Chemical reaction of titanium

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Posted on: 09 September 2021 by chen shanshan

Chemical reaction of titanium

Titanium can react with many elements and compounds at higher temperatures. Various elements can be divided into four categories according to their different reactions with titanium:

The first category: halogen and oxygen group elements form covalent bond and ionic bond compounds with titanium;

The second category: transition elements, hydrogen, beryllium, boron, carbon and nitrogen elements form intermetallic compounds and finite solid solutions with titanium;

The third category: zirconium, hafnium, vanadium, chromium, scandium and titanium form an infinite solid solution;

The fourth category: inert gases, alkali metals, alkaline earth metals, rare earth elements (except scandium), actinium, thorium, etc. do not react or basically do not react with titanium. It reacts with the compound HF and fluoride hydrogen fluoride gas to produce TiF4 when heated, and the reaction formula is

Ti+4HF=TiF4+2H2+135.0kcal

The non-aqueous hydrogen fluoride liquid can form a dense titanium tetrafluoride film on the titanium surface, which can prevent HF from immersing into the titanium. Hydrofluoric acid is the strongest solvent for titanium. Even hydrofluoric acid with a concentration of 1% can react violently with titanium:

2Ti+6HF=2TiF3+3H2

Anhydrous fluoride and its aqueous solution do not react with titanium at low temperatures, only the fluoride that melts at high temperatures reacts significantly with titanium. HCl and chloride hydrogen chloride gas can corrode metal titanium, and dry hydrogen chloride reacts with titanium to form TiCl4 at >300°C:

Ti+4HCl=TiCl4+2H2+94.75kcal

Hydrochloric acid with a concentration of <5% will not react with titanium at room temperature, and 20% of hydrochloric acid will react with titanium at room temperature to produce purple TiCl3:

2Ti+6HCl=2TiCl3+3H2

When the temperature is high, even dilute hydrochloric acid will corrode titanium. Various anhydrous chlorides, such as magnesium, manganese, iron, nickel, copper, zinc, mercury, tin, calcium, sodium, barium and NH4+ ions and their aqueous solutions, do not react with titanium. Titanium is in these chlorides Has good stability. Sulfuric acid and titanium hydrogen sulfide have obvious reactions with 5% sulfuric acid. At room temperature, about 40% sulfuric acid has the fastest corrosion rate on titanium. When the concentration is greater than 40% and reaches 60%, the corrosion rate becomes slower, 80% Reached the fastest. Heated dilute acid or 50% concentrated sulfuric acid can react with titanium to form titanium sulfate:

Ti+H2SO4=TiSO4+H2

2Ti+3H2SO4=Ti2(SO4)3+3H2

The heated concentrated sulfuric acid can be reduced by titanium to generate SO2:

2Ti+6H2SO4=Ti2(SO4)3+3SO2+6H2O+202 kcal

Titanium reacts with hydrogen sulfide at room temperature to form a protective film on its surface, which can prevent further reaction of hydrogen sulfide with titanium. But at high temperature, hydrogen sulfide reacts with titanium to produce hydrogen:

Ti+H2S=TiS+H2+70 kcal

The powdered titanium reacts with hydrogen sulfide to form titanium sulfide at 600°C. The reaction product is mainly TiS at 900°C and Ti2S3 at 1200°C. The dense and smooth surface of nitric acid and aqua regia titanium has good stability to nitric acid. This is because nitric acid can quickly form a strong oxide film on the surface of titanium, but the surface is rough, especially sponge titanium or powder titanium. Second, hot dilute nitric acid reacts:

3Ti+4HNO3+4H2O=3H4TiO4+4NO

3Ti+4HNO3+H2O=3H2TiO3+4NO

Concentrated nitric acid above 70℃ can also react with titanium:

Ti+8HNO3=Ti(NO3)4+4NO2+4H2O

At room temperature, titanium does not react with aqua regia. When the temperature is high, titanium can react with aqua regia to generate TiCl2.

In summary, the properties of titanium have an extremely close relationship with temperature, its existence form, and purity. The dense metallic titanium is quite stable in nature, but powdered titanium can cause spontaneous combustion in the air. The presence of impurities in titanium significantly affects the physical, chemical, mechanical, and corrosion resistance of titanium. Especially some interstitial impurities, they can distort the titanium lattice and affect the various properties of titanium. The chemical activity of titanium is very small at room temperature, and it can react with a few substances such as hydrofluoric acid, but the activity of titanium increases rapidly when the temperature increases, especially at high temperatures, titanium can react violently with many substances. The smelting process of titanium is generally carried out at a high temperature above 800 ℃, so it must be operated in a vacuum or under the protection of an inert atmosphere. The physical properties of titanium metal titanium (Ti), gray metal. The atomic number is 22 and the relative atomic mass is 47.87. The arrangement of extranuclear electrons in the sublayer is 1s2 2s2 2p6 3s2 3p6 3d2 4s2. Metal mobility is between magnesium and aluminum, and it is not stable at room temperature. Therefore, it only exists in a chemical state in nature. Common titanium compounds include ilmenite (FeTiO3) and rutile (TiO2). The content of titanium in the earth's crust is relatively high, ranking ninth, reaching 5600ppm, which is converted into a percentage of 0.56%. The density of pure titanium is 4.54×103 kg/m3, the molar volume is 10.54 cm3/mol, the hardness is poor, and the Mohs hardness is only about 4, so it has good ductility. Titanium has good thermal stability, with a melting point of 1668°C and a boiling point of 3287°C. The chemical properties of titanium metal  The reduction ability of titanium metal is extremely strong in high-temperature environments. It can combine with oxygen, carbon, nitrogen and many other elements, and it can also extract oxygen from some metal oxides (such as aluminum oxide). Titanium combines with oxygen at room temperature to form an extremely thin and dense oxide film. This oxide film does not react with nitric acid, dilute sulfuric acid, dilute hydrochloric acid, and the king of acids-aqua regia at room temperature. It reacts with hydrofluoric acid, concentrated hydrochloric acid, and concentrated sulfuric acid.

Titanium is corrosion resistant, so it is often used in the chemical industry.

In electrochemistry, titanium is a one-way valve type metal with very negative potential, and it is usually impossible to use titanium as an anode for decomposition.

The biggest disadvantage of titanium is that it is difficult to extract. The main reason is that titanium has a strong ability to combine with oxygen, carbon, nitrogen and many other elements at high temperatures. When smelting titanium, air and water are of course strictly forbidden. Even the alumina crucible commonly used in metallurgy is also forbidden to use, because titanium will take oxygen from the alumina.

People take advantage of the extremely strong chemical ability of titanium at high temperatures. During steelmaking, nitrogen is easily dissolved in molten steel. When the steel ingot is cooled, bubbles are formed in the steel ingot, which affects the quality of steel. Therefore, the steel workers add titanium metal to the molten steel to combine with nitriding to become slag—titanium nitride, which floats on the surface of the molten steel, so that the steel ingot is relatively pure.

 

Titanium compounds

The oxide of titanium is titanium dioxide, natural TiO2 is rutile, and pure TiO2 is a white powder. It is the best white pigment, commonly known as titanium white, which is white when cold and light yellow when hot. Titanium dioxide has strong adhesion and is not easy to undergo chemical changes. It is always white and is an excellent white paint. It has high refractive index, strong coloring, large hiding power and stable chemical properties.

Titanium dioxide is the whitest thing in the world. 1 gram of titanium dioxide can paint an area of more than 450 square centimeters white. It is 5 times whiter than the commonly used white pigment-Lithopone, so it is the best pigment for white paint. Titanium dioxide used as a pigment in the world can reach hundreds of thousands of tons a year. Titanium dioxide can be added to paper to make the paper white and opaque. The effect is 10 times greater than other substances. Therefore, it is necessary to add titanium dioxide to banknote paper and art paper.

Titanium tetrachloride is very interesting. Under normal conditions, it is a colorless liquid (melting point: -25°C, boiling point: 136.4°C). It has a pungent odor. It will emit white smoke in moist air—it is hydrolyzed and becomes White hydrogel of titanium dioxide. In water, it is strongly hydrolyzed to metatitanic acid H2TiO3.

TiCl3 is a purple crystal, and its aqueous solution can be used as a reducing agent. Ti3+ has stronger reducibility than Sn2+.

Barium titanate crystal has the characteristic: when it changes shape under pressure, it will generate electric current, and it will change shape when it is energized. Therefore, when people put barium titanate in ultrasonic waves, it generates electric current when it is pressed, and the strength of ultrasonic waves can be measured by the magnitude of the electric current generated by it. On the contrary, by passing high-frequency current through it, ultrasonic waves can be generated. Barium titanate is used in almost all ultrasonic instruments.

When smelting titanium, it has to go through complicated steps. Turn ilmenite into titanium tetrachloride, put it in a sealed stainless steel tank, and fill it with argon to make them react with metallic magnesium to obtain "sponge titanium". This porous "sponge titanium" cannot be used directly, and it must be melted into a liquid in an electric furnace before it can be cast into a titanium ingot.

 

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rempel dayton posted 10 September 2021

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