Thermal Isomerization of 1,1,2,2-Tetrafluoroethane (FC-134) to 1,1,1,2-Tetrafluoroethane (FC-134a) in the Presence of Hydrogen

Romelaer, Raphaele; Baker, and J. Marshall

doi:10.1021/ja002359t

Cited by 6 publications

(5 citation statements)

References 13 publications

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“…This lack of observation of CHF 2 CHF 2 in the CHF 3 pyrolyses is undoubtedly the result of its H 2 -promoted isomerization to CF 3 CH 2 F at these high temperatures. This isomerization, which does not occur thermally in the absence of H 2 , is the subject of the accompanying paper …”

Section: Resultsmentioning

confidence: 88%

“…Reports of fluorine atom shifts in carbon radical systems are rare, but such rearrangements are apparently feasible. − In the accompanying paper, UB3LYP/6-311+G(2df,2p)//UB3LYP/6-31G(d) calculations provided an estimated barrier ( E ⧧ ) of 29.2 kcal/mol for this rearrangement . On the basis of these calculations, we believe that the unimolecular 1,2-fluorine atom shift of CHF 2 CF 2 · should be competitive with its second, bimolecular H atom abstraction.…”

Section: Resultsmentioning

confidence: 88%

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Pyrolyses of Chlorodifluoromethane and Trifluoromethane in the Presence of Hydrogen. Mechanism and Optimization of Reaction Conditions

et al. 2001

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When CHClF 2 and CHF 3 are subjected to high-temperature, gas-phase flow pyrolysis in the presence of H 2 , they are converted, via a free radical chain mechanism, to CH 2 F 2 , CHF 2 CHF 2 , and CF 3 CH 2 F in good yield. Optimal conditions for pyrolysis of CHClF 2 involve a high conversion (92%) at 650 °C with an observed yield of products ) 18, 17, and 28%, respectively, whereas optimal conditions for CHF 3 involve a low conversion (24%) at 775 °C, but a higher yield of products (26, 6, and 39%, respectively).

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Section: Resultsmentioning

confidence: 88%

Section: Resultsmentioning

confidence: 88%

Pyrolyses of Chlorodifluoromethane and Trifluoromethane in the Presence of Hydrogen. Mechanism and Optimization of Reaction Conditions

et al. 2001

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“…It was also noted by Dolbier that the presence of H 2 in the pyrolytic mixture can isomerize 134 to 134a. 601 An alternative strategy proposed by Shields (ICI) prescribes subjecting the 134/134a mixture to a commercially available zeolite (AW-500, for example) at between 200 and 400 °C, though this method is only particularly suitable to reduce the 134 concentration from around 10 000 ppm to <20 ppm. 602 Rao and Subramanian (Du Pont) used their cubic CrF 3 catalyst to effect the disproportionation of a mixture of 124/ 124a (98.5/1.4) to 123 and 125.…”

Section: Kellner Et Al (Du Pontmentioning

confidence: 99%

“…The advantage of this invention in practice is that crude 114 / 114a can be dehydrohalogenated to 134 / 134a and that this mixture can then be isomerized to enrich the 134a fraction. It was also noted by Dolbier that the presence of H 2 in the pyrolytic mixture can isomerize 134 to 134a . An alternative strategy proposed by Shields (ICI) prescribes subjecting the 134 / 134a mixture to a commercially available zeolite (AW-500, for example) at between 200 and 400 °C, though this method is only particularly suitable to reduce the 134 concentration from around 10 000 ppm to <20 ppm …”

Section: Hydrofluorocarbons (Hfcs3rd Generation)mentioning

confidence: 99%

Fluorocarbon Refrigerants and their Syntheses: Past to Present

2020

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This Review chronicles the progress made in the field of small fluorocarbon synthesis since their invention in the early 1930s by Thomas Midgley, Jr., and his coworkers, with special focus on their application as refrigerants, foam expansion agents, aerosol propellants, and precision solvents. Divided into four generations of C1–C4 halocarbons from CFCs through HCFCs, HFCs, and HFOs, the merits and challenges of each will be discussed in the context of market demands, as well as the evolution of industrial manufacturing methods. Vital transformations, such as exchange (Swarts) fluorination, hydrodehalogenation, dehydrohalogenation, and additions (Kharasch or Prins) will feature prominently and will be discussed in detail, as well as catalysts therefor. Of the myriad of fluorocarbons described herein, the models which have reached particular commercial significance (such as chlorodifluoromethane and 1,1,1,2-tetrafluoroethane) are given special consideration as flag-bearers for the generation to which they belong. Regulatory constraints to which this industry is bound will be outlined in brief, as well as an introduction to safety designations and nomenclature put forth by the American Society for Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE). This Review includes predominantly works which can only be found in the patent literature, but should be of equal interest to both academic and industrial practitioners of the art as it centers on fundamentals of organofluorine chemistry, which could equally be applied to the synthesis of larger molecules and building blocks for other applications.

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“…However, experimental studies of the pyrolysis of CHF 2 -CHF 2 found that the major products were CF 3 CH 2 F (HFC 134a) and C 2 HF 3 under condition of low conversion (2-3%) at 973 K 34. This indicates that if C 2 HF 3 is formed via R14-R17, even larger quantities of CHF 2 -CHF 2 and HFC 134 should be observed.…”

mentioning

confidence: 99%

Synthesis of Vinylidene Fluoride via Reaction of Chlorodifluoromethane (HCFC-22) with Methane

Han

Kennedy

Mackie

et al. 2010

Ind. Eng. Chem. Res.

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The gas-phase reaction of CH4 and CHClF2 (HCFC-22, R22) has been studied in an alumina tubular reactor at atmospheric pressure and in the temperature range of 673−1073 K. The motivation of the investigation is to assess this process as a potential route for the treatment of CHClF2, as well as a technology for the synthesis of CH2CF2 (vinylidene fluoride, VDF). Under the conditions studied, the major products are C2F4, CH2CF2, HF, and HCl. Minor products detected include C2HF3, C2H2, CHF3, C2H3F, C2H2F4, CH2F2, C3F6, CH3Cl. A mechanistic interpretation of the results is proposed, including the reactions involved in the initial decomposition of CHClF2, those contributing to the activation of CH4 and developing the pathways leading to the formation of product species. The result of changing feed ratio experiments is consistent with the reaction mechanism developed. The introduction of small amounts of O2 improves the conversion of CH4 and formation of CH2CF2 markedly.

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Thermal Isomerization of 1,1,2,2-Tetrafluoroethane (FC-134) to 1,1,1,2-Tetrafluoroethane (FC-134a) in the Presence of Hydrogen

Cited by 6 publications

References 13 publications

Pyrolyses of Chlorodifluoromethane and Trifluoromethane in the Presence of Hydrogen. Mechanism and Optimization of Reaction Conditions

Pyrolyses of Chlorodifluoromethane and Trifluoromethane in the Presence of Hydrogen. Mechanism and Optimization of Reaction Conditions

Fluorocarbon Refrigerants and their Syntheses: Past to Present

Synthesis of Vinylidene Fluoride via Reaction of Chlorodifluoromethane (HCFC-22) with Methane

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