Formation and inhibition of chloroaromatic micropollutants formed in incineration processes.
The formation pathways for chlorinated aliphatic and chlorinated aromatic compounds in technical incineration processes are reviewed. It is shown that acetylene is converted to chloroaromatic compounds including PCDD/F in a special flow reactor by catalytic activity of CuCl2 in the temperature regime of a post-combustion zone of technical incinerators. Mechanistic pathways begin with chlorination of acetylene. Dichloroacetylene is further condensed to C-4 and C-6 units. Hexachlorobenzene is the dominant aromatic compound and a likely precursor to chlorinated phenols and PCDD/F. Two specific mechanisms of formation of chlorinated aromatic compounds including PCDD/F have been advanced. Both mechanisms begin with the formation of dichloroacetylene from flame pyrolysis products like acetylene. Condensation of dichloroacetylene is mediated by copper species via metallacyclic intermediates and/or a catalytic cycle involving copper stabilized trichlorovinyl radicals. The final pathways of conversion of chlorinated benzenes to PCDD/F via chlorophenols are under active investigation.
Institüt für Okologisehe Chemie, GSF-Forschungszentrum für Umwelt und Gesundheit GmbH, Neuherberg, Germany. lenoir@gsf.de
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Lenoir
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Wehrmeier
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Sidhu
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Taylor
D000114:Acetylene / Q000737:chemistry*; D000397:Air Pollution; D001554:Benzene / Q000737:chemistry*; D001572:Benzofurans / Q000737:chemistry*; D017606:Chlorine Compounds / Q000737:chemistry; D004785:Environmental Pollutants; D017745:Incineration; D000072317:Polychlorinated Dibenzodioxins / Q000031:analogs & derivatives* / Q000737:chemistry*; D013696:Temperature
D001572:Benzofurans; D017606:Chlorine Compounds; D004785:Environmental Pollutants; D000072317:Polychlorinated Dibenzodioxins; D001554:Benzene; D000114:Acetylene