Heterogeneously catalysed hydrolytic decomposition of CFCs . How to deal with CFCs still deposited in refrigerators and foams

Abstract

The hydrolytic decomposition of dichlorodifluoromethane (CFC-12) on modified zirconium oxide surfaces and on charcoal has been studied. The reaction was carried out under flow conditions at 450 °C. Complete CFC-12 conversion was obtained by employing a molar excess of water in the gas phase which depresses the formation of poisoning zirconium oxofluoride phases. These phases are responsible for the formation of unwanted monochlorodifluoromethane (CFC-13). The long-term stability of the catalysts was found to depend strongly on the CFC concentration in the gas phase. The lower the CFC concentration, the better the catalyst stability and catalytic activity. Pure charcoal can also be used as a catalyst for CFC hydrolysis. However, charcoal, owing to its reductive nature, may result in the formation of unwanted by-products and, thus, cannot be considered either as a serious catalyst nor as a suitable support.

References

1. C. S. Kellner andV. N. M. RaoUS Patent, 4 873 381 1989.
2. L. E. Manzer and V. N. M. Rao, Adv. Catal., 1993, 39, 329.
3. B. Coq, S. Hub, F. Figueras and D. Tournigant, Appl. Catal. A, 1993, 101, 41.
4. G. M. Bickle, T. Suzuki and Y. Mitarai, Appl. Catal. B, 1994, 4, 141.
5. B. Coq, F. Figueras, S. Hub and D. Tournigant, J. Phys. Chem., 1995, 99, 11159.
6. K. Early, V. I. Kovalchuk, F. Lonyi, S. Deshmukh and J. L. d'Itri, J. Catal., 1999, 182, 219.
7. E. R. Ritter, Combust Sci. Technol., 1994, 101, 171.
8. S. K. Jo and J. M. White, Surf. Sci., 1991, 245, 305.
9. Y. Nagata, K. Hirai, K. Okitsu, T. Dohmaru and Y. Maeda, Chem. Lett., 1995, 203.
10. A. Oku, K. Kimura and M. Sato, Ind. Eng. Chem. Res., 1989, 28, 1055.
11. A. J. Colussi and V. T. Amorebieta, J. Chem. Soc., Faraday Trans., 1987, 83, 3055.
12. S. Imamura, T. Shiomi, S. Ishida, K. Utani and H. Jindai, Ind. Eng. Chem. Res., 1990, 29, 758.
13. T. Aida, R. Higuchi and H. Niiyama, Chem. Lett., 1990, 2247.
14. S. Immura, T. Higashihara and H. Jindai, Chem. Lett., 1993, 1667.
15. S. Imamura, H. Shimizu, T. Haga, S. Tsuji, K. Utani and M. Watanabe, Ind. Eng. Chem. Res., 1993, 32, 3146.
16. S. Imamura, T. Higashihara and K. Utani, Ind. Eng. Chem. Res., 1995, 34, 967.
17. S. Karmakar and H. L. Greene, J. Catal., 1995, 151, 394.
18. S. W. Park, J. H. Yoon and H. Lee, Korean J. Chem. Eng., 1996, 13, 640.
19. E. Kemnitz, A. Kohne and E. Lieske, J. Fluorine Chem., 1997, 81, 197.
20. A. Hess and E. Kemnitz, Catal. Lett., 1998, 49, 199.
21. E. Kemnitz and D.-H. Menz, Prog. Solid State Chem., 1999, 26, 97.