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Whats the difference between molecular sieves and activated alumina?

Molecular sieve and activated alumina (activated alumina) are both porous, highly dispersive solid materials, with a large specific surface area, and are widely used in industrial production, but they have significant differences in structure, performance and application.

 

1. Structural differences

Activated Alumina:

Molecular formula: Al₂O₃-x(OH)₂x, 0<x<0.8.

Pore structure: The distribution is relatively chaotic, generally divided into micropores, mesopores, and macropores according to the proportion of pore size distribution, and the pore size distribution is uneven.

Molecular sieve:

Molecular formula: (M)₂/nO·Al₂O₃·xSiO₂·pH₂O, M represents metal ions (such as Na⁺, K⁺, Ca²⁺, etc.), n represents the valence of metal ions, x represents the moles of SiO₂, and p represents the moles of water.

Pore structure: There are many pores with uniform pore sizes and neatly arranged pores. According to the different molecular ratios of SiO₂and Al₂O₃, molecular sieves with different pore sizes can be obtained, such as 3A, 4A, 5A, 13X and other models.

2. Performance differences

Adsorption properties:

Activated alumina: has a strong affinity for water and is suitable for drying gases and liquids, but the pore size distribution is uneven and the selective adsorption performance is relatively poor. When the gas moisture content is high, the water absorption rate is much higher than that of molecular sieve.

Molecular sieve: It has extremely high adsorption capacity and selective adsorption performance, and can be adsorbed and separated according to the size and polarity of the molecule. In low humidity environments, the water absorption rate of molecular sieves is stronger than that of activated alumina, and the drying depth can reach -70℃.

Other performance:

Activated alumina: high mechanical strength, strong hygroscopicity, does not swell or crack after absorbing water, remains intact, non-toxic, odorless, insoluble in water, and ethanol. In addition to being used as a desiccant, it can also be used as a catalyst and a catalyst support.

Molecular sieve: In addition to adsorption properties, it also has ion exchange properties and catalytic properties. Molecular sieves are acidic and selective to molecular size and can be used as a catalyst or support.

 

Molecular sieve and activated alumina (activated alumina) are both porous, highly dispersive solid materials, with a large specific surface area, and are widely used in industrial production, but they have significant differences in structure, performance and application.

 

1. Structural differences

Activated Alumina:

Molecular formula: Al₂O₃-x(OH)₂x, 0<x<0.8.

Pore structure: The distribution is relatively chaotic, generally divided into micropores, mesopores, and macropores according to the proportion of pore size distribution, and the pore size distribution is uneven.

Molecular sieve:

Molecular formula: (M)₂/nO·Al₂O₃·xSiO₂·pH₂O, M represents metal ions (such as Na⁺, K⁺, Ca²⁺, etc.), n represents the valence of metal ions, x represents the moles of SiO₂, and p represents the moles of water.

Pore structure: There are many pores with uniform pore sizes and neatly arranged pores. According to the different molecular ratios of SiO₂and Al₂O₃, molecular sieves with different pore sizes can be obtained, such as 3A, 4A, 5A, 13X and other models.

2. Performance differences

Adsorption properties:

Activated alumina: has a strong affinity for water and is suitable for drying gases and liquids, but the pore size distribution is uneven and the selective adsorption performance is relatively poor. When the gas moisture content is high, the water absorption rate is much higher than that of molecular sieve.

Molecular sieve: It has extremely high adsorption capacity and selective adsorption performance, and can be adsorbed and separated according to the size and polarity of the molecule. In low humidity environments, the water absorption rate of molecular sieves is stronger than that of activated alumina, and the drying depth can reach -70℃.

Other performance:

Activated alumina: high mechanical strength, strong hygroscopicity, does not swell or crack after absorbing water, remains intact, non-toxic, odorless, insoluble in water, and ethanol. In addition to being used as a desiccant, it can also be used as a catalyst and a catalyst support.

Molecular sieve: In addition to adsorption properties, it also has ion exchange properties and catalytic properties. Molecular sieves are acidic and selective to molecular size and can be used as a catalyst or support.