to 0.5 nm), ten-membered rings (0.5 to 0.6 nm), and twelve-membered rings (0.7 to 0-9 nm).
Price of molecular sieve
Molecular sieve particle size and purity will affect the product's Price, and the purchase volume can also affect the cost of the molecular sieve. A large amount of large amount will be lower. The Price of the molecular sieve can be found on our company's official website.
Molecular sieve supplier
Luoyang Tongrun Nano Technology Co. Ltd. (TRUNNANO) Luoyang City, Henan Province, China, is a reliable and high-quality global chemical material supplier and manufacturer. It has more than 12 years of experience providing ultra-high quality chemicals and nanotechnology materials, including molecular sieve, nitride powder, graphite powder, sulfide powder, and 3D printing powder. If you are looking for a high-quality and cost-effective molecular sieve, you are welcome to contact us or inquire at any time.
Molecular sieve is a kind of synthetic hydrated aluminosilicate (foamed zeolite) or natural zeolite that has the function of screening molecules. Its chemical formula is (M ′ 2M) O · Al2O3 · xSiO2 · yH2O, M ′, and M are monovalent and divalent cations, such as K+, Na+, Ca2+, Ba2+, etc. It has several pores with uniform pore size and well-arranged pores in structure. Molecular sieves with different pore size separate molecules of different sizes and shapes. According to the different molecular ratios of SiO2 and Al2O3, Molecular sieves with different pore sizes are obtained. Their models include 3A (potassium A type), 4A (sodium A type), 5A (calcium A type), 10Z (calcium Z type), 13Z (sodium Z type), Y (sodium Y type), sodium mordenite type, etc. Its adsorption capacity is high, selectivity is strong, and high-temperature resistance. It is widely used in organic and petrochemical industries and is an excellent adsorbent for gas dehydration. It is also increasingly valued in waste gas purification.
The initial silica-alumina ratio of the reactant greatly influences the final reaction product, but there is no corresponding relationship between the two. Generally speaking, LTA molecular sieves with low silica-alumina ratio, SOD molecular sieves, FAU molecular sieves, etc., are crystallized from the original feeding system with low silica-alumina ratio and high alkalinity. High-silicon zeolites such as ZSM-5 and Beta are often obtained from the original feeding system with a high silica-alumina ratio and low alkalinity. Increasing the Si-Al ratio of the feed can often increase the Si-Al ratio of the product within a certain range. Still, not all molecular sieves can synthesize products with high or low silicon by adjusting the Si-Al ratio of the raw material, such as high-silicon LTA molecular sieves, low-silicon ZSM-5 molecular sieves, and other products beyond the normal Si-Al ratio range are difficult to synthesize. In addition, the Si-Al ratio obtained in the final product is often lower than the Si-Al ratio of the original feed because OH - preferentially dissolves the silicon species; almost all aluminum species enter the skeleton, leaving excess soluble silicon in the mother liquor.
Because the AlO4 tetrahedron has a negative charge, it can combine with sodium plasma and become electrically neutral. In an aqueous solution, Na is easily exchanged with other cations. Most molecular sieve catalysts are multivalent metal cations or H exchange compounds. A molecular sieve has acidity and selectivity for molecular size and can be used as a catalyst or carrier. High silica zeolites show a high affinity for organic groups.
In contrast, Low-silica zeolites exhibit hydrophilicity due to their Lewis and Bronsted acid properties. Silicon and aluminum atoms form oxygen rings through oxygen. The size of the oxygen ring determines the pore size of the zeolite/the number of oxygen atoms in each oxygen ring is 4 to 12. Generally, there are eight-membered rings (0.4 to 0.5 nm), ten-membered rings (0.5 to 0.6 nm), and twelve-membered rings (0.7 to 0-9 nm).
Price of molecular sieve
Molecular sieve particle size and purity will affect the product's Price, and the purchase volume can also affect the cost of the molecular sieve. A large amount of large amount will be lower. The Price of the molecular sieve can be found on our company's official website.
Molecular sieve supplier
Luoyang Tongrun Nano Technology Co. Ltd. (TRUNNANO) Luoyang City, Henan Province, China, is a reliable and high-quality global chemical material supplier and manufacturer. It has more than 12 years of experience providing ultra-high quality chemicals and nanotechnology materials, including molecular sieve, nitride powder, graphite powder, sulfide powder, and 3D printing powder. If you are looking for a high-quality and cost-effective molecular sieve, you are welcome to contact us or inquire at any time.
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