- A novel method of CCl4 disposal by disproportionation with CH4 over Pt on various supports
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In disproportionation of CCl4 with CH4 into CH3Cl and CHCl3, platinum supported on SrCO3, SiO2, MgO and MgAl2O4 showed stable activity and high selectivities around 700 K, providing a novel disposal method of ozone-depleting CCl4.
- Bae, Jong Wook,Lee, Jae Sung,Lee, Kyung Hee,Lee, Byeongno,Yang, Duck Joo
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- Mechanistic modeling of the wall reactions in the pyrolysis of pentachloroethane
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The thermal dehydrochlorination C2HCl5 → C2Cl4 + HCl has been studied in a static system between 565 and 645 K at pressures ranging from 5 to 21 torr. The course of the reaction was followed by measuring the pressure rise in the conditioned quartz reaction vessel and by analyzing the products by gas chromatography. The observed experimental results and data from the literature for flow systems can be explained quantitatively in terms of a radical reaction model involving heterogeneous chain initiation and termination steps. The rate constants have been deduced for reactions of Cl, Cl2, and C2HCl5 over reactor walls covered with a pyrolytic carbon film and for reactions of adsorbed Cl atoms.
- Huybrechts,Daniels,Van Assche,Van Mele
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- Influence of amine buffers on carbon tetrachloride reductive dechlorination by the iron oxide magnetite
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The influence of amine buffers on carbon tetrachloride (CCI4) reductive dechlorination by the iron oxide magnetite (FeIIFe II2O4) was examined in batch reactors. A baseline was provided by monitoring the reaction in a magnetite suspension containing NaCl as a background electrolyte at pH 8.9. The baseline reaction rate constant was measured at 7.1 × 10-5 ± 6.3 × 10-6 L m-2 h-1. Carbon monoxide (CO) was the dominant reaction product at 82% followed by chloroform (CHCI3) at 5.2%. In the presence of 0.01 M tris-(deuteroxymethyl) aminomethane (TRIS d), the reaction rate constant nearly tripled to 2.1 × 10 -4 ± 6.5 × 10-6 L m-2 h -1 but only increased the CHCI3 yield to 11% and did not cause any statistically significant changes to the CO yield. Reactions in the presence of triethylammonium (TEAd) (0.01 M) increased the rate constant by 17% to 8.6 × 10-5 ± 8.1 × 10 -6 L m-2 h-1 but only increased the CHCI 3 yield to 8.8% while leaving the CO yield unchanged. The same concentration of N,N,N′,N′-tetraethylethylenediamine (TEEN) increased the reaction rate constant by 18% to 8.7 × 10-5 ± 4.8 × 10-6 L m-2 h-1 but enhanced the CHCI3 yield to 34% at the expense of the CO yield that dropped to 35%. Previous work has shown that CHCI3 can be generated either through hydrogen abstraction by a trichloromethyl radical ( .CCI3), or through proton abstraction by the trichlorocarbanion (-:CCI3). These two possible hydrogenolysis pathways were examined in the presence of deuterated buffers. Deuterium tracking experiments revealed that proton abstraction by the trichlorocarbanion was the dominant hydrogenolysis mechanism in the magnetite-buffered TRISd and TEAd systems. The only buffer that had minimal influence on both the reaction rate and product distribution was TEAd. These results indicate that buffers should be prescreened and demonstrated to have minimal impact on reaction rates and product distributions prior to use. Alternatively, it may be preferable, to utilize the buffer capacity of the solids to avoid organic buffer interactions entirely.
- Danielsen, Karlin M.,Gland, John L.,Hayes, Kim F.
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- Novel photocatalytic mechanisms for CHCl3, CHBr3, and CCl3CO2 degradation and the fate of photogenerated trihalomethyl radicals on TiO2
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The photocatalytic degradation of CHCl3, CHBr3, CCl4, and CCl3CO2- is investigated in aqueous TiO2 suspensions. A common intermediate, the trihalomethyl radical, is involved in the degradation of each substrate except for CCl3CO2-, CHCl3 and CHBr3 are degraded into carbon monoxide and halide ions in the absence of dissolved oxygen. The anoxic degradation proceeds through a dihalocarbene intermediate, which is produced by sequential reactions of the haloform molecule with a valence band hole and a conduction band electron. Carbon dioxide and halide ion are formed as the primary products during CHCl3 degradation in the presence of oxygen. Under these conditions, the trihalomethyl radicals react rapidly with dioxygen. At pH > 11, degradation of the haloforms is enhanced dramatically. This enhancement is ascribed to photoenhanced hydrolysis. The secondary reactions of the trichloromethyl radical generated during CCl4 photolysis is strongly influenced by the nature of the electron donors. Both ·CCl3 and Cl- production increase substantially when 2-propanol is present as an electron donor. A new photocatalytic mechanism for CCl3CO2- degradation, which involves the formation of a dichlorocarbene intermediate, is proposed.
- Choi, Wonyong,Hoffmann, Michael R.
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- Dynamic behaviour of chlorofluoroethanes at fluorinated chromia aerogels and fluorinated zinc(II) or magnesium(II) doped chromia aerogels
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The preparation and characterisation of two series of fluorinated chromia aerogel materials, lightly doped with zinc(II) or magnesium(II), are described. They behave as heterogeneous catalysts for transformations of 1,1,2-trichlorotrifluoroethane under HF
- Bozorgzadeh, Hamid,Kemnitz, Erhard,Nickkho-Amiry, Mahmood,Skapin, Toma?,Winfield, John M.
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- Generation of radical species in surface reactions of chlorohydrocarbons and chlorocarbons with fluorinated gallium(III) oxide or indium(III) oxide
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The reactions of C1 and C2 chlorohydrocarbons and chlorocarbons have been studied with the Lewis acid catalysts fluorinated gallium(III) oxide and fluorinated indium(III) oxide, respectively. Product analysis shows chlorine-for-fluorine exchange reactions together with the formation of 2-methylpropane and its chlorinated analogues 2-chloromethyl-1,3-dichloropropane and 2-chloromethyl-1,2,3-trichloropropane. Reactivities of the chlorohydrocarbon probe molecules show fluorinated gallium(III) oxide to be a stronger Lewis acid than fluorinated indium(III) oxide. The formation of the symmetrical butyl compounds is consistent with the generation of surface radical species and is also consistent with a 1,2-migration mechanism operating within radical moieties at the Lewis acid surface.
- Thomson
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- Chlorination and dehydrochlorination reactions relevant to the manufacture of trichloroethene and tetrachloroethene: Part 1. Reaction pathways
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Factors which affect the selectivity of the chlorination of 1,2-dichloroethane and the associated dehydrochlorination reactions have been examined using approximate thermodynamic calculations, equilibrium measurements, and a continuous flow micro-reactor. There is a balance between surface and gas-phase chemistry within the system. Heterogeneous catalysis is not necessary to effect dehydrochlorination of 1,1,2,2-tetrachloroethane to trichloroethene but an attapulgite-supported copper(II) chloride catalyst favours formation of pentachloroethane and its dehydrochlorination product, tetrachloroethene. The latter is the thermodynamic minimum of the system. Below 473 K and with long reaction times (2 h, batch reactor), radical chlorination to form pentachloroethane is dominant. Above 573 K and under flow conditions, free radical dehydrochlorination to form trichloroethene becomes dominant. Heterogeneous chlorination under flow conditions provides a route to pentachloroethane and thence tetrachloroethene. High conversions favour the formation of oligomeric products.
- Sutherland, Iain W.,Hamilton, Neil G.,Dudman, Christopher C.,Jones, Peter,Lennon, David,Winfield, John M.
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- Hydrodechlorination of Tetrachloromethane over Supported Pt Catalysts
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In the selective hydrodechlorination of tetrachloromethane to chloroform, long catalytic life as well as high selectivity to chloroform is achieved over a platinum catalyst supported on MgO.
- Kim, Sang Y.,Choi, Hyun C.,Yanga, O B.,Lee, Kyung H.,Lee, Jae S.,Kim, Young G.
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- The pyrolysis of CCl4 and C2Cl6 in the gas phase. Mechanistic modeling by thermodynamic and kinetic parameter estimation
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A detailed radical reaction mechanism is proposed to describe the thermal reactions of CCl4 and C2Cl6 in the gas phase quantitatively. A consistent set of activation energies and preexponential factors for all elementary reactions, in combination with enthalpies of formation and entropies for all species involved, is computer optimized to fit experimental pressure-rise curves and concentration profiles. For this purpose new experimental results on the pyrolysis of CCl4 are used, together with published kinetic data on the pyrolysis of C2Cl6 (in the absence and in the presence of Cl2).
- Huybrechts,Narmon,Van Mele
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- A homoleptic tetravalent cerium silylamide
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Treatment of Ce[N(SiHMe2)2]3(thf) 2 with the chlorinating agents PhICl2, Ph3CCl or C2Cl6 gave the homoleptic Ce(iv) silylamide Ce[N(SiHMe2)2]4. When performed in the absence of donating (solvent) molecules, the trivalent cluster Ce 5[N(SiHMe2)2]8Cl7 was isolated.
- Crozier, Alan R.,Bienfait, Andre M.,Maichle-Moessmer, Caecilia,Toernroos, Karl W.,Anwander, Reiner
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- Activation of Chemical Reaction by Impact of Molecules on a Surface
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Molecules of C2Cl6, Cl3CCHCl2, CCl4, and W(CO)6 have been accelerated to speeds up to 1900 m s-1 in seeded molecular beams expanded from a nozzle and then suddenly brought to rest by collision with a glass surface.For W(CO)6 there is a clear threshold near 1750 m s-1, corresponding to a kinetic energy of 540 kJ mol-1, above which the speeds became sufficient to cause reaction; for the chlorinated hydrocarbons much lower speeds caused reactions.The yields of volatile and nonvolatile products resulting from the impacts vary with the speed of the molecules and the temperature of the nozzle.This permits some comparision of the relative effectiveness with which the kinetic and internal energies of the molecules promote their reactions.
- Connolly, M. S.,Greene, E. F.,Gupta, C.,Marzuk, P.,Morton, T. H.,et al.
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- Dichloroketen; Gas Phase Preparation and Characterisation by Photoelectron Spectroscopy
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Dechlorination of trichloroacetyl chloride, CCl3COCl, at low pressure, leads to the formation of dichloroketen, Cl2C=C=O, which is studied by HeI photoelectron spectroscopy.
- Colbourne, David,Frost, David C.,McDowell, Charles A.,Westwood, Nicholas P. C.
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- Effects of AgI, AuIII, and CuII on the reductive dechlorination of carbon tetrachloride by green rust
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Green rusts (GRs), mixed iron(II)/iron(III) hydroxide minerals found in many suboxic environments, have been shown to reduce a range of organic and inorganic contaminants, including several chlorinated hydrocarbons. Many studies have demonstrated the catalytic activity of transition metal species in the reduction of chlorinated hydrocarbons, suggesting the potential for enhanced reduction by GR in the presence of an appropriate transition metal catalyst. Reductive dechlorination of carbon tetrachloride (CT) was examined in aqueous suspensions of GR amended with AgI, AuIII, or CuII. The CT reduction rates were greatly increased for systems amended with CuII, AuIII, and AgI (listed in order of increasing rates) relative to GR alone. Observed intermediates and products included chloroform, dichloromethane, chloromethane, methane, acetylene, ethene, ethane, carbon monoxide, tetrachloroethene, and various nonchlorinated C3 and C4 compounds. Product distributions for the reductive dechlorination of CT were highly dependent on the transition metal used. A reaction pathway scheme is proposed in which CT is reduced primarily to methane and other nonchlorinated end products, largely through a series of one-electron reductions forming radicals and carbenes/carbenoids. Recently, X-ray absorption fine structure analysis of aqueous GR suspensions amended with AgI, AuIII, or CuII showed that the metals were reduced to their zerovalent forms. A possible mechanism for CT reduction is the formation of a galvanic couple involving the zerovalent metal and GR, with reduction of CT occurring on the surface of the metal and GR serving as the bulk electron source. The enhanced reduction of CT by GR suspensions amended with AgI, AuIII, or CuII may prove useful in the development of improved materials for remediation of chlorinated organic contaminants.
- O'Loughlin, Edward J.,Kemner, Kenneth M.,Burris, David R.
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- Chlorination reactions relevant to the manufacture of trichloroethene and tetrachloroethene; Part 2: Effects of chlorine supply
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The behaviour of 1,1,2,2-tetrachloroethane and trichloroethene in chlorination reactions where the supply of chlorine is varied, either by change in chlorocarbon: Cl2 feed ratio or the quantity of supported copper(II) chloride catalyst or by the use of an anhydrous hydrogen chloride/dioxygen feed as the source of chlorine, i.e. oxychlorination conditions, is described. Depending on the exact conditions used, the products are trichloroethene, pentachloroethane or tetrachloroethene. The products and the conditions under which they are observed are both in harmony with a previously proposed reaction scheme in which there is interplay between heterogeneous and homogeneous reactions. It is possible to define sets of reaction conditions which lead to improvements in selectivity towards the formation of either CHCl=CCl2 or CCl2=CCl2 without significant formation of oligomeric species.
- Sutherland, Iain W.,Hamilton, Neil G.,Dudman, Christopher C.,Jones, Peter,Lennon, David,Winfield, John M.
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- MULTIPHOTON IONIZATION OF CHLOROMETHANES WITH 193-NM EXCIMER LASER RADIATION IN ARGON MATRICES
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The 193-nm output of an excimer laser has been coupled with the matrix isolation technique to demonstrate the feasibility of multiphoton ionization of matrix-isolated species.CCl4, CHCl3, and CH2Cl2 were, in turn, deposited in argon and (in some cases) nitrogen matrices and irradiated for between 5 min and 3 h.For CCl4 and CH2Cl2, the major product was the parent cation or species derived directly thereform, while more varied species, including the CHCL3(-) anion, were observed in the CHCl3 studies.In addition, neutral fragments were observed in a manner similar to previous resonance radiation and proton-beam radiolysis studies.Irradiation of the sample mixture during the deposition process led to increased product yield, as well as additional products for some of the systems.The laser irradiation time, power, and repetition rate were varied over a wide range, and a relative insensitivity to these parameters was noted.
- Machara, Nicholas P.,Ault, Bruce S.
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- Conversion of 1,1,2-trichlorotrifluoroethane to 1,1,1-trichlorotrifluoroethane and 1,1-dichlorotetrafluoroethane over aluminium-based catalysts
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Conversion of CCl2FCClF2 to CCl2FCF3 is achieved in the temperature range, 593-713 K, under flow conditions by using the catalysts, β-AlF3 or γ-alumina, prefluorinated with CCl2F2/sub
- Bozorgzadeh,Kemnitz,Nickkho-Amiry,Skapin,Winfield
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- Experimental study on the thermal oxidation of 1,3-hexachlorobutadiene at 500-1100°C
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Thermal degradation processes of 1,3-hexachlorobutadiene (C4Cl6) have been studied using a tubular flow reactor at 1 atm over the temperature range 500-1100°C for residence times of 2 seconds. Kinetic studies were performed with mixtures of 1000 ppmV of C4Cl6 in air. Overall Arrhenius parameters for the destruction of C4Cl6 were determined between 700 and 850°C. About 30 molecular halogenated products from C1 to C8 formed by pyrolysis or oxidation of 1,3-hexachlorobutadiene over the investigated temperature range were identified. Concentration profiles of major products (CO2, Cl2, CO, COCl2, C2Cl4, CCl4) and some minor products (C3Cl4O, C4Cl4O, C6Cl6, C3Cl4 and C3Cl6) have been measured as a function of temperature. Phosgene is the major chlorinated intermediate product. Detection of some aromatics such as hexachlorobenzene and octachlorostyrene show the importance of the molecular growth pathways in the chemical mechanism. Reaction pathways of main products are proposed and corresponding reaction enthalpies are estimated.
- Baillet,Fadli,Sawerysyn
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- Metal-mediated chlorinated dibenzo-p-dioxin (CDD) and dibenzofuran (CDF) formation from phenols
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Heterogeneous formation of chlorinated dibenzo-p-dioxins (CDDs) and dibenzofurans (CDFs) on CuCl2 from three phenols without ortho chlorine and one phenol with two ortho chlorines was studied in a flow reactor over a temperature range of 325-450°C. Heated nitrogen gas streams containing 8% oxygen, 1.5% benzene vapor, and equal amounts of phenol, 3-chlorophenol, 3,4-dichlorophenol and 2,4,6-trichlorophenol vapor (700 ppmv, each) were passed through a 1 g particle bed of silica and 0.5% (Cu mass) CuCl2. Maximum product yields of greater than 1.4% phenol conversion to CDD and 5.7% phenol conversion to CDF were observed between 400 and 450°C. CDDs formed with loss of one chlorine atom were favored. While total CDD/F yield varied with temperature, CDD/F homologue and isomer distributions did not vary significantly with temperature. Based on the results of experiments with single phenol precursors, phenol precursors could be assigned to all PCDD/F products. Of the chlorinated phenols without ortho chlorine that were studied, 3,4-dichlorophenol was found to have the greatest propensity to form CDFs.
- Ryu, Jae-Yong,Mulholland, James A.
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- Reductive dechlorination of carbon tetrachloride in aqueous solutions containing ferrous and copper ions
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Fe(II) associated with iron-containing minerals has been shown to be a potential reductant in natural subsurface environments. While it is known that the surface-bound iron species has the capacity to dechlorinate various chlorinated compounds, the role of transition metals to act as catalysts with these iron species is of importance. We previously observed that the reduction of Cu(II) by Fe(II) associated with goethite enhanced the dechlorination efficiency of chlorinated compound. In this study, the reductive dechlorination of carbon tetrachloride (CCl4) by dissolved Fe(II) in the presence of Cu(II) ions was investigated to understand the synergistic effect of Fe(II) and Cu(II) on the dechlorination processes in homogeneous aqueous solutions. The dechlorination efficiency of CCl4 by Fe(II) increased with increasing Cu(II) concentrations over the range of 0.2-0.5 mM and then decreased at high Cu(II) concentrations. The efficiency and rate of CCl4 dechlorination also increased with increasing dissolved Fe(II) concentration in the presence of 0.5 mM Cu(II) at neutral pH. When the Fe(II)/Cu(II) ratio varied between 1 and 10, the pseudo-first-order rate constant (fabs) increased 250-fold from 0.007 h-1 at 0.5 mM Fe(II) to 1.754 h-1 at 5 mM Fe(II). X-ray powder diffraction and scanning electron microscopy analyses showed that Cu(II) can react with Fe(II) to produce different morphologies of ferric oxides and subsequently accelerate the dechlorination rate of CCl4 at a high Fe(II) concentration. Amorphous ferrihydrite was observed when the stoichiometric Fe(II)/Cu(II) ratio was 1, while green rust, goethite, and magnetite were formed when the molar ratios of Fe(II)/Cu(II) reached 4-6. In addition, the dechlorination of CCl4 by dissolved Fe(II) is pH dependent. CCl4 can be dechlorinated by Fe(II) over a wide range of pH values in the Cu(II)-amended solutions, and the kobs increased from 0.0057 h-1 at pH 4.3 to 0.856 h-1 at pH 8.5, which was 9-25 times greater than that in the absence of Cu(II) at pH 7-8.5. The high reactivity of dissolved Fe(II) on the dechlorination of CCl4 in the presence of Cu(II) under anoxic conditions may enhance our understanding of the role of Fe(II) and the long-term reactivity of the zerovalent iron system in the dechlorination processes for chlorinated organic contaminants.
- Maithreepala,Doong, Ruey-An
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- Transformation of chlorinated aliphatic compounds by ferruginous smectite
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A series of chlorinated aliphatic compounds (RCI, including carbon tetrachloride (PCM), 1,1,1-trichloroethane (TCA), 1,1,2,2-tetrachloroethane (TeCA), pentachloroethane (PCA), hexachloroethane (HCA), trichloroethene (TCE), tetrachloroethene (PCE), trichloronitromethane (chloropicrin, CP), and trichloroacetonitrile (TCAN)) was reacted with ferruginuous smectite (sample SWa-1 from The Source Clays Repository), SWa, in aqueous suspension under anoxic conditions. Compounds highly polarizable or sharing substituents that facilitate charge delocalization adsorbed faster by reduced (SWa-R) than by unaltered (SWa-U) clay, indicating stronger dipole-dipole interactions between the substituents and the clay surface and/or hydrating water molecules. The reduction of the clay accelerated RCI adsorption up to 100-fold. Incubations with SWa-R promoted RCI reduction (CP, TCAN) or dehydrochlorination (TeCA and PCA). The reduction of structural Fe catalyzes the transformation of RCI via Bronsted and Lewis-basic promoted pathways. This study indicates that oxidation state of the structural Fe in SWa greatly alters surface chemistry and has a large impact on clay-organic interactions.
- Cervini-Silva,Larson,Wu,Stucki
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- Kinetics and mechanism of the enhanced reductive degradation of CCl4 by elemental iron in the presence of ultrasound
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Enhanced rates of sonolytic degradation of CCl4 in the presence of Fe0 are demonstrated. In Ar-saturated solutions, the first-order rate constant for CCl4 degradation is k(US) = 0.107 min-1, whereas in the presence of Ar and Fe0, the apparent first-order rate constant is found to depend on the total surface area of elemental iron in the following fashion: k(obs) = (k(US) + k(Fe)0A(Fe)0) min-1, where k(US) = 0.107 min-1, k(Fe)0 = 0.105 L m-2 min-1 and A(Fe)0) = reactive surface area of Fe0 in units of m2 L-1. In the coupled ultrasound and iron system, the contribution to the overall degradation rate by direct reaction with Fe0 results in an overall rate enhancement by a factor of 40. These enhancements are attributed (1) to the continuous cleaning and chemical activation of the Fe0 surface by the combined chemical and physical effects of acoustic cavitation and (2) to accelerated mass transport rates of reactants to the Fe0 surfaces. Additional kinetic enhancements are due to the production of H+ during the course of the reaction. Furthermore, the concentrations of the principal reaction intermediates, C2Cl6 and C2Cl4, are influenced substantially by the total available surface area of Fe0. Enhanced rates of sonolytic degradation of CCl4 in the presence of Fe0 are demonstrated. In Ar-saturated solutions, the first-order rate constant for CCl4 degradation is kUS = 0.107 min-1, whereas in the presence of Ar and Fe0, the apparent first-order rate constant is found to depend on the total surface area of elemental iron in the following fashion: kobs = (kUS+kFe0AFe0) min-1, where kUS = 0.107 min-1, kFe0 = 0.105 L m-2 min-1, and AFe0) = reactive surface area of Fe0 in units of m2 L-1. In the coupled ultrasound and iron system, the contribution to the overall degradation rate by direct reaction with Fe0 results in an overall rate enhancement by a factor of 40. These enhancements are attributed (1) to the continuous cleaning and chemical activation of the Fe0 surface by the combined chemical and physical effects of acoustic cavitation and (2) to accelerated mass transport rates of reactants to the Fe0 surfaces. Additional kinetic enhancements are due to the production of H+ during the course of the reaction. Furthermore, the concentrations of the principal reaction intermediates, C2Cl6 and C2Cl4, are influenced substantially by the total available surface area of Fe0.
- Hung, Hui-Ming,Hoffmann, Michael R.
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- Infrared Multiphoton Decomposition and the Possibilities of Laser-Based Heavy Water Processes
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The selective multiphoton decomposition (MPD) process has the potential to provide a stand-alone heavy water process which is competitive with conventional processes.Twelve criteria are discussed for selecting a working molecule to give a process economically competitive with the Girdler-Sulphide process.The dependence of the MPD process on interacting parameters such as laser fluence, intensity and bandwidth as well as collisional effects are discussed.Finally, several potential working molecules are reviewed.
- Ivanco, Michael,Evans, D. K.,McAlpine, Robert D.,McRae, Glenn A.,Yamashita, Brian
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- Kinetics and mechanism of the sonolytic degradation of CCL4: Intermediates and byproducts
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The sonolytic degradation of aqueous carbon tetrachloride is investigated at a sound frequency of 20 kHz and 135 W (112.5 W cm-2) of power. The observed first-order degradation rate constant in an Ar-saturated solution is 3.3 x 10-3 s-1 when the initial CCh concentration, [CCl4](i), is 1.95 x 10-4 mol L-1 and increases slightly to 3.9 x 10-3 s-1 when [CCl4](i) = 1.95 x 10-5 mol L-1. Low concentrations (10-8-10-7 mol L-1) of the organic byproducts, hexachloroethane and tetrachloroethylene, are detected, as well as the inorganic products chloride ion and hypochlorous acid. The chlorine mass balance after sonolysis is determined to be >70%. The reactive intermediate, dichlorocarbene, is identified and quantified by means of trapping with 2,3-dimethyl-2-butene. The presence of ozone in the sonicated solution does not significantly effect the rate of degradation of carbon tetrachloride; however, O3 inhibits the accumulation of hexachloroethane and tetrachloroethylene. Ultrasonic irradiation of an aqueous mixture of p-nitrophenol (p-NP) and carbon tetrachloride results in the acceleration of the sonochemical degradation of p-NP. The sonolytic rate of degradation of p-NP appears to be enhanced by the presence of hypochlorous acid, which results from the sonolysis of CCl4.
- Hua, Inez,Hoffmann, Michael R.
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- Reactions in low temperature solid co-condensates and size effects
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The interaction of magnesium atoms, clusters and nanoparticles with different organic and inorganic substances were studied in low temperature solid cocondensates. A combination of matrix isolation techniques and preparative cryochemistry was applied to distinguish the activity of metal species of different sizes.
- Sergeev, Gleb B.
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- Kinetics of the reduction of hexachloroethane by juglone in solutions containing hydrogen sulfide
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Hexachloroethane was converted to tetrachloroethene and unknown products in solutions containing juglone and hydrogen sulfide. Measured rates of disappearance in solutions containing hydrogen sulfide alone were approximately a factor of 10 slower than rates containing micromolar concentrations of juglone and hydrogen sulfide. Electrochemically-reduced juglone was unreactive with respect to hexachloroethane reduction. Reaction of hexachloroethane with polysulfides produced in the reaction of elemental sulfur with hydrogen sulfide in the experimental solutions also could not account for the rate observed in solutions containing juglone and hydrogen sulfide. Evidence is provided to indicate the reaction of hexachloroethane with the Michael addition product of hydrogen sulfide and juglone. No conclusions can be drawn from the present results as to whether the reaction mechanism is a one- or a two-electron transfer. This study points out the importance of the geochemistry of sulfur and organic matter in the transformation of halogenated alkane pollutants in reducing environments.
- Perlinger, Judith A.,Angst, Werner,Schwarzenbach, Rene P.
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- Kinetics and Thermochemistry of the Cl(2PJ) + C2Cl4 Association Reaction
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A laser flash photolysis-resonance fluorescence technique has been employed to study the kinetics of the Cl(2PJ) + C2Cl4 association reaction as a function of temperature (231-390 K) and pressure (3-700 Torr) in nitrogen buffer gas.The reaction is found to be in the falloff regime between third and second order over the range of conditions investigated, although the second-order limit is approached at the highest pressures and lowest temperatures.At temperatures below 300 K, the association reaction is found to be irreversible on the experimental time scale of ca. 20 ms.The kinetic data at T 0298 = -18.1 +/- 1.3 kcal mol-1, ΔH00 = -17.6 +/- 1.3 kcal mol-1, and ΔS0298 = -27.7 +/- 3.0 cal mol-1 K-1.In conjunction with the well-known heats of formation of Cl(2PJ) and C2Cl4, the above ΔH values lead to the following heats of formation for C2Cl5 at 298 and 0 K: ΔH0f,298 = 8.0 +/- 1.3 kcal mol-1 and ΔH0f,0 = 8.1 +/- 1.5 kcal mol-1.The kinetic and thermochemical parameters reported above are compared with other reported values, and the significance of reported association rate coefficients for understanding tropospheric chlorine chemistry is discussed.
- Nicovich, J. M.,Wang, S.,McKee, M. L.,Wine, P. H.
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- Natural organic matter as reductant for chlorinated aliphatic pollutants
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Humic acids (HA) are ubiquitous redox-active compounds of natural aquatic and soil systems. Here we studied the potential of HA as reductants for chlorinated aliphatic pollutants. To avoid artifacts potentially involved when studying chemically reduced HA, we prepared electrochemically reduced soil, aquatic and synthetic HA, and anthrahydroquinone-2,6-disulfonic acid (AHQDS), a model compound for hydroquinone moieties in HA. Both reduced HA and AHQDS reduced hexachloroethane (HCE) at appreciable rates. Some reduction of HCE by HA, however, occurred even before electrochemical reduction of the humic acids. This indicates that a small fraction of reduced moieties in HA persists at oxic conditions for some time. The initial reaction followed pseudo-first-order reaction kinetics, and tetrachloroethylene was the only halogenated product. The relatively small variations in carbonnormalized rate constants, kDOC, found indicate that despite inherent variations in concentration, accessibility, and reactivity of redox-active groups in HA of various origins their overall dechlorination activity is fairly constant. However, HCE transformation rate constants and reducing capacities of different HA did not correlate. Rate constants normalized to both carbon content and reducing capacity of HA clearly indicate that reduced functional groups in different HA exhibit different reactivities. Our results together with the factthat reduced HA can be formed by a variety of microbiological and chemical processes suggest that HA could play a significant role as reductants in the reductive transformation of subsurface contaminants and that such a process could potentially be enhanced at contaminated sites by addition of reducible natural organic matter.
- Kappler, Andreas,Haderlein, Stefan B.
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- Role of copper species in chlorination and condensation reactions of acetylene
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We examined the thermally induced acetylene chlorination and condensation reactions on different types of copper salt impregnated surfaces. The System for Thermal Diagnostic Studies provided a powerful tool to study these reactions under defined reaction conditions, which were related to typical conditions in postcombustion incineration processes. Experiments were conducted with acetylene or acetylene/HCl mixtures in a quarts reactor filled with a borosilicate foam of known pore size at temperatures between 150 and 500 °C. Borosilicate was also used as the catalytic support for gas-solid reactions of acetylene and acetylene/HCl mixtures with CuCl2 and CuO. Reaction products were trapped in-line and analyzed by GC/MS. It was shown that borosilicate is not able to catalyze acetylene condensation reactions. CuCl2-impregnated borosilicate was a highly effective catalyst for acetylene chlorination/condensation reactions at temperatures above 150 °C. The same behavior was found for CuO- impregnated borosilicate in the presence of HCl. However, temperatures above 300 °C were required for this catalytic system. Mainly perchlorinated C-2 to C-8 hydrocarbons were trapped as reaction products in the gas phase. Maximum yields for acetylene chlorination/condensation reactions in each related catalytic system were found at temperatures between 300 and 400 °C. Results of the surface-catalyzed acetylene chlorination and condensation reactions were summarized in a global mechanism. A ligand transfer oxidative chlorination of acetylene with CuCl2 was proposed to be the initiation of acetylene with CuCl2 was proposed to be the initiating step. Chlorinated acetylene then condenses to higher molecular weight compounds, catalyzed by CuCl in metallacyclization reactions. We examined the thermally induced acetylene chlorination and condensation reactions on different types of copper salt impregnated surfaces. The System for Thermal Diagnostic Studies provided a powerful tool to study these reactions under defined reaction conditions, which were related to typical conditions in postcombustion incineration processes. Experiments were conducted with acetylene or acetylene/HCl mixtures in a quartz reactor filled with a borosilicate foam of known pore size at temperatures between 150 and 500 °C. Borosilicate was also used as the catalytic support for gas-solid reactions of acetylene and acetylene/HCl mixtures with CuCl2 and CuO. Reaction products were trapped in-line and analyzed by GC/MS. It was shown that borosilicate is not able to catalyze acetylene condensation reactions. CuCl2-impregnated borosilicate was a highly effective catalyst for acetylene chlorination/condensation reactions at temperatures above 150 °C. The same behavior was found for CuO-impregnated borosilicate in the presence of HCl. However, temperatures above 300 °C were required for this catalytic system. Mainly perchlorinated C-2 to C-8 hydrocarbons were trapped as reaction products in the gas phase. Maximum yields for acetylene chlorination/condensation reactions in each related catalytic system were found at temperatures between 300 and 400 °C. Results of the surface-catalyzed acetylene chlorination and condensation reactions were summarized in a global mechanism. A ligand transfer oxidative chlorination of acetylene with CuCl2 was proposed to be the initiating step. Chlorinated acetylene then condenses to higher molecular weight compounds, catalyzed by CuCl in metallacyclization reactions.
- Wehrmeier, Andreas,Lenoir, Dieter,Sidhu, Sukh S.,Taylor, Philip H.,Rubey, Wayne A.,Kettrup, Antonious,Dellinger, Barry
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- Reductive dehalogenation of hexachloroethane, carbon tetrachloride, and bromoform by anthrahydroquinone disulfonate and humic acid
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The reductive dehalogenation of hexachloroethane (C2Cl6), carbon tetrachloride (CCl4), and bromoform (CHBr3) was examined at 50 °C in aqueous solutions containing either (1) 500 μM of 2,6-anthrahydroquinone disulfonate (AHQDS), (2) 250 μM Fe2+, or (3) 250 μM HS-. The pH ranged from 4.5 to 11.5 for AHQDS solutions and was 7.2 in the Fe2+ solutions and 7.8 in the HS- solutions. The observed disappearance of C2Cl6 in the presence of AHQDS was pseudo-first-order and fit k'(CCl4) = k0[A(OH)2] + k1[A(OH)O-] + k2[A(O)22-] where A(OH)2, A(OH)O-, and A(O)22- represent the concentrations of the three forms of the AHQDS in solution. The values of k0, k1, and k2 were ~0, 0.031, and 0.24 M-1 s-1, respectively. The addition of 25 mg of C/L of humic acid or organic matter extracted from Borden aquifer solids to aqueous solutions containing 250 μM HS- or Fe2+ increased the reduction rate by factors of up to 10. The logarithms of the rate constants for the disappearance of C2Cl6 and CCl4 in seven different experimental systems were significantly correlated; log k'(CCl4) = 0.64 log k'(C2Cl4)-0.83 with r2 = 0.80. The observed trend in reaction rates of C2Cl6 > CCl4 > CHBr3 is consistent with a decreasing trend in one-electron reduction potentials. The reductive dehalogenation of hexachloroethane (C2Cl6), carbon tetrachloride (CCl4), and bromoform (CHBr3) was examined at 50°C in aqueous solutions containing either (1) 500 μM of 2,6-anthrahydroquinone disulfonate (AHQDS), (2) 250 μM Fe2+, or (3) 250 μM HS-. The pH ranged from 4.5 to 11.5 for AHQDS solutions and was 7.2 in the Fe2+ solutions and 7.8 in the HS- solutions. The observed disappearance of C2Cl6 in the presence of AHQDS was pseudo-first-order and fit k′CCl(4) = k0[A(OH)2] + k1[A(OH)O-] + k2[A(O)22-] where A(OH)2, A(OH)O-, and A(O)22- represent the concentrations of the three forms of the AHQDS in solution. The values of k0, k1, and k2 were approximately 0, 0.031, and 0.24 M-1 s-1, respectively. The addition of 25 mg of C/L of humic acid or organic matter extracted from Borden aquifer solids to aqueous solutions containing 250 μM HS- or Fe2+ increased the reduction rate by factors of up to 10. The logarithms of the rate constants for the disappearance of C2Cl6 and CCl4 in seven different experimental systems were significantly correlated; log k′CCl(4) = 0.64 log k′C(2)Cl6 approximately 0.83 with r2 = 0.80. The observed trend in reaction rates of C2Cl6 > CCl4 > CHBr3 is consistent with a decreasing trend in one-electron reduction potentials.
- Curtis,Reinhard
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- Kinetics of the transformation of halogenated aliphatic compounds by iron sulfide
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The transformation of nine halogenated aliphatic compounds, i.e., pentachloroethane (PCA), 1,1,2,2- and 1,1,1,2-tetrachloroethanes (1122-TeCA and 1112-TeCA), 1,1,1- and 1,1,2-trichloroethanes (111-TCA and 112-TCA), 1,1- and 1,2-dichloroethanes (11-DCA and 12-DCA), carbon tetrachloride (CT), and tribromomethane (TBM), by 10 g/L FeS at pH 8.3 was investigated in batch experiments. 11-DCA, 12-DCA, and 112-TCA showed no significant transformation by FeS over ~ 120 days, but the other compounds were transformed with half-lives of hours to days. PCA and 1122-TeCA underwent dehydrohalogenation faster than FeS-mediated reductive dehalogenation reactions. The remaining compounds for which considerable transformation was observed underwent FeS-mediated reactions more rapidly than hydrolysis or dehydrohalogenation. For 1112-TeCA, the dihaloelimination product, i.e., 1,1-dichlroethylene, was the only reaction product observed. For 111-TCA, CT, and TBM, hydrogenolysis products were the only products detected, even though their mass recoveries were significantly 100%. Two simple log-linear correlations between rate constants and either one-electron reduction potentials or homolytic bond dissociation enthalpies were developed, with determination coefficients of 0.48 and 0.82, respectively. These results were consistent with a rate-limiting step involving homolytic bond dissociation. However, neither correlation precisely characterized the reactivity of all the compounds, indicating distinctions among the mechanisms for reductive dehalogenation of the compounds by FeS or the influence of additional molecular or thermodynamic parameters on rate constants.
- Hayes,Butler
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- Pyrolysis of hexachloroethane in the gas phase: computer aided kinetic study
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The pyrolysis of C2Cl6 has been studied between 652 and 735 K at pressures ranging from 19 to 50 torr. The observed total pressure- and Cl2 pressure-time curves show S-shapes with an induction period depending on temperature and pressure. Further, the total pressure goes through a maximum to finally reach a lower constant value. These curves are explained in terms of a recently proposed reaction model using a parameter optimization computer program.
- Huybrechts,Theys,Van Mele
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Read Online
- Three-dimensionally ordered macroporous Cr2O3?CeO2: High-performance catalysts for the oxidative removal of trichloroethylene
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Three-dimensionally ordered macroporous (3DOM) CeO2, 3DOM Cr2O3, 3DOM xCr2O3?CeO2 (x (the weight percentage of Cr2O3) = 3.5, 5.5, and 8.0 wt%), and 5.5 wt% Cr2O3/3DOM CeO2 samples were prepared using the polymethyl methacrylate (PMMA)-templating and incipient wetness impregnation methods, respectively. A number of techniques were used to characterize physicochemical properties of the materials, and their catalytic activities were evaluated for the oxidation of trichloroethylene (TCE). These samples possessed a good-quality 3DOM structure and a surface area of 35?47 m2/g. The 3DOM 5.5Cr2O3?CeO2 sample performed the best (the temperature at TCE conversion = 90% = 255 °C at a space velocity of 20,000 mL/(g h)). Effects of water vapor and carbon dioxide on activity of the 5.5Cr2O3?CeO2 sample were also examined. It is observed that partial deactivation induced by H2O introduction of the 5.5Cr2O3?CeO2 sample was reversible, while that induced by CO2 addition was irreversible. Based on the activity data and characterization results, it is concluded that the good catalytic activity and thermal stability of 3DOM 5.5Cr2O3?CeO2 was associated with its high adsorbed oxygen species concentration, good low-temperature reducibility, and strong interaction between Cr2O3 and CeO2. We believe that the 3DOM 5.5Cr2O3?CeO2 catalyst is promising in the application for oxidative removal of chlorinated volatile organic compounds.
- Zhang, Xing,Liu, Yuxi,Deng, Jiguang,Zhao, Xingtian,Zhang, Kunfeng,Yang, Jun,Han, Zhuo,Jiang, Xiyun,Dai, Hongxing
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p. 200 - 209
(2019/02/14)
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- Method for eliminating hydrogen chloride by catalytic cracking of chloralkane
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The invention discloses a method for eliminating hydrogen chloride by catalytic cracking of chloralkane, comprising the following steps of: carrying out a cracking reaction on chloralkane under the action of a biomass-based nitrogen-doped carbon catalyst to eliminate hydrogen chloride so as to prepare corresponding olefin, wherein the biomass-based nitrogen-doped carbon catalyst is prepared by carbonizing biomass or a mixture of biomass and a nitrogen source at 400-1000 DEG C, and the biomass is selected from at least one of bamboo processing leftovers, wood processing leftovers, plant straws,plant leaves, cereals, beans, cereal processing leftovers, bean processing leftovers and livestock manure. The method disclosed by the invention has the advantages of simple preparation process, easily available raw materials, low cost, strong process controllability, easiness in large-scale production, high catalytic cracking conversion rate of the chloralkane, high product selectivity, low energy consumption and the like.
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Paragraph 0106-0111
(2020/08/06)
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- Rational design of CrOx/LaSrMnCoO6 composite catalysts with superior chlorine tolerance and stability for 1,2-dichloroethane deep destruction
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1,2-dichloroethane (1,2-DCE) is a representative industrial chlorinated volatile organic compound (CVOC) making great hazardous to the environment and human health. In this work, LaSrMnCoO6 (LSMC) double perovskite-type materials with high thermal stability and coke resistance in 1,2-DCE oxidation were prepared by a facile sol-gel method. Based on this, a series of CrOx/LaSrMnCoO6 catalysts (Cr/LSMC, CrOx loading = 5 to 20 wt.%) which combine the merits of CrOx (high activity and chlorine tolerance) and LaSrMnCoO6 were synthesized and adopted in deep oxidation of 1,2-DCE for the first time. As expected, obvious synergistic effects between CrOx and LSMC on 1,2-DCE destruction were observed. Amongst, 10 wt.% CrOx/LaSrMnCoO6 (10Cr/LSMC) shows the best catalytic activity with 90% of 1,2-DCE destructed at 400 °C. Furthermore, the outstanding catalytic durability and water resistance of 10Cr/LSMC in 1,2-DCE oxidation were also demonstrated. In addition to this, the reaction pathway of 1,2-DCE decomposition over Cr/LSMC materials was discussed based on the results of online product analysis. We found that the enhanced catalytic performance of Cr/LSMC materials can be reasonably attributed to their high reducibility, excellent 1,2-DCE adsorption capability, and large amounts of surface active lattice oxygen species. It can be anticipated that the Cr/LSMC catalysts are promising materials for CVOC elimination and the results from this work could also provide some new insights into the design of catalysts for CVOC efficient destruction.
- Tian, Mingjiao,Jian, Yanfei,Ma, Mudi,He, Chi,Chen, Changwei,Liu, Chao,Shi, Jian-Wen
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- METHOD OF PRODUCING VINYL CHLORIDE
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A method of producing vinyl chloride is provided in the present invention. The method includes the following steps. First, 1,2-dichloroethane (EDC) is introduced into a reactor, and a residence time of the EDC in an ionic liquid catalyst is 5 seconds to 100 seconds, so as to perform a catalytic cleavage reaction. The ionic liquid catalyst is in a liquid phase. The ionic liquid catalyst includes tributylalkyl phosphonium halide, and the alkyl includes an alkyl group having 3 to 16 carbon atoms.
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Paragraph 0031; 0038; 0039
(2020/01/27)
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- A CHLORINOLYSIS PROCESS FOR PRODUCING CARBON TETRACHLORIDE
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A chlorinolysis process for producing carbon tetrachloride comprising providing a chlorination zone at an operating temperature of from 400 to 600°C with i) chlorine, ii) a C1 chlorinated compound comprising 1 to 3 chlorine atoms and iii) a carbon/second chlorine source to produce a reaction mixture, and, after a residence time, extracting a product mixture from the chlorination zone, the product mixture comprising carbon tetrachloride and optionally perchloroethylene, wherein the product mixture comprises a higher molar content of carbon tetrachloride than perchloroethylene, if present.
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Page/Page column 32-34
(2018/03/25)
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- Method for comprehensive utilization of hexachloroethane
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The invention relates to a comprehensive utilization method of a dichloroethane chlorination byproduct namely hexachloroethane. The comprehensive utilization method comprises the following steps: adding a hexachloroethane solution, glycerin, a hydrogenation catalyst and a chlorination catalyst into a high-pressure kettle; after feeding is finished, performing hydrodechlorination and glycerin chlorination reaction at the same time at certain temperature and under certain hydrogen pressure; after reaction is finished, maintaining the temperature for 4h, and then reducing the temperature to the room temperature; performing filtering separation to obtain the hydrogenation catalyst, layering reaction liquid to obtain a solvent layer and a glycerin layer, wherein the solvent layer contains a solvent, pentachloroethane, pentachloroethane and trichloroethane, and the glycerin layer contains the glycerin, dichloropropanol, water, the chlorination catalyst and monochlorohydrin.
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Paragraph 0015; 0017-0019; 0021; 0023; 0025; 0027; 0030
(2017/10/27)
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- A method for preparing of PCE
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The invention discloses a tetrachloroethylene preparation method, which comprises the following steps: simultaneously introducing a mixture of perchloroethane and carbon tetrachloride as well as chloralkane in a reactor for reacting, wherein the mass ratio of perchloroethane to carbon tetrachloride is 1: 0.1-2.0, volume ratio of the mixture of perchloroethane and carbon tetrachloride to chloralkane is 1: 0.05-1.5, reaction temperature is 150-800 DEG C, and reaction contact time is 0.1-10s; condensing the reaction products, and rectifying to obtain the tetrachloroethylene product. The preparation method has the advantages of simple process, mild reaction condition, high yield, low cost, less three wastes and continuous reaction, and has industrial production prospect.
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Paragraph 0032; 0033
(2017/01/23)
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- A method for preparing of PCE
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The invention discloses a method for preparing tetrachloroethylene. The method is characterized by comprising the following steps: simultaneously introducing aluminum trichloride and a total chlorine-1,3-butadiene mixture and chlorine into a gasifier, preheating to 250-450 DEG C, further introducing the components into a reactor for reaction, and condensing and distilling a pyrolysis gas which is obtained from the reaction, thereby obtaining a tetrachloroethylene product, wherein the mass ratio of aluminum trichloride to total chlorine-1,3-butadiene is (0.01-0.5):1, the mole ratio of chlorine to total chlorine-1,3-butadiene is (1-8):1, the reaction temperature is 300-1000 DEG C, and the reaction contact time is 0.1-10 seconds. The method has the advantages that the process is simple, the raw materials are easy to obtain, the cost is low and the yield is high.
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Paragraph 0036; 0037
(2017/02/02)
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- METHOD OF PREPARING HALOGENATED SILAHYDROCARBYLENES
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A method comprises separate and consecutive steps (i) and (ii). Step (i) includes contacting a copper catalyst with hydrogen gas and a halogenated silane monomer at a temperature of 500 °C to 1400 °C to form a silicon-containing copper catalyst comprising at least 0.1 % (w/w) of silicon. Step (ii) includes contacting the silicon-containing copper catalyst with an organohalide at a temperature of 100°C to 600 °C to form a reaction product. The organohalide has formula HaCbXc, where X is a halogen atom, subscript a is an integer of 0 or more, subscript b is an integer of 1 or more, and subscript c is an integer of 2 or more. The method produces a reaction product. The reaction product includes a halogenated silahydrocarbylene.
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Paragraph 0042
(2014/05/07)
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- Noncatalytic Conversion of Carbon Tetrachloride to Perchloroethylene
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Perchloroethylene is made by thermal noncatalytic pyrolysis of carbon tetrachloride in the presence of chlorine and methyl chloride, or methane, or natural gas. Vapor carbon tetrachloride is used both as a raw material and a diluent, and reaction takes place under conditions with high consumption of maximize conversion of carbon tetrachloride to perchloroethylene and minimum formation of heavies, especially, low formation of hexchlorobenzene, another environmental undesirable chemical compound.
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Page/Page column 2
(2009/02/11)
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- PROCESS FOR PRODUCING FLUORINE-CONTAINING COMPOUND BY REARRANGEMENT REACTION
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The present invention provides a process for producing a compound represented by general formula (I): wherein X, Y and Z are same or different, and each represent H, F, Cl or an alkyl group, provided that the alkyl group and F are each not more than one; the process comprising contacting a fluorine-containing compound represented by general formula (II): wherein X, Y and Z are as defined above, with a Lewis acid catalyst to cause a chlorine rearrangement reaction. The present invention provides a novel reaction step, which can be used in the production process of a compound represented by the chemical formula CF3CF=CH2.
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Page/Page column 12
(2009/12/28)
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- Addition of tetrachloromethane to oct-1-ene initiated by amino alcohols
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The kinetics and mechanism of an addition of CCl4 to oct-1-ene initiated by amines, aromatic alcohols, and amino alcohols (structural analogs of ephedrin) were studied. The radical mechanism of the reaction was established by ESR using the technique of spin traps. Aromatic amino alcohols as initiators are more active than amines and aromatic alcohols of similar structure. They are more selective compared to the amines and aromatic alcohols and react with CCl4 already at room temperature to form predominantly benzaldehyde. The scheme of initiation by aromatic amino alcohols of the addition of CCl 4 to olefins was proposed on the basis of the experimental data.
- Tarkhanova,Gantman,Chizhov,Smirnov
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p. 1624 - 1630
(2007/10/03)
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- Method for reusing heavy end by-products in the manufacture of polychlorinated alkanes
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A method for recovering much of the carbon and chlorine value in the heavy ends and other undesired by-products formed during the production of a C3 or higher polychlorinated alkane through the reaction of carbon tetrachloride with an olefine or chlorinated olefine, the improvement comprising the step of first separating the heavy ends and any other higher or lower boiling chlorohydrocarbon impurities from most of the desired product, and subjecting the separated heavy ends and impurities therewith to a high temperature exhaustive chlorination to produce carbon tetrachloride, tetrachloroethene, and minor amounts of hexachlorobutadiene and hexachlorobenzene by-products.
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Page/Page column 3-4
(2008/06/13)
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- Methane to olefins
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The specification discloses a process for the production of olefins, including ethylene, propylene and butenes, from methane, the process comprising first, second and third reaction steps operated in tandem. In the first reaction step, hydrogen chloride, perchloroethylene and oxygen are reacted in the presence of a catalyst, using methane as a diluent, to yield hexachloroethane and water. In the second reaction step, the hexachoroethane from the first reaction step is reacted with methane to produce methyl chloride, hydrogen chloride and perchloroethylene. In the third reaction step, the methyl chloride from the second reaction step is reacted to give the desired olefins and hydrogen chloride. By recycling the perchloroethylene from the second reaction step and the hydrogen chloride from both the second and third reaction steps to the first reaction step, a balanced process is achieved that is self-sufficient in chlorine values.
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- Reactivity of Fe(II)-Bearing Minerals toward Reductive Transformation of Organic Contaminants
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Fe(II) present at surfaces of iron-containing minerals can play a significant role in the overall attenuation of reducible contaminants in the subsurface. As the chemical environment, i.e., the type and arrangement of ligands, strongly affects the redox potential of Fe(II), the presence of various mineral sorbents is expected to modulate the reactivity of surficial Fe(II)-species in aqueous systems. In a comparative study we evaluated the reactivity of ferrous iron in aqueous suspensions of siderite (FeCO 3), nontronite (ferruginous smectite SWa-1), hematite (α-Fe2O3), lepidocrocite (γ-FeOOH), goethite (α-FeOOH), magnetite (Fe3O4), sulfate green rust (FeII4FeIII2(OH)12SO 4·4H2O), pyrite (FeS2), and mackinawite (FeS) under similar conditions (pH 7.2, 25 m2 mineral/L, 1 mM Fe(II)aq, O2 (aq) 0.1 g/L). Surface-area-normalized pseudo first-order rate constants are reported for the reduction of hexachloroethane and 4-chloronitrobenzene representing two classes of environmentally relevant transformation reactions of pollutants, i.e., dehalogenation and nitroaryl reduction. The reactivities of the different Fe(II) mineral systems varied greatly and systematically both within and between the two data sets obtained with the two probe compounds. As a general trend, surface-area-normalized reaction rates increased in the order Fe(II) + siderite Fe(II) + iron oxides Fe(II) + iron sulfides. 4-Chloronitrobenzene was transformed by mineral-bound Fe(II) much more rapidly than hexachloroethane, except for suspensions of hematite, pyrite, and nontronite. The results demonstrate that abiotic reactions with surface-bound Fe(II) may affect or even dominate the long-term behavior of reducible pollutants in the subsurface, particularly in the presence of Fe(III) bearing minerals. As such reactions can be dominated by specific interactions of the oxidant with the surface, care must be taken in extrapolating reactivity data of surface-bound Fe(II) between different compound classes.
- Elsner, Martin,Schwarzenbach, Rene P.,Haderlein, Stefan B.
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p. 799 - 807
(2007/10/03)
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- Method for purifying tetrachloroethylene and process for producing hydrofluorocarbons
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Tetrachloroethylene containing a stabilizer is contacted with a zeolite having an average pore size of 3.4 to 11 ? and/or a carbonaceous adsorbent having an average pore size of 3.4 to 11 ? in a liquid phase to obtain a high purity tetrachloroethylene. A halogenated alkene and/or a halogenated alkane are reacted with hydrogen fluoride in the presence of a fluorination catalyst to produce a first hydrofluorocarbon, a halogenated alkene and/or a halogenated alkane are reacted with hydrogen fluoride in the presence of a fluorination catalyst to produce a second hydrofluorocarbon, and the products are joined and then distilled to obtain the first and second hydrofluorocarbons.
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Page/Page column 6
(2008/06/13)
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- Effect of chemical composition on the neutral reaction products produced during electron beam irradiation of carbon tetrachloride/water (ice) films
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The neutral reaction products formed during electron beam irradiation of CCl4/H2O (ice) films were studied as a function of the film's initial CCl4/H2O ratio using a combination of reflection absorption IR spect
- Wagner,Vecitis,Wolfe,Perry,Fairbrother
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p. 3806 - 3813
(2007/10/03)
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- Transient puffs of trace organic emissions from a batch-fed waste propellant incinerator
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Emissions data have been obtained from a waste propellant incinerator. The incinerator is a dual fixed hearth, controlled air incinerator equipped with acid gas and particulate scrubbing. Puffing has been evident in this waste propellant incinerator by spikes in the CO concentration. Transient puffs of organics may travel down the combustion chambers and lead to stack emissions. The major conclusions from this study are that (1) transient puffs are formed due to the semi-batch feed nature of the combustion process (causing a local oxygen deficiency) and high water content of the desensitized propellant; (2) in batch-fed combustors, puffs can contribute to most of the organic emissions (which are relatively low) measured with US EPA sampling and analytical methods; (3) it is estimated that batch-fed combustion contributes up to 7-18 times more emissions than steady-state combustion will generate; (4) by applying dispersion analyses to determine the amount of oxygen deficiency in the flame zone, the combustion zone concentration of CO during batch-fed operation could be as high as 160,000 ppm, compared to a measured peak stack concentration of 1200 ppm CO; and (5) an organic sample is collected and averaged over at least a 2-h period that smooths out the transient peaks of organics emissions during batch-fed operation. For emissions that are associated with long-term potential health impacts, this is an appropriate sampling method. However, if a compound has a short-term potential health impact, it may be important to measure the time-resolved emissions of the compound.
- Hart, John R.
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p. 559 - 569
(2007/10/03)
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- Experimental determination of the Cr-C2Cl4 bond dissociation enthalpy in Cr(CO)5(C2Cl4): Quantifying metal-olefin bonding interactions
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The bond dissociation enthalpy for the Cr-C2Cl4 bond in gas-phase Cr(CO)5(C2Cl4) has been determined to be 12.8 ± 1.6 kcal/mol using transient infrared spectroscopy. The results of a density functional theory-based energy decomposition analysis are used to quantify the metal-olefin bonding interactions in terms of the bonding description provided by the Dewar-Chatt-Duncanson model (? donation and back-bonding). The bond energy decomposition analysis reveals that metal-olefin bond strengths can be strongly influenced by the Pauli repulsion energy and by the energy necessary to deform the olefin and the metal-centered moiety from their equilibrium geometries to their geometry in the final complex. Further, a comparison between the metal-olefin bond strengths and the magnitude of the electronic interactions demonstrates that the energy associated with these deformations is the determining factor in the trends in bond enthalpies in the series of complexes Cr(CO)5(C2X4) (X = H, F, Cl). Though deformation of the Cr(CO)5 moiety contributes to the overall deformation energy, the major contribution involves deformation of the olefin. This occurs as a consequence of rehybridization of the olefin as a result of metal-olefin back-bonding. The results are discussed in terms of the Dewar-Chatt-Duncanson model, which provides the accepted qualitative description of bonding in organometallic olefin complexes.
- Cadenno, David L.,Weitz, Eric
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p. 12857 - 12865
(2008/10/08)
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- Hazardous air pollutants formation from reactions of raw meal organics in cement kilns
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Thermally induced chlorination, condensation, and formation reactions of raw meal organic surrogates were investigated on different types of surfaces. The System for Thermal Diagnostic Studies provided a powerful tool to study these reactions under defined reaction conditions, which were related to typical conditions in the preheater zone of cement kiln. Experiments were conducted with benzene and benzene/myristic acid (C6H6/C13H27COOH) mixtures in a quartz reactor containing different chlorinating catalysts/reagents over a temperature range of 300-500°C. Reaction products were trapped in-line and analyzed by GC-MS. A mixture of chlorides of calcium, potassium, aluminium and iron was highly effective for chlorination/condensation reactions of benzene and benzene/myristic acid mix at temperatures above 300°C. The same behavior was observed only when calcium chloride and potassium chloride were used as chlorinating catalyst/reagent. This result showed that transition metal chlorides like FeCl3 are not necessary for chlorination/condensation of organics under post-combustion conditions. Methylene chloride was the major chlorinated product followed by chloroform and various other C1, C2 and C6 chlorinated products. Yields of chlorinated aliphatics were highest at 400°C for both benzene and benzene/myristic acid mix. C6 products were mainly mono- to hexa-chlorinated benzenes with trace amounts of chlorinated phenols. The major chlorinated products observed in this study (i.e., methylene chloride, chloroform, chloroethanes and monochlorobenzene) were also present as major chlorinated hydrocarbons in the cement kiln field emission data.
- Sidhu, Sukh,Kasti, Nabil,Edwards, Phil,Dellinger, Barry
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p. 499 - 506
(2007/10/03)
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- Copper-catalyzed chlorination and condensation of acetylene and dichloroacetylene
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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. (C) 2000 Elsevier Science Ltd.
- Taylor, Philip H.,Wehrmeier, Andreas,Sidhu, Sukh S.,Lenoir, Dieter,Schramm,Kettrup
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p. 1297 - 1303
(2007/10/03)
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- Reaction between chlorocarbon vapors and sodium carbonate
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The kinetics of the reactions between tetrachloromethane (CCl4), 1,2- dichloroethane (C2H4Cl2), or chlorobenzene (C6H5Cl) and sodium carbonate were investigated using evolved gas analysis-Fourier transform infrared spectroscopy. Sodium carbonate reacted with CCl4 between 600 and 900 K to form over 90% carbon dioxide (CO2) and less than 10% tetrachloroethene (C2Cl4). This reaction followed the three-dimensional diffusion mechanism and had an activation energy of 105 ± 10 kJ/mol and a steric factor of 5000 ± 3000 min-1. The reaction between C2H4Cl2 and sodium carbonate produced CO2, ethanal (C2H4O), water (H2O), vinyl chloride (C2H3Cl), ethene (C2H4), and ethyne (C2H2) between 600 and 900 K from at least two different pathways. The product temperature profiles indicated that CO2, C2H4O, and C2H3Cl were formed initially and that approximately 10% of the product is C2H4 at 900 K. The reaction kinetics followed the Ginstling- Brounshtein diffusion mechanism and had an activation energy of 100 ± 10 kJ/mol and a steric factor of approximately 104 min-1. Benzene was produced from the reaction between chlorobenzene and sodium carbonate at temperatures above 800 K. This reaction followed the three-dimensional diffusion mechanism and had an activation energy of 80 ±10 kJ/mol and a steric factor of approximately 500 min-1. The kinetics of the reactions between tetrachloromethane (CCl4), 1,2-dichloroethane (C2H4Cl2), or chlorobenzene (C6H5Cl) and sodium carbonate were investigated using evolved gas analysis-Fourier transform infrared spectroscopy. Sodium carbonate reacted with CCl4 between 600 and 900 K to form over 90% carbon dioxide (CO2) and less than 10% tetrachloroethene (C2Cl4). This reaction followed the three-dimensional diffusion mechanism and had an activation energy of 105 ± 10 kJ/ mol and a steric factor of 5000 ± 3000 min-1. The reaction between C2H4Cl2 and sodium carbonate produced CO2, ethanal (C2H4O), water (H2O), vinyl chloride (C2H3Cl), ethene (C2H4), and ethyne (C2H2) between 600 and 900 K from at least two different pathways. The product temperature profiles indicated that CO2, C2H4O, and C2H3Cl were formed initially and that approximately 10% of the product is C2H4 at 900 K. The reaction kinetics followed the Ginstling-Brounshtein diffusion mechanism and had an activation energy of 100 ± 10 kJ/mol and a steric factor of approximately 104 min-1. Benzene was produced from the reaction between chlorobenzene and sodium carbonate at temperatures above 800 K. This reaction followed the three-dimensional diffusion mechanism and had an activation energy of 80 ± 10 kJ/mol and a steric factor of approximately 500 min-1.
- Parrett Jr.,Sumner,Devore
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p. 1691 - 1696
(2007/10/03)
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- Formation of complex organochlorine species in water due to cavitation
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Sonication at 900 kHz was carried out on aqueous solutions of chloroform in the concentration range 25 to 500 mg/L. The formation of chlorinated hydrocarbons was detected by means of GC/MS analyses. For instance, carbon tetrachloride, chlorinated ethanes, and chlorinated ethenes were formed after 10 min of sonication. The greatest concentration of any product was 6 mg/L. Sonication of aqueous chloroform with phenol present produced chlorophenols, and with benzene present produced phenol, chlorobenzene and chlorophenols. These results are significant for the evaluation of sonication as a method of eliminating chlorinated organic compounds from water. They also have significance in supporting the notion that some complex organochlorines may be formed naturally in the environment. Some chloroform and methyl chloride are produced in nature and could react with other organic compounds to form more complex organochlorines through natural processes which have an action similar to cavitation, e.g. waterfalls and breaking waves.
- Kruus, Peeter,Beutel, Lise,Aranda, Rocio,Penchuk, Jaan,Otson, Rein
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p. 1811 - 1824
(2007/10/03)
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- Reactions of N,N-dichloramines with trichloroethylene
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The reaction of alkyldichloramines with trichloroethylene in an inert medium initiated thermally, photochemically, or chemically yields products of trichloroethylene chlorination: tetrachloroethylene, pentachloroethane, and amine hydrochlorides or free 2-cyanoisopropylamine. In the presence of oxygen the corresponding dichloroacetamides were isolated.
- Levkovskaya,Mirskova
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p. 786 - 789
(2007/10/03)
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- Formation of octachloroacenaphthylene in the pyrolysis of decachlorobiphenyl
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The pyrolytic degradation of decachlorobiphenyl (PCB 209) in the temperature range of 700-1000°C and at a pyrolysis time of 10 seconds generated one main chloroaromatic product. This compound has been identified by HPLC-UV, GC-MS, GC-FTIR and 13C-NMR as octachloroacenaphthylene (OCAN). The mechanism of the nearly quantitative formation of octachloroacenaphthylene (OCAN) occurs via a nonachlorobenzobarrylene radical (Z1R) as an intermediate followed by a rearrangement and further dechlorination to form OCAN. Calculations with the program THERM based on the Benson-group-theory indicated that this mechanism is not possible for lower or nonchlorinated biphenyls.
- Bleise,Kleist,Guenther,Schwuger
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p. 655 - 666
(2007/10/03)
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- High utility of Saccharomyces cerevisiae harboring rat liver cytochrome P450 1A2 cDNA in haloethanes dehalogenations
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Yeast harboring rat liver P450 1A2 efficiently degraded trichloroethylene, pentachloroethane and hexachloroethane. Since liver P450s catalyze degradation of thousands of chemicals, this method is promising for chemical-directed degradation of environmental pollutants.
- Yanagita, Kazutaka,Sagami, Ikuko,Shimizu, Toru
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p. 561 - 562
(2007/10/03)
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