Effect of calcination temperature on CrO_x-Y2O3 catalysts for fluorination of 2-chloro-1,1,1-trifluoroethane to 1,1,1,2-tetrafluoroethane

摘要

A series of CrO_x-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°C,with 19% of CF3CH2Cl conversion at 320°C.The effect of the calcination temperature on the CrO_x species was investigated.X-ray diffraction and Raman results indicated that the CrO_x species(Cr(VI))were well dispersed on the catalyst surface when the catalyst was calcined at 400°C.With increasing calcination temperature,most of the CrO_x species changed from high oxidation state Cr(VI)to low oxidation state Cr(V)or Cr(III)species,which resulted in difficulty in pre-fluorination of the catalyst.It was also found that the CrF_x,CrO_xF_y or Cr(OH)_xF_y,phases originated from high oxidation state Cr(VI)species were the active sites for the fluorination reaction.