- Insertion of difluorovinylidene into hydrogen and methane
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Insertion reactions of difluorovinylidene 1b into H2, CH4, and CD4 have been observed in argon matrixes at 20-40 K. These reactions are controlled by diffusion of trapped species rather than by activation barriers, indicat
- Koetting, Carsten,Sander, Wolfram
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Read Online
- H atom formation dynamics in the dissociation of CH3-CF2Cl (HCFC-142b) after UV and VUV laser photoexcitation
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Using the laser photolysis/laser-induced fluorescence (LIF) "pump-and-probe" technique, the dynamics of H atom formation in the photodissociation of CH3-CF2Cl (HCFC-142b) after excitation at 193 nm and the Lyman-α wavelength were studied under collision-free conditions in the gas-phase at room temperature. The H atoms produced were detected by (2p2P←1s2S)-LIF using tunable narrow-band Lyman-α laser radiation (λLα ≈ 121.6 nm) generated by resonant third-order sum-difference frequency conversion of pulsed dye laser radiation. In the VUV photodissociation experiments the Lyman-α laser radiation was used both to photodissociate the parent molecules and to detect the produced nascent H atoms via laser induced fluorescence. The following quantum yields ΦH for H atom formation were determined by a photolytic calibration method: ΦH(193 nm) = (0.06±0.02) and ΦH(Lα) = (0.53±0.12). From the measured H atom Doppler profiles the average H atom kinetic energy was determined to be ET(193 nm) = (51 ±10) kJ/mol and ET(Lα) = (72±4) kJ/mol, respectively.
- Brownsword,Hillenkamp,Laurent,Volpp,Wolfrum,Vatsa,Yoo
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Read Online
- Highly Active Cross-Metathesis of Tetrafluoroethylene with a Seven-Membered N-Heterocyclic-Carbene-Ruthenium Catalyst
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A drastic increase in catalyst turnover number (TON) was accomplished in the cross-metathesis of tetrafluoroethylene (TFE) and vinyl ethers. Under a continuous flow of TFE, catalyst Ru7, which contains a seven-membered N-heterocyclic carbene (NHC) ligand, reached a TON of 4100; this is 2 orders of magnitude higher than the highest hitherto reported value. Mechanistic studies revealed that the expanded NHC successfully destabilizes the stable intermediates with a difluorocarbene structure, which strongly promotes the reaction.
- Mori, Kenta,Akiyama, Midori,Inada, Ko,Imamura, Yutaka,Ishibashi, Yuichiro,Takahira, Yusuke,Nozaki, Kyoko,Okazoe, Takashi
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supporting information
p. 20980 - 20987
(2021/12/14)
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- PRODUCTION METHOD OF ALKENE
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PROBLEM TO BE SOLVED: To provide a method of producing alkene, which is capable of further improving a yield of the alkene that is a reaction product, in a method of producing the alkene by contacting a gaseous alkane halide with an alkaline aqueous solution under the presence of a phase transfer catalyst. SOLUTION: A production method of alkene includes a step of contacting a liquid phase containing an alkaline aqueous solution and a nonaqueous solvent and a gaseous phase containing alkane halide soluble in the nonaqueous solvent under the presence of a phase transfer catalyst. SELECTED DRAWING: None COPYRIGHT: (C)2019,JPOandINPIT
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Paragraph 0060-0065
(2019/10/16)
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- 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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p. 1691 - 1700
(2019/03/19)
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- Exploiting the trifluoroethyl group as a precatalyst ligand in nickel-catalyzed Suzuki-type alkylations
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We report herein the exploitment of the partially fluorinated trifluoroethyl as precatalyst ligands in nickel-catalyzed Suzuki-type alkylation and fluoroalkylation coupling reactions. Compared with the [LnNiII(aryl)(X)] precatalysts, the unique characters of bis-trifluoroethyl ligands imparted precatalyst [(bipy)Ni(CH2CF3)2] with bench-top stability, good solubilities in organic media and interesting catalytic activities. Preliminary mechanistic studies reveal that an eliminative extrusion of a vinylidene difluoride (VDF, CH2CF2) mask from [(bipy)Ni(CH2CF3)2] is a critical step for the initiation of a catalytic reaction.
- Yang, Yi,Zhou, Qinghai,Cai, Junjie,Xue, Teng,Liu, Yingle,Jiang, Yan,Su, Yumei,Chung, Lungwa,Vicic, David A.
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p. 5275 - 5282
(2019/05/29)
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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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- Process for Making 2,3,3,3-Tetrafluoropropene and/or Vinylidine Fluoride
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Disclosed is a process for the formation of a mixture of the compounds 2,3,3,3-tetrafluoropropene (1234yf) and vinylidine fluoride, comprising pyrolyzing 1,1,2-trifluoro-2-trifluoro-methyl-cyclobutane under conditions effective to produce a reaction product comprising 1234yf and vinylidine fluoride in a 1234yf:vinylidine fluoride molar ratio of from about 0.5 to about 1.2.
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Paragraph 0049-0052
(2017/06/12)
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- Preparative Scale Demonstration and Mechanistic Investigation of a Visible Light-Mediated Radical Smiles Rearrangement
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A visible light-mediated Smiles rearrangement providing the difluoroethanol motif has been shown to reliably operate on preparative scale up to 100 g of starting material. Mechanistic investigation has revealed the reaction proceeds predominantly via a radical chain process that in some instances can be initiated via visible light or thermal activation in the absence of a photocatalyst. The reaction was demonstrated in continuous flow, with visible light and thermal initiation using a thiophene substrate relevant to pharmaceutical development.
- Douglas, James J.,Sevrin, Martin J.,Cole, Kevin P.,Stephenson, Corey R. J.
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supporting information
p. 1148 - 1155
(2016/07/23)
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- Preparing method of vinylidene fluoride monomer with high purity and conversion, and apparatus therefor
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The present invention relates to a method and an apparatus for preparing vinylidene fluoride (VDF), a base monomer for manufacturing a polyvinylidene fluoride (PVDF) which is a kind of fluorinated resins. The apparatus and the method for preparing the VDF in accordance with the present invention have almost 100% of a conversion ratio and less than or equal to 0.1% of a CH_3F generation rate, which is difficult to be separated from the VDF, thereby easily preparing the high purity VDF. The method for preparing VDF comprises: a step of heating liquid 1-chloro-1,1-difluoroethane at 500-700anddeg;C, which is a temperature efore the pyrolysis to obtain a gas compound; mixing the gas compound with steam at 800-1,000anddeg;C; and inserting the mixed gas into a reactor at 800-1,000anddeg;C, and pyrolyzing the 1-chloro-1,1-difluoroethane.(10) Mass flow controller(21) Evaporator(22) Preliminary heater(23) High temperature heater(31) Steam boiler system(32) High temperature steam heater(40) Pyrolysis reactor(AA) Mixture including VDF and the like(BB) WaterCOPYRIGHT KIPO 2016
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Paragraph 0070 - 0073
(2016/10/07)
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- Preparation method of vinylidene fluoride (VDF)
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The invention discloses a preparation method of vinylidene fluoride (VDF). The preparation method is characterized by adding inorganic alkali liquor with mass percentage concentration of 10-70%, a phase transfer agent and 1,1-difluoro-1-chloroethane to a reaction kettle to react at a temperature of 60-200 DEG C, controlling the pressure of the reaction kettle at 0.8-5.0MPa by extracting and collecting gas phase materials in the reaction process, stopping collecting the gas phase materials after reacting for 0.5-5 hours, cooling reaction liquor, releasing the pressure and collecting the gas phase materials in the reaction kettle and mixing the gas phase materials collected before and after, thus obtaining crude VDF, wherein the mass ratio of the phase transfer agent to the inorganic alkali liquor is (0.0001-0.01) to 1; the mass ratio of the phase transfer agent to 1,1-difluoro-1-chloroethane is (0.0003-0.06) to 1. The preparation method has the advantages of simple process, mild reaction conditions, low equipment investment, low energy consumption and less byproduct.
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Paragraph 0032; 0033
(2016/10/20)
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- PRODUCTION METHOD OF 2,3,3,3-TETRAFLUOROPROPENE AND 1,1-DIFLUOROETHYLENE
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PROBLEM TO BE SOLVED: To provide an economically advantageous method for producing HFO-1234yf (2,3,3,3-tetrafluoropropene) that is useful as a new coolant with a high yield through one-time reaction accompanying thermal decomposition. SOLUTION: A method for producing HFO-1234yf and VdF (1,1-difluoroethylene) is provided, which is carried out by a synthetic reaction accompanying thermal decomposition from a raw material composition comprising R22 and/or TFE, and methane in the presence of a heat medium. The method includes: (a) a step of supplying the R22 and/or the TFE and the methane as in preliminarily mixed state or separately to a reactor, and retaining the mixture in the reactor for a predetermined time; and (b) a step of supplying a heat medium to the reactor to bring the heat medium into contact with the raw material composition in the reactor. SELECTED DRAWING: Figure 1 COPYRIGHT: (C)2016,JPOandINPIT
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Paragraph 0046-0048
(2017/02/23)
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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 0354; 0355; 0356; 0357; 0358; 0359
(2017/01/17)
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- 2, 3, 3, 3-tetrafluoropropene and 1,1-difluoro ethylene production method
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Provided is an economically advantageous method for producing industrially useful HFO-1234yf and VdF by a single-pass reaction accompanied by pyrolysis using readily available starting materials. Provided is a method for producing, from octafluorocyclobutane and chloromethane, 2,3,3,3-tetrafluoropropene and 1,1-difluoroethylene by a one-step reaction process that includes synthesis accompanied by pyrolysis.
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Paragraph 0044-0049; 0051
(2016/11/07)
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- METHOD OF PRODUCING TRIFLUOROETHYLENE
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PROBLEM TO BE SOLVED: To provide an economically advantageous method for producing industrially useful trifluoroethylene with high productivity by using easily available HCFC-124 as raw material while not using any catalyst. SOLUTION: A method of producing trifluoroethylene includes the step of bringing a reductive compound and 1,1,1,2-tetrafluoro-2-chloroethane into contact with each other, without using any catalyst, at a temperature of 400-1200°C. COPYRIGHT: (C)2016,JPO&INPIT
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Paragraph 0056-0058; 0065
(2017/01/02)
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- METHOD OF PRODUCING 2,3,3,3-TETRAFLUOROPROPENE AND 1,1-DIFLUOROETHYLENE
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PROBLEM TO BE SOLVED: To provide an economically advantageous method that produces industrially useful HFO-1234yf and VdF by a single reaction associated with heat decomposition by use of easily available raw material. SOLUTION: This invention provides a method of producing 2,3,3,3-tetrafluoropropene and 1,1-difluoroethylene by a synthetic reaction associated with heat decomposition from a raw material composition comprising octafluorocyclobutane and methane. COPYRIGHT: (C)2015,JPOandINPIT
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Paragraph 0050-0054; 0059
(2016/12/22)
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- Ruthenium-Catalyzed Olefin Cross-Metathesis with Tetrafluoroethylene and Analogous Fluoroolefins
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This Communication describes a successful olefin cross-metathesis with tetrafluoroethylene and its analogues. A key to the efficient catalytic cycle is interconversion between two thermodynamically stable, generally considered sluggish, Fischer carbenes. This newly demonstrated catalytic transformation enables easy and short-step synthesis of a new class of partially fluorinated olefins bearing plural fluorine atoms, which are particularly important and valuable compounds in organic synthesis and medicinal chemistry as well as the materials and polymer industries.
- Takahira, Yusuke,Morizawa, Yoshitomi
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supporting information
p. 7031 - 7034
(2015/06/25)
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- PRODUCTION METHOD FOR 2,3,3,3-TETRA-FLUOROPROPENE
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To provide an economically advantageous process for producing industrially useful HFO-1234yf efficiently and in a sufficiently controlled state by one reaction involving thermal decomposition, by using readily available raw material. A process for producing 2,3,3,3-tetrafluoropropene from a raw material composition containing chlorodifluoromethane and chloromethane, by a synthetic reaction involving thermal decomposition, which comprises (a) a step of supplying the chlorodifluoromethane and the chloromethane to a reactor, as preliminarily mixed or separately, in such amounts that the chloromethane would be in a ratio of from 0.01 to 3 mol to 1 mol of the chlorodifluoromethane, (b) a step of supplying a heat medium to the reactor, and (c) a step of bringing the heat medium in contact with the chlorodifluoromethane and the chloromethane in the reactor to form the 2,3,3,3-tetrafluoropropene.
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Paragraph 0082
(2015/02/02)
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- PRODUCTION METHOD FOR 2,3,3,3-TETRA-FLUOROPROPENE AND 1,1-DIFLUOROETHYLENE
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To provide an economically advantageous process for producing HFO-1234yf useful as a new refrigerant in sufficiently high yield by one reaction involving thermal decomposition. A process for producing HFO-1234yf and VdF from raw material containing R22, R40 and TFE, by a synthetic reaction involving thermal decomposition, which comprises (a) a step of supplying the R22, the R40 and the TFE to a reactor, as preliminarily mixed or separately, (b) a step of supplying a heat medium to the reactor, and (c) a step of bringing the heat medium in contact with the R22, the R40 and the TFE in the reactor to form the HFO-1234yf and the VdF.
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Paragraph 0087
(2015/02/02)
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- METHOD FOR PREPARING VINYLIDENE FLUORIDE
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The present invention relates to the method for obtaining vinylidene fluoride and the subject matter thereof is more particularly the production of vinylidene fluoride by pyrolysis of 1,2-dichloro-2,2-difluoroethane in the presence of hydrogen at a temperature of greater than or equal to 400° C.
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Page/Page column 1-2
(2012/06/01)
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- SYNTHESIS OF FLUORINATED OLEFINS FROM FLUORINATED ALCOHOLS
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Disclosed is a process for producing a hydrofluoroalkene, RfCF=CH2 comprising contacting a hydrofluoroalkanol of structure RfCF2CH2OH, with a lewis acid to produce a mixture, diluting said mixture with a solvent to produce a solvent mixture, contacting the solvent mixture with a reactive metal, heating the solvent mixture and reactive metal for a sufficient amount of time to produce a hydrofluoroalkene, and condensing and collecting the volatile products comprising the hydrofluoroalkene, wherein Rf is F, or a fluorine-substituted alkyl group.
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Page/Page column 7-8
(2011/08/08)
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- Selective liquid-phase hydrodechlorination of chlorotrifluoroethylene over palladium-supported catalysts: Activity and deactivation
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Liquid-phase hydrodechlorination of chlorotrifluoroethylene (CTFE) to trifluoroethylene (TrFE) with molecular hydrogen was studied over palladium-supported catalysts. BaSO4, Al2O3 and activated carbon (AC) were used as supports, respectively. The results showed that the Pd/AC catalysts exhibit higher activity than Pd/BaSO4 and Pd/Al2O3. The treatment of activated carbon with HNO 3 led to a considerable increase of surface functional groups containing oxygen atoms, which resulted in a higher dispersion of palladium on the supports and enhancement of catalytic activity. The stability of the catalyst was investigated, one reason for the inhibition was the accumulation of NaCl on the surface of Pd/AC that blocks the pores of carbon support. The activity of Pd/AC could partially recovered by washing with water. The other irreversible deactivation of the catalyst are from the change of particle size and the pore structure, leaching of Pd, a decrease of BET surface area and Pd surface area of Pd/AC catalyst.
- Meng, Bao-Chuan,Sun, Zhao-Yang,Ma, Jin-Peng,Cao, Gui-Ping,Yuan, Wei-Kang
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experimental part
p. 68 - 75
(2010/11/05)
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- Experimental and chemical kinetic study of the pyrolysis of trifluoroethane and the reaction of trifluoromethane with methane
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A detailed reaction mechanism is developed and used to model experimental data on the pyrolysis of CHF3 and the non-oxidative gas-phase reaction of CHF3 with CH4 in an alumina tube reactor at temperatures between 873 and 1173 K and at atmospheric pressure. It was found that CHF3 can be converted into C2F4 during pyrolysis and CH2=CF2 via reaction with CH4. Other products generated include C3F6, CH 2F2, C2H3F, C2HF 3, C2H6, C2H2 and CHF2CHF2. The rate of CHF3 decomposition can be expressed as 5.2×1013[s-1]e -295[kJmol-1]/RT. During the pyrolysis of CHF3 and in the reaction of CHF3 with CH4, the initial steps in the reaction involve the decomposition of CHF3 and subsequent formation of CF2 difluorocarbene radical and HF. It is proposed that CH4 is activated by a series of chain reactions, initiated by H radicals. The NIST HFC and GRI-Mech mechanisms, with minor modifications, are able to obtain satisfactory agreement between modelling results and experimental data. With these modelling analyses, the reactions leading to the formation of major and minor products are fully elucidated.
- Han, Wenfeng,Kennedy, Eric M.,Kundu, Sazal K.,MacKie, John C.,Adesina, Adesoji A.,Dlugogorski, Bogdan Z.
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scheme or table
p. 751 - 760
(2010/09/04)
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- Tetrafluoropropene Production Processes
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A process is disclosed for producing 2,3,3,3-tetrafluoropropene and 1,3,3,3-tetrafluoropropene. The process involves pyrolyzing 1,1,1,2,3-pentafluoropropane.
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Page/Page column 2-3
(2009/10/30)
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- PROCESS FOR MAKING 1,1,1,4,4,4-HEXAFLUORO-2-BUTENE
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A process is disclosed for making 1,1,1,4,4,4-hexafluoro-2-butene. The process involves reacting 2,2-dichloro-1,1,1-trifluoroethane with copper in the presence of an amide solvent and 2,2'-bipyridine. A process is also disclosed for making 1,1,1,4,4,4-hexafluoro-2-butene. The process involves reacting 2,2-dichloro-1,1,1-trifluoroethane with copper in the presence of an amide solvent and a Cu(I) salt. A process is further disclosed for making 1,1,1,4,4,4-hexafluoro-2-butene. The process involves reacting 2,2-dichloro-1,1,1-trifluoroethane with copper in the presence of an amide solvent, 2,2'-bipyridine and a Cu(I) salt.
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Page/Page column 8-9
(2009/10/22)
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- Conversion of CHF3 to CH2=CF2 via reaction with CH4 and CaBr2
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Reaction of CHF3 and CH4 over CaBr2 was investigated at 400-900°C as a potential route for transforming the highly potent greenhouse gas, CHF3, into the valuable product CH 2=CF2. The homogeneous reaction of CHF3 with CH4 was also studied to assist in understanding the chemistries involved. Compared to the gas phase reaction, the addition of CaBr2 as a reactant increases the conversion of CHF3 and CH4 significantly at low temperatures while to a lesser extent at higher temperatures. In the absence of CaBr2, besides the target product, CH2=CF2, a large amount of C2F4 forms. On addition of CaBr2, the rate of formation of C 2F4 drops dramatically to near zero, while the rate of formation of CH2=CF2 increases considerably at temperatures below 880°C. Experimental and theoretical studies suggest that CHF3 strongly interacts with CaBr2, resulting in the fluorination of CaBr2 to CaF2, the release of active Br species results in the selective formation of CBrF3. The subsequent reactions involving Br, methane, and CBrF3 play a major role in the observed enhanced yield of CH2=CF2.
- Han, Wenfeng,Yu, Hai,Kennedy, Eric M.,Mackie, John C.,Dlugogorski, Bogdan Z.
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p. 5795 - 5799
(2008/12/22)
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- 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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- Simultaneous conversion of CHClF2 and CH3Br to CH2CF2
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Gas phase reaction of CHClF2 with CH3Br in an alumina tube reactor at 773-1123 K as a function of various input ratios of CH3Br to CHClF2 is presented. The major products detected include C2F4, CH2CF2, and CH4. Minor products include CH3Cl, CHF3, C2H4, C2H2, CH2CF-CF3, and C2H3F. The reaction produces a high yield of CH2CF2 (53% based on CHClF2 feed) at 1123 K and an input molar ratio of CH3Br to CHClF2 of 1.8, suggesting that the reaction potentially can be developed as a process to convert two ozone depleting substances (CHClF2 and CH3Br) to a highly valuable chemical, CH2CF2. The reaction of CHClF2 with CH3Cl and CH3I was also investigated under similar reaction conditions, to assist in understanding the reaction chemistry involved in the reaction of CHClF2 with CH3Br.
- Yu, Hai,Kennedy, Eric M.,Mackie, John C.,Dlugogorski, Bogdan Z.
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p. 2003 - 2006
(2008/02/04)
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- PYROLYSIS PROCESS
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The present invention relates to the pyrolysis of hydrochlorofluorocarbons to form fluoromonomers such as tetrafluoroethylene, the pyrolysis being carried out in a reaction zone lined with nickel and mechanically supported by a jacket of other corrosion resistant metal, the nickel lining providing an improved yield of valuable reaction products.
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Page/Page column 5
(2008/06/13)
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- Materials and methods for the conversion of hydrofluorocarbons
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Methods and materials are disclosed for the recovery of valuable hydrofluorocarbons and subsequent conversion to environmentally inert compounds. More specifically methods and materials are provided for recovering hydrofluorocarbons such as HFC-227, HFC-236, HFC-245, HFC-125, HFC-134, HFC-143, HFC-152, HFC-32, HFC-23 and their respective isomers. Processes are provided for converting hydrofluorocarbons such as these to fluoromonomer precursors such as CFC-217, CFC-216, CFC-215, CFC-115, CFC-114, CFC-113, CFC-112, HCFC-22, CFC-12, CFC-13 and their respective isomers. Materials, methods and schemes are provided for the conversion of these fluoromonomer precursors to fluoromonomers such as HFP, PFP, TFP, TFE, and VDF.
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- A Shock-Tube, Laser-Schlieren Study of the Dissociation of 1,1,1-Trifluoroethane: An Intrinsic Non-RRKM Process
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We report a shock-tube, laser-schlieren investigation of the molecular dissociation of the title trifluoroethane, CF3CH3 → CH2CF2 + HF, over very high temperatures, 1600-2400 K, and a wide range of sub-atmospheric pressures, 15-550 Torr. The density gradients are well fit by a simple two-reaction mechanism and accurate dissociation rates obtained. The results are compared with a k∞ calculated from a G3 TS for this molecular elimination, which is a superb fit to the available lower-T data and a reliable extrapolation of k∞ to high temperatures. The derived rate constants show a very deep falloff from, this extrapolation but surprisingly little variation with pressure. This peculiarity is so severe that RRKM calculations dramatically fail to account for the behavior. The dissociation seems to be a clear example of an intrinsic non-RRKM process (nonstatistical dissociation). This conclusion is strongly supported by the observation of double vibrational relaxation at both dissociating and nondissociating temperatures, an unambiguous demonstration of slow IVR. Using a simple model with division into two groups of states, the deep falloff is found to be consistent with a rate-controlling slow IVR, not with low collision efficiency. The model suggests an IVR rate of ~108 s-1 for dissociation energies.
- Kiefer,Katopodis,Santhanam,Srinivasan,Tranter
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p. 2443 - 2450
(2007/10/03)
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- Preparation of tri- and difluoromethylsilanes via an unusual magnesium metal-mediated reductive tri- and difluoromethylation of chlorosilanes using tri- and difluoromethyl sulfides, sulfoxides, and sulfones
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A new and efficient method for the preparation of tri- and difluoromethylsilanes using magnesium metal-mediated reductive tri- and difluoromethylation of chlorosilanes is reported using tri- and difluoromethyl sulfides, sulfoxides, and sulfones. The byproduct of the process is diphenyl disulfide. Since phenyl trifluoromethyl sulfone, sulfoxide, and sulfide are readily prepared from trifluoromethane (CF3H) and diphenyl disulfide, the method can be considered to be catalytic in diphenyl disulfide for the preparation of (trifluoromethyl)trimethylsilane (TMS-CF3) from non-ozone-depleting trifluoromethane.
- Prakash, G.K. Surya,Hu, Jinbo,Olah, George A.
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p. 4457 - 4463
(2007/10/03)
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- Anomalous elimination of HCl from 2-chloro-1,1-difluoroethane. Likely involvement of a 1,2-FCl interchange mechanism
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A novel 1,2-FCl interchange mechanism is proposed to be involved in the unexpected thermal conversion of CH2ClCHF2 to 1,2-difluoroethylene.
- Dolbier Jr., William R.,Romelaer, Raphaele,Baker, J.Marshall
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p. 8075 - 8077
(2007/10/03)
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- Chloropentafluoroethane hydrodechlorination over tungsten carbides: Influence of surface stoichiometry
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The relationship between the mode of activation and the catalytic properties of tungsten carbides was studied. Tungsten carbides were prepared by temperature-programmed reaction of WO3 with methane/hydrogen mixture and activated according to several thermal treatments by varying the temperature or the feed composition. The acid-base characteristic increased with the extent of decarburization of the surface. The surface properties of WC could be adjusted toward the formation of unsaturated compounds or alternatively toward hydrogenolysis compounds. However, the convergence observed in the temperature-programmed selectivity curves, whatever the initial C/W ratio, showed that the sample surfaces reach similar compositions by recarburization during reaction. Such acidic properties were involved in the dehydrohalogenation of chloropentafluoroethane responsible mainly for the formation of unsaturated compounds.
- Granger,Giraudon,Delannoy,Leclercq,Leclercq
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p. 358 - 362
(2007/10/03)
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- Super-electrophilic carbenes and the concept of Philicity
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Electron affinities and ionization potentials were calculated for a number of carbenes and compared with the carbene philicity scale mCXY defined by Moss. It is suggested that a two-dimensional rather than a one-dimensional scale is used to classify the carbenes. Examples of extremely electrophilic carbenes with electron affinities above 2 eV are difluorovinylidene with a singlet ground state and 4-oxo-2,3,5,6-tetrafluorocyclohexa-2,5-dienylidene with a triplet ground state. The reactivity of these carbenes towards small molecules under the conditions of matrix isolation is discussed. Copyright
- Sander, Wolfram,Koetting, Carsten,Huebert, Rolf
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p. 561 - 568
(2007/10/03)
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- Pyrolysis of 1-chloro-1,1-difluoroethane: Considerations about its molecular nature
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A new insight into the contested origin of the absence of radical reaction in the pyrolysis of CF2ClCH3 is given. This chain reaction would be too slow compared with the molecular reaction because of a too slow homogeneous initiation leading to a too fast wall recombination of the Cl atom chain carriers.
- Huybrechts,Van Assche
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p. 283 - 289
(2007/10/03)
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- Catalytic reaction of methane with CBrF3
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The catalytic reaction of CH4 with CBrF3 over Co, Cu and Mn ZSM-5 zeolites is described; major products (at low temperatures) are those expected for simple hydrodebromination: CH3Br and CHF3.
- Li, Kai,Kennedy, Eric,Dlugogorski, Bogdan,Howe, Russell
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p. 709 - 710
(2007/10/03)
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- Kinetic stability of 1,1,1-trifluoroethane
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1,1,1-Trifluoroethane has been decomposed in comparative rate single-pulse shock-tube experiments. The rate expression for elimination at ca. 2.5 bar and in the temperature range of 1050 to 1200 K has been found to be k(CF3 - GH → HF + CF2 = CH2) = 7.0 × 1014 exp(- 37260/T)s-1 The experimental conditions appear to be such that the unimolecular reaction is at the beginning of the fall-off region and we find that for step sizes down between 500 and 1000 cm-1 the high-pressure rate expression is in the range k(CF3 - CH3 → HF + CF2 = CH2) = 2.0 × 1015 exp(-38300/T) to 4 × 1015 exp(-39000/T)s-1 where the smaller rate parameters refer to the larger step size down. The results are compared with those from an earlier study and the anomalously high A-factor is noted. It is suggested that the existing rate expressions for the fluorinated ethanes may need to be reevaluated.
- Tsang, Wing,Lifshitz, Assa
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p. 621 - 628
(2007/10/03)
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- Novel catalysts effective for dehydrofluorination of CF3CH3 (HFC143a) into CF2CH2
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The catalytic dchydrofluorination of CF3CH3 into CF2CH2 was studied over various metal phosphates in a fixed-bed reactor. The Mg2P2O7 catalyst exhibited moderate activity, higher selectivity and greater stability. The active sites for CF2CH2 formation are weak acid sites of the catalysts.
- Li, Gong-Liang,Ishihara, Tatsumi,Nishiguchi, Hiroyasu,Moro-Oka, Yoshihiko,Takita, Yusaku
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p. 507 - 508
(2007/10/03)
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- Ion-Molecule Reactions of CF3+ with Simple Unsaturated Aliphatic Hydrocarbons at Near-Thermal Energy
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Ion-molecule reactions of CF3+ with C2H2, C2H4, and C3H6 have been studied at near-thermal energy (0.05 eV) by using an ion beam apparatus.Initial product ion distributions and reaction rate constants were determined and compared with previous beam and selected ion flow tube (SIFT) data.The CF3+/C2H2 reaction produces exclusively the electrophilic adduct C3H2F3+ ion.For C2H4 and C3H6, hydride abstraction and electrophilic addition followed by HF elimination or fluoride transfer occur in parallel.The branching ratios of the former and latter reactions are 0.29 +/- 0.04:0.71 +/- 0.06 for the CF3+/C2H4 reaction and 0.07 +/- 0.02:0.93 +/- 0.07 for the CF3+/C3H6 reaction.On the basis of theoretical calculations of potential energies for the CF3+/C2H2 and CF3+/C2H4 systems, the lack of the HF elmination channel in the CF3+/C2H2 reaction, whereas the lack of the initial adduct ion in the CF3+/C2H4 reaction, is attributed to the different stability of the intermediate adduct ions for HF elimination.The reaction rate constants were 0.45 x 1E-9, 1.3 x 1E-9, and 1.6 x 1E-9 cm3 s-1 for C2H2, C2H4, and C3H6, respectively, which correspond to 46percent, 120percent, and 130percent of calculated rate constants from Langevin theory or a parametrized trajectory model.Although there are significant discrepancies in the product ion distributions between the present beam experiment and the previous beam data, the product ion distributions and the reaction rate constants obtained here are in reasonable agreement with the previous SIFT data.
- Tsuji, Masaharu,Aizawa, Masato,Nishimura, Yukio
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p. 3195 - 3200
(2007/10/02)
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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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- Effect of fluorination on thiol reactivities. Reaction of 2,2,2-trifluoroethanethiol on Mo(110)
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The reactions of 2,2,2-trifluoroethanethiol on Mo(110) were studied using temperature-programmed reaction, Auger electron, and infrared spectroscopies. Most significant is the evolution at 265 K of tritluoroethyl radical from a saturation coverage of CF3CH2S-. The strong coverage dependence for trifluoroethyl radical evolution and models depicting trifluoroethyl thiolate orientation at saturation coverage strongly suggest that surface crowding plays a significant role in radical formation. The stability of the radical and the steric inhibition to finding an adsorption site explain the evolution of the radical into the gas phase. C-S bond hydrogenolysis, yielding trifluoroethane, and defluorination, yielding difluoroethylene, are of nearly equal importance in the reaction of trifluoroethyl thiolate, whereas C-S bond hydrogenolysis of ethyl thiolate to form ethane predominates. The C-S bond hydrogenolysis pathway is similar for the two thiols, occurring at approximately 300 K in both cases. Dehydrogenation and alkene elimination from CH3CH2S- occur at approximately 340 K, as the supply of surface hydrogen is depleted through hydrogen recombination. In contrast, defluorination and fluoroalkene elimination from CF3CH2S- occur over a wide temperature range, 200-520 K. The formation of difluoroethylene on Mo(110) is nearly thermoneutral, due to the comparable strengths of the C-F and Mo-F bonds and the stability of difluoroethylene.
- Napier,Friend
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p. 8750 - 8757
(2007/10/02)
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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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- KINETICS AND MECHANISM OF THE SYNTHESIS OF DIFLUOROBENZENES BY THERMAL REACTION OF DIFLUOROCARBENE WITH BUTADIENE
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Reaction of butadiene with difluorocarbene, resulting in the formation of difluorobenzenes, and its main steps have been systematically studied.The kinetics of thermal conversions of intermediately formed 2,2-difluorovinylcyclopropane and 2,2,3,3-tetrafluorovinylcyclobutane has been examined.The synthesis of difluorobenzenes has been optimized.The results obtained are used as a basis for domestic technology of production of difluorobenzenes.
- Shipilov, A. I.,Zabolot-skikh, V. F.,Nefedov, O. M.
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- HIGH-ENERGY TRANSFORMATIONS OF POLYFLUOROALKANES. IX. PYROLYSIS OF 1,1-DIFLUOROETHANE
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Kinetics of the unimolecular thermal dehydrofluorination of 1,1-difluoroethane in a flow reactor is reported. The first-order rate constant is determined: logk = (-60,000+/-2000)/4.569*T+13.33+/-0.10. 1,1-Difluoroethylene, as a by-product of the pyrolysis of 1,1-difluoroethane, is formed by a radical mechanism, for which a heterogeneous initiation stage is proposed. MNDO calculations show the predominant formation of the CH3-C.F2 radical at the initiation stage. For this radical, rate constants of unimolecular 1->2 and 2->1 hydrogen shifts are determined within the framework of the PPKM statistical theory.
- Mitin, P. V.,Golovin, A. V.,Grigor'eva, T. Yu.,Barabanov, V. G.
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- Infrared Laser-induced Chemistry of Chlorodifluoromethane-Silane Mixtures at Two Irradiating Wavelengths
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Chemical reactions induced by single- and two-wavelenght CO2 laser radiation in a mixture of silane and chlorodifluoromethane are initiated by the reaction between: CF2 and SiH4 and afford volatile carbonaceous products with C-H bonds, together with a solid deposit consisting of silicon carbide and highly reactive Si/C/H/F polymeric material.The results are in line with the reduction of the strong C-F bond of difluorocarbene and with the production of H2Si=CF2 silene as intermediate which undergoes dehydrofluorination and polymerization.
- Diaz, L.,Santos, M.,Sigueenza, C. L.,Simeonov, S. A.,Gonzalez-Diaz, P. F.,et al.
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p. 3907 - 3912
(2007/10/02)
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- Dehydrofluorination and dehydrogenation of fluorinated alkanes
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Fluorinated alkanes are converted into correspond-ing unsaturated dehydrofluorination products by contact with a catalyst bed containing γ-fluorided alumina in the presence of a co-reactant gas at a reaction temperature of from about 200°C to about 700°C, the catalyst bed having been prepared by the steps of (a) flowing air over a catalyst bed containing γ-alumina for a contact time of from about 5 seconds to about 150 seconds, at a temperature of from about 600°C to about 750°C, and (b) thereafter flowing hydrogen fluoride over the air-treated catalyst bed at elevated temperature to convert the γ-alumina to γ--fluorided alumina. The co-reactant gas contains oxygen, carbon dioxide or mixtures thereof. The γ-fluorided alumina-containing catalyst may also be utilized to convert 1,1-difluoroethane to its dehydrogenation product, vinylidene fluoride at a reaction temperature of from about 300°C to about 700°C.
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- CHEMICAL REACTIONS AND LASERS: ELEMENTARY STEPS AND COMPLEX SYSTEMS
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In recent years, various methods have been developed to observe and influence the course of chemical reactions using laser radiation.By selectively increasing the translational, rotational, and vibrational energies of the reaction partners with high intensity visible and UV lasers, direct insight can be gained into the molecular course of the breaking and the re-forming of chemical bonds.The production of free radicals by laser radiation can be used in chemical synthesis for the production of monomers.As example the kinetics of the UV-laser induced dehydrochlorination of CH3CClF2 is described.The application of linear and non-linear laser spectroscopic methods allows a non-intrusive observation of the interaction of transport processes with chemical reactions used with high temporal, spectral and spatial resolution.As a simple test system the ignition of O2-O3 mixtures by irradiation with a CO2 laser along the axis of a cylindrical vessel is considered.Mathematical simulation of the ignition process is simulated mathematically by solving the corresponding system of conservation equations.Experimental data are presented for velocity components of the flame front from IR-UV double resonance experiments and for the temperature history from infrared absorption measurements using tuneable diode lasers.
- Wolfrum, J.
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p. 567 - 575
(2007/10/02)
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