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PCDD/F formation from heterogeneous oxidation of wood pyrolysates
Journal article   Peer reviewed

PCDD/F formation from heterogeneous oxidation of wood pyrolysates

N. Tame, B. Dlugogorski and E. Kennedy
Fire Safety Science, Vol.9, pp.1189-1200
2008
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Abstract

This paper examines the formation of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/F) during oxidative pyrolysis of wood. Model lignocellulosic compounds and fractions isolated from wood serve to generate volatiles which then interact with copper-loaded surrogate ash to produce PCDD/F. The measurements indicate a preference for the formation of PCDF over PCDD in all experiments. Lignin yields considerably more PCDD/F than the carbohydrates, in agreement with the previous measurement in experiments performed under inert conditions [Tame, Dlugogorski, Kennedy, Conversion of Wood Pyrolysates to PCDD/F, Proc. Combust. Inst. 32, submitted]. The ratio of PCDD to PCDF varies according to the chemical structure of the feed; with carbohydrates demonstrating greater relative propensity for PCDF than lignin. The lignin monomers with methyl ether subsitituents (i.e., vanillin and syringol) produce less PCDD/F than those without (i.e., catechol and p-hydroxybenzaldehyde). Ensuing experiments, to examine yield of PCDD/F as a function of temperature and mass loading of vanillin, reveal the mechanism of heterogeneous condensation of chlorophenols with subsequent chlorination/ dechlorination.

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