In situ XPS and MS study of methanol decomposition and oxidation on Pd(111) under millibar pressure range

Каичев, В. В.; Miller, A. V.; Prosvirin, Igor P.; Bukhtiyarov, Valerii I.

doi:10.1016/j.susc.2011.11.001

Cited by 43 publications

(53 citation statements)

References 51 publications

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“…The authors suggested that the palladium surface is deactivated by adsorbed oxygen species (O ads ) and that an oxygen-free metal surface, where ethene can dissociate, is necessary for a high activity [16]. Since carbon species produced via the hydrocarbon decomposition can dissolve in the Pd bulk and then segregate at the Pd surface [15,21,28], the temperature hysteresis may be due to a temperature-and time-dependent interplay of segregation and re-segregation of carbon and oxygen adsorbed species [16].…”

Section: Resultsmentioning

confidence: 99%

“…The first two peaks correspond to the carbon species adsorbed on the surface and dissolved in the Pd bulk [15,21,28]. Indeed, this temperature is sufficient for the dissociative adsorption of propylene, resulting in the formation of carbon species on the surface.…”

Section: Resultsmentioning

confidence: 99%

“…The reasons for the decrease or increase in activity of palladium were unraveled by X-ray photoelectron spectroscopy (XPS) and temperatureprogrammed reaction spectroscopy (TPRS). XPS is one of the powerful tools in the catalytic surface science to investigate both the surface composition and the nature of adsorbed species; while TPRS can provide direct information about catalytic properties of samples under study [19][20][21][22]. A Pd(5 5 1) single crystal was used as a model catalyst.…”

Section: Introductionmentioning

confidence: 99%

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Oxidation of propylene over Pd(5 5 1): Temperature hysteresis induced by carbon deposition and oxygen adsorption

et al. 2015

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a b s t r a c tThe oxidation of propylene over a Pd(5 5 1) single crystal surface has been studied by X-ray photoelectron spectroscopy (XPS) and temperature-programmed reaction spectroscopy during both heating and cooling in various oxygen/propylene mixtures. In all the experiments, the partial pressure of propylene was approximately 1 × 10 −7 mbar and the partial pressure of oxygen was varied to achieve molar oxygen/propylene ratios of 1, 3, 10, and 100. Under all these conditions, we observed a temperature hysteresis: temperature dependences of the catalyst activity and product distribution were different during heating and cooling. It was shown that the temperature hysteresis was due to concurrent accumulation of carbon and oxygen atoms on the palladium surface. At low temperatures, a high concentration of carbonaceous deposits detected by XPS resulted in a low catalytic activity due to blocking of the palladium surface. Increasing temperature led to full dehydrogenation of the carbonaceous species and dissolution of carbon atoms into subsurface palladium layers. As a result, even under oxygen-rich conditions, the formation of a PdC x phase was detected by XPS at 373 K. This process had no influence on the selectivity in the oxidation of propylene at least under UHV conditions. A shift of selectivity toward CO 2 was found to result from an increase in the oxygen concentration on the palladium surface. The state with a low catalytic activity in the oxidation of propylene was associated with palladium in the metallic state covered by carbon deposits. The high-active state of palladium was associated with palladium in the metallic state with a high concentration of chemisorbed oxygen and a moderate concentration of a surface oxide. Bulk PdO was not detected by XPS under all conditions used.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Oxidation of propylene over Pd(5 5 1): Temperature hysteresis induced by carbon deposition and oxygen adsorption

et al. 2015

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“…It should be noted that some reactions indeed can proceed via both the LangmuirHinshelwood and the Mars-van Krevelen mechanisms depending on experimental conditions and a catalyst type [65][66][67][68]. For instance, the oxidation of methane over Pt-based catalysts proceeds via the Langmuir-Hinshelwood mechanism, whereas over Pd-based catalysts, the oxidation of methane proceeds via the Mars-van Krevelen mechanism under the same experimental conditions [65].…”

Section: Discussionmentioning

confidence: 99%

Evolution of self-sustained kinetic oscillations in the catalytic oxidation of propane over a nickel foil

Каичев

Teschner

Saraev

et al. 2016

Journal of Catalysis

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The evolution of self-sustained reaction-rate oscillations in the catalytic oxidation of propane over a nickel foil has been studied in situ using X-ray photoelectron spectroscopy coupled with on line mass spectrometry and gas chromatography. Changes in the effective surface area and in the catalyst morphology under reaction conditions have been examined by scanning electron microscopy and a krypton adsorption technique. It is shown that the regular kinetic oscillations arise under oxygen-lean conditions. CO, CO 2 , H 2 , H 2 O, and propylene are detected as products.The conversion of propane oscillates in a range from 1% to 23%. During the half-periods with high activity, the main reaction pathway is the partial oxidation of propane: selectivity toward CO achieves 98%. In contrast, during the half-periods with low activity, the reaction proceeds through three competitive pathways: the partial oxidation of propane, the total oxidation of propane, and the dehydrogenation of propane to propylene. The driving force for the selfsustained kinetic oscillations is the periodic reoxidation of nickel. According to the Ni2p and O1s core-level spectra measured in situ, the high-active catalyst surface is represented by metallic nickel, whereas during the inactive half-periods the catalyst surface is covered with a thick layer of NiO. The intensity of O1s spectra follows the oscillations of O 2 in the gas phase during the oxidation of propane. It is found that during the induction period before the regular oscillations appear, a rough and porous structure develops because of strong reconstruction of the catalyst surface. The thickness of the reconstructed layer is approximately 10-20 µm. This process is accompanied with at least an 80-fold increase in the effective surface area compared with a clean, non-treated nickel foil, which undoubtedly leads to a drastic increase in the number of active sites. We believe that it is the main reason for the induction period always being  Corresponding author.E-mail address: vvk@catalysis.ru (V.V. Kaichev) 2 observed before the appearance of self-sustained oscillations in the catalytic oxidation of light hydrocarbons over catalysts with a low specific surface area (single crystals, foils, or wires).Moreover, without such reconstruction, the oscillations cannot arise due to low activity of such catalysts.

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“…Since in situ NAP XPS and XANES techniques can be used in the mbar pressure range [39,[54][55][56], the correct comparison of the spectroscopic data with the kinetics measurements performed in the flow reactor at atmospheric pressure (Table 2 and Fig. 3) could be possible only if there is no pressure gap.…”

Section: In Situ Nap Xps Xanes and Tpr Studymentioning

confidence: 99%

Selective oxidation of methanol to form dimethoxymethane and methyl formate over a monolayer V2O5/TiO2 catalyst

Каичев

Popova

Chesalov

et al. 2014

Journal of Catalysis

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address: vvk@catalysis.ru (V.V. Kaichev). A B S T R A C TThe methanol oxidation over highly dispersed vanadium oxide supported on TiO 2 (anatase) has been investigated by in situ Fourier transform infrared spectroscopy (FTIR), near ambient pressure X-ray photoelectron spectroscopy (NAP XPS), X-ray absorption near edge structure (XANES), and temperature-programmed reaction spectroscopy. The data were complimented with kinetics measurements in a flow reactor. It was found that at low temperatures dimethoxymethane competes with methyl formate, whereas the production of formaldehyde is greatly inhibited. FTIR shows the presence of non-dissociatively adsorbed molecules of methanol, as well as adsorbed methoxy, dioximethylene, and formate species under reaction conditions. According to the NAP XPS and XANES data, the reaction involves the reversible reduction of V 5+ cations, pointing that the vanadia lattice oxygen participates in the methanol oxidation through the classical Mars-van Krevelen mechanism. The detailed mechanism of the methanol oxidation on vanadia catalysts is discussed.

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In situ XPS and MS study of methanol decomposition and oxidation on Pd(111) under millibar pressure range

Cited by 43 publications

References 51 publications

Oxidation of propylene over Pd(5 5 1): Temperature hysteresis induced by carbon deposition and oxygen adsorption

Oxidation of propylene over Pd(5 5 1): Temperature hysteresis induced by carbon deposition and oxygen adsorption

Evolution of self-sustained kinetic oscillations in the catalytic oxidation of propane over a nickel foil

Selective oxidation of methanol to form dimethoxymethane and methyl formate over a monolayer V2O5/TiO2 catalyst

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