Halogen-promoted γ-alumina Part II. The catalytic dehydrochlorination of 1,1,1-trichloroethane at room temperature on chlorinated γ-alumina

Thomson, John F.; Webb, G.; Winfield, John M.

doi:10.1016/0304-5102(91)80092-h

Cited by 30 publications

(3 citation statements)

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“…However, it is well established that CH 3 CCl 3 in the presence of solid aluminium(III) chloride undergoes rapid dehydrochlorination at room temperature with concurrent formation on the inorganic surface of a purple organic layer which contains partially dehydrochlorinated oligomers, derived from the primary dehydrochlorinated product, 1,1-dichloroethene [17,18]. Similar behaviour has been observed also on the Brönsted and Lewis acid, g-alumina that had been chlorinated using carbon tetrachloride [19]. On SF 4 -fluorinated g-alumina, these reactions are accompanied by the fluorination of CH 3 CCl 3 to give the HCFC, CH 3 CCl 2 F, an observation that was crucial in the use of the material as a catalyst for room temperature halogen exchange [11,20].…”

Section: Resultsmentioning

confidence: 52%

“…Scheme 2. Behaviour of CH 3 CCl 3 on SF 4 -fluorinated g-alumina [19,20]. On the basis of our previous model for supported organic layer catalysts [20], it is concluded that both fluorinated precursors have the ability to oligomerise CH 2 CCl 2 (reaction ii in Scheme 2) hence forming an organic layer supported on the partially fluorinated surface that is able to trap CH 3 CCl 3 at the surface.…”

Section: Resultsmentioning

confidence: 97%

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γ-Alumina-supported boron trifluoride: Catalysis, radiotracer studies and computations

Klapötke¹,

McMonagle²,

Spence³

et al. 2006

Journal of Fluorine Chemistry

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Section: Resultsmentioning

confidence: 52%

Section: Resultsmentioning

confidence: 97%

γ-Alumina-supported boron trifluoride: Catalysis, radiotracer studies and computations

Klapötke¹,

McMonagle²,

Spence³

et al. 2006

Journal of Fluorine Chemistry

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“…Thomson et al , employed tracer techniques to differentiate the exchange activity of the halogen deposited on the γ-alumina as a result of conditioning. They found two kinds of chloride on the surface, (i) a mobile chloride which was very active toward exchange and which could be transferred into the gas molecule and (ii) an inert chloride which was so strongly bound in the solid that it was incapable of undergoing any exchange reaction.…”

Section: Resultsmentioning

confidence: 99%

Surface Characterization of Chromia for Chlorine/Fluorine Exchange Reactions

et al. 2005

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The dismutation of CCl(2)F(2) was used to probe the effect of halogenation of chromia by Cl/F exchange reactions to find out the difference between the halogenated inactive and active catalysts. The heterogeneous reactions were performed in a continuous flow Ni reactor and also under simulated reaction conditions in a reactor where after the reaction X-ray photoelectron spectroscopy (XPS) and X-ray excited Auger electron spectroscopy (XAES) analyses are possible without air exposure of the catalyst, i.e., under so-called "in situ" conditions. The Cr(III) 2p XP spectra, which revealed multiplet splitting features and satellite emission, were used for chemical analysis by using a simple evaluation procedure which neglects this inherent complexity. Chemical analysis was also applied by using chemical state plots for Cr 3s in order to cross-check Cr 2p related results. Both ex and in situ XPS show that as soon as Cr(2)O(3) is exposed to CCl(2)F(2) at 390 degrees C fluorination as well as chlorination takes place at the catalyst surface. When the XPS surface composition reaches approximately 4 at. % fluorination and 6 at. % chlorination, maximum catalytic activity was obtained. Application of longer reaction times did not change significantly the obtained surface composition of the activated chromia. The fluorination and chlorination of chromia was further investigated by various HF and HCl treatments. The activated chromia samples and the Cr(2)O(3), Cr(OH)(3), CrF(2)OH, CrF(3) x H(2)O, alpha-CrF(3), beta-CrF(3), and CrCl(3) reference samples with well-known chemical structures were also characterized by X-ray absorption near edge structure (XANES), time-of-flight secondary ion mass spectroscopy (TOF-SIMS), pyridine-FTIR, wet chemical (F and Cl) analysis, X-ray powder diffraction (XRD), and surface area (BET) analysis. The results suggest that the formation of chromium oxide chloride fluoride species, e.g., chromium oxide halides, at the surface is sufficient to provide catalytic activity. The presence of any CrF(3) and/or CrCl(3) phases on the activated chromia samples was not found.

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CFC alternatives and new catalytic methods of synthesis

Webb¹,

Winfield²

1995

Chemistry of Waste Minimization

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Halogen-promoted γ-alumina Part II. The catalytic dehydrochlorination of 1,1,1-trichloroethane at room temperature on chlorinated γ-alumina

Cited by 30 publications

References 16 publications

γ-Alumina-supported boron trifluoride: Catalysis, radiotracer studies and computations

γ-Alumina-supported boron trifluoride: Catalysis, radiotracer studies and computations

Surface Characterization of Chromia for Chlorine/Fluorine Exchange Reactions

CFC alternatives and new catalytic methods of synthesis

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