The differences between Molecular Sieves, Activated Alumina, and Silica-Alumina Gel

1. Molecular Sieve (Zeolite): Crystalline silicate of aluminium and silicon, with highly regular pore diameters (3A/4A/5A/13X), molecular sieving effect, capable of only adsorbing molecules smaller than the pore diameter, and selective adsorption is its unique advantage.

2. Activated Alumina: Porous γ-Al₂O₃, amorphous disordered pores with wide pore size distribution, no sieving ability; Major advantage: extremely high mechanical strength, resistant to liquid water erosion, and not prone to powdering.

3. Silica Alumina (Alumina Silica Gel): Amorphous mSiO₂·nAl₂O₃, silica gel mixed with alumina, classified as modified silica gel; no regular crystalline pore channels, no molecular sieving ability of molecular sieves; Compared to ordinary silica gel, it is more resistant to high temperatures and high humidity, and has a stronger water absorption capacity. There is water-resistant W silica alumina gel that can directly come into contact with liquid water. It is commonly used in natural gas light hydrocarbon removal.

Activated alumina: Pre-protection layer, rough drying

Compressed air, refinery gas, PSA oxygen production tower - The bottom layer is filled with it, to intercept the front-end condensate water and high-load water vapor, protecting the upper-layer molecular sieves from being wet and pulverized by liquid water; the desiccant machine is standard equipped.

Silica-alumina gel: Special filler for natural gas purification

It is commonly used in the natural gas industry: drying natural gas while adsorbing and recovering C5 + light hydrocarbons (natural gas gasoline) in the natural gas; resistant to high-temperature working conditions; resistant to water; W-type silica-alumina gel is used as the bottom waterproof protective layer; it cannot be used for selective drying of alkenes, as it lacks the screening function of molecular sieves.

Molecular sieve: Deep-end deep dehumidification layer

Activated alumina / silica-alumina gel are filled after this, for deep dehydration;

- 3A: Ethylene, propylene, cracking gas, only absorbs water, does not adsorb alkenes (alumina and silica-alumina gel cannot do this).

- 13X: Pre-purification for air separation, simultaneously removing water + CO₂.

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