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

Abstract

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. 1.5H(2)O which seems ineffective as a supporting material. The observation of beta-AlF3 in the XRD patterns of the aluminum-rich (Al/Mg > 1) catalysts implies that MgAlF5. 1.5H(2)O or MgF2 might be responsible for the transformation of gamma-AlF3 into beta-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. 1.5H(2)O in the catalyst support increases. (C) 1998 Elsevier Science B.V. All rights reserved.