Metal halide catalysts to synthesize dichloropentafluoropropanes by the reaction of dichlorofluoromethane with tetrafluoroethylene
A series of metal halides were studied as Lewis acid catalysts for the reaction of dichlorofluoromethane with tetrafluoroethylene to form dichloropentafluoropropanes (HCFC-225s) which are being manufactured as an alternative to CFC-113. Zirconium tetrachloride and hafnium tetrachloride had high catalytic activity in the reaction and much better selectivity towards HCFC-225ca and HCFC-225cb than conventional aluminum trichloride. The Cl-F exchange reaction of zirconium tetrachloride or titanium tetrachloride with chlorofluoromethane produced metal chlorofluorides. When chlorofluoromethane-treated ZrCl4 or TiCl4 were used as a catalyst the reaction of dichlorofluoromethane with tetrafluoroethylene proceeded without the induction period that was observed using ZrCl4 or TiCl4 without pretreatment, indicating that the metal chlorides needed an activation time to become chlorofluorides before developing catalytic activity. Trichlorofluoromethane-treated ZrCl4, metal chlorofluoride, was characterized by thermogravimetry (TG), differential thermal analysis (DTA), and X-ray diffraction.
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Journal: Applied Catalysis A: General - Volume 348, Issue 2, 15 October 2008, Pages 236–240