Preparation of 1,1,1,2-tetrafluoroethane by catalytic fluorination of 1,1,1-trifluoro-2-chloroethane over CrF₃/MgF₂-AlF₃

The heterogeneous fluorination reactions of CF₃CH₂Cl were performed over CrF₃ supported on MgF₂-AlF₃ and the catalytic activities were compared with those of single support catalysts, CrF₃/MgF₂ and CrF₃/AlF₃, in order to see any enhancing effect of the mixed support on the catalytic activity. The catalytic activities of CrF₃/MgF₂-AlF₃ catalysts were considerably low compared to those of single support catalysts, CrF₃/MgF₂ and CrF₃/AlF₃, indicating the existence of an antisynergy between MgF₂ and AlF₃. XRD measurements show that such an antisynergy effect is mostly attributed to the formation of MgAlF₅ · 1.5H₂O which seems ineffective as a supporting material. The observation of β-AlF₃ in the XRD patterns of the aluminum-rich (Al/Mg > 1) catalysts implies that MgAlF₅ · 1.5H₂O or MgF₂ might be responsible for the transformation of γ-AlF₃ into β-AlF₃. FT-IR studies reveal that the fluorination activity is highly dependent on the strength of Lewis and Bronsted acidities on the catalyst. The IR spectra of adsorbed CF₃CH₂Cl show that the intensities of adsorption bands of CF₃CH₂Cl diminish as the amount of MgAlF₅ · 1.5H₂O in the catalyst support increases.