3268-87-9Relevant articles and documents
The formation of polychlorinated dibenzo-p-dioxins/dibenzofurans from carbon model mixtures containing ferrous chloride
Ryan, Shawn P.,Altwicker, Elmar R.
, p. 1009 - 1014 (2000)
The potential to form polychlorinated dibenzo-p-dioxins/furans (PCDD/F) was investigated in carbon model systems containing ferrous chloride tetrahydrate and a matrix representative of that found in particle emission from the catalytic extraction process (CEP) for wastes. Various types of carbons were used resulting in different PCDD/F yields but, with one exception, similar homologue distributions. Due to the similarity between the turbostratic structure of the carbon in the representative CEP dusts and the carbon blacks used in the model system, experiments were performed using two carbon blacks (termed CBA and CBB). On a mass basis, CBB was more reactive over the temperature range of 275-325°C and reaction times of 20-60 min in the formation of PCDD/F; as well as more adsorptive in terms of the desorption of PCDD/F. On a volume basis, the reactivities and adsorptivities were similar. A maximum in PCDD/F formation occurred at an oxygen concentration of 2% in nitrogen. (C) 2000 Elsevier Science Ltd.
Formation of PCDD/Fs in the sintering process: Influence of the raw materials
Xhrouet, Celine,De Pauw, Edwin
, p. 4222 - 4226 (2004)
The sintering process is among the major sources of PCDD/Fs in the environment. This research studies the influence of the raw materials in this type of industrial plant on the amounts of PCDD/Fs generated. Particular interest is given to coke, which constitutes the principal source of carbon for the de novo synthesis of PCDD/Fs, and to the dust collected in the electrostatic precipitator (E.S.P. dust), usually recycled in the raw materials. The de novo synthesis of PCDD/Fs is simulated at the laboratory scale by thermal treatments of the samples. The use of a particular coke as a fuel does not drastically reduce the formation of PCDD/Fs. Actually, the global amounts of PCDD/Fs generated from the graphite and the two cokes tested are very similar. Only modifications in the fingerprint are observed. On the other hand, the addition of 10 wt % dust collected in the electrostatic precipitator leads to the formation of amounts of PCDD/Fs multiplied by a factor larger than 103. These results imply caution against the recycling of this E.S.P. dust in the raw materials.
Photochemistry of Polyhaloarenes. 4. Phototransformations of Perchloro-o-phenoxyphenol in Basic Media
Freeman, Peter K.,Srinivasa, Remanujan
, p. 3939 - 3942 (1986)
Irradiation of the sodium salt of the conjugate base of perchloro-o-phenoxyphenol (PreD-Na+) in methanol (300 nm) in the presence of sensitizer m-methoxyacetophenone generates ether cleavage products and mono- and di-dechlorination with no cycliozation to OCDD.In the presence of sensitizer and excess triethylamine, irradiation of perchloro-o-phenoxyphenol leads to OCDD as a major product with ether cleavage and dechlorination products representing important reaction pathways.Photodecomposition of the conjugate base of perchloro-o-phenoxyphenol in methanol reveals a small amount of cyclization, while irradiation in methanol in the presence of a 10-fold excess of triethylamine increases the quantum yield for cyclization 17-fold.The photolytic transformations of the conjugate base of perchloro-o-phenoxyphenol in the presence of excess triethylamine are dependent upon solvent polarity with the quantum yield for cyclization increasing strongly in methanol or water/acetonitrile (70:30) relative to that in dibutyl ether.These results are interpreted in terms of electron transfer to PreD- to form a radical dianion.
Formation of dioxins from sodium chloride-impregnated newspapers by combustion
Katami,Ohno,Yasuhara,Shibamoto
, p. 372 - 376 (2000)
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Dioxin production during the thermal treatment of meat and bone meal residues
Conesa, Juan A.,Fullana, Andres,Font, Rafael
, p. 85 - 90 (2005)
Safe animal by-product disposal is a priority target as a result of the Bovine Spongiform Encephalopathy crisis in the European beef industry. One such disposal option is the incineration of by-product material such as meat and bone meal residues (MBM) for the purpose of energy recovery. Although currently applied, the thermal decomposition of MBM wastes has not been scientifically studied until now. A series of experiments has been performed to study the thermal behavior of MBM both in inert (N2) and reactive atmosphere (air), both by thermogravimetry and in a horizontal laboratory furnace. As a general trend, MBM gives low PCDD/F values, compared with incineration of other wastes. Maximum yield of pollutants is observed at a nominal temperature between 700 and 800°C.
Understanding the Role of Iron Chlorides in the De Novo Synthesis of Polychlorinated Dibenzo-p-dioxins/Dibenzofurans
Ryan, Shawn P.,Altwicker, Elmar R.
, p. 1708 - 1717 (2004)
The formation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) was investigated for mixtures of carbon black and iron chloride supported on a ceramic glass powder matrix in a low (2%) oxygen environment. Three iron chloride types (iron(II) chloride tetrahydrate, iron(III) chloride hexahydrate, and iron(III) oxychloride) were studied to gain some insights into their role in de novo formation. The importance of iron(II) and iron(III) chlorides both as chlorinating agents and promoters of low-temperature carbon gasification was observed. Iron(III) oxychloride was shown to be a very effective promoter at 325 °C and above; its conversion to iron(III) chloride was suggested as a key step. The predominant product was octachlorodibenzofuran. The oxide support matrix was found to be an important parameter.
Formation rates of polychlorinated dibenzofurans and dibenzo-p-dioxins from polycyclic aromatic hydrocarbons, activated carbon and phenol
Iino,Imagawa,Takeuchi,Sadakata,Weber
, p. 2749 - 2756 (1999)
The formation rates of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) from polycyclic aromatic hydrocarbons (PAHs), activated carbon, and phenol were compared. The heat treatment at 300°C of all tested PAH on silica in the presence of CuCl2 preferred PCDFs over PCDDs. Perylene reproducibly gave a higher yield of PCDFs than activated carbon gave under the same conditions. The formation rate of PCDFs from perylene could be higher than the values in this study because the residence time of perylene in the reactor is shorter than that of activated carbon. PCDDs were mainly formed from phenol.
PCDD/F inhibition by prior addition of urea to the solid fuel in laboratory experiments and results statistical evaluation
Samaras,Blumenstock,Lenoir,Schramm,Kettrup
, p. 737 - 743 (2001)
The objectives of this work were to study the effect of urea addition to the fuel before the combustion on the suppression of PCDD/F emissions, to examine the influence of urea to PCDD/F isomer patterns by employing statistical analysis techniques and to determine the most effective method of urea addition. Urea in the form of powder and as an aqueous solution was mixed with RDF and the fuel mixtures were incinerated in a lab-scale reactor at 1000°C. PCDD/F emitted during combustion experiments were collected in a quartz wool filter downstream the reactor unit. Analysis and quantification of PCDD/F showed that urea significantly affected PCDD/F emissions. Combustion of RDF containing 10% w/w urea resulted in PCDD/F emissions lower than 8 I-TEQ ng/g RDF, while the corresponding average value from single RDF combustion was 17 I-TEQ ng/g RDF. The PCDD/F prevention capacity of urea was independent from the method of urea addition to the fuel, as similar results were obtained after the addition of urea in the solid and in the aqueous phases. Results assessment by statistical methods showed that isomer patterns remained almost stable and were not affected by the method of urea addition.
Formation of dioxins in the catalytic combustion of chlorobenzene and a micropollutant-like mixture on Pt/γ-Al2O3
De Jong, Vincent,Cieplik, Mariusz K.,Louw, Robert
, p. 5217 - 5223 (2008/01/27)
Catalytic combustion over a 2 wt % Pt/γ-Al2O3 catalyst of chlorobenzene (PhCl) and of a micropollutant-like mixture representative for a primary combustion offgas has been investigated. Typical conditions were 1000-1500 ppm of organics in the inflow, contact times ～0.3 s, 16% O2 in nitrogen at ～1 bar, and temperature range 200-550 °C. PhCl reacts considerably slower than when processing Cl-free compounds such as heptane. At intermediate temperatures-and incomplete conversion-byproducts are formed, especially polychlorobenzenes (PhCl x). These are accompanied by polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) at levels of about 10-6 relative to PhClx. Additional HCl-made by co-reacting PhCl with tert-butylchloride-leads to much higher levels of PhClx and PCDD/Fs. Using the micropollutant-like mixture, the total chlorine input is reduced almost 20-fold, but it nevertheless leads to a 30-fold higher PCDD/F output. This is ascribed to reaction of the small amounts of (chloro)phenols in the mixture. The congener/isomer patterns of the PCDD/Fs for the mixture and with PhCl per se are quite comparable with those found in emissions from incinerators. As carbon is not present nor formed on the catalyst surface, de-novo formation therefrom cannot be involved. Rather condensation of phenolic entities or like precursors must have occurred. Consequences and options to ensure safe application are briefly discussed as well.
