The catalytic activity of Pd on W-ZrO2 in the hydrodechlorination of CCl2F2 was studied by varying WO3 content. The TPR results of Pd/W-ZrO2 were related to effects caused by contact with hydrogen. XRD data of spent catalysts shows that there is no change in the structure of zirconia indicating that these catalysts are highly resistant to the corrosive reaction atmosphere. Addition of tungsten to Pd/ZrO2 system led to the formation of CHClF2 (HCFC-22) in the hydrodechlorination of CCl2F2. Thus, the role of WO3 istocatalyze the partial dechlorination of CCl2 F-2. (C) 2004 Elsevier B.V. All rights reserved.