SiO2, also known as silica, is a hard and refractory solid. 16 km from the ground, almost 65% of the ore is silica. Natural silica can be divided into crystalline and amorphous. Crystalline silica mainly exists in quartz ore. Pure quartz is colorless crystal, and large and transparent prismatic quartz is crystal. Silicon dioxide is a tetrahedral atomic crystal formed by silicon atoms and four oxygen atoms. The whole crystal can be regarded as a huge molecule. Amorphous silica is a white solid or powder with very stable chemical properties. It is insoluble in water and does not react with water. It is an acidic oxide and does not react with general acids. Gaseous hydrogen fluoride or hydrofluoric acid reacts with silica to form gaseous silicon tetrafluoride. React with hot strong alkali solution or molten alkali to form silicate and water, and react with a variety of metal oxides at high temperature to form silicate. It is used to manufacture quartz glass, optical instruments, chemical utensils, ordinary glass, refractory, optical fiber, ceramics, etc.

The chemical properties of silicon dioxide are very stable. It is insoluble in water and general acids, but it can react with hydrofluoric acid to produce silicon tetrafluoride gas. When silicon dioxide and strong alkali or carbonate of some metals are co melted at high temperature, silicate will be formed. Melt it at high temperature, and then let the melt cool. As the temperature decreases, the melt becomes more and more viscous, and finally hardens to obtain quartz glass. Containers made of quartz glass are not easy to crack in sudden cooling and heat. Quartz glass can also pass through ultraviolet rays. Therefore, quartz glass is used to make mercury vapor ultraviolet lamps and some optical instruments and high-temperature instruments using ultraviolet rays.


Preparation 
Colloidal silicon is prepared by introducing hydrogen chloride into ferrosilicon alloy to make silicon tetrachloride, and then heating and decomposing in oxyhydrogen flame. Wet silicon, which is decomposed and solidified by sodium silicate and sulfuric acid or hydrochloric acid to form silica gel. Then wash with water to remove impurities and dry.


Application 
The latest research report of "future market insight", an overseas market research organization, shows that it is optimistic about the global silica Market in 2026. The research report shows that due to its wide application in the plastic industry, the demand for special silica continued to grow strongly in 2016. As of 2016, the market valuation was $5.6 billion. The report points out that the rubber industry is its largest application field, which is mainly due to the industry's pursuit of improved fuel efficiency. Precipitated silica, as a functional additive popular in tire manufacturing industry, will continue to witness higher demand growth in the next decade. The report estimates that the global precipitated silica revenue in 2016 was close to US $4 billion. The Asia Pacific region (excluding Japan) will still be the largest special silica market, and China, as a major supplier of special silica, will continue to maintain its leading position in the global market.


Application of silica in trifluoromethanesulfonic acid


Fluoromethanesulfonic acid (cf3so3h) is a chemical intermediate and an important organic chemical raw material. In the electronic industry, it can be used as the raw material for making lithium-ion batteries and is widely used in electronic equipment. Trifluoromethanesulfonic acid is also extremely stable to redox reaction. It is a universal synthetic tool with considerable market prospect. At present, electrochemical fluorination is the main method to prepare trifluoromethanesulfonic acid. The trifluoromethanesulfonic acid prepared by this method contains high F - content, which is not conducive to the role of trifluoromethanesulfonic acid. Gaseous hydrogen fluoride or hydrofluoric acid reacts with silicon dioxide to form gaseous silicon tetrafluoride, reacts with hot strong alkali solution or molten alkali to form silicate and water, and reacts with a variety of metal oxides to form silicate at high temperature. Silica can be dissolved in concentrated hot strong alkali solution:



Under high temperature, silica can be reduced by carbon, magnesium and aluminum:


Hydrogen fluoride (hydrofluoric acid) is the only acid that can dissolve silica to form gaseous fluosilicic acid that is easily soluble in water:

F - in trifluoromethanesulfonic acid can be removed by using the characteristic that silica can react with hydrofluoric acid. F - reacts with silica in the presence of concentrated sulfuric acid, and F - escapes from the product in the form of SiF4 gas, which greatly reduces F - in the product.