(0.04 kW h kg21 H2O2). Therefore, a big improvement in energy
utilization could be anticipated in future work. Now, work has
been carried out in our laboratory to enhance the formation
efficiency of H2O2, and to increase the electric energy utilization by
optimizing the discharge conditions and the structure of the
discharge reactor.
would make the temperature of the gas mixture to increase to as
high as 195 uC under adiabatic condition. In reactor A, both
electric heat and reaction heat could be removed as soon as
possible by the liquid electrode, so that it could be operated
under 25 uC.
Besides, we also found that the liquid grounding electrode had
an addtional function in improving the discharge behavior of the
atmospheric pressure discharge.8 That is, it decreased the spark
filaments (local and highly ionized narrow pathways for the
conduction of current) in the discharge space and made the
discharge more homogenous and stable. In addition, the Pyrex-
covered copper HV electrode in reactor A is believed to be superior
to the naked metal electrode in preventing both O2 and H2O2 from
being consumed by the surface of the metal electrode. It might also
favor the formation of OH radicals according to Luo et al.9 OH
radicals are supposed to be one of the key intermediates leading to
H2O2 in the non-equilibrium plasma of H2/O2.10 These factors also
contributed to the H2O2 selectivity.
Juncheng Zhou, Hongchen Guo,* Xiangsheng Wang, Mingxing Guo,
Jiangli Zhao, Lixing Chen and Weimin Gong
Department of Catalytic Chemistry and Engineering & National Key
Laboratory of Fine Chemicals, Dalian University of Technology, Dalian,
116012, P. R. China. E-mail: hongchenguo@163.com;
Fax: (+86) 411-8368-9065
Notes and references
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V. V Krishnan, A. G. Dokoutchaev and M. E. Thompson, J. Catal.,
2000, 196, 366; (c) D. P. Dissanayake and J. H. Lunsford, J. Catal.,
2003, 214, 113; (d) J. H. Lunsford, J. Catal., 2003, 216, 455; (e)
G. Blanco-Brieva, E. Cano-Serrano, J. M. Campos-Martin and J. L.
G. Fierro, Chem. Commun., 2004, 1184.
3 (a) P. Landon, P. J. Collier, A. J. Papworth, C. J. Kiely and
G. J. Hutchings, Chem. Commun., 2002, 2058; (b) P. Landon,
P. J. Collier, A. F. Carley, D. Chadwick, A. J. Papworth, A. Burrows,
C. J. Kiely and G. J. Hutchings, Phys. Chem. Chem. Phys., 2003, 5,
1917.
4 (a) D. Bianchi, R. Bortolo, R. D. Aloisio and M. Ricci, Angew. Chem.
Int. Ed., 1999, 38, 706; (b) W. R. Thiel, Angew. Chem. Int. Ed., 1999, 38,
3157.
5 (a) V. R. Choudhary, A. G. Gaikwad and S. D. Sansare, Angew. Chem.
Int. Ed., 2001, 40, 1776; (b) V. R. Choudhary, C. Samanta and
A. G. Gaikwad, Chem. Commun., 2004, 2054.
6 (a) B. K. Morinaga, Bull. Chem. Soc. Jpn., 1962, 35, 345; (b)
B. K. Morinaga, Bull. Chem. Soc. Jpn., 1962, 35, 625; (c)
M. Venugopalan and R. A. Jones, Chem. Rev., 1966, 66, 133.
7 Y. Magara, M. Itoh and T. Morioka, Prog. Nucl. Energy, 1995, 29, 175.
8 (a) T. Czerfalvi, P. Mezei and P. Apai, J. Phys. D: Appl. Phys., 1993, 26,
2184; (b) P. Mezei, T. Czerfalvi and M. Janossy, J. Anal. At. Spectrom.,
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Mullen, Spectrochim. Acta, Part B, 2002, 57, 609.
9 J. Luo, S. L. Suib, Y. Hayashi and H. Matsumoto, J. Phys. Chem. A.,
1999, 103, 6151.
10 R. Atkinson, D. L. Baulch, R. A. Cox, R. F. Hampson, J. A. Kerr and
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In conclusion, the gaseous synthesis of H2O2 via the direct
reaction of H2/O2 non-equilibrium plasma seems promising. By
using the plasma method, it is possible to continuously generate
H2O2 aqueous solutions with different concentrations if the time
course of pre-discharge is properly selected and then the flow rate
of the stripping water (in) and the H2O2 product solution (out) is
precisely controlled. If the work volume of the discharge reactor
could be scaled up to 1 m3 with the same performance, aqueous
solutions of 30 wt% H2O2 could be produced continuously at a
rate of 48 kg h21 m23. Compared with other known methods, the
merits of the plasma method might include mild conditions, good
safety, environmentally friendly, virtually no separation/purifica-
tion process is needed, and being able to continuously generate
H2O2 with high concentration and purity. It may be developed as a
convenient and flexible H2O2-production process. The primary
issue concerning the plasma method is the electric energy
utilization. Although the actual electric energy consumption by
the discharge reactor is very high (80 kW h kg21 H2O2) currently,
the low activation energy of the plasma method for H2O2
synthesis, and the exothermic nature of the H2O2 forming reaction
indicate a fairly low theoretical electric energy consumption
This journal is ß The Royal Society of Chemistry 2005
Chem. Commun., 2005, 1631–1633 | 1633