What is the component of the adsorbent in ordinary molecular sieves? Such as adsorbing CO2 and CH3OH?

Molecular sieves are a class of crystalline silicoaluminates, consisting of a framework structure made up of SiO4 and AlO4 tetrahedra.

In the liquid nitrogen washing process, the main component of the adsorbent in the molecular sieve adsorber is unknown; it is known that the adsorbent used for CO2 removal via pressure swing adsorption is silica gel.

In a narrow sense, molecular sieves are crystalline silicates or aluminosilicates formed by silicon oxide tetrahedra or aluminum oxide tetrahedra connected together by oxygen bridge bonds. They possess a network of pores and cavities with molecular sizes ranging from 0.3 to 2.0 nm, which enables them to separate molecules. However, as research on the synthesis and application of molecular sieves has progressed, researchers have discovered phosphoaluminate molecular sieves. Moreover, the framework elements of molecular sieves (silicon, aluminum, or phosphorus) can also be replaced by elements such as B, Ga, Fe, Cr, Ge, Ti, V, Mn, Co, Zn, Be, and Cu. The size of their pores and cavities can exceed 2 nm as well. Therefore, molecular sieves can be classified based on their framework element composition into silicoaluminate molecular sieves, phosphoaluminate molecular sieves, and molecular sieves with heteroatoms in their frameworks ； Classified by pore size, molecular sieves with pore sizes of less than 2 nm, 2–50 nm, and greater than 50 nm are referred to as microporous, mesoporous, and macroporous molecular sieves, respectively. Due to their larger pore sizes, they serve as good carriers for reactions involving larger molecules. However, the pore walls of mesoporous materials are amorphous, which results in hydrothermal and thermal stability that does not meet the stringent requirements of applications in the petrochemical industry. 　　Due to the presence of metal ions with low ionization energies and large ionic radii, as well as water in a combined state, water molecules are continuously lost upon heating, yet the crystal lattice structure remains unchanged. This results in the formation of many cavities of equal size, which are in turn connected by numerous micropores of the same diameter. These tiny pores have uniform diameters, allowing them to adsorb molecules that are smaller than the pore diameter inside the pores, while rejecting those that are larger. As a result, molecules with different shapes and diameters, different degrees of polarity, different boiling points, and different degrees of saturation can be separated from one another; thus, they exhibit a function of \"sieving\" molecules, which is why they are called molecular sieves. Currently, molecular sieves are widely used in industries such as metallurgy, chemicals, electronics, petrochemicals, and natural gas.

Molecular sieves have an extremely strong moisture absorption capacity and are used for gas purification; they should be kept away from direct exposure to air when stored. Molecular sieves that have been stored for a long time and have absorbed moisture should be regenerated before use. Molecular sieves are sensitive to oil and liquid water. When in use, try to avoid contact with oil and liquid water. Gases that are dried in industrial production include air, hydrogen, oxygen, nitrogen, argon, etc. Two adsorption dryers are used in parallel: one is in operation while the other can be subjected to regeneration. Work and regeneration alternate with each other to ensure the continuous operation of the equipment. The dryer operates at 8-12°C and is regenerated by purging gas when heated to 350°C. The regeneration temperatures for molecular sieves of different specifications vary slightly. Molecular sieves exhibit good catalytic activity for certain organic gas-phase reactions. 　　Also known as zeolites or molecular sieves, it is a crystalline aluminosilicate whose crystal structure features regular and uniform pores with a diameter on the order of a few times that of molecules. It allows only molecules with a diameter smaller than that of the pores to pass through, thereby enabling the separation of molecules in a mixture based on their size. Thus it is called a molecular sieve. More than 200 years ago, B. Kronshtedt was the first to name aluminosilicates zeolites; their general chemical formula is , where M and n represent metal ions and their valencies respectively ； x is the number of silicon dioxide molecules; y is the number of water molecules ； p is the number of atoms of aluminum ； q is the number of silicon atoms. In the chemical industry, molecular sieves are used as solid adsorbents; the substances adsorbed by them can be desorbed, and molecular sieves can be regenerated after use. It is also used for the drying, purification, separation, and recovery of gases and liquids. Starting in the 1960s, they were used as cracking catalysts in the petroleum refining industry, and today a variety of molecular sieve catalysts suitable for different catalytic processes have been developed.