Interaction of O2, CO2, CO, C2H4 and C2H4O with Ag(110)

Backx, C.; Groot, C.P.M. De; Biloen, P.; Sachtler, W. M. H.

doi:10.1016/0039-6028(83)90383-7

Cited by 139 publications

(64 citation statements)

References 27 publications

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“…Additional criterion, which reinforced the assignment, was the temperature range in which they occurred. For example, assignment of an O1s feature at ~ 530.5 eV and a C1s feature at ~ 287.5 eV observed at T = 370 K to surface carbonates, CO 3,ads [6,[32][33][34][35], was based not only on the BE values, but also on their stability on silver surfaces at ambient temperatures only. At 420 K, carbonates decompose to adsorbed oxygen and CO 2 , which desorbs from the surface [6,[31][32][33][34].…”

Section: Resultsmentioning

confidence: 99%

“…A detailed comprehensive study of the nature of these atomic oxygen species by XPS, XAS, UPS and XANES can be found in our recent papers [9,10]. Briefly, nucleophilic oxygen has oxidic nature and is formed as result of silver surface reconstruction [9,10,[32][33][34][35] in the course of oxygen adsorption, while electrophilic oxygen is adsorbed on the silver surface without reconstruction. Electrophilic oxygen was identified as adsorbed oxygen by Rocca et al using HREELS [40,41] and Bukhtiyarov et al using angle-dependent XPS [42] on the basis of room-temperature experiments on O 2 adsorption at Ag(100) and Ag(111) single crystals surfaces.…”

Section: Resultsmentioning

confidence: 99%

“…This result can be explained by earlier reported activity of nucleophilic oxygen in total oxidation of ethylene only. Indeed, all attempts to produce ethylene oxide via titration of nucleophilic oxygen with ethylene have been unsuccessful [7,[33][34][35]. CO 2 and water were the only products of such a titration.…”

Section: Discussionmentioning

confidence: 99%

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Combined in situ XPS and PTRMS study of ethylene epoxidation over silver

Bukhtiyarov

Nizovskiĭ

Bluhm

et al. 2006

Journal of Catalysis

130

129

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Ethylene epoxidation over silver was investigated by combined in-situ X-ray photoelectron spectroscopy (XPS) and proton-transfer reaction mass-spectrometry (PTRMS) at temperatures from 300 to 520 K and in the pressure range from 0.07 to 1 mbar. Ethylene oxide was present among the reaction products at T ≥ 420 K and P ≥ 0.3 mbar. The catalytically active surface contains two oxygen species -nucleophilic and electrophilic oxygen. The observed correlation between the abundance of electrophilic oxygen and the yield of ethylene oxide expressed as C 2 H 4 O partial pressure indicates that namely this oxygen species oxidizes ethylene to ethylene oxide. Opposite trend is observed for nucleophilic oxygen: the higher is the abundance of this species, the lower is the yield of ethylene oxide. This result is in line with the known fact that nucleophilic oxygen due to its oxidic nature is active in total oxidation of ethylene to CO 2 and H 2 O. The low activity of silver at T < 420 K is caused by the presence of carbonates and carbonaceous residues at the silver surface that reduce the available silver surface area for the catalytic reaction. Reduction of the surface area available for the formation of active species due to accumulation of the embedded oxygen species explains also the decrease of the rate of ethylene oxide formation with time observed for T ≥ 470 K.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Combined in situ XPS and PTRMS study of ethylene epoxidation over silver

Bukhtiyarov

Nizovskiĭ

Bluhm

et al. 2006

Journal of Catalysis

130

129

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“…Different oxygen species have been detected as a result of oxygen adsorption on silver [19,20,25±27], some of which are responsible for partial, and some for complete oxidation reactions. Depending on temperature, oxygen adsorbs dissociatively on silver surfaces [23,24,28±31] and its adsorption is followed by the formation of oxide and subsurface oxygen [25,32]. Oxygen-covered Ag surfaces were found to be more reactive than clean metal surfaces.…”

Section: Introductionmentioning

confidence: 99%

“…Oxygen-covered Ag surfaces were found to be more reactive than clean metal surfaces. For example, while CO does not react with clean Ag surfaces, it reacts readily at room temperature to form CO 2 with oxygen-covered silver surfaces [32]. However, the role of various oxygen species in oxidation reactions is not well understood.…”

Section: Introductionmentioning

confidence: 99%

Deep oxidation of methane over zirconia supported Ag catalysts

Kundakovic

Flytzani‐Stephanopoulos

1999

Applied Catalysis A: General

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Zirconia supported silver catalysts were studied for deep oxidation of methane. The catalyst structure was examined by XRD, XPS, STEM-EDX, HR-TEM and UV±Vis spectroscopy and related to the catalyst activity. Methane conversion strongly depends on Ag state and dispersion. At low Ag loading (<2 at%), small Ag particles (<5 nm) have low activity. The turnover frequency for methane oxidation increases as the Ag particle size increases from 5 to 10 nm as determined from HRTEM, while the activation energy remains the same. Ag ion-exchanged ZSM-5 zeolite materials, containing Ag in highly dispersed state as isolated Ag were studied for comparison. High conversion of methane was found only in zeolite catalysts containing a large amount of silver, some of which was in particle form. The reaction rate on zirconia-supported Ag particles is 0.77 order in methane and 0.37 order in oxygen. The reaction products, carbon dioxide and water, do not affect the methane oxidation rate in levels up to of 1.7 and 3.5 mol% in the feedgas, respectively. The active phase under reaction conditions for both low and high Ag loading is the oxygen covered metallic Ag surface, as was con®rmed by XPS and UV±Vis spectrometry. # 1999 Elsevier Science B.V. All rights reserved.

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