ABSTRACT
High-temperature chlorination processes have been developed and, with increasing environmental pressures on the disposal of chlorine-containing wastes, they have become the major source for the production of perchloroethylene. First obtained by heating hexachloroethane, perchloroethylene was initially manufactured from acetylene. Perchloroethylene and trichloroethylene are coproduced by the chlorinated-oxychlorination of ethylene dichloride. The ratio of trichloroethylene to perchloroethylene can be varied by altering the chlorine-ethylene dichloride ratios. Perchloroethylene and trichloroethylene are separated by distillation, and any light and heavy fractions remaining are recycled. The principal product is perchloroethylene with carbon tetrachloride and hydrogen chloride as byproducts. The hydrocarbon mixture is fractionated and crude perchloroethylene and carbon tetrachloride are condensed and purified by distillation. Perchloroethylene is an important solvent because of its stability and non-flammability. Perchloroethylene vapour affects the central nervous system causing headaches, dizziness and finally unconsciousness. Perchloroethylene is normally inhibited to prevent decomposition; levels should be monitored regularly and good stock rotation practised.
