Abstract:

CrOx-Y2O3 catalystswere prepared by a deposition-precipitationmethod and tested by fluorinating 2-chloro-1,1,1-trifleuoroethane (HCFC-133a) to synthesize 1,1,1,2-tetrafluoroethane (HFC-134a). Using Raman spectrum and X-ray powder diffraction (XRD) technique, we found that the atmosphere and the temperature during the calcination process greatly influenced the CrOx species in the catalysts. When the catalyst was calcined in nitrogen and then in air at different temperatures (T) (NAT), the Cr species changed fromCrO3 to YCrO4 and YCrO3 with increasing calcination temperature. The NA500 catalyst showed better stability than the catalyst calcined in air at 350 ℃ (the A350 catalyst), because the YCrO4 species formed during calcination could transform into an active species during the pre-fluorination process and the coke deposition was inhibited on the catalyst surface during the reaction.

Key words: CrOx-Y2O3 catalyst, HFC-134a, Calcination atmosphere, Calcination temperature, Chlorine/fluorine exchange reaction