| Molecular Formula | mSiO2·nH2O |
| Physical and Chemical Properties | The chemical properties are hard glass-like transparent or translucent particles. Insoluble in water and inorganic acids (except hydrofluoric acid). Soluble in concentrated caustic soda and caustic potassium solution. |
| Use | Use as a purification agent for gas drying. |
sulfuric acid method is divided into oil column forming and air granulation. the former is a gradual elimination method.
In the gas phase granulation method, concentrated sulfuric acid is passed into the acid mixing tank of tap water in advance, stirred, cooled and prepared into a 20% dilute acid solution, and pumped into the dilute sulfuric acid storage tank for standby. Concentrated sodium silicate with modulus of 3.0~3.4 is put into a settling tank to settle out most of the water insoluble matter, pump into the sodium silicate storage tank, add water to dilute, stir evenly, prepare a dilute sodium silicate solution with SiO 215% ~ 20%, and settle for 48 hours before use. To make colorless and transparent silica gel, sodium silicate must be clear and transparent, which is one of the keys. The dilute sulfuric acid and the clarified dilute silica sodium solution are pumped into the pressure stabilizing tank of human acid and sodium silicate respectively, and compressed air is introduced to stabilize the pressure in the tank within a certain range. Open the valve, so that the sulfuric acid and sodium silicate solution enter the nozzle in a certain proportion at the same time, fully mix and evenly, and the neutralization reaction occurs quickly:
Na2O?mSiO2+H2SO4→NazSO4+mH4SiO4
The generated monosilicic acid (H4SiO2) is very unstable. It is rapidly condensed into dimer, cyclopolymer, polymer and colloidal particles. Silica sol containing a large amount of Na2SO4 is controlled at pH 6~7 and the reaction temperature is 20~30 ℃. The unstable silica sol leaves the nozzle and enters the air. Due to the effect of interfacial tension, spherical particles are formed, which gel before falling into the receiving tank, forming hydrogel balls and falling into the water. That is, the air granulation process is completed. Hydrogel balls are washed with water (Na2)4), dried, sieved, dried and prepared into fine-hole spherical silica gel.