The mobilities of active species in gamma-Al2O3-supported CuCl2-KCl-LaCl3 at a low temperature typical of oxyhydrochlorination of ethylene (498 K) have been studied in a fluidized bed lab reactor, Copper chloride and KCI are mobile under reaction conditions and in a C2H4/N-2 atmosphere, whereas LaCl3 is not. No mobility is observed in air or in HCl/air. It is suggested that the mobile species is cuprous, Mobility studies performed with catalysts supported on SiO2, alpha-Al2O3, and gamma-Al2O3 in reducing atmospheres show that copper chloride is not mobile on SiO2 and alpha-Al2O3, Results of selective extractions with acetone, XRD, and TPR show that a strong salt-support interaction occurs in gamma-Al2O3-, compared to alpha-Al2O3- and SiO2-supported copper chloride. Either promoter separates the CuCl2 from the gamma-Al2O3, but does not affect the mobility of the species on this oxide. Lanthanum chloride increases the activity with no effect on the apparent activation energy, It counteracts the adverse effect of KCl which is not a promoter since it causes a decrease in the activity up to 525 K. The promotion of KCl occurs at higher temperatures, This behavior is due to an increase in the apparent activation energy with the addition of KCl.