Evidence for a unified pathway of dioxin formation from aliphatic hydrocarbons

Philip H. Taylor, Sukh S. Sidhu, Wayne A. Rubey, Barry Dellinger, Andreas Wehrmeier, Dieter Lenoir, K. W. Schramm

Research output: Contribution to journalConference articlepeer-review

32 Scopus citations

Abstract

Acetylene is readily converted to perchlorinated gas-phase intermediates including hexachlorobenzene, hexachlorobutadiene, and tetrachloroethylene and heavier perchlorinated species via heterogeneous gas-solid reactions with HCl and cupric oxide on borosilicate under postcombustion conditions. Experiments were conducted using an integrated gas-solid flow-reactor and analytical system at temperatures ranging from 150 to 500 °C for gas-phase residence times of 2.0 s and total reaction times of 60 min. Chlorine addition and chlorine net substitution mechanisms mediated by the conversion of Cu(II)Cl2 to Cu(I)Cl are proposed to account for the observed or inferred C2 reaction products including tetrachloroethylene, trichloroethylene, and dichloroacetylene. The formation of condensation products including tetrachlorovinylacetylene, hexachlorobutadiene, and hexachlorobenzene are proposed to be catalyzed by copper chloride species and involve the following steps: (1) chemisorption of a chlorinated ethylene or acetylene by HCl elimination or 1,2-Cu-Cl addition, respectively; (2) physisorption of additional chlorinated ethylenes or acetylenes followed by cis-insertions; and (3) carbon-to-copper chlorine transfer followed by desorption of the molecular growth product. The mechanism accounts for product isomer distributions and branching, desorption of the higher molecular weight products, and regeneration of the copper chloride catalyst.

Original languageEnglish
Pages (from-to)1769-1775
Number of pages7
JournalSymposium (International) on Combustion
Volume27
Issue number2
DOIs
StatePublished - 1998
Externally publishedYes
Event27th International Symposium on Combustion - Boulder, CO, United States
Duration: 2 Aug 19987 Aug 1998

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