Ethylene is currently the predominant raw material for vinyl chloride production. The commercially practiced vinyl chloride production involves a balanced combination of Direct Chlorination (DC) and Oxy-Chlorination (OC) processes.
In the Direct Chlorination process, ethylene is first chlorinated to produce ethylene dichloride (CH2Cl-CH2Cl).
CH2=CH2 + Cl2 → CH2Cl-CH2Cl (1)
Ethylene dichloride is subsequently subjected to thermal cracking process (pyrolyzed) to produce vinyl chloride (CH2=CHCl) and hydrogen chloride (HCl).
CH2Cl-CH2Cl → CH2=CHCl + HCl (2)
In the Oxy-Chlorination process, ethylene, hydrochloric acid (HCl) from Reaction (2) and oxygen (O2) are reacted to form ethylene dichloride (CH2Cl-CH2Cl).
CH2=CH2 + Cl2 + ½ O2 → CH2Cl-CH2Cl + H2O (3)
Adding Reactions (1), (2) and (3) gives the overall reaction for balanced process:
2 CH2=CH2 + Cl2 + ½ O2 → 2 CH2=CHCl + H2O (4)