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[Physical and chemical properties] Alias silica silica, silicic acid gel, hydrous silica
[Preparation method] The production methods of silica gel include: sulfuric acid method, which is obtained by reacting sodium silicate and sulfuric acid (other acids can also be used); metathesis method, which is obtained by the action of sodium silicate and water-soluble salts; precipitation method, with the help of It is obtained by the precipitation of silica gel from various organic compounds from alkali metal silicate solutions; electrolysis is obtained by the electrolysis of sodium silicate
(1) Preparation of coarse and fine-pored block silica gel
The coarse and fine pore block silica gel is a glassy transparent or semi-transparent matte granular body or block with a microporous structure and high thermal stability
The raw materials used are sodium silicate with a modulus of 3.
Na 2 SiO 4 +H 2 SO 4 +H 2 O→Na 2 SO 4 +H 4 SiO 4
Silica sol is extremely unstable in acidic medium and immediately condenses into silica gel:
The silicone gel is aged for more than 36 hours in the aging tank, and then the gel is cut into pieces not larger than 3cm and washed with water to remove sodium sulfate (for fine-pored block silica gel, when the water is washed to a certain degree, it needs to be heated and diluted Acid repeated washing)
(2) Preparation of coarse and fine pore spherical silica gel
Spherical silica gel with coarse and fine pores is white transparent or opaque spherical particles
The production method adopts the sulfuric acid method.
Put the clarified sodium silicate solution with a density of 1.
Na 2 SiO 4 +H 2 SO 4 +H 2 O→Na 2 SO 4 +H 4 SiO 4
The silica sol is dispersed from the umbrella-shaped distribution plate into the oil bath of the forming column, and shrinks into a spherical shape by its own surface tension
The spherical gel is carried out by the circulating water at the bottom of the forming column, enters the sieve and is separated
For making coarse-pored spherical silica gel, steam the gel for more than 8 hours, soak it in a 0.
For fine-pored silica gel, the gel is directly subjected to acid exchange for 16 hours in a washing tank.
