- Estimation of atmospheric lifetimes of hydrofluorocarbons, hydrofluoroethers, and olefins by chlorine photolysis using gas-phase NMR spectroscopy
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An empirical correlation has been derived between accepted atmospheric lifetimes of a set of hydrofluorocarbons and hydrofluoroethers and relative rates of reaction with photolyzed chlorine in excess at ambient temperature. These kinetic systems were studied by nuclear magnetic resonance (NMR) spectroscopy in the gas phase, marking the first application of NMR spectroscopy to this field. The square of the Pearson coefficient R for the linear correlation between observed reaction rates and accepted atmospheric lifetimes was 0.87 for compounds of lifetime less than 20 years. The method was extended to the study of ethene and propene; the rate of reaction of propene was found to be 1.25 times that of ethene at 23°C. The chief advantage of this method is its simplicity and reliance only on common tools and techniques of an industrial chemical laboratory.
- Marchione, Alexander A.,Fagan, Paul J.,Till, Eric J.,Waterland, Robert L.,LaMarca, Concetta
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Read Online
- Method of producing 1,1-difluoroethane and application thereof for the production of 1,1-difluoroethylene
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Process for the manufacture of 1,1-difluoroethane by liquid-phase fluorination of 1,2-dichloroethane using hydrofluoric acid in the presence of a Lewis acid as catalyst and of FeCl3 as cocatalyst. Process for the manufacture of 1,1-difluoroethylene employing it.
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Page/Page column 2; 4
(2008/06/13)
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- γ-Alumina-supported boron trifluoride: Catalysis, radiotracer studies and computations
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The irreversible adsorption of boron trifluoride on calcined γ-alumina and amorphous chromia, in both cases at room temperature, has been studied using [18F]-labelled BF3. Although the resulting γ-alumina surface has some catalytic activity for the room temperature fluorination by anhydrous HF of CH3CCl3 under static conditions, its activity is far lower than that of γ-alumina, which has been fluorinated with SF4, nominally at room temperature. A possible explanation for the observed behaviour is given.
- Klap?tke, Thomas M.,McMonagle, Fiona,Spence, Ronald R.,Winfield, John M.
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p. 1446 - 1453
(2008/09/19)
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- Method of making difluoromethane, 1,1,1-trifluoroethane and 1,1-difluoroethane
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A process for the production of difluoromethane (HFC-32), 1,1,1-trifluoroethane (HFC-143a) and 1,1-difluoroethane (HFC-152a). In the process the following steps are employed: (a) providing a reaction vessel, (b) providing in the reaction vessel activated carbon impregnated with a strong Lewis acid fluorination catalys selected from halides of As, Sb, Al, TI, In, V, Nb, Ta, Ti, Zr and Hf, (c) activating the catalyst by passing through the activated carbon impregnated with a strong Lewis acid fluorination catalyst anhydrous hydrogen fluoride gas and chlorine gas, (d) contacting, in a vapor state in the reaction vessel containing the activated catalyst, hydrogen fluoride and one or more halogenated hydrocarbons selected from chlorofluoromethane, dichloromethane, 1,1,1-trichloroethane, vinyl chloride, 1,1-dichloroethylene, 1.2-dichloroethylene, 1,2-dichloroethane, and 1,1-dichloroethane for a time and at a temperature to produce a product stream comprising hydrofluorocarbon product(s) corresponding to the chlorinated hydrocarbon reactant(s), and one or more of hydrogen chloride, unreactacted chlorinated hydrocarbon reactant(s), under-fluorinated intermediates, and unreacted hydrogen fluoride, and (e) separating the hydrofluorocarbon product(s) from the product stream.
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Page/Page column 3
(2010/02/14)
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- Catalyst and method for producing 1,1-difluoroethane
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The present invention relates to a catalyst for producing 1,1-difluoroethane (HCFC-152a) and producing method thereof. More particularly, it is to provide the catalyst prepared by impregnating palladium on the active carbon pretreated with an aqueous hydrogen fluoride solution and an aqueous hydrogen chloride solution in series and its use in the production of 1,1-difluoroethane (HCFC-142b) by dehydrochlorinating 1,1-difluoro-1-chloroethane at 240-300° C. in the supplying molar ratio of 2-6 (H2/HCFC-142b) with maximizing a selectivity toward the product of HCFC-152a.
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- Radical addition of iodine monochloride to vinylidene fluoride
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The radical addition of iodine monochloride to 1,1-difluoroethylene or vinylidene fluoride (VDF) leading to a ClCF2CH2I (I)/ClCH2CF2I (II) mixture is described. Four different ways of initiation (thermal, photochemical, presence of radical initiators or redox catalysts) were used and all of them led to a high amount (≥98%) of isomer (I). The percentages of (I) and (II) isomers were determined by 19F NMR and they were also deduced from those of ClCF2CH3 and ClCH2CF2H obtained by selective reduction of the iodine atom of the product mixture, by tributylstannane. The reactivity of ICl to VDF and the high proportion of isomer (I) were interpreted by means of a thermodynamical approach from the enthalpy of formation of (I) and (II), respectively, determined by semi-empirical computations. In addition, heats of formation of both isomers and interactions between the SOMO of radicals and the HOMO of the fluoroolefin show that the mechanism of such a reaction occurs via the addition of I· to the less fluorinated side of VDF.
- Kharroubi,Manséri,Améduri,Boutevin
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p. 145 - 153
(2007/10/03)
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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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p. 1881 - 1885
(2007/10/03)
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- Liquid phase fluorination process and fluorinated organic products resulting therefrom
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In an improved process and plant for carrying out liquid phase fluorination in the presence of a catalyst, consisting in reacting hydrofluoric acid and an organic starting material in a reaction zone, and in separating, in a separating zone, reactional mixture and at least one light fraction containing the desired fluorinated organic products and at least a first part of the sub-fluorinated organic products formed, and a heavy fraction that includes the remainder of the sub-fluorinated organic products formed, and further comprising partial condensation of the said light fraction in order to obtain a gaseous phase containing the desired fluorinated organic products and a liquid phase containing said first part of the said sub-fluorinated organic products, said heavy fraction being returned to said reaction zone and said liquid phase being returned as a reflux to the top of the separation zone, intermediate recovery is carried out at, or in the proximity of, the lower portion of said separation zone.
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- CH3CF3-nCln haloalkanes and CH2=CF2-nCln halo-olefins on γ-alumina catalysts: reactions, kinetics and adsorption
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The heterogeneously catalyzed reactions of the haloalkane, CH3CF(3-n)Cln, and halo-olefin, CH2=CF(2-n)Cl(n), series have been studied on a γ-alumina catalyst and the experimental results compared with calculated thermodynamic data.The main reactions occurring in this system can be explained by the following reaction paths: dehydrohalogenation, hydrohalogenation, F/Cl and Cl/F exchange with hydrogen halides.Dismutation reactions which are observed in other halocarbon series are unimportant in this system.A survey of the dominant reactions is given.In addition, the kinetic behaviour of CH3CF2Cl on the γ-alumina catalyst and the adsorption of various halocarbons have been investigated.The isosteric enthalpies of adsorption demonstrate that the interaction between the haloalkanes and the solid surface is more dominant than simple condensation. - Keywords: Chlorofluorocarbons; γ-Alumina catalysts; Heterogeneous catalysis; Kinetics; Adsorption; Enthalpy of adsorption
- Hess, A.,Kemnitz, E.
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- INVESTIGATIONS IN THE REGION OF INDUSTRIAL FLUORINATED COMPOUNDS
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The synthesis and properties of ozone-friendly fluorohydrocarbons, fluoroolefins, and fluorinated compounds with functional groups (acids, alcohols, esters, and others), used for the creation of effective surfactants, ion-exchange membranes for various purposes, heat-resistant oils, and greases, were investigated.A technology was developed for the production of highly pure fluorinated compounds for microelectronics, fiber optics, and medicine.
- Maksimov, B. N.
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p. 1935 - 1940
(2007/10/03)
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- Room-temperature Catalytic Fluorination of C1 and C2 Chlorocarbons and Chlorohydrocarbons on Fluorinated Fe3O4 and Co3O4
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A study of the room-temperature reactions of a series of C1 and C2 chlorohydrocarbon and chlorocarbon substrate molecules with fluorinated iron(II,III) oxide and cobalt(II,III) oxide has been conducted.The results show that fluorinated iron(II,III) oxide exhibits an ability to incorporate fluorine into the following substrates in the order: Cl2C=CCl2 > H2C=CCl2 > CH3CCl3 > CHCl3 > CH2Cl2 > CH2ClCCl3 > CCl4 > CHCl2CHCl2.The fluorinated cobalt(II,III) oxide gave the reactivity series CHCl3 > CCl4 > H2C=CCl2 > CHCl2CHCl2 > CH2Cl2 > CH3CCl3 > CCl2CCl2 > CH2ClCl3.Reactions of C1 chlorohydrocarbon or chlorocarbon probe molecules with fluorinated Fe3O4 gave predominately C1 chlorofluorohydrocarbon and chlorofluorocarbon products, respectively, whereas fluorinated cobalt(II,III) oxide produced predominately C2 chlorofluorohydrocarbon and chlorofluorocarbons.For fluorinated Co3O4 the distribution of C2 products obtained from C1 chlorohydrocarbon precursor molecules is consistent with the formation of radical intermediates at strong Lewis acid surfaces.C2 chlorohydrocarbons exhibit a fluorine for chlorine (F-for-Cl) exchange reaction through the catalytic dehydrochlorination of the substrate to the alkenic intermediate.The F-for-Cl exchange process was dependent upon the ability of the substrate material to undergo dehydrochlorination; the inability of a substrate to undergo dehydrochlorination results in the fluorination process proceeding through the formation of chlorocarbon or chlorohydrocarbon radical intermediates.
- Thomson, James
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p. 3585 - 3590
(2007/10/02)
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- Two-Zone Ignition of 1,1-Difluoroethane-Chlorine Mixtures by Single Light Pulses
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A new phenomenon of two-center ignition was revealed in studies of 1,1-difluoroethane-chlorine mixtures ignited by single light pulses.The distance between the two hot spots and the time interval between successive ignitions depend on the mixture composition, initial temperature, pressure, light intensity, nature of additives, etc.
- Begishev, I. R.,Gromovenko, O. L.,Poluektov, V. A.
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p. 992 - 994
(2007/10/02)
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- Process for the purification of 1,1-dichloro-1-fluoroethane
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A process for purification of crude, 1,1-dichloro-1-fluoroethane includes the steps of treating a mixture of crude, 1,1-dichloro-1-fluoroethane and hydrogen fluoride with chlorine in the presence of a Lewis acid, and distilling to recover purified 1,1-dichloro-1-fluoroethane, wherein hydrogen fluoride is present during the treatment with chlorine at a ratio of at least 5% by weight with respect to the mixture of crude, 1,1-dichloro-1-fluoroethane and hydrogen fluoride.
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- Liquid-phase fluorination and dehydrochlorination of 1,1,1-trichloroethane
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During the liquid-phase fluorination of 1,1,1-trichloroethane with SbCl5*HF, 1,1-dichloroethene is formed.This reacts to give linear and branched oligomers.The hydrolysis of these by-products affords 3,5-dichlorophenol, 6-methyl-4-chloro-2-pyran-2-one and 2-methyl-5,7-dichlorochromone whose source is the acid-catalyzed reaction of water with the trimer and pentamer of 1,1-dichloroethene.
- Brunet, Sylvette,Batiot, Catherine,Barrault, Joeel,Blanchard, Michel,Coustard, Jean-Marie
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p. 227 - 232
(2007/10/02)
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- Liquid-phase fluorination of 1,1,1-trichloroethane
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The reaction of HF with SbCl5 at 60 deg C and 1 MPa provides antimony mixed halides whose empirical formulae have been determined.The product is a mixture of SbClF4 and SbClF2 solvated by HF and its activity has been measured for the conversion of 1,1,1-trichloroethane (F140a) into mono- and difluorochloroethane (F141b and F142b).
- Brunet, S.,Batiot, C.,Barrault, J.,Blanchard, M.
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- Fluorinated γ-Alumina. Catalytic Fluorination of 1,1,1-Trichloroethane at Ambient Temperature
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γ-Alumina, fluorinated with sulphur tetrafluoride followed by treatment with 1,1,1-trichloroethane, behaves as a catalyst for the room temperature fluorination of CH3CCl3 with anhydrous HF, giving a mixture of chlorofluorohydrocarbons.
- Thomson, James,Webb, Geoffrey,Winfield, John M.
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p. 323 - 324
(2007/10/02)
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- Threshold Energies and Substituent Effects for Unimolecular Elimination of HCl (DCl) and HF (DF) from Chemically Activated CF2ClCH3 and CF2ClCD3
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Chemically activated CF2ClCH3-d0 and -d3 were prepared with 101 and 102 kcal/mol of internal energy, respectively, by the combination of CF2Cl with methyl-d0 and -d3 radicals at 300 K.The CF2ClCH3 reacts by loss of HCl and HF with rate constants of (2.5 +/- 0.4) x 109 and (0.10 +/- 0.02) x 109 s-1, respectively, a branching ratio of 25:1 in favor of HCl.The CF2ClCD3 has rate constants of (0.78 +/- 0.12) x 109 for loss of DCl and 0.033 +/- 0.005 x 109 sec-1 for loss of DF.The combined primary and secondary isotope effect was 3.2 +/- 0.9 for HCl/DCl elimination and 3.0 +/- 0.9 for loss of HF/DF.RRKM theory was used to model these unimolecular rate constants to determine the threshold energy barriers, E0's, for the four-centered elimination reactions.The E0's were 55 +/- 2 kcal/mol for dehydrochlorination and 69.5 +/- 2 kcal/mol for dehydrofluorination.These threshold barriers are in sharp disagreement with prediction based on trends in the E0's for a series of mono-, di-, and trisubstituted chloroethanes and a similar series of fluoroethanes.An analysis of the E0's for the chloroethanes, fluoroethanes, and chlorodifluoroethane suggests that the carbon-halogen bond in the transition state changes from a nearly neutral C-Cl bond for HCl loss to a C-F bond that has much greater charge separation when HF is eliminated.
- Jones, Yukari,Holmes, Bert E.,Duke, David W.,Tipton, Debbie L.
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p. 4957 - 4963
(2007/10/02)
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- DIE ELEKTROFLUORIERUNG VON Α-CHLORETHYLSULFOCHLORID
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The electrochemical fluorination of CH3CHClSO2Cl was studied at different conditions.Besides methane- and ethane-derivates, SO2F2 and SF6, the products formed are the two sulfonylfluorides C2F5SO2F and CF3CFClSO2F.The yield of CF3CFClSO2F was greater at l
- Sartori, P.,Habel, W.
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p. 131 - 142
(2007/10/02)
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