Technical article

What is silica gel?


Silica gel is also called silicon. It is a highly active adsorption material, is an amorphous substance. The main component of silica gel is silicon dioxide, which is chemically stable and non-flammable. Here let’s talk about white silica gel, which is a transparent or milky white granular solid. It has an open porous structure, strong adsorption, and can adsorb a variety of substances. If it absorbs moisture, some silica gels can absorb about 40% of moisture. It is used for gas drying, gas absorption, liquid dehydration, chromatography analysis, etc. It is also used as a catalyst. If cobalt chloride is added, it turns blue when dry and red when it absorbs water, which can be regenerated and used repeatedly.
1st The pore size of silica gel
Silica gel is divided into: Coarse pored silica gel, B type silica gel, and narrow silica gel according to its pore size. Due to their different pore structures, the adsorption properties have their own characteristics. Coarse pored silica gel has a higher adsorption capacity when the relative humidity is high; while Narrow silica gel has a higher adsorption capacity than coarse pored silica gel when the relative humidity is low. Type B silica gel is between the pores, the adsorption capacity is also between the coarse and narrow pores.
2nd The difference between different types of silica gel
1. Narrow pore silica gel
Narrow pored silica gel is a colorless or slightly yellow transparent glass body, and its basic quality parameters are as follows: average pore distance 2.0-3.0nm, specific surface 650-800㎡/g, pore volume 0.35-0.4ml/g, specific heat 0.92KJ /kg.℃, thermal conductivity 0.63KJ/℃.
Application: Suitable for drying, moisture-proof and rust-proof. It can prevent instruments, meters, weapons and ammunition, electrical equipment, medicines, food, textiles and other packaging items from getting wet. It can also be used as catalyst carrier and dehydration and purification of organic compounds. It can also be used as an air purifier to control air humidity.
2. Type B silica gel
Properties: Type B silica gel is milky white transparent or translucent spherical or massive particles. The pore structure of type B glue is between the coarse pored silica gel and the narrow pored silica gel. Basic quality parameters: Pore volume is 0.60-0.85ml/g, average pore diameter is 4.5-7.0nm, specific surface area is 450-650m2/g.
Application: Mainly used as air humidity regulator, catalyst and carrier, pet bedding, and as raw material for fine chemical products such as chromatography silica gel.
3. Coarse pored silica gel
Coarse pored silica gel, also known as type C silica gel, is a kind of silica gel. It is a highly active adsorption material and is an amorphous substance. Its chemical formula is mSiO2·nH2O. It is insoluble in water and any solvent, non-toxic and tasteless, chemically stable, and does not react with any substances except strong alkali and hydrofluoric acid. The chemical composition and physical structure of coarse-pored silica gel determine that it has many characteristics that are difficult to replace by other similar materials: high adsorption performance, good thermal stability, stable chemical properties, and high mechanical strength. The appearance of coarse-pored silica gel is white, and there are three types of products: block, spherical and micro-spherical.
Application: Mainly used for gas purifier, desiccant and acid scavenger for insulating oil, etc; coarse pore block silica gel is mainly used for catalyst carrier, desiccant, gas and liquid purifier, etc.

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Tracy Chen
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