The catalytic process of ethylene oxychlorination can be split into two steps, viz. ethylene chlorination with the reduction of cupric chloride and reoxidation of the cuprous chloride by hydrogen chloride and oxygen. The transient process of 1,2-dichloroethane formation was observed by selected ion chromatography using a mass spectrometer. While the reaction exhibited first-order kinetics in regard to the concentration of cupric chloride, the dependency on ethylene concentration was interpreted by a Langmuir-Hinshelwood mechanism. Optimal performance was achieved by impregnating ca. 5 wt % of copper into gamma-alumina powder, and 64 % of the copper contained in the alumina powder contributed to the formation of 1,2-dichloroethane.