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Mechanistic evaluation of polychlorinated dibenzo-p-dioxin, dibenzofuran and naphthalene isomer fingerprints in microwave pyrolysis of biomass
Umeå University, Faculty of Science and Technology, Department of Chemistry.
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2016 (English)In: Chemosphere, ISSN 0045-6535, E-ISSN 1879-1298, Vol. 150, 168-175 p.Article in journal (Refereed) PublishedText
Abstract [en]

Isomer distribution patterns of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and naphthalenes (PCNs) were investigated in microwave-assisted pyrolysis (MAP) products of woody biomass. The feedstocks included bark and impregnated wood. The results indicated that isomer distributions in MAP are more selective compared to those reported from wood burning and waste incineration. Favored formation of 4-MoCDF and highly selective chlorine substitution at the 2,4-position observed during MAP suggested a preferred formation pathway of PCDFs involving (chloro)phenol precursors followed by subsequent chlorination. The PCDD distribution was dominated by isomers typically formed from chlorophenol condensation at relatively low temperature. The PCN isomer distributions showed a tendency for sequential chlorination from non-substituted naphthalene at successive positions. The presence of isomers such as 1-MoCDD, 4-MoCDF, 1,2,3-TriCN with low thermodynamic stability indicates that kinetic factors may be important in the MAP process.

Place, publisher, year, edition, pages
Elsevier, 2016. Vol. 150, 168-175 p.
Keyword [en]
PCDD, PCDF, Dioxin-like compounds, PCN, Persistent organic pollutants, Biomass thermochemical conversion
National Category
Organic Chemistry Environmental Sciences
URN: urn:nbn:se:umu:diva-118908DOI: 10.1016/j.chemosphere.2016.02.031ISI: 000372765100022PubMedID: 26901473OAI: diva2:917373
Available from: 2016-04-06 Created: 2016-04-06 Last updated: 2016-05-20Bibliographically approved
In thesis
1. Dioxins and dioxin-like compounds in thermochemical conversion of biomass: formation, distribution and fingerprints
Open this publication in new window or tab >>Dioxins and dioxin-like compounds in thermochemical conversion of biomass: formation, distribution and fingerprints
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In the transition to a sustainable energy supply there is an increasing need to use biomass for replacement of fossil fuel. A key challenge is to utilize biomass conversion technologies in an environmentally sound manner. Important aspects are to minimize potential formation of persistent organic pollutants (POPs) such as dioxins and dioxin-like compounds.

This thesis involves studies of formation characteristics of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and naphthalenes (PCNs) in microwave-assisted pyrolysis (MAP) and torrefaction using biomass as feedstock. The research focuses are on their levels, distributions, fingerprints (homologue profiles and isomer patterns) and the underlying formation pathways. The study also included efforts to optimize methods for extracting chlorinated aromatic compounds from thermally treated biomass. The overall objective was to contribute better understanding on the formation of dioxins and dioxin-like compounds in low temperature thermal processes.

The main findings include the following:

  • Pressurized liquid extraction (PLE) is applicable for simultaneous extraction of PCDDs, PCDFs, PCNs, polychlorinated phenols and benzenes from thermally treated wood. The choice of solvent for PLE is critical, and the extraction efficiency depends on the degrees of biomass carbonization.
  • In MAP experiments PCDDs, PCDFs and PCNs were predominantly found in pyrolysis oils, while in torrefaction experiments they were mainly retained in solid chars with minor fractions in volatiles. In both cases, highly chlorinated congeners with low volatility tended to retain on particles whereas the less chlorinated congeners tended to volatize into the gas phase.
  • Isomer patterns of PCDDs, PCDFs and PCNs generated in MAP were more selective than those reported in combustion processes. The presence of isomers with low thermodynamic stability suggests that the pathway of POPs formation in MAP may be governed not only by thermodynamic stabilities but also by kinetic factors.
  • Formation of PCDDs, PCDFs and PCNs depends not only on the chlorine contents in biomass but also the presence of metal catalysts and organic/metal-based preservatives.

Overall, the results provide information on the formation characteristics of PCDDs, PCDFs and PCNs in MAP and torrefaction. The obtained knowledge is useful regarding management and utilization of thermally treated biomass with minimum environmental impact.

Place, publisher, year, edition, pages
Umeå: Umeå University, 2016. 72 p.
Polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, polychlorinated naphthalenes, PCDD, PCDF, PCN, persistent organic pollutants, torrefaction, pyrolysis
National Category
Organic Chemistry
urn:nbn:se:umu:diva-118861 (URN)978-91-7601-451-6 (ISBN)
Public defence
2016-04-29, KBC-huset, KB3A9, Umeå universitet, Umeå, 10:00 (English)
Available from: 2016-04-08 Created: 2016-04-05 Last updated: 2016-04-20Bibliographically approved

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