A series of CrOx-Y2O3 catalysts were prepared by a deposition-precipitation method and tested for the fluorination of 2-chloro-1,1,1-trifluoroethane (CF3CH2Cl) to synthesize 1,1,1,2-tetrafluoroethane (CF3CH2F). The highest activity was obtained on a pre-fluorinated catalyst calcined at 400 degrees C, with 19% of CF3CH2Cl conversion at 320 degrees C. The effect of the calcination temperature on the CrO, species was investigated. X-ray diffraction and Raman results indicated that the CrOx species (Cr(Vl)) were well dispersed on the catalyst surface when the catalyst was calcined at 400 degrees C. With increasing calcination temperature, most of the CrOx species changed from high oxidation state Cr(VI) to low oxidation state Cr(V) or Cr(Ill) species, which resulted in difficulty in pre-fluorination of the catalyst. It was also found that the CrFx, CrOx F-y or Cr(OH)(x)F-y phases originated from high oxidation state Cr(VI) species were the active sites for the fluorination reaction. (c) 2007 Elsevier Inc. All rights reserved.