Kinetic and Mechanistic Study of the Reaction of CCl4with Prefluorided Chromia to Form CCl3F and CCl2F2

Farrokhnia, Abdolhadi; Sakakini, B.H.; Waugh, Kenneth C.

doi:10.1006/jcat.1998.1981

Cited by 13 publications

(8 citation statements)

References 11 publications

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“…The activation energy for mono chloro/fluoro exchange of CCl 4 is 65 kJ mol -1 . This is slightly higher than the value of 53 kJ mol -1 found here for CCl 3 F. Our previous paper 1 postulated that the ion exchange reaction proceeds by a Langmuir−Hinshelwood mechanism through a four-center intermediate.…”

Section: Resultsmentioning

confidence: 50%

“…It is clear from these figures that mono-exchange (producing CCl 2 F 2 ) and bi-exchange (producing CClF 3 ) occur simultaneously. Simultaneous mono- and bi-exchange had been observed previously with CCl 4 as the reactant 2 The temperature dependence of the rate production and curve fit (a) for CCl 2 F 2 , m / z = 85 and (b) for CClF 3 , m / z = 69.…”

Section: Resultsmentioning

confidence: 81%

“…Apparatus. The microreactor and gas-handling system have been previously reported . The microreactor is a U-shaped (30 cm long, 0.6 cm i.d.)…”

Section: Methodsmentioning

confidence: 99%

“…This mechanism (reactions 4−8) is based on our previously published work on the fluorination of CCl 4 in which we showed that the fluorination reaction proceeds by the exchange of the chlorine atom of the CCl 4 with the F atom/ion of the fluorided chromium (usually surface CrF 3 ). , The role of the HF was considered to be to refluoride the surface of the CrF 3 , which had been partially chlorided (reaction 6).…”

Section: Introductionmentioning

confidence: 99%

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A Kinetic and Mechanistic Study of the Cl/F Exchange Reaction of CCl₃F, CCl₂F₂, and CClF₃ with Prefluorided Chromia

Farrokhnia¹,

Sakakini²,

Waugh³

2002

J. Phys. Chem. B

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Chromium oxide has been fluorided to several monolayers depth by interaction with HF at 625 K. The interaction of CCl 3 F and CCl 2 F 2 with these surface chromium fluoride layers has been studied by temperatureprogrammed reaction. In the case of the reaction of CCl 3 F, mono-and bi-exchange occurs with the surface monolayer fluoride, forming CCl 2 F 2 and CClF 3 simultaneously at a peak maximum temperature of 520 K. Exchange with the subsurface fluoride layers occurs at a peak maximum temperature of 680 K, as the fluoride ions from the bulk migrate to the surface and chloride ions on the surface migrate inward. In both temperature regions, mono-exchange predominates by a factor of about 10 2 . Line-shape analysis of the temperature dependence of the rates of production of CCl 2 F 2 and CClF 3 gave activation energies of 53 and 54 kJ mol -1 for exchange with the surface fluoride, so the difference in rates must be the need for special dimer-type surface sites for the bi-exchange. The activation energy for exchange of F ions evolving from the bulk calculated by line-shape analysis is 83 kJ mol -1 for mono-exchange and 100 kJ mol -1 for bi-exchange. These higher values than those obtained by reaction with the surface fluoride ion derive from the added activation energy for migration of the fluoride ion from the bulk to the surface.

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Section: Resultsmentioning

confidence: 50%

Section: Resultsmentioning

confidence: 81%

“…Apparatus. The microreactor and gas-handling system have been previously reported . The microreactor is a U-shaped (30 cm long, 0.6 cm i.d.)…”

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A Kinetic and Mechanistic Study of the Cl/F Exchange Reaction of CCl₃F, CCl₂F₂, and CClF₃ with Prefluorided Chromia

Farrokhnia¹,

Sakakini²,

Waugh³

2002

J. Phys. Chem. B

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“…33 It was also observed that an increase in the Lewis acidity of oxides results from an interaction with CFCs. 34, 35 Corma et al concluded that for γ-Al 2 O 3 the total number of Lewis sites decreases with increasing fluorine content, but the concentration of strong Lewis acidic sites exhibits a maximum for fluorine concentrations between 2% and 4%. 36 Our FTIR spectroscopic study results of CO adsorption on γ-Al 2 O 3 samples pretreated with CF 3 CFCl 2 also demonstrate the strengthening of Lewis acidic sites (coordinatively unsaturated Al 3+ cations) upon CF 3 CFCl 2 chemisorption, especially after thermal decomposition of chemisorbed species.…”

Section: Discussionmentioning

confidence: 99%

FTIR Spectroscopic and Reaction Kinetics Study of the Interaction of CF₃CFCl₂ with γ-Al₂O₃

et al. 2000

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The interaction of CF3CFCl2 with γ-Al2O3 has been investigated by a combination of reaction kinetics experiments and FTIR spectroscopic studies. The reaction of fresh γ-Al2O3 with CF3CFCl2 at 573 K resulted in the fluorination of the γ-Al2O3 surface. The reaction also resulted in dehydroxylation of the γ-Al2O3 and an increase in both the number and strength of Lewis acid sites on the surface. The fluorinated γ-Al2O3 was catalytically active for the disproportionation of CF3CFCl2 to CF3CCl3 and CF3CF2Cl at 353 K. Adsorption of CF3CFCl2 on γ-Al2O3 at temperatures between 298 and 523 K resulted in the formation of surface trifluoroacetate species, which were stable up to 573 K. These species are likely to be the intermediates for the complete oxidation of CF3CFCl2 to CO and CO2. The transformation of γ-Al2O3 as a result of the CF3CFCl2 adsorption and reaction is discussed.

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Fluoride Catalysts: Their Application to Heterogeneous Catalytic Fluorination and Related Processes

Kemnitz

Winfield

2000

Advanced Inorganic Fluorides

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Kinetic and Mechanistic Study of the Reaction of CCl4with Prefluorided Chromia to Form CCl3F and CCl2F2

Cited by 13 publications

References 11 publications

A Kinetic and Mechanistic Study of the Cl/F Exchange Reaction of CCl₃F, CCl₂F₂, and CClF₃ with Prefluorided Chromia

A Kinetic and Mechanistic Study of the Cl/F Exchange Reaction of CCl₃F, CCl₂F₂, and CClF₃ with Prefluorided Chromia

FTIR Spectroscopic and Reaction Kinetics Study of the Interaction of CF₃CFCl₂ with γ-Al₂O₃

Fluoride Catalysts: Their Application to Heterogeneous Catalytic Fluorination and Related Processes

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Kinetic and Mechanistic Study of the Reaction of CCl4with Prefluorided Chromia to Form CCl3F and CCl2F2

Cited by 13 publications

References 11 publications

A Kinetic and Mechanistic Study of the Cl/F Exchange Reaction of CCl3F, CCl2F2, and CClF3 with Prefluorided Chromia

A Kinetic and Mechanistic Study of the Cl/F Exchange Reaction of CCl3F, CCl2F2, and CClF3 with Prefluorided Chromia

FTIR Spectroscopic and Reaction Kinetics Study of the Interaction of CF3CFCl2 with γ-Al2O3

Fluoride Catalysts: Their Application to Heterogeneous Catalytic Fluorination and Related Processes

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A Kinetic and Mechanistic Study of the Cl/F Exchange Reaction of CCl₃F, CCl₂F₂, and CClF₃ with Prefluorided Chromia

A Kinetic and Mechanistic Study of the Cl/F Exchange Reaction of CCl₃F, CCl₂F₂, and CClF₃ with Prefluorided Chromia

FTIR Spectroscopic and Reaction Kinetics Study of the Interaction of CF₃CFCl₂ with γ-Al₂O₃