The reaction of dichlorodifluoromethane and hydrogen has been studied in the gas phase at temperatures 438-538 K and atmospheric pressure over Pd and Ru supported AlF3 catalysts prepared by sol-gel method. For the hydrogenation of CF2Cl2, CH2F2 and CH4 represented more than 97% of the products. The catalytic proper-ties of the catalysts are unchanged with time and they showed no significant difference in their activities. At the steady state, the kinetics of the reaction described by a mechanism of a halogenation/debalogenation of the Pd and Ru surfaces by CF2Cl2 and H-2, respectively. The values of the respective rate constants were then determined. It was concluded that at 448 K, the interaction between the Pd and Ru surfaces with CF2Cl2 or H-2 is of the same order of magnitude. The conversion ratio on Ru/Pd supported catalysts within the temperature range used was increased from 1.5 to 4.1, while the selectivity of CH2F2/CH4 ratio was decreased from about 17.4 to 1.8 on the surfaces of both catalysts. This leads to the proposition that the high dispersion of Pd and Ru over the support are responsible for the high activity and high selectivity in CH2F2., (C) 2003 Elsevier B.V. All rights reserved.