benzofurans and cupric-chloride

The formation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) was explored during de novo tests designed to compare the catalytic activity of copper (II) chloride (CuCl2) with that of iron (III) oxide (Fe2O3) and to test some synergistic effect between these two catalytic compounds. Both copper chloride (CuCl2) and iron oxide (Fe2O3) were earlier proposed as catalysts to explain the PCDD/F emissions from, e.g. municipal solid waste incineration (MSWI). In addition, haematite (Fe2O3) is the main iron ore and could be responsible for the typical iron ore sintering plant fingerprint. A total of nine model fly ash (MFA) samples were prepared by mixing and grinding of sodium chloride (NaCl), activated carbon and a powder matrix of silica (SiO2) with the selected metal compound(s). The conditions of these de novo tests were 1 h in duration, 350 °C in a flow of synthetic combustion gas (10 vol.% oxygen in nitrogen). The effect of Fe-Cu catalyst concentration on yield and distribution pattern of PCDD/F was systematically explored; three strongly differing ratios of [Fe]:[Cu] were considered (1:1, 10:1 and 100:1) to study the potential interactions of Fe2O3 and CuCl2 suggested earlier. The results show some slight rise of PCDD/F formed with raising iron concentration from 0 to 10.1 wt% (no Cu added; 0.1 wt% Cu), as well as strong surging of both amount and average chlorination level of PCDD/F when rising amounts of copper (0 to 1.1 wt%) are introduced. The resulting fingerprints are compared with those from sintering and from MSWI.

Topics: Benzofurans; Catalysis; Coal Ash; Copper; Dioxins; Ferric Compounds; Incineration; Polychlorinated Dibenzodioxins

In this study, simulated fly ash containing CuO/CuCl2 was heated at 350 °C in a flow of N2 and also in a nitrogen flow containing 10 vol% H2, to evaluate the influence of hydrogen adding on dioxin formation. The total polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) output derived from the CuO sample under N2 and 10 % H2 was 7.382 and 0.708 ng/g, respectively. As for CuCl2, it was 589 and 46.1 ng/g, respectively. The results show that the hydrogen adding has a good inhibition effect on PCDD/F formation; the inhibition rate was higher than 90 % for PCDD/Fs. HCl and NH3 were detected by Gasmet in the flue gas; the probable inhibition mechanism of hydrogen reaction was proposed, based on our measurements and others' researches.

Topics: Benzofurans; Coal Ash; Copper; Dioxins; Hydrogen

Copper dichloride is an important catalyst both in the dechlorination of chlorinated aromatic compounds and the formation of PCDD/Fs. The effect of copper dichloride on polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs) was studied in treated soil and off gas after thermal desorption of PCB-contaminated soil at 300, 400, 500, 600 °C. The presence of copper dichloride clearly enhances thermal desorption by promoting PCBs removal, destruction, and dechlorination. After thermal treatment at 600 °C for 1 h, the removal efficiency and destruction efficiency for PCBs reached 98.1 and 93.9%, respectively. Compared with the positive influence on PCBs, copper dichloride catalyzed large amount of PCDFs formation at 300 °C, with the concentration ratio of 2.35. The effect of CuCl2 on PCDFs formation weakened with the rising temperature since PCDFs destruction became dominant under higher temperature. Different from PCDFs, PCDDs concentration in treated soil and off gas decreased continuously with the increasing temperature.

Topics: Benzofurans; Copper; Dibenzofurans, Polychlorinated; Dioxins; Environmental Pollution; Hot Temperature; Polychlorinated Biphenyls; Polychlorinated Dibenzodioxins; Soil; Soil Pollutants

Sulfur dioxide (SO2) gas has been reported to be an inhibitor of polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) formation in fly ash. However, other research has suggested little or no inhibitory effect of SO2 gas. Although these studies focused on reactions between SO2 gas and gas-phase chlorine (Cl) species, no attention was paid to thermochemical gas-solid reactions. In this study, we found contrasting effects of SO2 gas depending on the chemical form of copper (CuO vs CuCl2) with a solid-phase inorganic Cl source (KCl). Chlorinated aromatics (PCDD/Fs, polychlorinated biphenyls, and chlorobenzenes) increased and decreased in model fly ash containing CuO + KCl and CuCl2 + KCl, respectively, with increased SO2 injection. According to in situ Cu K-edge and S K-edge X-ray absorption spectroscopy, Cl gas and CuCl2 were generated and then promoted the formation of highly chlorinated aromatics after thermochemical reactions of SO2 gas with the solid-phase CuO + KCl system. In contrast, the decrease in aromatic-Cls in a CuCl2 + KCl system with SO2 gas was caused mainly by the partial sulfation of the Cu. The chemical form of Cu (especially the oxide/chloride ratio) may be a critical factor in controlling the formation of chlorinated aromatics using SO2 gas.

Topics: Benzofurans; Chlorides; Chlorobenzenes; Coal Ash; Copper; Dibenzofurans, Polychlorinated; Dioxins; Hydrocarbons, Chlorinated; Incineration; Models, Chemical; Polychlorinated Biphenyls; Potassium Chloride; Sulfur Dioxide; X-Ray Absorption Spectroscopy

A regioselective intramolecular cyclization/halogenation reaction of N-alkoxy-o-alkynylbenzamides with CuCl(2)/NCS was developed. The corresponding 3-(chloromethylene)isobenzofuran-1-ones were exclusively obtained via 5-exo-dig cyclization in moderate to excellent yields within 0.5-1 h. This approach has been successfully used to synthesize a biaryl compound by the Suzuki-Miyaura reaction.

Topics: Alkynes; Benzamides; Benzofurans; Catalysis; Copper; Cyclization; Molecular Structure

The effects of H(2)O vapor on de novo synthesis of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and biphenyls (PCB) were investigated at two levels (none and 10 vol.%) in various model systems containing five different carbons, CuCl(2), and quartz, exposed to a flow of 10% O(2)/N(2) at 300 degrees Celsius. The influence of H(2)O was studied on (1) speciation and behavior of copper compounds, (2) catalytic oxidation of carbons of distinct reactivity, and (3) formation of organic chlorine compounds, with the aim to investigate any effects on de novo synthesis. It is found that H(2)O converts CuCl(2) to CuCl(2) x CuO, and finally to CuO in a flow of 10% O(2)/N(2) at 300 degrees Celsius and that it decreases of organic chlorine (C-Cl) formation. When CuCl(2) is supported on carbon, the addition of H(2)O promotes the catalytic oxidation of this carbon. When CuCl(2) is supported on quartz, however, H(2)O inhibits carbon oxidation. A decrease in chlorination level of PCDD/Fs and PCBs with water addition is observed for all (six) model ashes; yet this addition affects the yields of PCDD/Fs and PCBs differently. Under the experimental conditions tested H(2)O does not react with Cu(2)Cl(2), which is the catalyst of carbon oxidation. On the basis of the experimental results, the following mechanism is proposed: conversion of CuCl(2) into CuO which is less reactive in de novo synthesis and promotion of catalytic oxidation of carbon by Cu(2)Cl(2).

Topics: Benzofurans; Carbon; Copper; Dibenzofurans, Polychlorinated; Oxidation-Reduction; Polychlorinated Biphenyls; Polychlorinated Dibenzodioxins; Water

Chlorination and thermal degradation of 2-chlorodibenzodioxin and dibenzofuran were investigated using sealed tubes at 350 degrees C in the presence of CuCl(2) or CuCl. Twelve organic species, including polychlorobenzenes, were identified and quantified as a function of residence time. Time behaviours of PCDDs and PCDFs regarding destruction processes were compared. The formation of polychlorobenzenes from the thermal heterogeneous degradation of PCDDs was only a minor pathway but it could contribute to the good linear correlation observed between the concentration of polychlorobenzenes and those of PCDD/Fs in the emissions of municipal solid waste incinerators.

Topics: Benzofurans; Carbon Dioxide; Chlorobenzenes; Copper; Dibenzofurans, Polychlorinated; Dioxins; Halogenation; Hot Temperature; Polychlorinated Dibenzodioxins

The oxidative degradation of 2-chlorophenol in air (equivalence ratio phi=0.8) was investigated at 350 degrees C by using the sealed tube technique under different conditions: in the gas phase and in the presence of copper chlorides (CuCl2 and CuCl in different proportions). Not only PCDD/Fs but carbon oxides and other organic products such as chlorophenols, chlorobenzenes, tetrachloroethylene and tetrachlorocyclopentenedione were quantified in order to evaluate the relative importance of reaction pathways. Additional experiments were performed to analyse the degradation products of octachlorodibenzodioxin and 2-monochlorodibenzodioxin. Although it was stated that chlorobenzenes could be formation precursors for PCDD/Fs, experimental data obtained in this work show that chlorobenzenes can also be degradation products of PCDD/Fs.

Topics: Air Pollutants; Benzofurans; Chlorobenzenes; Chlorophenols; Copper; Incineration; Oxidation-Reduction; Polychlorinated Dibenzodioxins; Time Factors

The effect of water vapor on catalyzed de novo formation of polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) was investigated through experiments conducted on a fixed-bed apparatus. The results indicated that water vapor could promote the formation of PCDD and PCDF. The dominant pathway was activating fly ash in this work, while water also reacted with chlorine to change the equilibrium of Deacon reaction, which influenced the final yield of PCDD/PCDF. Also a suppression effect of water on CuCl(2) was found according to the values of the catalysis indicator. It is possible that water reduced the catalysis of CuCl(2) or prevented its direct chlorination. But the overall effect of water on the formation of PCDD and PCDF was promotion rather than inhibition.

Topics: Benzofurans; Catalysis; Copper; Dioxins; Hazardous Substances; Industrial Waste; Polychlorinated Dibenzodioxins; Water

Polychlorinated dibenzo-p-dioxin (PCDD) and dibenzofuran (PCDF) byproducts can be formed in combustion systems by a variety of mechanisms. While total PCDD/F emissions and, to a lesser extent, homologue distributions from incinerators have been found to vary widely depending on combustion conditions, PCDD/F isomer distributions do not. Formation mechanisms can be grouped into two general categories: condensation of precursors, such as chlorinated phenols, and formation from particulate carbon, termed de novo synthesis. In addition to these mechanisms, chlorination and dechlorination reactions may affect isomer patterns. In this work, isomer patterns from field and laboratory municipal waste combustion samples are compared with computed thermodynamic distributions and those from the following experimental investigations: both gas-phase and metal-catalyzed condensation of chlorinated phenols, chlorination of dibenzo-p-dioxin and dibenzofuran, and dechlorination of octachlorodibenzo-p-dioxin and octachlorodibenzofuran. PCDD/F isomer patterns produced by different formation mechanisms in controlled experiments are distinct and robust, largely unaffected by combustion conditions. PCDD isomer patterns from municipal waste combustion are most similar to those produced by CuCl(2)-catalyzed phenol condensation from 10 chlorinated phenols. PCDF isomer patterns are most similar to those produced by chlorination and dechlorination.

Topics: Air Pollutants; Benzofurans; Carbon; Catalysis; Coal Ash; Copper; Dibenzofurans, Polychlorinated; Incineration; Isomerism; Particulate Matter; Phenols; Polychlorinated Dibenzodioxins

Homologue and isomer patterns of polychlorinated dibenzo-p-dioxin (PCDD) and polychlorinated dibenzofuran (PCDF) in CuCl2-catalyzed formation were studied in an isothermal flow reactor using a distribution of 20 phenols as measured in municipal waste incinerator (MWI) exhaust gases. A mixture of 20 phenols was synthesized and used as reactants for this study because phenols are known to be key precursors in the formation of PCDD/F. Experiments were conducted at 400 degrees C. The 92% of nitrogen (N2) and 8% of oxygen (O2) were used as a carrier gas. PCDD/F homologue and isomer patterns with dibenzo-p-dioxin (DD) and dibenzofuran (DF) were obtained from a mixture of 20 phenols. DF+PCDF formation was favored over DD+PCDD formation. The major homologue groups formed were non-chlorinated DD and DF, and PCDD/F homologue fraction decreased with the degree of chlorination. PCDD/F homologue and isomer distributions were almost constant. Phenol and lower chlorinated phenols present in high amount played an important role in PCDD/F congener distributions. The results presented here can be used as characteristics or fingerprints for homologue and isomer patterns of PCDD/F formation attribution in CuCl2-catalyzed reaction from phenols.

Topics: Benzofurans; Catalysis; Copper; Dibenzofurans, Polychlorinated; Environmental Pollutants; Incineration; Isomerism; Phenols; Polychlorinated Dibenzodioxins; Soil Pollutants; Temperature

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.

Topics: Benzofurans; Catalysis; Copper; Dioxins; Gas Chromatography-Mass Spectrometry; Incineration; Oxidation-Reduction; Refuse Disposal

Dibenzofuran (DF) is formed from phenol and benzene in combustion gas exhaust streams prior to particle collection equipment. Subsequent chlorination at lower temperatures on particle surfaces is a potential source of chlorinated dibenzofuran (CDF). Gas streams containing 8% O(2) and approximately 0.1% DF vapor were passed through particle beds containing copper (II) chloride (0.5% Cu, mass) at temperatures ranging from 200 to 400 degrees C to investigate the potential for CDF formation during particle collection. Experiment duration was sufficient to provide an excess amount of DF (DF/Cu=3). The efficiency of DF chlorination by CuCl(2) and the distribution of CDF products were measured, with effects of temperature, gas velocity, and experiment duration assessed. Results of a more limited investigation of dibenzo-p-dioxin (DD) chlorination by CuCl(2) to form chlorinated DD (CDD) products are also presented. The efficiency of DF/DD chlorination by CuCl(2) was high, both in terms of CuCl(2) utilization and DF/DD conversion. Total yields of Cl on CDF/CDD products of up to 0.5 mole Cl per mole CuCl(2) were observed between 200 and 300 degrees C; this suggests that nearly 100% CuCl(2) was utilized, assuming a conversion of two moles of CuCl(2) to CuCl per mole Cl added to DD/DF. In a short duration experiment (DF/Cu=0.3), nearly 100% DF adsorption and conversion to CDF was achieved. The degree of CDF chlorination was strongly dependent on gas velocity. At high gas velocity, corresponding to a gas-particle contact time of 0.3 s, mono-CDF (MCDF) yield was largest, with yields decreasing with increasing CDF chlorination. At low gas velocity, corresponding to a gas-particle contact time of 5 s, octa-CDF yield was largest. DF/DD chlorination was strongly favored at lateral sites, with the predominant CDF/CDD isomers within each homologue group those containing Cl substituents at only the 2,3,7,8 positions. At the higher temperatures and lower gas velocities studied, however, broader isomer distributions, particularly of the less CDD/CDF products, were observed, likely due to preferential destruction of the 2,3,7,8 congeners.

Topics: Air Movements; Benzene; Benzofurans; Copper; Dioxins; Incineration; Phenol; Refuse Disposal; Temperature

Na37Cl was used to study the role of chlorine in the formation of polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF) from carbon. Adding Na37Cl to fly ash showed that this compound was a (relatively) poor chloride source; chlorine naturally present on the ash - which could include both chlorine in residual carbon and (metal) chlorides - was found to be ca. 17x more reactive. When both Na37Cl and CuCl2 were added to aqueous extracted fly ash, the percentage of 37Cl from Na37Cl included in PCDD/F increased, compared to the combination of Na37Cl/fly ash. When Na37Cl and CuCl2 were exchanged in water, followed by evaporation of the solvent, and mixed with aqueous extracted fly ash, the percentage of 37Cl included in PCDD/F was much higher. Apparently, direct transfer of 37Cl from CuCl2 to carbon and PCDD/F was much faster than transfer of 37Cl- from Na37Cl via a metal chloride (such as CuCl2) to carbon and PCDD/F. In addition to chlorine in PCDD/F originating from exchanged NaCl/CuCl2, chloride left on the fly ash after aqueous extraction and chlorine present in residual carbon could also have been incorporated in PCDD/F.

Topics: Benzofurans; Carbon; Chlorine; Copper; Incineration; Polychlorinated Dibenzodioxins; Refuse Disposal; Sodium Chloride; Soil Pollutants; Solvents

The chlorination and condensation of acetylene at low temperatures is demonstrated using copper chlorides as chlorinated agents coated to model borosilicate surfaces. Experiments with and without both a chlorine source and borosilicate surfaces indicate the absence of gas-phase and gas-surface reactions. Chlorination and condensation occur only in the presence of the copper catalyst. C2 through C8 organic products were observed in the effluent; PCDD/F were only observed from extraction of the borosilicate surfaces. A global reaction model is proposed that is consistent with the observed product distributions. Similar experiments with dichloroacetylene indicate greater reactivity in the absence of the copper catalyst. Reaction is observed in the gas-phase and in the presence of borosilicate surfaces at low temperatures. The formation of hexachlorobenzene is only observed in the presence of a copper catalyst. PCDD/F were only observed from extraction of the borosilicate surfaces. A global reaction model is proposed for the formation of hexachlorobenzene from dichloroacetylene.

Topics: Acetylene; Benzofurans; Catalysis; Copper; Dibenzofurans, Polychlorinated; Gas Chromatography-Mass Spectrometry; Glass; Hexachlorobenzene; Hot Temperature; Hydrocarbons, Chlorinated; Models, Chemical; Polychlorinated Dibenzodioxins; Surface Properties; Temperature

The asymmetry of Escherichia coli F1-ATPase (ECF1) has been explored in chemical modification experiments involving two mutant enzyme preparations. One mutant contains a cysteine (Cys) at position 149 of the beta subunit, along with conversion of a Val to Ala at residue 198 to suppress the deleterious effect of the Cys for Gly at 149 mutation (mutant beta G149C:V198A). The second mutant has these mutations and also Cys residues at positions 381 of beta and 108 of the epsilon subunit (mutant beta G149C:V198A:E381C/epsilon S108C). On CuCl2 treatment of this second mutant, there is cross-linking of one copy of the beta subunit to gamma via the Cys at 381, a second to the epsilon subunit (between beta Cys381 and epsilon Cys108), while the third beta subunit in the ECF1 complex is mostly free (some cross-linking to delta); thereby distinguishing the three beta subunits as beta gamma, beta epsilon, and beta free, respectively. Both mutants have ATPase activities similar to wild-type enzyme. Under all nucleotide conditions, including with essentially nucleotide-free enzyme, the three different beta subunits were found to react differently with N-ethylmaleimide (NEM) which reacts with Cys149, dicyclohexyl carbodiimide (DCCD) which reacts with Glu192, and 7-chloro-4-nitrobenzofurazan (NbfCl) which reacts with Tyr297. Thus, beta gamma reacted with DCCD but not NEM or NbfCl; beta free was reactive with all three reagents; beta epsilon reacted with NEM, but was poorly reactive to DCCD or NbfCl. There was a strong nucleotide dependence of the reaction of Cys149 in beta epsilon (but not in beta free) with NEM, indicative of the important role that the epsilon subunit plays in functioning of the enzyme.

Topics: 4-Chloro-7-nitrobenzofurazan; Adenosine Diphosphate; Adenosine Triphosphate; Benzofurans; Binding Sites; Copper; Cross-Linking Reagents; Dicyclohexylcarbodiimide; Escherichia coli; Ethylmaleimide; Genes, Bacterial; Kinetics; Macromolecular Substances; Mutagenesis, Site-Directed; Point Mutation; Proton-Translocating ATPases; Recombinant Proteins