Mechanisms of Dioxin Formation from the High-Temperature Oxidation of 2-Chlorophenol

Evans, Catherine S.; Dellinger, Barry

doi:10.1021/es049355z

Cited by 95 publications

(115 citation statements)

References 34 publications

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“…The detection of trace amounts of PCDD/Fs is consistent with previous literature concerning the oxidation of chlorinated phenols, as well as the oxidation of phenol in the presence of HCl over fly ash and CuO [1]. In fact, chlorophenol is considered to be the predominant precursor in heterogeneously catalyzed reaction mechanisms of PCDD/Fs formation [21]. Furthermore, the chlorinated PCDD/Fs, ethers, and furans observed are condensation products resulting from reactions between either two adsorbed species (via a Langmuir-Hinshelwood mechanism) or a surface and gas-phase/weakly adsorbed species (via an Eley-Rideal-type mechanism).…”

Section: By-product Analysis and Catalytic Mechanismsupporting

confidence: 90%

Catalytic Degradation of Ortho-Chlorophenol Using Activated Carbon Modified by Different Methods

et al. 2018

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Abstract:The performance of activated carbon (AC) modified by different methods was compared for its catalytic degradation of ortho-chlorophenol (o-CP). For the chemically treated AC, the catalytic effect of AC-NH 3 ·H 2 O was superior to the other catalysts examined, having an o-CP removal efficiency of 82.2% at 330 • C. For the metal-modified catalysts, AC-V and AC-Co showed similar removal performances of 93.2% at 330 • C. N 2 adsorption-desorption isotherms, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and gas chromatography-mass spectrometry (GC-MS) analyses were used to characterize the reaction products, and different reaction mechanisms were proposed for both AC-NH 3 ·H 2 O and AC-V according to the results. Complete oxidative degradation of o-CP was achieved by AC-V, with AC-NH 3 ·H 2 O leading to the formation of additional dioxins. It can be deduced that a risk of dioxin synthesis and escape during the regeneration process is possible when nitrogen-modified carbon is used in selective catalytic reduction (SCR) denitrification reactions, especially in the presence of chlorine atoms, benzene rings, and oxygen.

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Section: By-product Analysis and Catalytic Mechanismsupporting

confidence: 90%

Catalytic Degradation of Ortho-Chlorophenol Using Activated Carbon Modified by Different Methods

et al. 2018

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“…Using our results and previously published work (Babushok and Tsang, 2003;Evans and Dellinger, 2005), we propose a pathway for the formation of PCDD/Fs during dicofol production. C 6 H 5 Cl and Cl 2 are used as raw materials, so the C 6 H 5 Cl that had not already reacted with CCl 3 CHO could react with Cl 2 to produce polychlorobenzenes (Liu et al, 2004).…”

Section: Ddtsupporting

confidence: 70%

The release of persistent organic pollutants from a closed system dicofol production process

Yang

Ding

et al. 2014

Chemosphere

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h i g h l i g h t sPCDD/Fs and RDDTs in dicofol production process were analyzed. The inhalation of RDDTs in the workplace was evaluated. The emissions of RDDTs and PCDD/Fs in dicofol were calculated.The formation pathway of PCDD/Fs was discussed. a r t i c l e i n f o b s t r a c tHigh concentrations of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) have been found to be produced in chemical processes in which chlorine is a raw material. Samples of workshop air, waste water, waste acid, and the dicofol product were collected from a pesticide factory in China that uses a closed-system dicofol production process, and were analyzed for PCDD/Fs and RDDTs. The RDDTs concentrations were 1.88-17.53 lg m À3 in the workshop air samples, 4.85-456 lg kg À1 in the waste water and waste acid samples, and 4.74 g kg À1 in the dicofol product. The total estimated daily intakes of RDDTs for workers by inhalation in the workplace were in the range of 0.38-3.51 lg kg À1 bw d À1 for moderate activities. The annual amounts of RDDTs and p,p 0 -DDT directly released to the environment via the use of dicofol were 9480 kg and 1080 kg, respectively. The PCDD/F toxicity equivalent values (I-TEQs) in the waste water and waste acid samples ranged from 1.5 to 122 pg I-TEQ kg À1 and 86.3 ng I-TEQ kg À1 in the dicofol sample. The annual amount of PCDD/Fs released to the environment was 0.17 g I-TEQ. From the PCDD/F distribution patterns, it is suggested that the major pathway for PCDD/ F formation involves precursor synthesis during the production of dicofol in the closed-system process.

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“…The formation reactions from these monocyclic aromatic compounds involve degradation of these precursors and the rearrangement of their structures. The key step is the formation of the phenoxy radical (Louw and Ahonkhai, 2002;Evans and Dellinger, 2005;Altarawneh et al, 2007). Other important reactions are the self-condensation of the precursors, cyclization of initial intermediates and chlorination/de chlorination reactions (Altarawneh et al, 2009).…”

Section: Formation and Decomposition Mechanisms Of Pcdd/fsmentioning

confidence: 99%

An Overview of PCDD/F Inventories and Emission Factors from Stationary and Mobile Sources: What We Know and What is Missing

Cheruiyot

Lee

Yan

et al. 2016

Aerosol Air Qual. Res.

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This overview attempts to outline what we currently know about the PCDD/F emission inventories and the source categories therein. Besides the best available control techniques, suggestions are offered on how to reduce the PCDD/F emission factors and emission quantity of some important PCDD/F emission sources. The PCDD/F combustion sources can be classified as either stationary or mobile or minimally/uncontrolled combustion sources. The major stationary sources of PCDD/Fs are metal production processes, waste incineration, heat and power plants, and fly ash treatment plant. Crematories, vehicles, residential boilers and stoves are of key concern due to their proximity to residential areas and their relatively lower lying stacks and exhaust gases, which may result in great impact to their surrounding environment.Moreover, we offered our perspectives on how to improve the quality and representative of the PCDD/F emission factors to attain PCDD/F inventories which correspond more to reality. These points of view include: (1) PCDD/F contributions during start-up procedures of MSWIs should be considered, (2) the sampling times of stack flue gases for EAFs and secondary metal smelters should correspond to whole smelting process stages, (3) longer flue gas sampling time should be executed for power plants, (4) direct exhaust samplings from tailpipes for mobile sources, (5) development of an open burn testing facility that can reflect the real open burning conditions, and (6) long-term sampling techniques like AMESA are suggested to used exclusively for the most contributed PCDD/F stationary sources.

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Mechanisms of Dioxin Formation from the High-Temperature Oxidation of 2-Chlorophenol

Cited by 95 publications

References 34 publications

Catalytic Degradation of Ortho-Chlorophenol Using Activated Carbon Modified by Different Methods

Catalytic Degradation of Ortho-Chlorophenol Using Activated Carbon Modified by Different Methods

The release of persistent organic pollutants from a closed system dicofol production process

An Overview of PCDD/F Inventories and Emission Factors from Stationary and Mobile Sources: What We Know and What is Missing

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