Extraction of Titanium

It is a transition metal.

Member of group four in periodic table.

it’s atomic number is 22.

It’s mass number is 47.87

It has 5 stable isotopes with mas number 46-50 respectively.

It also has 4 unstable isotopes with mass number 43,44,45 and 51.

Introduction Of Titanium

It was discovered by William Gregor in 1791 in England .

He recognized it to be present in ilmenite (FeTio3) from black sand due to its non-magnetic nature.

It is derived from Greek word titans.

In 1795 a German chemist martin klaproth is discovered it from rutile named it titanium after titans.

In 1910 hunter prepared metal by heating TiCl4 with sodium.

It is 0.6% of the earth’s crust.

It is 9th in order of abundance after oxygen and other 7 metals.

It’s main ores are rutile(TiO2), ilmenite(FeTio3) and sphene (CaTiSiO5).

History And Occurrence

It’s color is silvery metallic . It is solid at room temperature. Its M.P is 1668°C & B.P is 3287°C. Its density is 4.506g/cm3.

Strength of pure Ti decreases by 50% by increasing temperature up to 200°C.

It is light weight, corrosive resistant and can withstand at very high temperature.

It is less resistant to corrosion in strongly reducing media.

Properties

Extraction

The main source of Ti extraction is rutile. Rutile is converted into Ti by following processes:1. Chloride process2. Reduction with Carbon3. Electro winning

Chloride process

In this process rutile (TiO₂) is converted into TiCl₄ Calcined coke is used as reducing agent as it has low ash content Because of low volatile contents of coke no HCl will found TiO₂ + 2Cl₂ +C = TiCl₄ + CO₂ Because of the rise in temperature as this reaction proceeds, CO will form

from CO₂ from product & carbon from coke. CO₂ + C = 2CO. This is an endothermic process & temp. of system decreases. So we should introduce more oxygen with Cl to maintain temperature at

800-1200°C. Coke consumption per ton of TiO₂ is 250 to 300 Kg

Purification of TiCl₄

Crude TiCl₄

Preheating

Distillation <136°C SiCl₄,SnCl₄ H₂S, Cu Agitation and precipitation 90°C

VOCl₂

Distillation >136°C FeCl₃,AlCl₃ Pure TiCl₄

Purification of TiCl₄ As the ore contains different impurities they either may be

elements or dust. The elements form chlorides and are solid at room

temperature. These chlorides & dust are removed from TiCl₄ by

distillation at a temp. below 136°C i.e.SiCl₄,SnCl₄. Some chlorides like VCl₄,VOCl₃ can not be removed by

distillation as they have close boiling points. They are reduced to form solid of low value i.e. VCl₄ &

VOCl₂ . Reducing agents may be Cu,H₂S, hydrocarbons & amines In TiCl₄ there should be V less than 5 ppm Again distillation is done at temp.> 136°C to remove

FeCl₃,AlCl₃

Oxidation of TiCl₄ TiO₂ used in chloride process is not pure, so we convert it into TiCl₄

for its purification. Now we have to make TiO₂ again So we oxidize TiCl₄ TiCl₄ + O₂ = TiO₂ + 2Cl₂ It is a weakly exothermic reaction, temperature of reaction should

be high Temperature > 1000°C can be achieved by heating O₂. Hot TiCl₄ & O₂ are fed into a reaction chamber separately. They must be mixed rapidly & completely to give a high reaction

rate. The Cl can be removed either by liquefaction or by flushing N₂ or

air

Reduction of TiO₂: The reduction of titanium dioxide by carbon is only possible above

6000°c. A complete reduction of titanium dioxide is only possible with

alkaline earth metal. By dissolution of excess Ca and CaO in HCl at 600-1200°C in a

vacuum O content of 0.1-0.3% in Ti is obtained. Reduction with CaH₂ at 600-700°C gives TiH₂, which decompose

at 900°C in to Ti and H₂.

Reduction of Ticl₄(Kroll process): Reduction is as TiCl₄+2Mg Ti+2MgCl₂ It is discovered by Kroll. Mg boil at 1120°C and MgCl₂ melts at 711°C the resulting temperature

range and the high purity of Mg are advantages. The reactor constructed of plain c steel and (Cr- Ni) steel and interior was

clean by brushing or a (Ti) coated. The reactor is charged with oxide free lumps of Mg and filled with (Ar) and

(Mg) is melted at 651°C.

Continued When temperature reaches 700°C, purified TiCl₄ is run in

slowly form above or blown in as a vapour, such that a reaction temperature of 850-950°C.

The Ti sponge is deposited in the reactor walls and form the solid cake above the molten Mg.

The molten MgCl₂ collects beneath Mg and is drawn of. The Mg raises through the pours cake to it surface by

capillary action and reacts their gaseous TiCl₄.

Continued Temperature must not exceed 1025°C to prevent the reaction

between Ti and Fe of reactor. The amount of Ticl₄ reacted are 10-50% as some of Mg and Mgcl₂

in the Ti sponge . Excess of Ticl₄ leads to the formation of lower Ti chlorides and Fe

chloride. Generally temp ranges 850-950°C the lower temp give large

reaction time and pure sponge. And removing Mgcl₂ and when temp falls to 200°C the vessel is

opened in dry room because Mgcl₂ and Ticl₄ are hygroscopic. Crude sponge is purified by vacuum distillation and rarely leaching

is used. Leaching solution is H₂O, HCl and HNO₃.

Thermal decomposition of Ti halide:

The old process of VAN Arkel and DEBORE in which TiI₄ is decomposed on electrically heated tungsten wire at 1000˚C.

If wires of single Ti are used then high purity can be obtained. Librated I₂ reacted with corrode Ti to regenerate TiI₄.In same

vessel below 200˚C Over above 500˚Cabove 200 ˚C Lower Ti iodized are formed wich only act as Ti carries above

500 ˚C because of low volatility. Highest purity Ti is produced by crud Ti or Ti scrap.

Continued Very high purity Ti there also be obtained by thermal

disproportionation of Ti chloride and bromide. by passing TaCl₄ vapor over Ti containing material at 950-

1500˚C Ti chloride is formed. Ticl₂ vapor is condensed and is decomposed at 100O˚C 2TiCl₂ Ti+TiCl₄ TiCl₄ is fed back to the process .

Electro wining

High affinity of Ti for O₂ and H₂ prevents its deposition from aqueous solution hence molten salt electrolyses can be used .

Only halides are suitable for electrolyses Ti tetraflouride combine with alkali metal and alkaline earth metal fluoride to form complex hexafloro titanates and these compound decomposed below there melting point with the removal Ti tetrachloride .

These compound can be used in molten salt electrolyses as a component of molten salt bath .

We add oxide to salt bath, oxygen pick up by the titanium metal must be prevented by using low temperature by separating the anode to cathode and by turbulence in electrolyte.

Processing & reuse of scrap metal

Use of Ti scrap instead of Ti sponge. This scrap is produced during the production of semi finished

products, their processing to finish products Before remelting. Scrap must be pretreated. This scrap may be mixed with sponge & compressed. It may also be welded with sponge. This scrap can also be added to the melt in small pieces along with

sponge. The scrap may also be used to produce Ti instead of mixing it with Ti

sponge. Untreated scrap can be added to steel, Ni, Al, Cu & Zn alloys.

Uses

Titanium alloys are used in aircraft. These are also being used in naval ships, space crafts & missiles. In steel alloys to reduce grain size and as a deoxidizer. In stainless steel to reduce carbon content. Because it is considered to be physiologically inert, the metal is used

in joint replacement implants such as hip ball.

Uses

Since titanium is non-ferromagnetic, it is used for long term implants & surgical instruments for use in image-guided surgery.

95% of titanium is consumed for the production of TiO₂ which is used in paint, rubber, paper and many other materials.

TiO₂ is also used heat exchangers, airplane motors, bone pins and other things requiring light weight metals or metals that resist corrosion or high temperatures.

Due to excellent resistance to sea water, TiO₂ is used to make propeller shafts.