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5A molecular sieve is a type of zeolite with a pore diameter of 5A, widely used in adsorption and separation fields due to its unique structure. Its adsorption performance mainly depends on the molecular size and polarity, allowing it to selectively adsorb molecules with kinetic diameters less than 5A.
Gaseous molecules are among the main adsorbed substances by 5A molecular sieve. Nitrogen (N₂) with a kinetic diameter of about 3.64A, oxygen (O₂) at 3.46A, hydrogen (H₂) at 2.89A, carbon monoxide (CO) at 3.01A, and methane (CH₄) at 3.84A can all be effectively adsorbed. These small non-polar or weakly polar gases are commonly separated using 5A sieve in air separation, natural gas purification, etc.
Polar molecules are also easily adsorbed by 5A molecular sieve. Water vapor (H₂O) with a kinetic diameter of 2.6A, methanol (CH₃OH) at 3.7A, ethanol (C₂H₅OH) at 4.4A, and ammonia (NH₃) at 3.34A are all well adsorbed. This property makes 5A sieve an important desiccant in gas drying and solvent recovery processes.
It should be noted that molecules with kinetic diameters exceeding 5A cannot be adsorbed. For example, ethane (C₂H₆) with a diameter of 5.0A may have limited adsorption, while ethylene (C₂H₄) at 5.1A and benzene (C₆H₆) at 5.9A are excluded. The adsorption selectivity of 5A sieve is also related to molecular polarity, with polar molecules showing stronger adsorption than non-polar ones of similar sizes.
In practical applications, 5A molecular sieve is often used in packed towers (packing) with appropriate tower internals (tower internal) to enhance adsorption efficiency. Its excellent adsorption capacity makes it an indispensable material in chemical, energy, and environmental protection industries, playing a crucial role in molecular separation and purification.
