The Influence of Cu and Al Additives on Reduction of Iron(III) Oxide: <i>In Situ</i> XRD and XANES Study

Булавченко, О. А.; Винокуров, З. С.; Saraev, Аndrey А.; Tsapina, Anna M.; Trigub, Alexander L.; Gerasimov, E. Yu.; Gladky, A. Yu.; Fedorov, A. P.; Yakovlev, V. А.; Каичев, В. В.

doi:10.1021/acs.inorgchem.8b03403

Cited by 23 publications

(15 citation statements)

References 44 publications

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“…The fraction of Fe 3+ cations decreases to approximately 27 % at 500 °C (Table ). The obtained results are in full agreement with our recent in situ study of the Cu 5 Fe 78 Al 17 catalyst by XANES and XRD . It was established that during heating in a CO flow, the iron‐containing phases were reduced to Fe 3 O 4 ‐spinel modified by Al 3+ cations, which contained Fe 3+ and Fe 2+ cations.…”

Section: Resultssupporting

confidence: 90%

“…The lattice parameter of the spinel is 8.333 Å. This value is between the lattice parameter of CuFe 2 O 4 (8.400 Å, ICSD 39132) and AlFe 2 O 4 (8.204 Å, ICSD 86571), which probably indicates the formation of a mixed oxide (Cu,Al,Fe) 3 O 4 –,. The phase quantification by the Rietveld refinement gives approximately 80 % of Fe 2 O 3 and 20 % of Cu x Al y Fe 3‐x‐y O 4 spinel for the Cu 10 Fe 74 Al 16 catalyst.…”

Section: Resultsmentioning

confidence: 91%

“…Our previous investigations of these systems by various methods showed that, at low concentrations, copper mainly forms CuO and CuFeO x clusters –,. These clusters are not detected by XRD.…”

Section: Resultsmentioning

confidence: 97%

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Kinetic and mechanistic study of CO oxidation over nanocomposite Cu−Fe−Al oxide catalysts

et al. 2020

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The oxidation of CO has been studied over FeÀ Al and CuÀ FeÀ Al oxide nanocomposite catalysts prepared by melting of copper, iron, and aluminum nitrates. It was shown that the addition of copper significantly increases the catalytic activity of the FeÀ Al nanocomposites. The catalysts were characterized by lowtemperature nitrogen adsorption, X-ray diffraction (XRD), and Xray photoelectron spectroscopy (XPS). It was found that the catalysts contain Fe 2 O 3 with the hematite structure modified by aluminum. Copper in the three-component catalyst is in the Cu 2 + state, forming CuO and CuFeO x clusters on the catalyst surface. An increase in the copper content leads to the formation of a Cu x Al y Fe 3-x-y O 4 spinel phase. In situ XPS study showed that a treatment of the catalysts in a CO flow leads to the reduction of both copper and iron cations into the metallic state. In contrast, a treatment in a CO/O 2 flow leads only to partial reduction of Cu 2 + to Cu 1 + , while Fe 3 + are not reduced. The tests of catalytic activity performed in a flow fixed bed reactor using a CO pulse technique showed that the light-off temperature in the oxidation of CO over the CuÀ FeÀ Al nanocomposite catalysts depends on the copper content. The minimal light-off temperature was achieved over the catalyst containing 5 wt% CuO. In addition, we performed kinetic measurements in a differential reactor and obtained the activation energy and the reaction orders with respect to the reactants. The reaction mechanism of the catalytic oxidation of CO and the origin of active species are discussed.

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Section: Resultssupporting

confidence: 90%

Section: Resultsmentioning

confidence: 91%

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Kinetic and mechanistic study of CO oxidation over nanocomposite Cu−Fe−Al oxide catalysts

et al. 2020

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“…[28] Recently, Ek et al [29] explored the facetdependent reactivity of VO x species on TiO 2 previously observed in the selective reduction of NO to NH 3 [30] by visualizing redox dynamic processes over (001) and (101) facets of the oxide applying combined atomic-resolution TEM and electron energy loss spectroscopy (EELS) under alternated oxidizing and reducing environments. By applying in situ spectroscopic [31][32][33] and atomic-resolution imaging [34][35][36] techniques to monitor redox properties under a reaction environment, new ways are opened to move towards a more complete understanding of the reactivity in oxide-catalyzed processes.…”

Section: Introductionmentioning

confidence: 99%

Insights into Redox Dynamics of Vanadium Species Impregnated in Layered Siliceous Zeolitic Structures during Methanol Oxidation Reactions

et al. 2019

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Supported transition metal catalysts have been extensively applied to oxidative and reductive processes. The understanding of surface speciation and active site‐support interactions in these materials play a substantial role in developing improved heterogeneous catalysts. Herein, a series of impregnated 3D ferrierite and 2D ITQ‐6 siliceous supports with variable loading of vanadium oxide was prepared. Chemical and structural properties of the materials were studied by X‐ray diffraction, N2 physisorption, inductively coupled plasma – optical emission spectrometry, X‐ray absorption, Fourier transform infrared and diffuse reflectance UV‐vis spectroscopies, and temperature‐programmed reduction with H2. Reactivity of the catalyst surface, associated with the incidence of isolated silanol groups, was found to be more effective when vanadium oxides were better dispersed and stabilized than increases in surface area. Differences in activation and the oxidation state dynamic behavior of active sites were then probed by methanol oxidation as a model reaction monitored by in situ FTIR spectroscopy and XANES/MS. By applying isothermal periods of reaction under non‐oxidizing atmosphere and regeneration of catalysts by O2, it was found that, even at distinct rates, all types of sites are accessible during reaction, since a complete reduction to V4+ was observed. However, reoxidation of sites to V5+ is limited and sensitive to the different vanadium species on the surface, and probably, the determinant factor of the distinct V5+/V4+ equilibrium reached for the catalysts when the reaction is carried out under constant oxidizing atmosphere.

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“…Earlier, we have already tested oxide catalyst systems based on copper and iron for the oxidation of CO [27], in which they showed high activity. Therefore, based on the literature data and previously obtained results, it seemed advisable to investigate copper-iron catalysts in the reduced form in the hydrogenation of furfural, since spinel structures can increase the overall activity of the copper catalyst [28].…”

Section: Introductionmentioning

confidence: 99%

Highly Active CuFeAl-containing Catalysts for Selective Hydrogenation of Furfural to Furfuryl Alcohol

et al. 2019

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CuFe-containing catalysts with different copper oxide content were prepared by fusion of metal salts. The obtained catalyst showed high activity in the hydrogenation of furfural to furfuryl alcohol (FA) in the batch reactor in the presence of isopropanol as a solvent at a temperature of 100 °C and a hydrogen pressure of 6.0 MPa. The yield of FA and furfural conversion are 97% and 98%, respectively. In the solvent-free reaction in the flow-type reactor; the most active catalyst Cu20Fe66Al14 leads to the 96% formation of FA with 100% conversion of furfural at liquid hourly space velocity (LHSV) = 1 h−1; 160 °C and a hydrogen pressure of 5.0 MPa during 30 h. According to the X-ray diffraction (XRD) method, the active component of the spent and fresh Cu20Fe66Al14 catalyst is the same and is represented by metallic copper and Fe3O4-type spinel. Using different methods, the formation of active sites was investigated.

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The Influence of Cu and Al Additives on Reduction of Iron(III) Oxide: In Situ XRD and XANES Study

Cited by 23 publications

References 44 publications

Kinetic and mechanistic study of CO oxidation over nanocomposite Cu−Fe−Al oxide catalysts

Kinetic and mechanistic study of CO oxidation over nanocomposite Cu−Fe−Al oxide catalysts

Insights into Redox Dynamics of Vanadium Species Impregnated in Layered Siliceous Zeolitic Structures during Methanol Oxidation Reactions

Highly Active CuFeAl-containing Catalysts for Selective Hydrogenation of Furfural to Furfuryl Alcohol

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