1,2-dichloroethane,commonly known by its old name of ethylene dichloride (EDC), is
mainly used to produce vinyl chloride monomer (VCM) the major precursor for PVC production
EDC is made by the direct chlorination or oxychlorination of ethylene. Most EDC plants are integrated with VCM plants. The VCM process generates considerable quantities of hydrogen chloride (HCl), which is then recycled in the oxychlorination process to generate more EDC. By operating both the oxychlorination and the direct chlorination pathway at the same time, the overall process eliminates the problem of hydrogen chloride disposal. This technology (often known as «balanced process») is employed in the majority of the developed regions (see figure 1 for this process).
Direct chlorination is performed in the liquid phase where liquid chlorine and pure ethylene are reacted in the presence of ferric chloride. The reaction can be carried out at either low (20-70°C) or high (100-150°C) temperatures.
The low temperature process has the advantage of low by-product formation but requires more energy to recover the EDC. The high temperature process utilises the heat of reaction in the distillation of the EDC , leading to considerable energy savings.
In the oxychlorination process, pure ethylene and hydrogen chloride, mixed with
oxygen, are reacted at 200-300°C and 4-6 bar in the presence of a catalyst, usually cupric chloride. The reaction takes place in either a fixed bed or fluid bed reactor, the latter being preferred as it is easier to control the temperature.
Some recent development in the choice of the catalyst have been reported to produce EDC of high quality which eliminates the need for distillation.