The Vinnolit process for the production of vinyl chloride monomer (VCM) from ethylene and chlorine proceeds via two different routes.
In the direct chlorination as well as in the oxychlorination process, ethylene-dichloride (EDC) is produced. Both reactions proceed exothermally.
EDC produced by direct chlorination can be sent directly to cracking unit whereas the EDC from the oxychlorination process has to pass a purification stage (EDC distillation) before cracking.
In the EDC cracking unit, EDC is cracked to VCM and hydrogen chloride. These, together with any unconverted EDC, are separated in a VCM distillation unit. The VCM, as final product, is sent to the next production stage or for dispatch. The HCl is returned to the oxychlorination unit and the unconverted EDC via EDC distillation unit to the cracking section.
Direct chlorination: C2H4 + Cl2 ——> C2H4Cl2 + 218 kJ/mole
Oxychlorination: C2H4 + 2 HCl + ½ O2 ——> C2H4Cl2 + H2O + 238kJ/mole
EDC cracking: C2H4Cl2 ——> C2H3Cl + HCl – 71 kJ/mole
Water obtained from oxychlorination process is stripped free of chlorinated hydrocarbons and treated in appropriate water purification plants. Waste gases as well as liquid by-products are fed to the HCl recovery unit and converted to HCl.
The recovered HCl is re-used either for the production of hydrochloric acid or in the oxychlorination process. This leads to a complete usage of the chlorine input.