The catalytic oxidative dehydrogenation of ethane into ethylene was investigated over a series of alkali metal chloride supported on silica catalysts. It is found that alkali metal chloride modified silica catalysts show much higher activity in the selective oxidation of ethane than silica support itself, and their catalytic activity depends on the nature of alkali metal and its loading. LiCl/ SiO2 exhibits the highest ethane conversion and ethylene yield, giving 99% ethane conversion and 80% ethylene selectivity at 600 degrees C. However, it shows rapid deactivation. NaCl/SiO2 shows high conversion and a longer stability. On the contrary, KCl/SiO2 displays the lowest ethane conversion but a high deactivation rate. Characterization of the catalysts reveals that the activity variation can be related to the redox and acid-base properties of the catalysts. The deactivation of catalytic activity can be attributed to the loss of chlorine and chemical phase transformation.