Advertisement

Journal of Atmospheric Chemistry

, Volume 25, Issue 3, pp 229–250 | Cite as

The heterogeneous formation of N2O over bulk condensed phases in the presence of SO2 at high humidities

  • M. Pires
  • H. Van den Bergh
  • M. J. Rossi
Article

Abstract

In view of the uncertainty of the origin of the secular increase of N2O, we studied heterogeneous processes that contribute to formation of N2O in an environment that comes as close as possible to exhaust conditions containing NO and SO2, among other constituents. The N2O formation was followed using electron capture gas chromatography (ECD-GC). The other reactants and intermediates (SO2, NO, NO2 and HONO) were monitored using gas phase UV-VIS absorption spectroscopy. Experiments were conducted at 298 and 368 K as well as at dry and high humidity (approaching 100% rh) conditions. There is a significant heterogeneous rate of N2O formation at conditions that mimic an exhaust plume from combustion processes.The simultaneous presence of NO, SO2, O2 in the gas phase and condensed phase water, either in the bulk liquid or adsorbed state has been confirmed to be necessary for the production of significant levels of N2O. The stoichiometry of the overall reaction is: 2 NO+SO2+H2O → N2O+H2SO4. The maximum rate of N2O formation occurred at the beginning of the reaction and scales with the surface area of the condensed phase and is independent of its volume. A significant rate of N2O formation at 368 K at 100% rh was also observed in the absence of a bulk substrate. The diffusion of both gas and liquid phase reactants is not rate limiting as the reaction kenetics is dominated by the rate ofN2O formation under the experimental conditions used in this work. The simultaneous presence of high humidity (90–100% rh at 368 K) and bulk condensed phase results in the maximum rate and final yield of N2O approaching 60% and 100% conversion after one hour in the presence of amorphous carbon and fly-ash, respectively.

Key words

N2O formation heterogeneous reactions synthetic exhaust/flue gas soot fly-ash calcite sulfuric acid solutions high relative humidities 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Andrade, A., 1985: M.Sc. thesis, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil (in Portuguese).Google Scholar
  2. BardO. and ProbertS. D., 1993: Environmental impacts of atmospheric nitrous oxide, Appl. Energy 44, 197–231.Google Scholar
  3. BeckerK. H., KleffmannJ., KurtenbachR., WiesenP., 1996: Heterogeneous conversion of NO2 on acid surfaces, Faraday Discuss. 100, 121–127.Google Scholar
  4. BergesM. G. M., HofmannR. M., ScharffeD., and CrutzenP. J., 1993: Nitrous oxide emissions from motor-vehicles in tunnels and their global extrapolation, J. Geophys. Res. 98, 18527–18531.Google Scholar
  5. BouwmanA. F., Van derHoekK. W., and OlivierJ. G. J., 1995: Uncertainties in the global source distribution of nitrous oxide, J. Geophys. Res. 100, 2785–2800.Google Scholar
  6. CiceroniJ. R., 1989: Analysis of sources and sinks of atmospheric nitrous oxide (N2O), J. Geophys. Res. 94, 18,265–18,271.Google Scholar
  7. DeSantisF. and AllegriniI., 1992: Heterogeneous reactions of SO2 and NO2 on carbonaceous surfaces, Atmos. Environ. 26A, 3061–3064.Google Scholar
  8. DlugiR. and GüstenH., 1993: The catalytic and photocatalytic activity of coal fly ashes, Atmos. Environ. 17, 1765–1771.Google Scholar
  9. Fiedler, H. D., 1987: M.Sc. thesis, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil (in Portuguese).Google Scholar
  10. FisherG. L. et al., 1978: Physical and morphological studies of size-classified coal fly-ash, Env. Sci. & Tech. 12, 447–451.Google Scholar
  11. GhosalS. and SelfS. A., 1995: Particle size-density relation and cenosphere content of coal fly-ash, Fuel 74, 522–529.Google Scholar
  12. KhalilM. A. K. and RasmussenR. A., 1992: Nitrous oxide coal-fired power plants: Experiments in the plumes, J. Geophys. Res. 97, 14,645–14,649.Google Scholar
  13. LinakW. P., McSorleyJ. A., and HallR. E., 1990: Nitrous oxide emission from fossil fuel combustion, J. Geophys. Res. 95, 7533–7541.Google Scholar
  14. LinakW. P. and WendtJ. O. L., 1994: Trace-metal transformation mechanisms during coal combustion, Fuel Process. Technol. 39, 173–198.Google Scholar
  15. MeijR., 1994: Trace-element behavior in coal-fired power-plants, Fuel Process. Technol. 39, 199–217.Google Scholar
  16. MuzioL. J. and KramlichJ. C., 1988: An artifact in the measurements of N2O from combustion sources, Geophys. Res. Lett. 15, 1369–1372.Google Scholar
  17. Pires, M., 1988: M.Sc. thesis, Universidade Federal do Rio Grande do Sul, Brazil (in Portuguese).Google Scholar
  18. PiresM. and TeixeiraE., 1992: Geochemical distribution of trace elements in the Leao coal, Fuel 71, 1093–1096.Google Scholar
  19. PiresM., RossD. S., and RossiM. J., 1994: Kinetic and mechanistic aspects of the NO oxidation by O2 in aqueous-phase, Int. J. Chem. Kin. 26, 1207–1227.Google Scholar
  20. Pires, M., 1995: Ph.D. thesis, Ecole Polytechnique Fédérale de Lausanne, Switzerland.Google Scholar
  21. Pires, M. and Rossi, M. J., 1996: The heterogeneous formation of N2O in the presence of acidic solutions: Experiments and modeling, submitted to Int. J. Chem. Kin. Google Scholar
  22. SergidesC. A., JassimJ. A., ChughtaiA. R., and SmithD. M., 1987: The structure of hexane soot. Part III: Ozonation studies, Appl. Spectros. 41, 482–492.Google Scholar
  23. SmithD. M., WelchW. F., JassimJ. A., ChughtaiA. R., and StedmanD. H., 1988: Soot-ozone reaction kinetics: Spectroscopic and gravimetric studies, Appl. Spectros. 42, 1473–1483.Google Scholar
  24. SmithR. D., 1980: Trace elements chemistry of coal during combustion and emissions from coal fired plants, Prog. Energy Combust. Sci. 6, 53–119.Google Scholar
  25. StephensS., RossiM. J., and GoldenD. M., 1986: The heterogeneous reaction of ozone on carbonaceous surfaces, Int. J. Chem. Kin. 18, 1133–1149.Google Scholar
  26. TaborK., GutzwillerL., and RossiM. J., 1994: Heterogeneous chemical-kinetics of NO2 on amorphous-carbon at ambient-temperature, J. Phys. Chem. 98, 6172–6186.Google Scholar
  27. Teixeira, E. C., 1995: personal communication.Google Scholar
  28. ThiemensM. H. and TroglerW. C., 1991: Nylon production: An unknown source of atmospheric nitrous oxide, Science 251, 932–934.Google Scholar

Copyright information

© Kluwer Academic Publishers 1996

Authors and Affiliations

  • M. Pires
    • 1
  • H. Van den Bergh
    • 1
  • M. J. Rossi
    • 1
  1. 1.Laboratoire de Pollution Atmosphérique et Sol (LPAS)Ecole Polytechnique Fédérale de Lausanne (EPFL)LausanneSwitzerland

Personalised recommendations