An in situ cell for investigation of the catalyst structure using synchrotron radiation

Велигжанин, А. А.; Zubavichus, Ya. V.; Чернышов, А. А.; Trigub, Alexander L.; Khlebnikov, A.S.; Nizovskiĭ, A. I.; Khudorozhkov, Alexander K.; Beck, Irene E.; Bukhtiyarov, V. I.

doi:10.1007/s10947-010-0186-9

Cited by 14 publications

(12 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The XANES study was performed at the Structural Materials Science beamline at the Kurchatov Synchrotron Radiation Source (National Research Center “Kurchatov Institute”, Moscow, Russia). The experimental station was described in detail elsewhere . The spectra were obtained at the Cu K-edge in the transmission mode using a channel-cut Si(111) monochromator.…”

Section: Methodsmentioning

confidence: 99%

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

et al. 2019

View full text Add to dashboard Cite

The reduction of Fe-based nanocomposite catalysts doped with Al and Cu has been studied using in situ X-ray diffraction (XRD), in situ X-ray absorption near-edge structure (XANES), and temperature-programmed reduction (TPR) techniques. The catalysts have been synthesized by melting of iron, aluminum, and copper salts. According to XRD, the catalysts consist mainly of Fe2O3 and Al2O3 phases. Alumina is in an amorphous state, whereas iron oxide forms nanoparticles with the protohematite structure. The Al3+ cations are partially dissolved in the Fe2O3 lattice. Due to strong alumina–iron oxide interaction, the specific surface area of the catalysts increases significantly. TPR and XANES data indicate that copper forms highly dispersed surface CuO nanoparticles and partially dissolves in iron oxide. It has been shown that the reduction of iron(III) oxide by CO proceeds via two routes: a direct two-stage reduction of iron(III) oxide to metal (Fe2O3 → Fe3O4 → Fe) or an indirect three-stage reduction with the formation of FeO intermediate phases (Fe2O3 → Fe3O4 → FeO → Fe). The introduction of Al into Fe2O3 leads to a decrease in the rate for all reduction steps. In addition, the introduction of Al stabilizes small Fe3O4 particles and prevents further sintering of the iron oxide. The mechanism of stabilization is associated with the formation of Fe3–x Al x O4 solid solution. The addition of copper to the Fe–Al catalyst leads to the formation of highly dispersed CuO particles on the catalyst surface and a mixed oxide with a spinel-type crystalline structure similar to that of CuFe2O4. The low-temperature reduction of Cu2+ to Cu0 accelerates the Fe2O3 → Fe3O4 and FeO → Fe transformations but does not affect the Fe3O4 → FeO/Fe stages. These changes in the reduction properties significantly affect the catalytic performance of the Fe-based nanocomposite catalysts in the low-temperature oxidation of CO.

show abstract

Section: Methodsmentioning

confidence: 99%

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

et al. 2019

View full text Add to dashboard Cite

show abstract

“…According to EXAFS (data not shown), the local environment of Pt atoms in the as-prepared catalyst includes at least three well resolved coordination spheres, namely, Pt−O (5.3, 2.00 Å the first oxygen shell), Pt···Pt (5.6, 3.07 Å), and Pt···O (6.5, 3.66 Å the second oxygen shell) (the values in parentheses are best-fit coordination numbers and interatomic distances), which also correspond fairly well to crystallographic parameters of trigonal α-polymorph of PtO 2 . 37 As we mentioned above, the active component in such a catalyst should exhibit a high redox lability 6 and can easily change its state, depending on the composition of the reaction medium. Indeed, the treatment in the CH 4 + O 2 reaction mixture (CH 4 /O 2 ratio of 2) at 400°C reduces the Pt 4+ ions to metallic platinum: the corresponding XANES spectrum measured in situ agrees completely with the spectrum of Pt metal (Figure 1b).…”

Section: Resultsmentioning

confidence: 99%

Concentration Hysteresis in the Oxidation of Methane over Pt/γ-Al₂O₃: X-ray Absorption Spectroscopy and Kinetic Study

et al. 2015

View full text Add to dashboard Cite

It is found that CH 4 oxidation over Pt/Al 2 O 3 catalyst at 330− 460°C can stably proceed via two distinctly different regimes at identical feed gas composition: "low activity regime" and "high activity regime". Switching between the regimes depends on the O 2 concentration and the direction of its change. For the reaction mixture with constant methane concentration of 1%, the incremental decrease in O 2 concentration from 2.5% (O 2 /CH 4 ∼ 2.5, lean conditions) to ∼1% (O 2 /CH 4 ∼ 1, stoichiometric or rich conditions) results in the catalyst activation and its switching to the high activity regime. The catalyst remains active upon further incremental increase in O 2 concentration until reaching O 2 /CH 4 ∼ 2, when switching to low activity regime takes place. Such responses of the catalyst activity to the changes in the feed gas composition result in the appearance of the pronounced concentration hysteresis. The evident correlation between in situ X-ray absorption spectroscopy and catalytic data strongly suggests that the switching of the catalyst between low activity regime and high activity regime, which causes the concentration hysteresis, stems from the change in the electronic state of Pt particles. According to in situ XANES data, the electron density on the Pt particles decreases in the low activity regime, as evidenced by an increased Pt-L 3 white line intensity. In contrast, switching the catalyst to high activity regime is accompanied by a decrease in the white line intensity, indicating the electron density increase. In turn, the changes in the Pt electronic state are attributable to changes in the O/Pt surface ratio or formation/decomposition of a two-dimensional layer of surface Pt oxide triggered by variation of oxygen concentration in the reaction mixture. The addition of highly reactive CO or H 2 to the reaction mixture shifts the hysteresis loop toward higher oxygen concentration as a result of consuming oxygen in H 2 or CO oxidation, which decreases the effective oxygen concentration. In contrast to this, the increase in the methane concentration widens the hysteresis window, presumably because of the different stoichiometry of CH 4 oxidation upon catalyst activation (when partial CH 4 oxidation prevails) and deactivation (when total oxidation of CH 4 predominates).

show abstract

“…XAFS and XRD experiments were carried out at the "Structural Materials Science" beamline of the Kurchatov synchrotron radiation source [32,33] equipped by a dedicated in situ cell [34] with a high-temperature and reactive gas inlet systems. Eu L 3 -edge XAFS spectroscopy in situ was applied to monitor the chemical state of Eu atoms and changes in their surroundings during the treatment.…”

Section: Methodsmentioning

confidence: 99%

Investigation into the Palladium‐Europium Acetate Reductive Decomposition with Synchrotron Radiation‐Based X‐ray Diffraction and X‐ray Absorption Spectroscopy

Khramov¹,

Belyakova²,

Murzin³

et al. 2014

Zeitschrift anorg allge chemie

View full text Add to dashboard Cite

Abstract. The reductive decomposition of the complex Pd 2 Eu 2 (μ,η 2 -OOCMe) 2 (μ-OOCMe) 8 (H 2 O) 2 ·(HOOCMe) 2 upon heating from room temperature to 500°C in a hydrogen atmosphere was investigated by in situ synchrotron radiation-based X-ray absorption fine structure spectroscopy (XAFS) including observations of X-ray near-edge structure (XANES) and extended absorption fine structure (EXAFS) at Pd K-and Eu L 3 -edges and synchrotron X-ray diffraction (XRD). The Pd-Eu 2 O 3 nanocomposite was found to be the final thermolysis

show abstract

An in situ cell for investigation of the catalyst structure using synchrotron radiation

Cited by 14 publications

References 19 publications

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

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

Concentration Hysteresis in the Oxidation of Methane over Pt/γ-Al₂O₃: X-ray Absorption Spectroscopy and Kinetic Study

Investigation into the Palladium‐Europium Acetate Reductive Decomposition with Synchrotron Radiation‐Based X‐ray Diffraction and X‐ray Absorption Spectroscopy

Contact Info

Product

Resources

About

An in situ cell for investigation of the catalyst structure using synchrotron radiation

Cited by 14 publications

References 19 publications

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

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

Concentration Hysteresis in the Oxidation of Methane over Pt/γ-Al2O3: X-ray Absorption Spectroscopy and Kinetic Study

Investigation into the Palladium‐Europium Acetate Reductive Decomposition with Synchrotron Radiation‐Based X‐ray Diffraction and X‐ray Absorption Spectroscopy

Contact Info

Product

Resources

About

Concentration Hysteresis in the Oxidation of Methane over Pt/γ-Al₂O₃: X-ray Absorption Spectroscopy and Kinetic Study