Ethylene

vinyl chloride

To produce vinyl chloride monomer (VCM) from ethylene, oxygen, chlorine and hydrogen chloride.

Description: The process as presented here is for a "balanedintegrated" vinyl chloride plant wherein vinyl chloride monomer (VCM) is the sole product and all of the hydrogen chloride (HCI) produced from the cracking of ethylene dichloride (EDC) is recycled to the oxychloirination unit and no externally produced hydrogen chloride is used as feed. Under other circumstances, the process can be arranged to produce either one or both EDC and HCI as coproducts. The process also is well able lto receive externally produced hydrogen chloride as feed.
   In the "balanced-integrated" arrangement, EDC is produced in both direct chlorination and oxychlorination units.
   In the direct chlorination unit, chlorine is combined with ethylene in the liquid phase by the addition reaction (1,2) to produce EDC.
C2H4 + Cl2 --> C2H4Cl2

   In the oxychlorination unit, ethylene, oxygen and HCl are reacted in the vapor phase over a PPG-developed catalyst to produce EDC.

C2H4 + 2HCl + 1/2 O2 --> C2H4Cl2 + H2O

The heat of reaction is recovered as high-pressure steam and used in other portions of the process.
   Due to the use of oxygen and the judicious choice of design and materials, the oxychlorination unit (3,4) operates at a high onstream factor, under moderate pressure, employing a simplified condensation system to provide high yields and essentially corrosion free operation.
   The crude EDC from the oxychlorination and direct chlorination units is combined with the EDC recycled from the cracking unit and purified by distillation (5,6).
Vinyl chloride monomer is produced by thermally cracking (7) the purified EDC at high temperature.

C2H4Cl2 --> C2H3Cl + HCl

   The cracker effluent is quenched (8) and the HCl separated (8-10) and recycled to the oxychlorination unit. High-purity polymer-grade VCM is separated (11) from the unreacted EDC. The unreacted EDC is recycled to the purification unit.   The process has been designed and automated for safe low manpower, high yield and high-stream factor operation over a broad range of turndown. In addition to producing high-purity polymerization grade VCM, the process enjoys essentially corrosion-free operation, low catalyst cost, infrequent decoking and low maintenance cost.

Component Names and Formula