Tetrachloroethylene, also known as system name tetrachloroethylene or perchloroethylene, along with many other names (as well as abbreviations such as "PERC" or "perC" and "PCE"), is a chlorinated hydrocarbon with the chemical formula Cl2C=CCl2. It is a colorless liquid and is widely used in the dry cleaning of fabrics, hence it is sometimes called "dry cleaning liquid". It can also be used as an effective car brake cleaner. Most people can smell sweetness at a concentration of one part per million (1 PPM). Global production in 1985 was about 1 million tons (980,000 long tons; 1,100,000 short tons).
The British physicist and chemist Michael Faraday was the first to synthesize tetrachloroethylene in 1821 through the thermal decomposition of hexachloroethane.
C2Cl6 goes to C2Cl4 plus Cl2
Most tetrachloroethylene is produced by high temperature chlorination of light hydrocarbons. This method is related to Faraday's discovery because hexachloroethane is formed and thermally decomposed. Byproducts include carbon tetrachloride, hydrogen chloride and HCBD.
Several other methods have been developed to produce tetrachloroethylene by chemical reaction when 1, 2-dichloroethane is heated with chlorine to 400 °C:
Cl2ch2cl + 3 Cl2 → Cl2C= Cl2 + 4 HCl
The reaction may be catalyzed by a mixture of potassium chloride and aluminum chloride or by activated carbon. Trichloroethylene is the main by-product and is separated by distillation.
According to a 1976 REPORT by the U.S. Environmental Protection Agency (EPA), the total amount of pCE produced in the United States in 1973 was 320,000 metric tons (706 million pounds). By 1993, U.S. production had fallen to 123,000 metric tons (271 million pounds).
Tetrachloroethylene is an excellent solvent for organic materials. Otherwise, it is volatile, highly stable and non-flammable. For these reasons, it is widely used for dry cleaning. It is also used to degrease metal parts in the automotive and other metalworking industries, often as a mixture with other chlorofluorocarbons. It appears in a number of consumer products, including paint removers and stain removers. It is also used in aerosol preparations.
It is used in neutrino detectors, in which neutrinos interact with neutrons in chlorine atoms and convert them into protons to form argon gas.
Tetrachloroethylene has been widely used as an intermediate in the manufacture of HFC-134A and related refrigerants. In the early 20th century, tetrachloroethylene was used to treat hookworm infections.
