Influence of heat treatment conditions on the physicochemical and catalytic properties of a chromium-containing catalyst for tetrachloroethylene hydrofluorination to pentafluoroethane

Simonova, L. G.; Zirka, A. A.; Решетников, С. И.; Larina, T. V.; Litvak, G. S.; Пинаева, Л. Г.; Исупова, Л. А.

doi:10.1134/s0023158411030189

Cited by 6 publications

(1 citation statement)

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“…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. We have investigated the physicochemical properties of coprecipitated oxide systems 95% of Cr 2 O 3 -5% Al 2 O 3 , obtained by heat treatment in nitrogen and air in the temperature range 110-600°C, and their influence on the catalytic activity in the reaction of hydrocorisone perchloroethylene.…”

Section: Resultsmentioning

confidence: 96%

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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Section: Resultsmentioning

confidence: 96%