Titanium dioxide is an inorganic substance with the chemical formula TiO2, a white solid or powdered amphoteric oxide with a molecular weight of 79.9, non-toxic, the best opacity, the best whiteness and brightness, and is considered to be the best performance in the world today. a white paint. Titanium dioxide has strong adhesion, is not easy to chemically change, and is always white. Widely used in coatings, plastics, paper, printing ink, chemical fiber, rubber, cosmetics and other industries. It has a high melting point and is also used to make refractory glass, glaze, enamel, clay, high-temperature laboratory utensils, etc.
At the same time, titanium dioxide has a good UV shielding effect, and is often incorporated into textile fibers as a sunscreen agent. Ultrafine titanium dioxide powder is also added to sunscreen creams to make sunscreen cosmetics.
Titanium dioxide can be extracted from rutile by acid decomposition or obtained by decomposition of titanium tetrachloride. Titanium dioxide has stable properties and is widely used as a white pigment in paints. It has good hiding power, similar to lead white, but does not turn black like lead white; it has the same persistence as zinc white. Titanium dioxide is also used as a matting agent for enamels, producing a very bright, hard and acid-resistant enamel glaze finish.
Titanium dioxide is generally divided into anatase type (Anatase, referred to as A type) and rutile type (Rutile, referred to as R type).
gas phase oxidation
Gas phase oxidation with dry oxygen at 923K-1023K:
TiCl4+O2=TiO2+2Cl2
Sulfuric acid method
First, use ground ilmenite and sulfuric acid (concentration ≥ 80%, temperature 343K-353K) to react under the condition of continuous air and stirring to obtain soluble sulfate:
FeTiO3+H2SO4=TiOSO4+FeSO4+2H2O
Since this reaction is exothermic, the temperature can reach 473K when the reaction is vigorous.
When preparing titanium dioxide, the key step is to hydrolyze the titanium liquid:
TiOSO4+2H2O=TiO2·H2O↓+H2SO4
The concentration, acidity and temperature of the titanium liquid will affect the progress of the hydrolysis reaction. The smaller the concentration, the smaller the acidity, and the higher the temperature, the easier the reaction will occur. In order to increase the temperature, the reaction is often carried out under pressure, which can also make the precipitated particles more compact and make the product have better physical properties.