Introduction and classification of silica gel

Silica gel introduction: Silica gel is a kind of highly active adsorption material, the main component is silica (SiO2), is an amorphous substance, its chemical formula is mSiO2. nH2O. It is usually made by the reaction of sodium silicate and sulfuric acid, and a series of post-treatment processes such as aging and acid bubble. The physical structure of silica gel is rich in micropores and high specific surface area. Its surface is silicon hydroxyl structure, so it has strong adsorption on water vapor or other polar substances and selective adsorption and separation ability. It has a wide range of applications in adsorption, drying, separation of substances, purification, high purity preparation and other fields. In chemical engineering, silica gel can be used as a catalyst or catalyst carrier.

Due to its chemical composition and physical structure characteristics, silica gel has the following advantages in application: (1) stable chemical properties, except hydrofluoric acid (HF) and strong alkali, insoluble in any other solvents and solutions; (2) Good thermal stability, A type of porous silica gel can be used within 300℃ temperature, and other types of silica gel can be used for a long time under the high temperature of 500-600℃ strip; (3) Silica gel has a rigid skeleton structure, good wear resistance and compressive strength. Each variety of silicone series products has its own characteristics, this is because silicone in the manufacturing process can be controlled by the corresponding process conditions to get different types of pore structure and adapt to different application fields. Classification of silica gel: silica gel according to the size of its aperture is divided into: coarse pore silica gel, B type silica gel, fine pore silica gel. Because of the different pore structure, their adsorption properties have their own characteristics. Coarse pore silica gel has a higher adsorption capacity in the case of high relative humidity, fine pore silica gel in the case of low relative humidity adsorption capacity is higher than coarse pore silica gel, and B type silica gel due to the pore structure between coarse and fine pores, its adsorption capacity is also between coarse and fine pores. Therefore, different varieties should be selected according to different uses.