R.F. Howe et al. / Journal of Molecular Catalysis A: Chemical 181 (2002) 63–72
71
zeolites such as beta may provide similar advantages.
Other high surface area supports for the transition
metal component also need to be explored.
generally, both synthesis and inter-conversion, offers
many opportunities for innovative research, both with
zeolites and with other types of catalyst.
The product of hydrodebromination of Halon 1301,
CHF3, has potential as a precursor for the production
of the replacement for the Halon, CF3I. This mate-
rial, known commercially as triiodide, is non-ozone
depleting and has fire suppressant properties only
slightly inferior to those of Halons [27]. A new cat-
alytic technology for CF3I production from CHF3 has
been recently described [28]. This involves gas phase
reaction of CHF3 with I2 in the presence of oxygen
over a carbon supported alkali metal salt catalyst, at
Acknowledgements
This work has received partial support from the
Australian Research Council Small Grant Scheme.
EXAFS measurements at the Photon Factory were
supported by the Australian Synchrotron Research
Program, and at SSRL by the Access to Major Re-
search Facilities Program.
◦
temperatures between 400 and 600 C. The reaction
ostensibly could be written as
References
CHF3 + I2 → CF3I + HI
but it has been shown that the actual reaction stoi-
chiometry is [29]
[
1] G.M. Bickle, T. Suzuki, Y. Mitarai, Chem. Eng. Trans. I 70
1992) 449.
(
[
2] M. Tajima, M. Niwa, Y. Fujii, Y. Koinuma, R. Aizawa, S.
Kushiyama, S. Kobayashi, K. Mizuno, H. Ohuchi, Appl.
Catal. B14 (1997) 97.
3
CHF3 + I2 → 2CF3I + C + 3HF
[
[
[
[
[
[
[
3] K.U. Niedersen, E. Lieske, E. Kemnitz, Green Chem. 1 (1999)
The role of oxygen in the reaction is to inhibit carbon
deposition and poisoning of the catalyst.
The pyrolysis and/or hydrodehalogenation of other
Halons offers further opportunities for catalysis. For
example, the elimination of bromine from Halon 2402
may provide a useful route to perfluoroethene:
225.
4] B. Coq, J.M. Cognion, F. Figueras, D. Tournigant, J. Catal.
141 (1993) 21.
5] B. Coq, F. Figueras, S. Hub, D. Tournigant, J. Phys. Chem.
9
9 (1995) 11159.
6] E. Kemnitz, D.H. Menz, Progr. Solid State Chem. 26 (1998)
7.
7] W. Juszczyk, A. Malinowski, Z. Karpinski, Appl. Catal. A166
1998) 311.
8] R. Ohnishi, W.L. Wang, M. Ichikawa, Appl. Catal. A113
1994) 29.
9] Z. Karpinski, K. Early, J. D’Itri, J. Catal. 164 (1996) 378.
9
C2F4Br2 → C2F4 + Br2
The homogeneous reaction of Halon 1211 with
methane in the gas phase has been shown recently to
give high yields of the coupling product C2H2F2 at
(
(
[
10] A. Malinowski, W. Juszczyk, M. Bonarowska, M.
Wojciechowska, Z. Kowalczyk, Z. Karpinski, React. Kinet.
Catal. Lett. 68 (1999) 53.
1
073 K [30]. This reaction can be formally written as
CF2ClBr + CH4 → CF2CH2 + HCl + HBr
[11] T. Mori, Y. Morikawa, Elsevier studies in surface science and
catalysis 130 (2000) 1985.
although the actual reaction pathway is more com-
plex than this, involving free radical abstraction and
coupling reactions. The possibility of enhancing this
reaction at lower temperatures with heterogeneous
catalysts is intriguing, both from the viewpoint
of Halon conversion to useful products, and from
the more fundamental aspect of catalytic methane
activation.
Finally, the catalytic hydrodehalogenation of CFCs
with methane rather than hydrogen clearly needs to be
pursued further, given the success of this process with
Halons. The catalytic chemistry of fluorocarbons more
[12] T. Mori, W. Ueda, Y. Morikawa, Catal. Lett. 38 (1996) 73.
[13] H.J.P. de Lijser, R. Louw, P. Mulder, J. Chem. Soc., Perkin
Trans. II (1994) 139.
[14] S. Gulati, M. Lavid, Chemical Processes in Combustion, 1993,
p. 69.
[15] K. Li, E.M. Kennedy, B. Moghtaderi, B.Z. Dlugogorski, et
al., Environ. Sci. Tech. 34 (2000) 584.
[16] K. Li, F. Oghanna, E.M. Kennedy, B.Z. Dlugogorski, A.
Fazeli, S. Thomson, R.F. Howe, Microp. Mesop. Mater. 35/36
(
2000) 219.
17] K. Li, E.M. Kennedy, B.Z. Dlugogorski, Chem. Eng. Sci. 55
2000) 4067.
18] Z. Konya, I. Kannus, I. Kiricsi, Elsevier studies in surface
science and catalysis 105 (1997) 1509.
[
[
(