Quickly understand the classification of activated carbon
Activated carbon is a kind of black porous solid carbon, which is produced by pulverizing and shaping coal or carbonizing and activating uniform coal particles. The main component is carbon, and contains a small amount of oxygen, hydrogen, sulfur, nitrogen, chlorine and other elements. The specific surface area of ordinary activated carbon is between 500 and 1700 m2/g. It has strong adsorption performance and is an industrial adsorbent with a wide range of uses. Activated carbon is a traditional and modern man-made material, also known as carbon molecular sieve. Classification: According to the different sources of raw materials, manufacturing methods, appearance and shape, and application occasions, there are many types of environmentally friendly activated carbon. Up to now, there are no measurable statistical materials, and there are about thousands of varieties. According to the source of raw materials: 1. Wooden activated carbon; 2. Animal bones, blood charcoal; 3. Mineral raw material activated carbon; 4. Other raw material activated carbon; 5. Regenerated activated carbon. According to the manufacturing method: 1. Chemical activated carbon (chemical carbon); 2. Physical activated carbon; 3. Chemical-physical or physical-chemical activated carbon. According to appearance shape: 1. Powdered activated carbon; 2. Granular activated carbon; 3. Unshaped granular activated carbon; 4. Cylindrical activated carbon; 5. Spherical activated carbon; 6. Activated carbon of other shapes. According to the aperture: Macropore radius>20 000nm; transition pore radius 150-20000nm; micropore radius<150nm The surface area of activated carbon is mainly provided by micropores. Classified by material: Coconut shell activated carbon; nut shell activated carbon (including apricot shell activated carbon, fruit core shell activated carbon, walnut shell activated carbon); wooden activated carbon; coal-based activated carbon.
Activated alumina as a catalyst and carrier for chemical reactions
Activated alumina has a large specific surface area, a variety of pore structures and pore size distributions, and rich surface properties. Therefore, it has a wide range of uses in adsorbents, catalysts and catalyst carriers. Alumina for adsorbent and catalyst carrier is a fine chemical and also a special chemical. Different uses have different requirements for physical structure, which is the reason for its strong specificity and many varieties and grades. According to statistics, the amount of alumina used as catalysts and carriers is more than the total amount of catalysts using molecular sieve, silica gel, activated carbon, diatomaceous earth and silica alumina gel. This shows the pivotal position of alumina in catalysts and carriers. Among them, η-Al2O3 and γ-Al2O3 are the most important catalysts and supports. They are both spinel structures containing defects. The difference between the two is: the tetrahedral crystal structure is different (γ>η), and the hexagonal layer stack The row regularity is different (γ>η) and the Al—O bond distance is different (η>γ, the difference is 0.05～0.1nm).
Carbon molecular sieves is a new type of non-polar adsorbent
The ability of molecular sieve to separate air depends on the diffusion speed of various gases in the air in the pores of Carbon Molecular Sieves, or the adsorption force, or both. Carbon Molecular Sieves PSA air separation nitrogen production is based on this performance. Carbon Molecular Sieves are used to produce nitrogen. The N2 concentration and gas production volume can be adjusted according to the user's needs. When the gas production time and operating pressure are determined, the gas production volume will be lowered, and the N2 concentration will increase, otherwise, the N2 concentration will decrease. Users can adjust according to actual needs.
Influence of molecular sieve in PSA nitrogen generator
Carbon molecular sieve PSA nitrogen generator production relies on van der Waals force to separate oxygen and nitrogen. Therefore, the larger the specific surface area of the molecular sieve, the more uniform the pore size distribution, and the greater the number of micropores or submicropores, the greater the adsorption capacity; , If the pore size can be as small as possible, the van der Waals force field overlaps, and it has a better separation effect on low-concentration substances. Carbon molecular sieve is a non-quantitative compound, and its important properties are based on its microporous structure. Its ability to separate air depends on the different diffusion speeds of various gases in the air in the pores of the carbon molecular sieve, or different adsorption forces, or both effects work at the same time. Under equilibrium conditions, the adsorption capacity of carbon molecular sieve for oxygen and nitrogen is quite close, but the diffusion rate of oxygen molecules through the narrow gaps of the carbon molecular sieve microporous system is much faster than that of nitrogen molecules. Carbon molecular sieve air separation nitrogen production is based on this Performance, before the time to reach equilibrium conditions, the nitrogen is separated from the air through the PSA process.
Principles and characteristics of common adsorbents (activated carbon, molecular sieve, silica gel, activated alumina)
1. Overview of the adsorption and separation process Adsorption means that when a fluid (gas or liquid) is in contact with a solid porous substance, one or more components in the fluid are transferred to the outer surface of the porous substance and the inner surface of the micropores to be enriched on these surfaces to form a monolayer or multiple molecules Layer process. The adsorbed fluid is called adsorbate. Due to the different physical and chemical properties of adsorbate and adsorbent, the adsorption capacity of adsorbent for different adsorbates is also different. Therefore, when the fluid is in contact with the adsorbent, the adsorbent will affect one of the fluids. Or some components have higher adsorption selectivity compared to other components, and the components of the adsorption phase and the resorbance phase can be enriched, so as to realize the separation of substances. 2. The adsorption/desorption process Adsorption process: It can be considered as a process of concentration or liquefaction. Therefore, the lower the temperature and the higher the pressure, the greater the adsorption capacity. For all adsorbents, the more easily liquefied (the higher the boiling point), the greater the amount of gas adsorbed, and the less likely to liquefy (the lower the boiling point), the lower the amount of gas adsorbed. Desorption process: It can be considered as a process of gasification or volatilization. Therefore, the higher the temperature and the lower the pressure, the more complete the desorption. For all adsorbents, the gas that is more easily liquefied (the higher the boiling point) is less likely to be desorbed, and the gas that is less likely to be liquefied (the lower the boiling point) is, the easier it is to desorb. Adsorption is divided into physical adsorption and chemical adsorption. The principle of physical adsorption separation: use the difference in the adsorption force (van der Waals force, electrostatic force) between the atoms or groups on the solid surface and the foreign molecules to achieve separation. The size of the adsorption force is related to the properties of both the adsorbent and the adsorbate. The principle of chemical adsorption separation: based on the adsorption process that chemical reactions occur on the surface of the solid adsorbent to combine the adsorbate and the adsorbent with a chemical bond, so the selectivity is strong. Chemical adsorption is generally slow, can only form a monolayer and is irreversible. 3. characteristics of different adsorbents Activated carbon: It has a rich microporous and mesoporous structure, the specific surface area is about 500-1000m2/g, and the pore size distribution is mainly 2-50nm. Activated carbon mainly relies on the van der Waals force generated by the adsorbent to produce adsorption, and is mainly used for adsorption of organic compounds, adsorption and removal of heavy hydrocarbons, deodorants, etc.; Molecular sieve: It has a regular microporous pore structure with a specific surface area of about 500-1000m2/g, mainly micropores, with a pore size distribution between 0.4-1nm. The adsorption characteristics of molecular sieve can be changed by adjusting molecular sieve structure, composition and type of balance cation. Molecular sieves mainly rely on the characteristic pore structure and the Coulomb force field between the equilibrium cations and the molecular sieve framework to produce adsorption. It has good thermal and hydrothermal stability. It is widely used in the separation and purification of various gas and liquid phases. When used, the adsorbent has the characteristics of strong selectivity, high adsorption depth and large adsorption capacity; Silica gel: The specific surface area of silica gel adsorbent is about 300-500m2/g, mainly mesoporous, with a pore size distribution of 2-50nm, and the internal surface of the pore channel has abundant surface hydroxyl groups, which are mainly used for adsorption drying and pressure swing adsorption for CO2 production, etc.; Activated alumina: specific surface area 200-500m2/g, mainly mesoporous, pore size distribution in 2-50nm, mainly used in dry dehydration, acid waste gas purification, etc.
What is carbon molecular sieve？
carbon molecular sieve - Adsorbent for metal heat treatment, etc. Carbon molecular sieve is a new type of adsorbent developed in the 1970s. It is a kind of excellent non-polar carbon-based cellulose material. Carbon Molecular Sieves (CMS) is used for separation and enrichment of air. Nitrogen adopts a normal temperature and low pressure nitrogen production process, which has the advantages of less investment cost, faster nitrogen production speed, and lower nitrogen cost than the traditional cryogenic high pressure nitrogen production process. Therefore, it is currently the preferred pressure swing adsorption (PSA) nitrogen-rich adsorbent for air separation in the engineering industry. This nitrogen is used in the chemical industry, oil and gas industry, electronics industry, food industry, coal industry, pharmaceutical industry, cable industry, and metal It is widely used in heat treatment, transportation and storage. R & D background In the 1950s, with the tide of the industrial revolution, the application of carbon materials became more and more extensive. Among them, the application field of activated carbon was PSA carbon molecular sieve for nitrogen production. The expansion is the fastest, from the initial filtration of impurities to the separation of different components. At the same time, with the advancement of technology, mankind's ability to process materials has become stronger and stronger. In this case, carbon molecular sieves have emerged. Main components of carbon molecular sieve The main component of carbon molecular sieve is elemental carbon, and the appearance is a black columnar solid. Because it contains a large number of micropores with a diameter of 4 angstroms, the micropores have a strong instantaneous affinity for oxygen molecules and can be used to separate oxygen and nitrogen in the air. The pressure swing adsorption device (PSA) is used in industry to produce nitrogen. Carbon molecular sieve has large nitrogen production capacity, high nitrogen recovery rate and long service life. It is suitable for various types of PSA nitrogen generators and is the first choice for PSA nitrogen generators. Carbon molecular sieve air separation nitrogen production has been widely used in petrochemical, metal heat treatment, electronics manufacturing, food preservation and other industries. working principle Carbon molecular sieve uses the characteristics of sieving to achieve the purpose of separating oxygen and nitrogen. When the molecular sieve adsorbs impurity gas, the macropores and mesopores only play the role of channels, transporting the adsorbed molecules to the micropores and submicropores, and the micropores and submicropores are the real adsorption volume. As shown in the previous figure, the carbon molecular sieve contains a large number of micropores. These micropores allow molecules with a small dynamic size to rapidly diffuse into the pores while restricting the entry of large-diameter molecules. Due to the difference in the relative diffusion rate of gas molecules of different sizes, the components of the gas mixture can be effectively separated. Therefore, when manufacturing carbon molecular sieves, according to the size of the molecules, the distribution of micropores inside the carbon molecular sieve should be 0.28 to 0.38 nm. Within the size range of the micropores, oxygen can quickly diffuse into the pores through the pores of the micropores, but it is difficult for nitrogen to pass through the pores of the micropores, thereby achieving oxygen and nitrogen separation. The pore size of the carbon molecular sieve is the basis for the separation of oxygen and nitrogen. If the pore size is too large, oxygen and nitrogen molecular sieves can easily enter the pores and cannot separate; and if the pore size is too small, neither oxygen nor nitrogen can enter. In the micropores, there is no separation effect. SLCMS-USP | Carbon Molecular Sieve PSA Nitrogen Equipment SLCMS-HP1 3A Molecular Sieve We are carbon molecular sieve,If you are interested in carbon molecular sieve,You can browse related products and initiate consultations on our website.
