In chemistry, oxychlorination is a process for generating the equivalent of chlorine gas (Cl<sub>2</sub>) from hydrogen chloride and oxygen. This process is attractive industrially because hydrogen chloride is less expensive than chlorine.
The reaction is usually initiated by copper(II) chloride (CuCl<sub>2</sub>), which is the most common catalyst in the production of 1,2-dichloroethane. In some cases, CuCl<sub>2</sub> is supported on silica in presence of KCl, LaCl<sub>3</sub>, or AlCl<sub>3</sub> as cocatalysts. Aside from silica, a variety of supports have also been used including various types of alumina, diatomaceous earth, or pumice. Because this reaction is highly exothermic (238 kJ/mol), the temperature is monitored, to guard against thermal degradation of the catalyst. The reaction is as follows:
The copper(II) chloride is regenerated by sequential reactions of the cuprous chloride with oxygen and then hydrogen chloride:
Oxychlorination is employed in the conversion of ethylene into vinyl chloride. In the first step in this process, ethylene undergoes oxychlorination to give ethylene chloride:
Oxychlorination is of special importance in the making of 1,2-dichloroethane, which is then converted into vinyl chloride. As can be seen in the following reaction, 1,2-dichloroethane is cracked:
The HCl from this cracking process is recycled by oxychlorination in order to reduce the consumption of raw material HCl (or Cl<sub>2</sub>, if direct chlorination of ethylene is chosen as main way to produce 1,2-dichloroethane).
Iron(III) chloride is produced commercially by oxychlorination (and other methods). For example, dissolution of iron ores in hydrochloric acid gives a mixture of ferrous and ferric chlorides:
The iron(II) chloride is converted to the iron(III) derivative by treatment with oxygen and hydrochloric acid: