TITANIUM
This page deals with the uses of titanium and its extraction from the ore, rutile. Introduction Uses of titanium Titanium is corrosion resistant, very strong and has a high melting point. It has a relatively low density (about 60% that of iron). It is also the tenth most commonly occurring element in the Earth's crust. That all means that titanium should be a really important metal for all sorts of engineering applications. In fact, it is very expensive and only used for rather specialised purposes. Titanium is used, for example:
Titanium is very expensive because it is awkward to extract from its ores - for example, from rutile, TiO2. You can't use carbon reduction Titanium can't be extracted by reducing the ore using carbon as a cheap reducing agent. The problem is that titanium forms a carbide, TiC, if it is heated with carbon, so you don't get the pure metal that you need. The presence of the carbide makes the metal very brittle. That means that you have to use an alternative reducing agent. In the case of titanium, the reducing agent is either sodium or magnesium. Both of these would, of course, first have to be extracted from their ores by expensive processes. Other problems
The ore rutile (impure titanium(IV) oxide) is heated with chlorine and coke at a temperature of about 900°C. | |
Note: There are other reactions occurring as well in which the other product is either carbon dioxide or carbonyl chloride, COCl2. The equation given is the one UK A level students are likely to need. | |
Other metal chlorides are formed as well because of other metal
compounds in the ore. Very pure liquid titanium(IV) chloride can be
separated from the other chlorides by fractional distillation under an
argon or nitrogen atmosphere, and is stored in totally dry tanks. | |
Note: Titanium(IV) chloride is a typical covalent chloride. It is a colourless liquid which fumes in moist air due to reaction with water to give titanium(IV) oxide and fumes of hydrogen chloride. Everything has to be kept very dry to prevent this happening. | |
Reduction of the titanium(IV) chloride Reduction by sodium This is the method which is used in the UK. The titanium(IV) chloride is added to a reactor in which very pure sodium has been heated to about 550°C - everything being under an inert argon atmosphere. During the reaction, the temperature increases to about 1000°C. After the reaction is complete, and everything has cooled (several days in total - an obvious inefficiency of the batch process), the mixture is crushed and washed with dilute hydrochloric acid to remove the sodium chloride. | |
Note: To save you the bother of asking, I have no idea why hydrochloric acid is used to do this rather than just water! | |
Reduction by magnesium This is the method used in the rest of the world. The method is similar to using sodium, but this time the reaction is: The magnesium chloride is removed from the titanium by distillation under very low pressure at a high temperature. |
Thursday, 5 September 2013
TITANIUM
Labels:
Inorganic Chemistry
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