ChemInform Abstract: Structure Sensitivity of Methane Oxidation Over Platinum and Palladium.

Hicks, Robert F.; Qi, Haihua; Young, Michael L.; Lee, R. G.

doi:10.1002/chin.199028047

Cited by 28 publications

(61 citation statements)

References 1 publication

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Several authors reported that the turnover rate of methane oxidation increases as the Pd particle size increases [10,11,13]. Otto [17] reported that highly dispersed Pt on alumina, present at low Pt loading (<1.4 wt% Pt) has low activity compared to the larger particles of Pt, present at higher Pt loading (>1.4 wt% Pt).…”

Section: Discussionmentioning

confidence: 99%

Deep oxidation of methane over zirconia supported Ag catalysts

Kundakovic

Flytzani‐Stephanopoulos

1999

Applied Catalysis A: General

View full text Add to dashboard Cite

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.

show abstract

Section: Discussionmentioning

confidence: 99%

Deep oxidation of methane over zirconia supported Ag catalysts

Kundakovic

Flytzani‐Stephanopoulos

1999

Applied Catalysis A: General

View full text Add to dashboard Cite

show abstract

“…Hysteresis in the activity during the oxidation of methane was also observed as the reaction temperature was cycled up and down. This behaviour, commonly seen with palladium during methane oxidation, has been studied by a number of researchers [14][15][16].…”

Section: Oscillations Of Methane Oxidation Over Pd Foil and Wirementioning

confidence: 94%

“…However, there is some disagreement in the literature over the surface form which is most active. Oh and co-workers [19,20]and Hicks et al [15,16] argue that the metal surface is more active than the oxide surface, whereas Burch and co-workers [21][22][23], Farrauto et al [24,25]and Primet and co-workers [26][27][28] consider the oxide surface as the most active phase.…”

Section: Relative Reactivity Of the Metal And Oxidementioning

confidence: 99%

Oscillatory behaviour during the oxidation of methane over palladium metal catalysts

Zhang

Lee

Mingos

et al. 2003

Applied Catalysis A: General

View full text Add to dashboard Cite

Oscillatory reactions over palladium foil and wire catalysts during the oxidation of methane have been investigated over a wide range of reaction temperatures and argon/methane/oxygen feed gas compositions. Characterisation of the catalyst has also been carried out using scanning electron microscopy (SEM) techniques, which revealed the presence of a porous surface. This suggested that the metal surface has undergone a change since the reaction commenced, and using X-ray powder diffraction (XRD) techniques the palladium phase was shown to be the dominant phase present. Hysteresis phenomena were observed in the activity of the reaction as the temperature was cycled up and down, showing that the metal surface was continually changing throughout the reaction. The activation energies of the reaction during the high reactivity mode, PdO, and low reactivity mode, Pd, were also calculated. Oscillation rates were observed to depend on the dominant surface. Oscillations were frequent when the high reactivity mode was dominant while the activation energy of this mode was found to be low. When the low reactivity mode was dominant, the oscillations were slower and the activation energy was three times larger. The results obtained imply that the behaviour of the palladium surface, switching back and forth from the reduced state to the oxidised state, is responsible for the oscillatory behaviour seen in this system.

show abstract

“…Among many catalysts, the aluminasupported palladium catalysts are renowned for their high activity in methane combustion under lean-burn conditions [23][24][25]. However, the thermal stability of the catalyst is a limiting factor in this application, especially when additional water vapor is included in the feed stream [12][13][14]26,27]. The addition of promoters such as metal oxide to alumina-supported palladium catalysts could be useful to enhance both catalytic activity and stability.…”

Section: Introductionmentioning

confidence: 99%