Study of the Real Structure of Silver Supported Catalysts of Different Dispersity

Tsybulya, S. V.; Kryukova, G. N.; Goncharova, S. N.; Shmakov, A. N.; Бальжинимаев, Б. С.

doi:10.1006/jcat.1995.1160

Cited by 63 publications

(39 citation statements)

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“…It is also known that the ethylene epoxidation rate over Ag/Al 2 O 3 catalysts increases when the Ag particle size increases above 50 nm. Tsybulya et al [39] correlated the proportionately lower number of grain boundaries in these large Ag particles (>50 nm) with the epoxidation activity. Their result shows the importance of intergrain boundaries of silver particles for the reactivity of Ag.…”

Section: Discussionmentioning

confidence: 99%

“…This drop in activity has been attributed to the increased rate of hydrocarbon combustion at higher Ag loading, but the reasons for the observed behavior are not clear. Related to this is the observed dependence of the ethylene epoxidation rate on Ag particle size [39]. The ethylene epoxidation rate increases as silver particle size increases above 50 nm [39].…”

Section: Introductionmentioning

confidence: 86%

“…Related to this is the observed dependence of the ethylene epoxidation rate on Ag particle size [39]. The ethylene epoxidation rate increases as silver particle size increases above 50 nm [39]. Also, the ethylene oxide deep oxidation rate to carbon dioxide is higher on small Ag particles (16 nm) than on large (100 nm) particles [40].…”

Section: Introductionmentioning

confidence: 92%

“…the (1 1 1) faces are relatively inert compared to the (1 1 0) and (1 0 0) faces [23]. It is also known that the ethylene epoxidation rate over Ag/Al 2 O 3 catalysts increases when the Ag particle size increases above 50 nm, and this can be related to the structure of Ag particles [39]. Structural differences between low-and highAg-containing samples may explain their different catalytic behavior in the complete oxidation of methane.…”

Section: Catalyst Characterizationmentioning

confidence: 99%

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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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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 86%

Section: Introductionmentioning

confidence: 92%

Section: Catalyst Characterizationmentioning

confidence: 99%

See 2 more Smart Citations

Deep oxidation of methane over zirconia supported Ag catalysts

Kundakovic

Flytzani‐Stephanopoulos

1999

Applied Catalysis A: General

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“…Sajkowski and Boudart have suggested that the epoxidation reaction is structure-insensitive, which would imply that there is little need to tune the Ag morphology [5]. However, several studies have shown that particle size does affect the catalyst performance [6][7][8][9]. Wu and Harriott reported that increasing the Ag particle size from 6 to 50 nm caused a 3-fold increase in the EO selectivity [6].…”

Section: Introductionmentioning

confidence: 94%

Effect of Preparation Conditions on Ag Catalysts for Ethylene Epoxidation

2009

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The effect of calcination of silver catalysts supported on foamed monoliths was examined for the epoxidation of ethylene. Previous results suggested that calcination at 673 K for 3 h would give a maximum conversion. Further study revealed that calcination for [3 h reduced the catalyst surface area and therefore the conversion seen in reactor studies. This phenomenon has been attributed to sintering, with the migration of Ag from mesopores of the catalysts to macropore regions and the eventual formation of a Ag film covering the walls of the macropores. Studies of the metal loading showed that a tradeoff exists between metal loading and calcination time. Increasing the amount of silver can have a detrimental effect on catalysts calcined for 12 h, however the opposite trend, an increased conversion with higher loadings, was observed for catalysts calcined for 2 h. These results imply that the sintering of Ag can play a dramatic effect on catalyst design for optimum performance.

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Catalytic Oxidations of Inorganic and Organic Compounds

Bartholomew

Farrauto²

2005

Fundamentals of Industrial Catalytic Processes

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Study of the Real Structure of Silver Supported Catalysts of Different Dispersity

Cited by 63 publications

References 0 publications

Deep oxidation of methane over zirconia supported Ag catalysts

Deep oxidation of methane over zirconia supported Ag catalysts

Effect of Preparation Conditions on Ag Catalysts for Ethylene Epoxidation

Catalytic Oxidations of Inorganic and Organic Compounds

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