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 a carbon molecular sieve for PSA nitrogen production.
The expansion is the fastest, from the initial filtering of impurities to the separation of different components. At the same time, with the advancement of technology, human's ability to process substances has become stronger and stronger. In this case, carbon molecular sieves came into being.
Main ingredient
The main component of the 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. Industrially, pressure swing adsorption (PSA) is used to produce nitrogen. Carbon molecular sieve has large nitrogen production, a high nitrogen recovery rate, and long service life. It is suitable for various types of pressure swing adsorption nitrogen generators and is the first choice for pressure swing adsorption nitrogen generators.
Carbon molecular sieve air separation nitrogen production has been widely used in petrochemical, metal heat treatment, electronic manufacturing, food preservation, and other industries.
Working principle
A 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, and the adsorbed molecules are transported into the micropores and submicron pores. The micropores and submicron pores are the real adsorption volumes. As shown in the previous figure, the carbon molecular sieve contains a large number of micropores, which allow the rapid diffusion of molecules with small kinetic sizes into the pores, while restricting the entry of large-diameter molecules. Due to the differences in the relative diffusion rates of gas molecules of different sizes, the components of gas mixtures can be effectively separated. Therefore, in the manufacture of a carbon molecular sieve, according to the size of the molecular size, the distribution of micropores in the carbon molecular sieve should be 0.28-0.38 nm. Within this micropore size range, oxygen can quickly diffuse into the pores through the orifice of the micropore, while nitrogen is difficult to pass through the orifice of the micropore, thereby achieving the separation of oxygen and nitrogen. The pore size of the micropores is the basis for the separation of oxygen and nitrogen by carbon molecular sieves. If the pore size is too large, oxygen and nitrogen molecular sieves can easily enter the micropores and cannot achieve separation; and if the pore size is too small, neither oxygen nor nitrogen can enter. In the micropores, there is no separation effect.
The domestic molecular sieve is not well controlled for the pore size due to the limitation of conditions. The pore size distribution of carbon molecular sieves on the market ranges from 0.3 to 1 nm, and only Iwatani molecular sieves achieve 0.28 to 0.36 nm. The raw materials of the carbon molecular sieve are coconut shell, coal, resin, etc. The first step is to pulverize after processing and then knead with the base material. The base material is mainly a material that increases strength and prevents crushing and pulverization; the second step is to activate the activator introduced into the hole at a temperature of 600 to 1000 ° C. The commonly used activators are water vapor, carbon dioxide, oxygen, and mixtures. They are thermochemically reacted with more active amorphous carbon atoms to expand the specific surface area and gradually form pores. The activation time varies from 10 to 60 minutes; the third step is to adjust the pore structure, using the vapor of chemical substances: such as benzene in carbon Molecular sieve micropore walls are deposited to adjust the size of the pores to meet the requirements.
