The invention provides a catalyst containing active elements including copper deposited on alumina containing at least 0.03 g of titanium, expressed in metal form, per kg of alumina and use thereof in gas hase reactions, such as the oxychlorination of ethylene to 1,2-dichloroethane. This catalyst is suitable for maintaining a constant oxygen content in the tail gases and hence in the recycled gases. The invention further pertains to the use of an alumina containing at least 0.03g titanium, expressed in metal form, per Kg of alumina, as catalyst support and as catalyst diluent. In an example a catalyst containing CuCl.sub.2, MgCl.sub.2, KCl and LiCl deposited on alumina containing 1.13 g of titanium, expressed in metal form, per Kg of alumina was used for the oxychlorination of ethylene to 1,2-dichloroethane in a fluidized bed reactor.