What Is Titanium Oxide?
Titanium oxide is an insoluble titanium oxide obtained by finely grinding titanopyrite, a type of oxide mineral.
It is often used as a white pigment due to its extremely high chemical stability and excellent whiteness and coloring power. There are three types of titanium oxide, depending on the oxidation number.
Of these, titanium dioxide is the most stable and can be used in diverse applications. Titanium dioxide is also called titanium oxide or titania.
Uses of Titanium Oxide
Titanium dioxide is widely used as a white pigment in paints, pigments, glazes, printing inks, and textile compounds, taking advantage of its excellent whiteness, hiding power, coloring power, and extremely high chemical stability. In addition, titanium oxide’s photocatalytic properties are used to break down industrially persistent substances.
Titanium oxide is also used in sunscreen products, cosmetics, facial cleansers, soaps, nail products, etc. Uses of titanium oxide include safe coloring agents and for its UV protective properties.
Properties of Titanium Oxide
Titanium oxide is soluble in hot concentrated sulfuric acid, hydrofluoric acid, and molten alkali salts, but insoluble in acids such as nitric acid. It is also insoluble in alkalis, water, and organic solvents.
The refractive index of titanium oxide is higher than that of diamond. It has photocatalytic properties, and when exposed to light, a strong oxidizing power is generated on its surface.
Structure of Titanium Oxide
Titanium oxide (IV) has anatase, rutile, and brookite crystal structures. The anatase and rutile types are tetragonal, while the brookite type is orthorhombic.
When the anatase type is heated above 1,652° F (900°C) and the brookite type above 1202° F (650°C), the rutile type is transformed into the rutile type. The most stable structure is the rutile type. Therefore, once the rutile type has been transformed into the rutile type, the structure of the rutile type is maintained even when the temperature is returned to low.
The crystal structures of rutile and anatase are used for industrial applications. The refractive index and other properties and applications are different. In nature, titanium oxide (IV) occurs as a major component of wolframite, pyrite, and titanopyrite. Titanite and pyrite have a tetragonal crystal structure, while titanite has an orthorhombic crystal structure.
Other Information on Titanium Oxide
1. Production of Titanium Oxide
Rutile ore and ilmenite ore (FeTiO3) are used as raw materials. The main methods for industrial production are the chlorine method and the sulfuric acid method.
The chlorine method is also called the gas phase method. First, rutile ore is reacted with coke and chlorine to produce gaseous titanium tetrachloride. Then, the ore is cooled to a liquid state and reacted with oxygen at high temperatures to separate the chlorine gas to produce titanium oxide.
The sulfuric acid method is also called the liquid-phase method. Ilmenite ore is dissolved in concentrated sulfuric acid, and impurities are separated as iron sulfate to form titanium oxytitanate. Titanium oxyhydroxide is precipitated by hydrolysis, and titanium oxide can be obtained by washing, drying, and calcination.
2. Reduction of Titanium Oxide by Hydrogen
Above 1112° F (600°C), titanium oxide (IV) is partially reduced by hydrogen gas to form an oxide with blue titanium (III). However, it quickly reverts to titanium oxide (IV) when exposed to oxygen.
When precious metal catalysts supported on titanium oxide (IV) are reduced at high temperatures, they are prone to SMSI (Strong Metal Support Interaction), a phenomenon in which the activity of the catalyst changes significantly when the metal nanoparticles supported on the oxide support are exposed to the reaction gas. SMSI is a phenomenon in which the activity of the catalyst changes significantly when metal nanoparticles supported on oxide are exposed to a reaction gas.
When hydrogen is reduced at temperatures above 1,652 °F (900°C), TiOx (x=1.85-1.94) is produced, which is dark blue and has an indeterminate composition. This composition is stable when exposed to oxygen at room temperature and pressure.