Reverse Osmosis Separation of Organic Liquid Molecules Using Carbon Molecular Sieve Membrane
Separation and purification are very important in production and life. About 40-60% of the energy in the production process is used for separation and purification; the separation of substances with similar physical properties is also very difficult, such as the separation between isomers. Membrane-based separation methods, if the separation efficiency can be improved, can greatly reduce energy consumption. For example, organic solution nanofiltration membranes are used for the purification of high-value products, but cannot effectively separate molecules of similar molecular size due to insufficient molecular specificity. In order to obtain a better separation and purification method, effectively reduce the energy consumption, and improve the separation efficiency, researchers still need to continue research. Results introduction On August 19, Ryan P. Lively, School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, USA, reported an asymmetric carbon molecular sieve (CMS) hollow fiber membrane in Nature as a potential organic solvent reverse osmosis technology (OSRO). Material. The organic solvent reverse osmosis technology using carbon molecular sieve not only does not need to change the phase of the organic matter, reduces the energy loss in the separation process, but also effectively separates the organic matter with similar molecular sizes. The authors used the changes in the permeability of para-xylene and ortho-xylene in CMS films to reflect the permeation performance of CMS. Using carbon molecular sieve membrane, the reverse osmosis separation of organic liquid molecules can be achieved, and the separation can be efficiently completed without changing the phase morphology and reducing energy consumption. Outlook The use of the dialysis separation technology under the low temperature and high pressure of the separation membrane can greatly reduce the energy consumption, but the separation efficiency and separation selectivity are still great challenges, and the continuous efforts of the majority of researchers are still needed.
Common faults and treatment methods of PSA nitrogen generator
1. During operation, the large pressure displayed on the meter head can not reach the set value. It is caused by the leakage device. Perform a comprehensive leak detection on the gas circuit, especially the drying room and the battery. 2. Check whether the battery is leaking or broken 3. There is noise during the operation of the instrument It is the solenoid valve sound: use a 14 wrench to properly adjust the tightness of the nut on the solenoid valve, not too tight; if not, you need to disassemble the solenoid valve to clean the interior (the sound is mainly due to impurities in the solenoid valve internal organs), and return it after cleaning. No, it must be replaced with a new one. Four, there is gas output when starting up When the pressure rises just after the start-up, you must press the red delay switch on the front, and then the output pressure will be released from the output and wait for 10 minutes before it can be used. The above is the most common troubleshooting of PSA nitrogen generator.
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.
What is carbon molecular sieve？
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.
