一、For which devices is 3A molecular sieve used?
3A molecular sieves are mostly used as catalysts, and can also be used in the drying towers of cracking gas in ethylene plants and in air separation units. 3A molecular sieves are generally expressed in mesh as their unit, and their predecessors, “zeolites”, are commonly seen.
Zeolite is processed into powder form and is called zeolite powder. During the processing, its properties need to be treated, such as by adding strong acids and other treatments. After high-temperature calcination, the moisture is burned off, and it then has the ability to absorb water by itself. It can also adsorb other molecules.
Common molecular sieves can be classified into types such as A, X, and Y. Among them, type A can be further divided into 3A, 4A, and 5A; type X is divided into 10X and 13X. Type Y is mostly used as an additive in catalysts, often applied in petroleum cracking and detailed project analysis with specific requirements.
The adsorption principle of molecular sieves is different from that of silica gel and anhydrous calcium chloride. The latter occurs through physical surface adsorption and simple chemical bonding, while the former locks water through its own lattice structure. Generally speaking, after adsorption, water or other adsorbed molecules will not be released at room temperature. Only when the temperature reaches around 650 degrees Celsius will water or other molecules be released. It is worth noting that different types of molecular sieves will have different exhaust volumes at different temperatures, and this temperature is approximately 100 degrees Celsius.
The adsorption time of molecular sieves is relatively fast. Generally speaking, after 5 hours of contact (which may vary due to differences in contact area and contact rate),
二、Precautions for the Application of 3A Molecular Sieve:
3A molecular sieve is mainly used for the drying of petroleum cracking gas, refinery gas, oil field gas and olefins, etc.
The drying of ethylene, acetylene, propylene, butadiene, and the dehydration of alcohol and various solvents. To prevent the adsorption of hydrocarbons above ethane, 3A molecular sieves are also used in the dehydration of rich natural gas. Some application examples are as follows:
The Application of 3A Molecular Sieve in the Dehydration of Isopropyl Alcohol
Isopropyl alcohol is an important chemical raw material and organic solvent, widely used in the chemical and pharmaceutical industries. A large amount of mixed waste liquid of isopropyl alcohol and water is produced in the industrial production process. It is of great significance to achieve complete separation of isopropyl alcohol and water.
3A molecular sieve has a strong adsorption effect on water in isopropyl alcohol and has a good regeneration effect, which can directly obtain high-concentration isopropyl alcohol. The adsorption dehydration of isopropyl alcohol by 3A molecular sieve can directly obtain high-concentration isopropyl alcohol. Moreover, the water absorption capacity of 3A molecular sieve is not significantly related to the state of isopropyl alcohol (gaseous or liquid), but is closely related to the adsorption state. The adsorption capacity is smaller in gaseous state. Nearly a hundred experiments have confirmed that the molecular sieve has a good regeneration effect, a long service life, and is easy to operate.
Since 3A molecular sieve can dehydrate isopropyl alcohol vapor, it can be combined with a common distillation column for operation to achieve the purpose of energy conservation.
The adsorption effect of 3A molecular sieve on trace moisture in ethyl acetate solution.
Ethyl acetate often contains water, forming an azeotrope with it. At normal pressure, the azeotrope contains 8.5% water by mass. To obtain high-purity ethyl acetate, it is necessary to refine ethyl acetate. Commonly used refining methods mainly include: extraction refining process; azeotropic distillation with a constant boiling agent and ethyl acetate extraction reactive distillation process, etc. The energy consumption of the above refining processes is relatively high.
3A molecular sieve has a strong adsorption effect on moisture and is easy to operate and regenerate. By using 3A molecular sieve to adsorb moisture in ethyl acetate solution, high-purity ethyl acetate can be directly obtained. Moreover, the production process is simple and energy consumption is low.
三、Further research is needed on the regeneration conditions of 3A molecular sieves during the cyclic adsorption process, the adsorption effect after regeneration, and the structural changes within the molecular sieves and their causes after cyclic adsorption, with the aim of reducing the deactivation rate of the molecular sieves as much as possible while maintaining the adsorption effect.
