Investigation of the active state of supported palladium catalysts in the combustion of methane

Burch, R.; Urbano, Francisco J.

doi:10.1016/0926-860x(94)00252-5

Cited by 284 publications

(153 citation statements)

References 20 publications

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“…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

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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.

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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

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“…The adsorption of O 2 on oxygen vacancies, presumably followed by its dissociation is expected to play a major role in the oxidation reaction. It is generally accepted that the prevalent mechanism of the high temperature CH 4 catalytic oxidation involves a redox Mars-van Krevelen-type reaction [20,34,66]. In the present catalysts, the point of interaction between Pd and CeO 2 and/or the intrinsic oxygen vacancies presumably acted as centers for dissociating molecular oxygen into chemisorbed oxygen (O*) which were then consumed in the oxidation reaction.…”

Section: Catalytic Activitymentioning

confidence: 97%

Active and Stable Methane Oxidation Nano-Catalyst with Highly-Ionized Palladium Species Prepared by Solution Combustion Synthesis

et al. 2018

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We report on the synthesis and testing of active and stable nano-catalysts for methane oxidation. The nano-catalyst was palladium/ceria supported on alumina prepared via a one-step solution-combustion synthesis (SCS) method. As confirmed by X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HTEM), SCS preparative methodology resulted in segregating both Pd and Ce on the surface of the Al 2 O 3 support. Furthermore, HTEM showed that bigger Pd particles (5 nm and more) were surrounded by CeO 2 , resembling a core shell structure, while smaller Pd particles (1 nm and less) were not associated with CeO 2 . The intimate Pd-CeO 2 attachment resulted in insertion of Pd ions into the ceria lattice, and associated with the reduction of Ce 4+ into Ce 3+ ions; consequently, the formation of oxygen vacancies. XPS showed also that Pd had three oxidation states corresponding to Pd 0 , Pd 2+ due to PdO, and highly ionized Pd ions (Pd (2+x)+ ) which might originate from the insertion of Pd ions into the ceria lattice. The formation of intrinsic Ce 3+ ions, highly ionized (Pd 2+ species inserted into the lattice of CeO 2 ) Pd ions (Pd (2+x)+ ) and oxygen vacancies is suggested to play a major role in the unique catalytic activity. The results indicated that the Pd-SCS nano-catalysts were exceptionally more active and stable than conventional catalysts. Under similar reaction conditions, the methane combustion rate over the SCS catalyst was~18 times greater than that of conventional catalysts. Full methane conversions over the SCS catalysts occurred at around 400 • C but were not shown at all with conventional catalysts. In addition, contrary to the conventional catalysts, the SCS catalysts exhibited superior activity with no sign of deactivation in the temperature range between~400 and 800 • C.

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“…[1][2][3][4] Among the noble-metal catalysts, palladium and platinum on various wash coats have been reported as the most active catalysts for methane combustion, due to their high thermal stability, but easily deactivated by sulphur poison. [5][6][7][8][9][10][11] Recent reports portray that bimetallic catalysts exhibit better properties like improved activity, selectivity, and thermal stability than monometallic catalysts. Many reports revealed the improved activity of Pt-Pd bimetallic catalysts over monometallic Pd catalysts, [12][13][14] as metal-metal interactions are believed to overcome deactivation of catalysts with time on stream.…”

Section: Introductionmentioning

confidence: 99%

Effect of Bimetallic Pt-Rh and Trimetallic Pt-Pd-Rh Catalysts for Low Temperature Catalytic Combustion of Methane

Bhagiyalakshmi¹,

Anuradha²,

Park³

et al. 2010

Bulletin of the Korean Chemical Society

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Monometallic, bimetallic and trimetallic particles consisting of different weight compositions of Pt-Pd-Rh over pure alumina wash coats have been synthesized and their catalytic performance on methane conversion was studied from 150 to 600 o C. Different catalyst formulations with variable Pt, Pd and Rh contents for bimetallic and trimetallic systems were tried and Pt(1.5)Rh(0.3)/Al2O3 and Pt(1.0)Pd(1.0)Rh(0.3)/Al2O3 shows low T50 and T90 temperatures. Bimetallic and trimetallic particle synergism acts as three way catalysts and therefore, all the catalysts show 100% methane conversion. The effect of supports such as ZrO2 and TiO2 on methane combustion was investigated; from T50 and T90 results both Al2O3 and ZrO2 are suitable supports for low temperature methane combustion.

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Investigation of the active state of supported palladium catalysts in the combustion of methane

Cited by 284 publications

References 20 publications

Oscillatory behaviour during the oxidation of methane over palladium metal catalysts

Oscillatory behaviour during the oxidation of methane over palladium metal catalysts

Active and Stable Methane Oxidation Nano-Catalyst with Highly-Ionized Palladium Species Prepared by Solution Combustion Synthesis

Effect of Bimetallic Pt-Rh and Trimetallic Pt-Pd-Rh Catalysts for Low Temperature Catalytic Combustion of Methane

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