Fachdokumente Online der Landesanstalt für Umwelt Baden-Württemberg

zur LUBW   zum Ministerium für Umwelt, Klima und Energiewirtschaft   zum Ministerium für Ländlichen Raum und Verbraucherschutz   zum Ministerium für Verkehr und Infrastruktur  

Summary

Two approaches are attempted in this project towards model improvement, (i) development and application of sensitive measurement techniques and (ii) investigation of some selected elementary reactions. To this end, our Jet-REMPI apparatus was coupled to the KLEAA model reactor leading to quite promising results. Although a lot of improvements could be achieved, the apparatus is still lacking the reliabilty needed for an analytical tool under practical conditions.

Concerning kinetics, we studied the reactions of phenoxy radicals with halogenated benzenes between 728 and 984 K, benzenes being used as substitutes for phenols. The results are in disagreement to the more recent literature, yet they support an earlier study which arrives at the conclusion that gas phase dioxin formation via this route is insignificant. Using a fast flow reactor, our kinetic studies were extended to include fast radical radical reactions. Chlorination of phenoxy radicals by Cl atoms could be shown qualitatively as well as the competing selfreaction.

Potential implications of this study on gas phase dioxin formation can only be assessed when a model of the complex chemistry in the turbulent flow field is available. Potential flow effects are dicussed in the light of recent publications.

In addition, it can be concluded from this study that gasphase dioxin formation via brominated phenols is hardly faster than the one via chlorinated phenols.

 


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