Halogen exchange reactions for CFC alternatives. . The behaviour of fluorine-18 labelled hydrogen fluoride towards prefluorinated chromia containing nickel(II) or zinc(II)

Abstract

Highly active catalysts are required for the conversion of CF₃CH₂Cl to the CFC-alternative refrigerant, CF₃CH₂F, by HF vapour under heterogeneous conditions. Chromia impregnated with a very low level of zinc(II) is a superior catalyst precursor to chromia alone. The behaviour of prefluorinated chromia and prefluorinated chromia containing zinc(II) or nickel(II) towards fluorine-18 labelled HF indicates that two types of labile surface fluoride are present, only one of which is catalytically active. Proposals are made to account for the role of Zn^II and Ni^II.

References

1. (a) S. Brunet, B. Requieme, E. Colnay, J. Barrault and M. Blanchard, Appl. Catal. B, 1995, 5, 305; (b) S. Brunet, B. Requieme, E. Matouba, J. Barrault and M. Blanchard, J. Catal., 1995, 152, 70; (c) S. Brunet, B. Boussand, A. Rousset and D. Andre, Appl. Catal. A, 1998, 168, 57.
2. A. Kohne and E. Kemnitz, J. Fluorine Chem., 1995, 75, 103.
3. H. Kim, H. S. Kim, B. G. Lee, H. Lee and S. Kim, J. Chem. Soc., Chem. Commun., 1995, 2384; H. Lee, H. D. Jeong, Y. S. Chung, H. G. Lee, M. J. Chung, S. Kim and H. S. Kim, J. Catal., 1997, 167, 307.
4. J. A. Lu, H. Yang, S. K. Chen, L. Shi, J. G. Pen, H. L. Li and S. Y. Peng, Catal. Lett., 1996, 41, 221.
5. H.-d. Quan, Z. Li, Z.-x. Zhao, H.-e. Yang, J. Lu, J.-g. Pen, S.-k. Chen, H.-f. Li and H.-l. Li, Appl. Catal. B, 1996, 8, 209.
6. D. R. Coulson, J. Catal., 1993, 142, 289.
7. K. Niedersen, E. Schreier and E. Kemnitz, J. Catal., 1997, 167, 210.
8. A. S. Al-Ammar and G. Webb, J. Chem. Soc., Faraday Trans. 1, 1978, 74, 195.
9. J. Kijowski, G. Webb and J. M. Winfield, Appl. Catal., 1986, 27, 181.