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IJC-A Vol.48A(04) [April 2009] >


Title: Characterization of CrOx-Y2O3 catalysts for fluorination of 2-chloro-1,1,1-trifluoroethane
Authors: He, Jun
Lu, Ji-Qing
Xie, Guan-Qun
Qian, Lin
Chen, Ke-Feng
Zhang, Xue-Liang
Luo, Meng-Fei
Keywords: Catalysts
Supported catalysts
Fluorination
Oxides
Chromium oxides
Yttrium oxide
Issue Date: Apr-2009
Publisher: CSIR
IPC CodeInt. Cl.8 B01J23/26; B01J37/26; B01J39/10; C07C17/00
Abstract:  The fluorination of 2-chloro-1,1,1-trifluoroethane (CF3CH2Cl) to synthesize 1,1,1,2-tetrafluoroethane (CF3CH2F) has been carried out on various CrOx-Y2O3 catalysts with different Cr loadings. The effect of Cr loading on the catalyst composition and structure has been investigated. X-ray diffraction and Raman results indicate that the CrOx species with high oxidation state (Cr(VI)) are well dispersed on the catalyst surface when the Cr loading was lower than 19.5 %. With increase in Cr loading, crystalline Cr2O3 and polymeric chromate are formed, which inhibit pre-fluorination of the catalysts. The catalysts are stable under the reaction conditions and the catalytic activity is strongly dependant on the pre-fluorinated CrOx content. The highest activity is obtained on a pre-fluorinated catalyst with a Cr loading of 19.5, with a 19 % CF3CH2Cl conversion at 320 oC, corresponding to a formation rate of 2.03 mmol h-1 g-1cat, which is 3-fold higher than the best result obtained over a Cr/MgF2 catalyst (0.68 mmol h-1 g-1cat) under similar conditions. The Cr-Al2O3 catalyst has also been prepared and tested for the probe reaction in this study. The activity is lower as compared to that of the Cr-Y2O3 catalyst with the same Cr content. The higher activity of Cr-Y2O3 catalyst may be due to the higher degree of dispersion of the Cr(VI) species on the Y2O3 support than on other supports. It is also found that the CrFx, CrOxFy or Cr(OH)xFy phases originating from higher oxidation state Cr(VI) species are the active sites for the fluorination reaction.
Page(s): 489-497
ISSN: 0376-4710
Source:IJC-A Vol.48A(04) [April 2009]

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