- EDTA-assisted hydrothermal synthesis of cubic SrF2 particles and their catalytic performance for the pyrolysis of 1-chloro-1,1-difluoroethane to vinylidene fluoride
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Uniform, free-standing and cubic SrF2 microparticles were successfully fabricated by a facile hydrothermal method with ethylenediaminetetraacetic acid (EDTA) as the chelating agent. The influences of preparation conditions, such as the pH value, amount of EDTA and hydrothermal time, on the formation of SrF2 crystals were investigated. The formation mechanism of cubic SrF2 particles was proposed based on the experimental results. Following calcination in air at 500 °C, SrF2 particles were evaluated as the catalyst for the pyrolysis of 1-chloro-1,1-difluoroethane (HCFC-142b, CH3CClF2) to vinylidene fluoride (VDF, CH2═CF2) at 350 °C and a space velocity of 600 h?1. The results indicate that SrF2 cubes exhibit high catalytic activity with a HCFC-142b conversion of about 70% and a selectivity to VDF of 80-87%. No significant deactivation was observed within the time on stream of 30 h. With the reaction temperature increased to 450 °C, the conversion of HCFC-142b is close to 94%, while the selectivity to VDF remains almost unchanged. Although the SrF2 catalyst prepared by the conventional precipitation method also shows high conversion, its selectivity to VDF is only around 50-70%. We suggest that the surface acidity and specific surface area play major roles in the catalytic performance. Compared with the temperatures for industrial manufacture of VDF of 650-700 °C, the SrF2 catalysts provide a promising pathway to produce VDF at much lower temperatures.
- Wang, Zhikun,Han, Wenfeng,Liu, Huazhang
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- Pyrolysis of 1,1-dichloro-1-fluoroethane in the absence and presence of added propene or CCl4: A computer-aided kinetic study
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The thermal dehydrochlorination CCl2FCH3→CClF double bond CH2+HCl has been studied in a static system between 610 and 700 K at pressures ranging from 14 to 120 torr. The experiments were performed in the absence and presence of an added inhibitor (0.5 to 7 torr of C3H6) or catalyst (2 to 8 torr of CCl4). The evolution of the reaction was followed by measuring the pressure rise in the quartz reaction vessel and analyzing the products by gas chromatography. All the experimental results can be explained quantitatively in terms of a reaction model both radical and molecular. The molecular dehydrochlorination has an activation energy of 52.05 kcal/mol and a preexponential factor of 1014.02 s-1.
- Huybrechts,Eerdekens
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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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- Dehalogenation of 1,1,2-trichloro-1-fluoroethane over ?±-Cr2O3 (101ì?12)
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The reaction of CFCl2CH2Cl over the stoichiometric Cr2O3 (1012) surface yields CFCl=CH2, HCa??CH, and surface halogen. The 1,2-dihalo-elimination reaction to CFCl=CH2 is initiated via C-Cl bond cleavage at the CFCl2-end of the molecule to give a -CFClCH2Cl haloalkyl surface intermediate. A rate-limiting ?2-chlorine elimination from the surface alkyl gives rise to the CFCl=CH2 product. Acetylene is formed by the subsequent reaction of CFCl=CH2 in series. The chlorine liberated from CFCl2CH2Cl binds at the five-coordinate surface Cr3+ sites on the stoichiometric surface and shuts down the dehalogenation chemistry by site blocking. No carbon buildup is observed on deactivated surfaces, and no evidence is seen for the replacement of surface lattice oxygen by halogen under the conditions of this study. At elevated temperatures, the thermal removal of surface chlorine is observed, and it is attributed to migration into the sample bulk.
- York, Steven C.,Cox, David F.
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- METHOD FOR PRODUCING OLEFIN
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A method for producing at least one olefin compound selected from the group consisting of a compound of formula (51), a compound of formula (52), a compound of formula (53), and a compound of formula (54), the method including reacting an olefin compound of formula (21) with a olefin compound of formula (31) in the presence of at least one metal catalyst selected from the group consisting of a compound of formula (11), a compound of formula (12), a compound of formula (13), a compound of formula (14), and a compound of formula (15).
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Paragraph 0150-0154; 0168-0171
(2017/11/01)
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- Method for producing fluorine-containing olefin
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A method for producing at least one compound selected from the group consisting of a compound represented by formula (10), a compound represented by formula (11), a compound represented by formula (12), and a compound represented by formula (13), by reacting a compound represented by formula (2) and a compound represented by formula (7) in the presence of at least one compound selected from the group consisting of a compound represented by formula (1), a compound represented by formula (3), a compound represented by formula (4), a compound represented by formula (8), and a compound represented by formula (9).
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Paragraph 0348; 0349; 0350; 0351; 0352; 0353
(2017/01/17)
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- GASEOUS DIELECTRICS WITH LOW GLOBAL WARMING POTENTIALS
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A dielectric gaseous compound which exhibits the following properties: a boiling point in the range between about ?20° C. to about ?273° C.; non-ozone depleting; a GWP less than about 22,200; chemical stability, as measured by a negative standard enthalpy of formation (dHf0); a toxicity level such that when the dielectric gas leaks, the effective diluted concentration does not exceed its PEL; and a dielectric strength greater than air.
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- PURIFICATION METHOD, PRODUCTION PROCESS, AND USE OF, 1, 1-DIFLUOROETHANE
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Crude 1,1-difluoroethane containing at least one compound selected from the group consisting of unsaturated compounds each having two carbon atoms within the molecule and saturated chlorine-containing compounds each having two carbon atoms within the molecule is brought into contact with a zeolite and/or a carbonaceous adsorbent, or crude 1,1-difluoroethane containing hydrogen fluoride and, as impurities, at least one compound selected from the group consisting of unsaturated compounds each having two carbon atoms within the molecule is brought into contact with a fluorination catalyst in a gas phase state. High-purity 1,1-difluoroethane usable as a cryogenic refrigerant, or as an etching gas, can be produced in an industrially advantageous manner.
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Page/Page column 20-22
(2008/06/13)
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- Substituent effects and threshold energies for the unimolecular elimination of HCl (DCl) and HF (DF) from chemically activated CFCl2CH3 and CFCl2CD3
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Combination of CFCl2 and methyl-d0 and -d3 radicals form CFCl2CH3-d0 and -d3 with 100 and 101 kcal/mol of internal energy, respectively. An upper limit for the rate constant ratio of disproportionation to combination, kd/kc, for Cl transfer is 0.07 ± 0.03 for collision of two CFCl2 radicals and 0.015 ± 0.005 for CH3 and CFCl2 radicals. The chemically activated CFCl2CH3 undergoes 1,2-dehydrochlorination and 1,2-dehydrofluorination with rate constants of 3.9 × 109 and 4.9 × 107 s-1, respectively. For CFCl2CD3 the rate constants are 8.7 × 108 s-1 for loss of DCl and 1.1 × 107 s-1 for DF. The kinetic isotope effect is 4.4 ± 0.9 for HCl/DCl and appears to be identical for HF/DF. Threshold energies are 54 kcal/mol for loss of HCl and 68 kcal/mol for HF; the E0's for the deuterated channels are 1.4 kcal/mol higher. Comparison of these threshold energies with other haloethanes suggests that for HF and HCl elimination the transition states are developing charges of different signs on the carbon containing the departing halogen and that chlorine and fluorine substituents exert similar inductive effects.
- McDoniel, J. Bridget,Holmes, Bert E.
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p. 3044 - 3050
(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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- 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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- Pulse-Duration Effects on Competitive Reactions in Infrared Multiple-Photon Decomposition of CH2ClCHClF and CHClFCHClF
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Vibrationally excited 1,2-dichlorofluoroethane and 1,2-dichloro-1,2-difluoroethane have been observed to dissociate competitively via two channels to form vibrationally excited HCl and HF.The fluence dependences of the branching ratio have been measured for both "short"-pulse (80-ns fwhm) and "long"-pulse (80-ns fwhm with 1-μs-fwhm tail) irradiations.The branching ratio shows not only fluence dependence but also pulse-duration dependence, that is, intensity dependence.When the reactant pressure is 1.0 Torr, collisional deactivation is expected to occur to a considerable extent under long-pulse irradiation while it can be ignored under short-pulse irradiation.The experimental results are interpreted by using the exact stochastic method based on the energy-grained master equations, which take into account collisional deactivation.
- Ishikawa, Yo-ichi,Sugita, Kyoko,Arai, Shigeyoshi
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p. 5067 - 5071
(2007/10/02)
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- CO2 Laser-induced Decomposition of 1,2-Dichloro-1-fluoroethane
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CH2ClCHFCl was photolyzed with a TEA CO2 laser at 1033.5 cm-1.The infrared multiphoton dissociation mechanism of CH2ClCHFCl was investigated under various conditions: Sample gas pressure, additive gas presure, pulse number, pulse energy, and pulse duration.It is concluded that primary process of the IRMPD is direct eleimination of molecular HCl and HF, HCl elimination being predominant channel.Primary HCl elimination products cis-and trans-CHF=CHCl, and CH2=CFCl are formed at high vibrational levels, from which additional photon absorption occures in the secondary photolysis to give rise to CH=CCl, CH=CF, and CH2=CHF.All of the secondary products are concluded to be derived from mainly CH2=CFCl among the chlorofluoroethene isomers.CH2=CFCl decomposes via HF and HCl elimination channels together with the C-Cl bond repture channel. appears to be generated by the H atom abstraction reaction of C2H. radical, which may result from further decomposition of and/or .The neat IRMPD at higher pressures gives quite similar primary product distribution, but markedly different secondary product distribution from those in shock tube pyrolysis.
- Ogura, Hiroo,Yano, Takayuki
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p. 1239 - 1250
(2007/10/02)
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- Infrared Laser Multiphoton Dissociation of CF2ClCH2Cl
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The infrared multiphoton decomposition (IRMPD) of CF2ClCH2Cl was studied with focusing geometry using the P(34) line of the 9.6-μm CO2 band (1033.6 cm-1).The principal reaction product is CF2CHCl.Other products of significance include CFClCHCl, CF2CH2, and CFCH.It is concluded that the primary processes of photodecomposition involve the molecular elimination of HCl and HF and, to a very minor extent, C-C bond rupture.The relative importance of the primary steps is approximately 1000:30:1, respectively.From a series of diagnostic experiments in the presence of hydrogen donors and D2, it is shown that CF2CH2 derives from the secondary photolysis of CF2CHCl.The decomposition yield, the HF/HCl ratio, and the CF2CH2/CF2CHCl ratio were investigated as a function of reactant and argon pressure, the latter serving as a buffer gas.From the dependence of the decomposition yield on pulse number at different pulse energies, E0, the specific rate of decomposition, b, was found to be proportional to b E01.8, the power dependence being somewhat higher than the standard 3/2 power law for focusing geometry.These phenomena are interpreted in terms of a simple geometric fluence model which includes contributions from collisionally induced reactions in the outermost (lower fluence) irradiated region.The nonresonant photodecomposition of C2H6 and C2H4 at 1033.6 cm-1 observed in auxiliary, diagnostic experiments is interpreted in terms of photosensitization processes.
- Yano, T.,Ozaki, S.,Ogura, H.,Tschuikow-Roux, E.
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p. 1108 - 1116
(2007/10/02)
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- Process for the preparation of fluorinated nitroalkanes
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In the conjugated nitrofluorination of an olefin by reacting an olefin of the formula STR1 in which R1, R2, R3 and R4 each independently is hydrogen, fluorine, chlorine, bromine, alkyl, halogenoalkyl or cycloalkyl, or R2 and R4 together are an alkylene radical of 3 to 6 carbon atoms, with hydrogen fluoride and nitric acid to produce an α-fluorinated nitroalkane of the formula STR2 the improvement which comprises effecting the reaction in a vessel protected against corrosion employing about 1 to 1.1 mols of hydrogen fluoride and about 1 to 2 mols of nitric acid per mol of olefin. The process uses much less HF than heretofore and the products are useful intermediates in making herbicides. Some of the products are new.
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