AbstractIn this work we have studied the effect of adding Li, Na or K chloride to CuCl2supported on α‐Al2O3, on its catalytic activity for the oxyhydrochlorination of ethylene to dichloroethane in a fixed bed reactor, at 573 K and atmospheric pressure. Both NaCl and KCl show a strong promoting effect. For the case of KCl, this effect has been further examined for a wide range of concentrations and a fixed amount of CuCl2supported on either α‐Al2O3, γ‐Al2O3or SiO2gel. The catalytic and thermogravimetric results obtained indicate that KCl is very effective on the overall rate, even at low concentrations, particularly because it increases considerably the rate of reoxidation of the reduced form of the catalyst. In the case of the γ‐Al2O3series, the promoting effect is only moderate.Ethylene oxyhydrochlorination data for a series of α‐Al2O3supported catalysts containing a constant K+/Cu2+atomic ratio and increasing total amount of KCl + CuCl2are shown. The activity curve shows a maximum for about 18 wt % total active phase.Finally, the influence of Ce, Nd and Pr chlorides on the activity of CuCl2+ KCl supported on α‐Al2O3is also shown. In the case of Pr, the entire range of Pr3+/Cu2+atomic ratios has been examined. The results indicate that the rare earths, especially praseodymium, also have an additional positive e