An evaluation of the heat of formation of chlorinated dioxins and its application to isomer abundance predictions

Thompson, D.

doi:10.1016/0045-6535(94)90056-6

Cited by 22 publications

(21 citation statements)

References 6 publications

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“…The theoretical values depicted in Figures −6 were based on calculations of Δ G ° f,T for all tetra−hepta CDD/F. Calculations by Thompson ( , ) and Unsworth et al () gave values of Δ G ° f,T that were quite comparable. Also, the values of Δ G ° f,T within a certain homologue were quite close for all isomers within that homologue.…”

Section: Resultsmentioning

confidence: 87%

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Isomer Distributions of Polychlorinated Dibenzo-p-dioxins/Dibenzofurans Formed during De Novo Synthesis on Incinerator Fly Ash

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Govers

Olie

1998

Environ. Sci. Technol.

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Polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF) emitted from municipal waste incinerators appear to have a chlorination pattern that is quite constant across various samples and conditions. This suggested that these patterns may be controlled by thermodynamic properties of the individual PCDD/F congeners, such as the free Gibbs energy of formation (∆G°f ,T ). This would make prediction of the isomer composition of a particular sample (and hence its TEQ value) possible, based on values of ∆G°f ,T . A laboratory scale study was carried out with activated carbon on fly ash as the source of PCDD/F formation. Although it was found that the isomer distributions within homologues were independent of the reaction time (proof of thermodynamic control), other observations (lack of equilibrium/isomerization between isomers and lack of similarity between isomer distributions measured and predicted by ∆G°f ,T ) contradicted the possibility of thermodynamic control. Hence, this study could not confirm that de novo formation of PCDD/F could explain thermodynamically controlled isomer distributions in incinerators. Some recommendations for further workstime-based studies with precursors, isomerization studies with single congeners, and more data on ∆G°f ,T values of PCDD/ Fswere made.

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Section: Resultsmentioning

confidence: 87%

“…Values of Δ H ° f,T and Δ G ° f,T for the various PCDD/F congeners were reported by a number of authors ( − ). These thermodynamic data could then be used to compare isomer distributions measured in effluents and predicted by theory.…”

Section: Introductionmentioning

confidence: 99%

Isomer Distributions of Polychlorinated Dibenzo-p-dioxins/Dibenzofurans Formed during De Novo Synthesis on Incinerator Fly Ash

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Govers

Olie

1998

Environ. Sci. Technol.

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“…However, when Koester and Hites [19] used the MNDO method to calculate the ideal gas enthalpies of formation for all of the tetra-through octa-chlorinated dibenzo-pdioxins, they obtained enthalpy of formation results higher than Shaub's [16,17] by 83 kJ/mol on average. A similar comparison of Thompson's [18] variation of Shaub's method to the MNDO method showed substantial but less dramatic differences in enthalpy of formation values. Unsworth and Dorans [20], however, indicated that the MNDO method predicted the most reliable data for dioxins when compared with the AM1, PM3, and Shaub's methods.…”

Section: Ideal Gas Enthalpy Of Formationmentioning

confidence: 84%

Gibbs free energies of formation of pcdds: Evaluation of estimation methods and application for predicting dehalogenation pathways

Huang

Harrison

Madura

et al. 1996

Enviro Toxic and Chemistry

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Gibbs free energies of formation for the ideal gas, liquid phase, and species in solution were estimated for 75 polychlorinated dibenzo‐p‐dioxins (PCDDs) at 298.15 K and 100,000 Pa. These values were used to calculate standard redox potentials, with H2 as the electron donor. Owing to the lack of experimental thermodynamic data for the involved chemical species, the standard‐state ideal gas enthalpies of formation were evaluated by several semiempirical methods including the Modified Neglect of Diatomic Differential Overlap (MNDO), Austin Model 1 (AM1), and MNDO–Parametric Method 3 (PM3). Three different implementations of Benson's group additivity method for estimation of ideal gas enthalpies of formation were also evaluated. As a result of the evaluation, the CHETAH program based on Benson's group additive method was chosen for ideal gas enthalpy of formation calculations. Entropies, vapor pressure, and aqueous solubility were calculated by existing methods in order to complete the thermodynamic cycle. Calculated redox potentials indicate that chlorodioxins, including 2,3,7,8‐tetrachlorodioxin, can serve as electron acceptors in anaerobic environments, at least from a thermodynamic perspective.

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“…The stable pattern implies that the formation could be controlled by thermodynamic properties. The 2,3,7,8-substituted CDD congeners have been shown to be more thermodynamically stable than the 1,4,6,9-substituted ( − ). However, the thermodynamically controlled model is not able to entirely explain the stable extensive congener pattern in the flue gas from MSW incineration.…”

Section: Resultsmentioning

confidence: 99%

Influence of Variation in Combustion Conditions on the Primary Formation of Chlorinated Organic Micropollutants during Municipal Solid Waste Combustion

Wikström

Tysklind

Marklund

1999

Environ. Sci. Technol.

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The aim of this study was to investigate the influence of variation in combustion conditions on the primary formation of organic micropollutants (OMPs). The flue gas samples were taken at a relatively high flue gas temperature (650 °C), to enable mechanistic studies on the high temperature formation (primary formation). Eleven experiments were performed in a laboratory scale fluidized bed reactor fed with an artificial municipal solid waste (MSW). The samples were analyzed for mono- to octachlorinated dibenzo-p-dioxins and dibenzofurans (CDDs/Fs), tri- to decachlorinated biphenyls (CBs), di- to hexachlorinated benzenes (CBzs), and di- to pentachlorinated phenols (CPhs). In addition to chlorinated OMPs, nonchlorinated dibenzo-p-dioxin (DD), dibenzofuran (DF), and biphenyl (BP) were analyzed. The experiments show that variations in the CE influence the degree of chlorination of the organic micropollutants. A correlation between low CE and formation of non- and low-chlorinated OMPs was seen and a distinct relationship of higher chlorinated homologues and efficient combustion condition. Thus, the DiCDFs and DiCBzs are formed during low combustion efficiency (CE), while the PeCDF and PeCBzs formation take place at higher CE. The distribution between primary and secondary air is important for the formation of higher CDD/Fs and CBzs. The primary formation of CDDs and CDFs is through different mechanisms. The CDDs are mainly formed by condensation of CPhs, while the CDFs are formed through a non- or a low-chlorinated precursor followed by further chlorination reactions.

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An evaluation of the heat of formation of chlorinated dioxins and its application to isomer abundance predictions

Cited by 22 publications

References 6 publications

Isomer Distributions of Polychlorinated Dibenzo-p-dioxins/Dibenzofurans Formed during De Novo Synthesis on Incinerator Fly Ash

Isomer Distributions of Polychlorinated Dibenzo-p-dioxins/Dibenzofurans Formed during De Novo Synthesis on Incinerator Fly Ash

Gibbs free energies of formation of pcdds: Evaluation of estimation methods and application for predicting dehalogenation pathways

Influence of Variation in Combustion Conditions on the Primary Formation of Chlorinated Organic Micropollutants during Municipal Solid Waste Combustion

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