92341-07-6Relevant academic research and scientific papers
Role of copper chloride in the formation of polychlorinated dibenzo-p-dioxins and dibenzofurans during incineration
Hatanaka, Takeshi,Kitajima, Akio,Takeuchi, Masao
, p. 73 - 79 (2007/10/03)
Combustion experiments in a laboratory-scale fluidized-bed reactor were performed to elucidate the role of copper chloride in formation of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) during model waste incineration. The amounts of PCDDs and PCDFs formed, the homologue profiles, and the isomer distributions were measured in the flue gas from incineration of model wastes containing various levels of copper. A correlation was found between the Cu content of the waste and the proportion of each congener. An increase in copper enhanced the formation of certain congeners, showing that copper acts as a catalyst for formation of PCDDs and PCDFs. An increase in the copper content of the waste decreased the CO concentration in the flue gas and reduced the formation of PCDDs and PCDFs during incineration. This indicates that copper also works as an oxidation catalyst to promote combustion, leading to lower concentrations of products of incomplete combustion. It is indispensable to consider both roles of the catalyst, i.e., enhancement and suppression, in the formation of PCDDs and PCDFs during waste incineration, which are estimated separately from the isomer distributions and the amounts of PCDDs and PCDFs formed.
Prediction of polychlorinated dibenzofuran congener distribution from gas-phase phenol condensation pathways
Ryu, Jae-Yong,Mulholland, James A.,Oh, Jeong-Eun,Nakahata, Duane T.,Kim, Do-Hyong
, p. 1447 - 1455 (2007/10/03)
A model for predicting the distribution of dibenzofuran and polychlorinated dibenzofuran (PCDF) congeners from a distribution of phenols was developed. The model is based on a simplified chemical mechanism. Relative rate constants and reaction order with respect to phenol precursors were derived from experimental results using single phenols and equal molar mixtures of up to four phenols. For validation, experiments were performed at three temperatures using a distribution of phenol and 19 chlorinated phenols as measured in municipal waste incinerator exhaust gas. Comparison of experimental measurements and model predictions for PCDF isomer distributions and homologue pattern shows agreement within measurement uncertainty. The R-squared correlation coefficient exceeds 0.9 for all PCDF isomer distributions and the distribution of PCDF homologues. These results demonstrate that the distribution of dibenzofuran and the 135 PCDF congeners from gas-phase condensation of phenol and chlorinated phenols can be predicted from measurement of the distribution of phenol and the 19 chlorinated phenol congeners.
De novo synthesis mechanism of polychlorinated dibenzofurans from polycyclic aromatic hydrocarbons and the characteristic isomers of polychlorinated naphthalenes
Iino,Imagawa,Takeuchi,Sadakata
, p. 1038 - 1043 (2007/10/03)
Polychlorinated dibenzofurans (PCDFs) and polychlorinated naphthalenes (PCNs) are known to be emitted from municipal waste incinerators (MWIs) with polychlorinated dibenzo-p-dioxins (PCDDs). Two formation paths for PCDD/Fs could mainly work, which are condensation of the precursors such as chlorophenols and 'de novo' formation from carbon. However the correlation between the chemical structure of carbon and the resulting PCDD/Fs still remains unknown. In this study, the PCDD/Fs formation from polycyclic aromatic hydrocarbons (PAHs) and CuCl was examined at 400 under 10% O2. Coronene among the PAHs characteristically gave 1,2,8,9-T4CDF and the derivatives. These isomers clearly indicate that chlorination causes the cleavage of the C-C bonds in a coronene molecule and also that oxygen is easily incorporated from its outside to form 1,2,8,9-T4CDF. The symmetrical preformed structures in the coronene molecule enabled to amplify the de novo formation of the isomer. PCNs are also formed directly from these PAHs. Since there have been few reports on the formation mechanism of PCNs, this study will be a first step to know the whole formation paths. We also define the de novo synthesis as the breakdown reaction of a carbon matrix, since the word has been used without the precise definition.
Isomer distributions of polychlorinated dibenzo-p-dioxins/dibenzofurans formed during de novo synthesis on incinerator fly ash
Addink, Ruud,Govers, Harrie A. J.,Olie, Kees
, p. 1888 - 1893 (2007/10/03)
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 (Δg°(f,T)). This would make prediction of the isomer composition of a particular sample (and hence its TEQ value) possible, based on values of ΔG°(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 ΔG°(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 work- time-based studies with precursors, isomerization studies with single congeners, and more data on ΔG°(f,T) values of PCDD/F-were made. 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 (ΔG°f,T). This would make prediction of the isomer composition of a particular sample (and hence its TEQ value) possible, based on values of ΔG°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 ΔG°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 work - time-based studies with precursors, isomerization studies with single congeners, and more data on ΔG°f,T values of PCDD/F - were made.
A COMPARATIVE STUDY OF THE PHOTOLYTIC DEGRADATION OF OCTACHLORODIBENZOFURAN (OCDF) AND OCTACHLORODIBENZO-P-DIOXIN (OCDD)
Wagenaar, W. J.,Boelhouwers, E. J.,Kok, H. A. M. de,Groen, C. P.,Govers, H. A. J.,et al.
, p. 2983 - 2992 (2007/10/03)
Photolysis at 290 nm and higher wavelengths of octachlorodibenzofuran (OCDF) and octachlorodibenzp-p-dioxin (OCDD) was studied in three organic solvents hexane, 1,4-dioxane and methanol. It appeared that the degradation kinetics strongly depended on the type of solvent. OCDD degraded fastest in hexane, whereas OCDF degraded fastest in methanol. Less than 5 percent of the total loss of OCDD degraded by reductive dechlorination, with preferential loss of chlorine atoms at the 1 or 9 positions. 25 to 50 percent of the total loss of OCDF degraded via reductive dechlorination, with preferential loss of lateral chlorine. OCDF degraded faster than OCDD in all studied solvents. Photolysis at 290 nm and higher wavelengths of OCDD and OCDF adsorbed onto alumina impregnated with copper (alumina/Cu) in the presence of natural and distilled water was also investigated. Under these more relevant environmental aquatic conditions, photolysis of OCDD and OCDF was much slower than photolysis in the studied organic solvents. Significant loss was only found for OCDF. A part of the loss OCDF could be explained by reductive dechlorination; the results suggested that other mechanisms of degradation occurred in addition to reductive dechlorination. All photolysis experiments showed that OCDF was photochemically less stable than OCDD.
