In situ Raman spectroscopy studies on chromium oxide catalyst in an anhydrous hydrogen fluoride atmosphere

Changes of different chromium oxide species Cr(VI), Cr(V) and Cr(III)] were investigated using in situ Raman spectroscopy in an anhydrous hydrogen fluoride (AHF) atmosphere. It was found that the Cr(VI) (CrO₃) and Cr(V) (YCrO₄) species were easy to fluorinate, and generated CrO₂F₂ or/and CrOF₃, while the Cr(III) (Cr₂O₃) species was difficult to fluorinate. Moreover, the CrO₂F₂ and CrOF₃ species were stable in the AHF atmosphere, but they easily transform into CrO₃ in N₂ atmosphere and further decomposed to Cr₂O₃ at 400 °C. Moreover, Cl/F exchange reaction of CF₃CH₂Cl to CF₃CH₂F over these Cr species indicated that the high‐oxidation‐state CrO_xF_y (CrO₂F₂ and CrOF₃) species exhibited much higher reactivities than Cr₂O₃, suggesting that these species (CrO₂F₂ and CrOF₃) may be the active phases of the reaction. Copyright © 2010 John Wiley & Sons, Ltd.