359-10-4Relevant academic research and scientific papers
An efficient synthesis of 1-chloro-2,2-difluoroethylene via the reductive dechlorination of 1,2,2-trichloro-1,1-difluoroethane
Wang, Nong,Yang, Lijuan,Xiang, Shaoji
, p. 273 - 275 (2013)
1-Chloro-2,2-difluoroethylene was prepared from 1,2,2-trichloro-1,1- difluoroethane by reductive dechlorination in the presence of zero-valent zinc. Eleven different solvents were investigated and the best results were obtained in methanol, dimethyl formamide and ethanol at 80 °C. A large-scale experiment using ethanol as a solvent gave 1-chloro-2,2-difluoroethylene in high yield. These results provide a method for producing 1-chloro-2,2- difluoroethylen e on an industrial scale because 1,2,2-trichloro-1,1- difluoroethane is the waste material arising from 2,2-dichloro-1,1,1- trifluoroethane production. These results can also provide a method for solving the recycling problem of 1,2,2- trichloro-1,1-difluoroethane in 2,2-dichloro-1,1,1-trifluoroethane production.
Effects of Addition Gases on the IR Multiphoton Dissociation of Haloethanes
Sakka, Tetsuo,Furuya, Hiroyuki,Iwasaki, Matae,Ogata, Yukio
, p. 983 - 986 (1995)
The effects of addition gases on the rate of the IR multiphoton dissociation (IRMPD) of CClF2CH2Cl have been studied.He, CF4, CF3CDBrCl and CCl2CF2 were employed as the addition gases and IRMPD yield was measured as a function of addition gas mole fraction.The results revealed that molecular collisions play an important role in the excitation process and that the reaction rate is determined by the competition of two collision induced processes, one of which suppresses, and the other enhances, the reaction.In the case of 961.9 cm-1 irradiation, both effects have been clearly observed, whereas in the case of 1023.2 cm-1 irradiation, the latter effect seems weak.The results also show that the addition of CF4 or He always lowers the reaction rate.We conclude that the relaxation of the anharmonicity bottleneck by a resonant vibrational-energy transfer is important for IRMPD of this molecule.
Infrared Multiphoton Absorption and Reaction of 2-Chloro-1,1,1-trifluoroethane
Setser, D.W.,Lee, Tsae-Shyan,Danen, Wayne C.
, p. 5799 - 5805 (1985)
The infrared multiphoton absorption and dissociation of CF3CH2Cl has been studied by measuring the dependence of the reaction probability and product distribution on the laser fluence and bath gas pressure.Absorption measurements were performed at two laser frequencies to estabilish the absorbed laser energy: the absorption measurements displayed Beer's law behavior except at very low laser fluence.Sensitized reactions with SiF4 were conducted for comparison to the direct laser-induced process: the effective temperature within the irradiated volume for the SiF4 experiments was determined as a function of incident laser energy.The three main reaction channels are four centered HF elimination, three-centered HCl elimination, and C-Cl homolysis: the product ratios were very dependent on the incident laser fluence.Addition of toluene as a bath gas significantly lowered the reaction probability, especially at lower laser fluence, but had only a minor influence on the product distribution.The infrared laser-induced energy absorption and reaction processes of CF3CH3, CF3CH2Cl, and CF3CH2Br are compared.The data provide evidence for a fluence-dependent fractionation of absorbed laser energy producing a two-component energy distribution for the former two compounds.
Effect of Megnesium Fluoride in Chromium-Magnesium Catalysts on the Fluorination Reaction of 1,1,1-Trifluoro-2-chloroethane
Kim, Honggon,Kim, Hoon S.,Lee, Byung G.,Lee, Hyunjoo,Kim, Sehoon
, p. 2383 - 2384 (1995)
Magnesium fluoride, mixed with chromium fluoride, enhances the activity, selectivity and lifetime of the chromium catalyst for the vapour-phase fluorination of CF3CH2Cl with anhydrous HF to give CF3CH2F.
Characterization by Temperature-Programmed Reduction and by Temperature-Programmed Oxidation (TPR-TPO) of Chromium (III) Oxide-Based Catalysts: Correlation with the Catalytic Activity for Hydrofluoroalkane Synthesis
Brunet, S.,Requieme, B.,Matouba, E.,Barrault, J.,Blanchard, M.
, p. 70 - 74 (1995)
The catalytic activity of chromium (III) oxide for the fluorination of CF3CH2Cl (HCFC 133a) is proportional to the number of reversibly oxidized sites.The proportionality coefficient depends on the atmosphere employed during the pretreatment of the catalyst.The temperature-programmed reduction and temperature-programmed oxidation experiments constitute a simple technique that allows the number of reversibly oxidized chromium atoms to be measured.The method of preparation of the chromium hydroxide has little effect on the catalytic properties of chromium (III) oxide.The activation atmosphere and the temperature are essential parameters in the formation of chromium (III) oxide from hydroxide.Indeed, the most active chromium (III) oxide for the fluorination of CF3CH2Cl is obtained by thermal treatment of hydroxide at 380 deg C under nitrogen.
Properties of chromium (III) oxides involved in the catalytic gas phase fluorination of CF3CH2Cl
Brunet,Boussand,Martin
, p. 287 - 292 (1997)
The fluorination of chromium oxides reduces the chromium species on the surface. A low fluorination by HF does not modify the total amount of reversibly oxidizable chromium sites, but increases the strength of these sites. Mobile dioxygen (measured by isotopic exchange) was required to obtain a good fluorination activity. These dioxygen species would be exchanged by HF which is probably active in the fluorination of CF3CH2Cl and would prevent the irreversibly catalyst fluorination.
Vacuum-ultraviolet (147 nm) photodecomposition of 1,1,2-trichloro-2,2-difluoroethane
Yano, T.,Tschuikov-Roux, E.
, p. 3401 - 3409 (1980)
The 147 nm photolysis of CF2ClCHCl2 has been investigated at 25 deg C as a function of reactant pressure, conversion, and nitric oxide as additive.In the absence of NO the observed reaction products are CF2CHCl, CF2CCl2, and the diastereomers of (CF2ClCHCl)2.At constant reactanr pressure the quantum yields of the olefin decrease with increasing conversion and there is a corresponding increase in the quantum yield of the C4 product.For fixed values of conversion the olefin quantum yields decrease with increasing reactant pressure and approach limiting values at ca. 100 Torr.The addition of NO completely suppresses the formation of the chlorofluorobutanes, while it enhances the olefin quantum yields at higher conversion.These observations are interpreted in terms of reactions of chlorine atoms which result either directly (by near simultaneous expulsion of two Cl atoms), or via the dissociation of an excited Cl2* molecule produced by molecular elimination in the primary process.Chlorine atoms abstract hydrogen from the parent or add to the product olefins.These processes provide the principal source of halo-ethyl radicals in the system.The addition reaction leads to chemically activated radicals with a mean lifetime of τ ca. 0.8*10-8 sec which is commensurate with RRKM-theory predictions.The addition of nitric oxide provides a competing channel for chlorine atom removal by way of their NO-catalyzed recombination.The functional dependence of the olefin quantum yields with conversion in the absence and presence of NO suggests that the major fraction of the principal product, CF2CHCl, derives directly from a primary process, while CF2CCl2 is formed via both, the molecular elimination of HCl and from radical precursors.The limiting quantum yields of CF2CHCl and CF2CCl2 are found to be φ0 ca. 0.68 and φ0' ca. 0.19, in the absence of NO, respectively, and φ0,NO ca. 0.56 and φ0,NO' ca. 0.087 in the presence of NO.The extinction coefficient for CF2ClCHCl2 at 147 nm and 25 deg C has been determined: ε = (1/PL)ln(I0/It) = 404 +/- 40 atm-1cm-1.
Mechanistic aspects of the isomerization reactions of 1,1,2,2-tetrafluoroethane on a CFC-conditioned chromia catalyst
Kemnitz,Niedersen
, p. 111 - 119 (1996)
The mechanism of the isomerization reactions of 1,1,2,2-tetrafluoroethane on a CFC-conditioned chromia catalyst was investigated. The desired 1,1,1,2-tetrafluoroethane can be obtained from its symmetric isomer in the presence of a chromia catalyst conditioned exclusively with chlorine-free fluorocarbons. In the presence of chlorofluorocarbons, hydrogen chloride is formed as a result of the decomposition reactions of the haloalkane used and is strongly adsorbed on to the surface. This HCl causes a very complex system of side-reactions. In addition, a second kind of chlorine, inactive chloride bonded to chromium, is formed which can only be removed as the result of a very slow solid-gas reaction. Mechanistic information was obtained by examining the effects of substituting DCl for HCl as the chlorine source for the reaction with consecutive isomerization products of 1,1,2,2-tetrafluoroethane. Thus, it is most probable that dehydrohalogenation/hydrohalogenation processes (elimination/addition mechanism) are mainly responsible for the formation of the halo-olefins and halocarbons observed on chromia. As the HCl/DCl adsorbed on the surface is very quickly removed by the reactions with the halocarbons and halo-olefins, it is advantageous to employ pulse techniques to evaluate this reaction system.
Photodissociation of 1,1,1-Trifluorodichloroethane at 147 nm. Evidence for Chlorine Atom Reactions
Yano, T.,Jung, K.-H.,Tschuikow-Roux, E.
, p. 2146 - 2151 (1980)
The 147-nm photolysis of CF3CHCl2 has been investigated at 23 deg C as a function of reactant pressure and conversion (It/N), with and without nitric oxide as additive.The principal reaction product is CF2CHF, with lesser yields of CF2CFCl, CF2CHCl, and four chlorofluorobutanes.At constant CF3CHCl2 pressure the observed quantum yields of the olefins decrease with increasing It/N and there is a corresponding increase in the yields of the C4 products.The quantum yields of the olefins also decrease with increasing reactant pressure at the same values of It/N.The addition of NO completely suppresses the formation of the chlorofluorobutanes, but there is a marked increase in the olefin quantum yields.These observations are interpreted in terms of reactions of chlorine atoms which derive, primarily, from the α,α elimination of the elements of (Cl)2 in the primary process.Clorine atoms so produced abstract hydrogen from the parent and add to the product olefins, processes which are the source of haloethyl radicals in the system.Nitric oxide provides an additional and dominant channel for chlorine atom removal by way of their NO-catalyzed recombination which proceeds through CINO as an intermediate.A reaction mechanism consistent with the observations is proposed and, from the functional dependence of the olefin quantum yields on It/N, limiting values have been obtained by extrapolation.The rate constant ratio for hydrogen abstraction from CF3CHCl2 by Cl atoms to Cl addition to CF2CHF was found to be k5/k6 = (2.2 +/- 0.5)*E-4.The extinction coefficient for CF3CHCl2 at 147 nm (296 K) has been determined as ε = (1/PL) ln(I0/It) = 590 +/- 60 atm-1Cm-1.
Preparation of Substitutes for CFCs. Catalytic Properties of Chromia for Halogen Exchange involving Hydrogen Fluoride and Trifluorochloroethane
Barrault, J.,Brunet, S.,Requieme, B.,Blanchard, M.
, p. 374 - 375 (1993)
The catalytic activity of chromia for F to Cl exchange in trifluorochloroethane is proportional to the number of chromium atoms which are reversibly oxidized.
