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) (CrO(3)) and Cr(V) (YCrO(4)) species were easy to fluorinate, and generated CrO(2)F(2) or/and CrOF(3), while the Cr(III) (Cr(2)O(3)) species was difficult to fluorinate. Moreover, the CrO(2)F(2) and CrOF(3) species were stable in the AHF atmosphere, but they easily transform into CrO(3) in N(2) atmosphere and further decomposed to Cr(2)O(3) at 400 degrees C. Moreover, Cl/F exchange reaction of CF(3)CH(2)Cl to CF(3)CH(2)F over these Cr species indicated that the high-oxidation-state CrO(x)F(y) (CrO(2)F(2) and CrOF(3)) species exhibited much higher reactivities than Cr(2)O(3), suggesting that these species (CrO(2)F(2) and CrOF(3)) may be the active phases of the reaction. Copyright (C) 2010 John Wiley & Sons, Ltd.