•Promoter yttrium can efficiently improve the selectivity of Cr2O3 catalyst.•1Y2O3-Cr2O3(F) catalyst maintains the highest selectivity after 100 h reaction.•Surface CrOxFy content of Y2O3-Cr2O3(F) catalysts is responsible for selectivity.The synthesis of 2-chloro-3,3,3-trifluoropropene (HCFC-1233xf) from 1,1,2,3-tetrachloropropene was performed over a series of Y2O3-Cr2O3(F) catalysts and the effect of yttrium-doping on the performance of Cr2O3 catalysts was investigated. Various characterization results showed that the addition of yttrium in the Cr2O3 led to the formation of high valent Cr species in the samples, which could be consequently converted to catalytically active CrOxFy species during the pre-fluorination process. Although the Cr2O3 catalyst with or without yttrium-doping showed very high 1,1,2,3-tetrachloropropene conversion in long term reaction, the addition of yttrium in the Cr2O3 helped to maintain the high selectivity to HCFC-1233xf, with the highest selectivity (97%) obtained on a 1 mol% yttrium-doped Cr2O3 after 100 h reaction. X-ray photon spectroscopy results on the spent Cr2O3(F) and 1Y2O3-Cr2O3(F) catalysts indicated that the content of the active CrOxFy species declined after 70 h reaction, which was responsible for the loss of selectivity (from 97% to 88%), while it remained almost unchanged on the spent 1Y2O3-Cr2O3(F) catalyst.The conversion of 1,1,2,3-tetrachloropropene is 99.6% and selectivity to HCFC-1233xf is 97.0% over 1Y2O3-Cr2O3(F) catalyst after 100 h reaction.

Ru/C catalysts were prepared by an impregnation method and their catalytic properties were tested for hydrogenolysis methyl difluoroacetate to difluoroethanol. The catalysts were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), CO chemisorption and H2 temperature-programmed reduction (H2-TPR). The effects of reaction temperature, Ru content and reduction temperature of the Ru/C catalysts on the reaction were investigated. It was found that with increasing Ru contents in the Ru/C catalysts, the methyl difluoroacetate conversion, the selectivity to difluoroethanol and the TOF value first increased and then decreased. A 3Ru/C catalyst reduced at 400 °C exhibited the highest selectivity to difluoroethanol (93.5%) and the highest activity (39.5%). It was also found that the Ru/C catalyst showed a good stability of catalytic hydrogenolysis of methyl difluoroacetate within 100 h.Graphical abstractA process and catalyst for synthesis of difluoroethanol are shown in this study.Highlights► 240 °C was the optimum reaction temperature for hydrogenolysis methyl difluoroacetate to difluoroethanol. ► 3Ru/C catalyst reduced at 400 °C exhibited the highest activity and selectivity to difluoroethanol. ► Ru/C catalyst showed a good reaction stability within 100 h.