Properties of Chromium (III) Oxides Involved in the Catalytic Gas Phase Fluorination of CF3CH2Cl

Brunet, Sylvette; Boussand, B.; Martin, D.

doi:10.1006/jcat.1997.1806

Cited by 21 publications

(7 citation statements)

References 15 publications

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“…Indeed the chromium atoms need to have oxygen in their vicinity in order to have good reversible oxidable properties. This provides labile fluorine atoms which constitute the nucleophilic species for the Cl/ F exchange [11,12]. The catalytic performances of the chromium based catalysts were improved by the presence of small amounts of zinc (Zn/(Zn ?…”

Section: Resultsmentioning

confidence: 99%

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Catalytic Fluorination of Various Chlorinated Hydrocarbons by HF and a Chromium Based Catalyst: Effect of the Presence of Zinc

et al. 2010

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International audienceThe Cl/F exchange of chlorinated hydrocarbons with HF was carried out in the gas phase (P = 1 atm. and T = 380 A degrees C) on chromium catalysts doped with zinc. A promoting effect of zinc has been found for various chlorinated hydrocarbons. This positive effect was more significant for CF(3)CH(2)Cl than for CF(3)CHCl(2) or CH(2)Cl(2). CF(3)CH(2)Cl was less reactive than the two other reactants. The promoting effect observed for an atomic ratio Zn/(Zn + Cr) = 0.15 was higher with a low (Zn + Cr) content, which corresponds to a better dispersion of the different elements on the surface. The presence of zinc is supposed to promote the dispersion of chromium and to favour its fluorination to form the centers which are active in Cl/F exchange and were characterized in XPS by energies corresponding to the presence of "CrOF" and "Cr-F" species

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Section: Resultsmentioning

confidence: 99%

“…To be active, a chromium based catalyst must have some specific properties. Our previous studies [9][10][11][12][13] indicated that to be active, the chromium species must be reversibly oxidizable [9]. This corresponds also to the presence of Cr VI in the initial material [9,10].…”

Section: Introductionmentioning

confidence: 93%

Catalytic Fluorination of Various Chlorinated Hydrocarbons by HF and a Chromium Based Catalyst: Effect of the Presence of Zinc

et al. 2010

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“…In the literature it is noted that the activity of Cr-catalysts of the gas-phase fluorination depends on chromium oxidation state [6]. We have shown [12] that in Cr-Al catalysts for the fluorination of chromium oxidation state of Cr depend essentially on the conditions of heat treatment: temperature and composition of the gas medium.…”

Section: Resultsmentioning

confidence: 70%

“…The most promising in this regard are chladones of the ethane row, namely, pentafluoroethane CHF 2 -CF 3 (HFC-125), which is produced by the gas-phase catalytic hydrofluorination of perloroethylene Cl 2 C=CCl 2 . A fluorination catalyst based on of an amorphous Cr (III) compounds in combination with promoting and stabilizing admixtures of aluminum, magnesium, nickel, zinc and others [5,6]. Rare-earth metal oxides are used as promoters also, namely, lanthanum [7], scandium [8,9], and yttrium [10,11].…”

Section: Introductionmentioning

confidence: 99%

Chromium-based catalyst for HFC-125 synthesis: promoters effect

Решетников

Simonova

Zirka

et al. 2016

IOP Conf. Ser.: Mater. Sci. Eng.

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Abstract.A variation of promoters, including rare-earth elements, allows to control of the specific surface and, perhaps, oxidation state of chromium and, consequently, catalyst activity and selectivity of chromium-based catalyst for HFC-125. To improve the catalytic properties of the 15% Cr 2 O 3 -85% -Al 2 O 3 oxide system were added promoters (Ni or Cu or Co) in an amount of 5 wt% in terms of oxides. It was found that additional promotion Cr-Al samples by nickel and copper allow to increase the specific surface area of about 25-40% and the activity increased about 2 times. Modification of cobalt resulted in a decrease of the surface by 20% and the activity decreased by about 2 times. IntroductionVarious rare-earth metal oxides were widely investigated as promoters of heterogeneous catalysts for enhancing their activity, selectivity, and stability [1]. In particular, the ceria-containing catalysts use for diesel soot combustion and the reduction NO x [2,3] hydrogen purification reactions, namely the water gas shift reaction [4] and etc. It is known, that the promoters affect the textural characteristics: specific surface area, pore diameter, and on the electronic state of the active component. Despite the large number of works, studying the role of promoters in the formation of the main characteristics of catalysts and their role in the formation of the active sites of the catalyst are still unclear.In recent decades, considerable efforts have been focused on the synthesis of chladones, having zero ozone depletion potential. The most promising in this regard are chladones of the ethane row, namely, pentafluoroethane CHF 2 -CF 3 (HFC-125), which is produced by the gas-phase catalytic hydrofluorination of perloroethylene Cl 2 C=CCl 2 . A fluorination catalyst based on of an amorphous Cr (III) compounds in combination with promoting and stabilizing admixtures of aluminum, magnesium, nickel, zinc and others [5,6]. Rare-earth metal oxides are used as promoters also, namely, lanthanum [7], scandium [8,9], and yttrium [10,11]. However, systematic studies of the mechanism of influence of promoters on the catalytic properties of chromium-containing fluorination catalysts are absent. These issues are of great scientific and practical interest.In this work, we studied chromium-containing catalyst (~15% Cr 2 O 3 -85% -Al 2 O 3 ) and the effect of promoters (~5% Ni, Cu and Co) on physicochemical and catalytic properties of the catalysts for the gas-phase hydrofluorination of perchloroethylene to pentafluoroethane (chladone HFC-125). Kinetic regularities of the reaction were also considered.

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“…Consequently, Cr 2 O 3 was partially converted to CrOxFy by HF. It was suggested that CrOxFy is the active species in dehydrofluorination reactions [27,28,29]. Therefore, Cr 2 O 3 exhibits stable activity in HF atmosphere.…”

Section: Resultsmentioning

confidence: 99%

Solution Combustion Synthesis of Cr2O3 Nanoparticles and the Catalytic Performance for Dehydrofluorination of 1,1,1,3,3-Pentafluoropropane to 1,3,3,3-Tetrafluoropropene

Wang

Han

et al. 2019

Molecules

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Cr2O3 nanoparticles were prepared by solution combustion synthesis (SCS) with chromium nitrate as the precursor and glycine as the fuel. Commercial Cr2O3 and Cr2O3 prepared by a precipitation method were also included for comparison. The morphology, structure, acidity and particle size of fresh and spent Cr2O3 catalysts were investigated by techniques such as XRD, SEM, TEM, BET and NH3-TPD. In addition, catalytic performance was evaluated for the dehydrofluorination of 1,1,1,3,3-pentafluoropropane (CF3CH2CHF2, HFC-245fa) to 1,3,3,3-tetra-fluoropropene (CF3CH=CHF, HFO-1234ze). The catalytic reaction rate of Cr2O3 prepared by SCS method is as high as 6 mmol/h/g, which is about 1.5 times and 2 times higher than that of precipitated Cr2O3 and commercial Cr2O3, respectively. The selectivity to HFO-1234ze for all the catalysts maintains at about 80%. Compared with commercial and precipitated Cr2O3, Cr2O3-SCS prepared by SCS possesses higher specific surface area and acid amount. Furthermore, significant change in the crystal size of Cr2O3 prepared by SCS after reaction was not detected, indicating high resistance to sintering.

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Properties of Chromium (III) Oxides Involved in the Catalytic Gas Phase Fluorination of CF3CH2Cl

Cited by 21 publications

References 15 publications

Catalytic Fluorination of Various Chlorinated Hydrocarbons by HF and a Chromium Based Catalyst: Effect of the Presence of Zinc

Catalytic Fluorination of Various Chlorinated Hydrocarbons by HF and a Chromium Based Catalyst: Effect of the Presence of Zinc

Chromium-based catalyst for HFC-125 synthesis: promoters effect

Solution Combustion Synthesis of Cr2O3 Nanoparticles and the Catalytic Performance for Dehydrofluorination of 1,1,1,3,3-Pentafluoropropane to 1,3,3,3-Tetrafluoropropene

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