Support effect of zeolite on the methane combustion activity of palladium

Okumura, Kazu; Matsumoto, Sachi; Nishiaki, Noriko; Niwa, Miki

doi:10.1016/s0926-3373(02)00149-2

Cited by 132 publications

(99 citation statements)

References 18 publications

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“…[7][8][9][10][11] Several studies have shown that PdO is the active phase for the catalytic combustion of methane. 5,12 The mixture of Pd metal and PdO was proposed to be key for the activity in Pd loaded on zeolites. 13 Furthermore palladium supported on acid silica-alumina amorphous mesoporous supports, such as Al-MCM-41 or SBA-15, is an excellent heterogeneous catalyst for the direct oxidation of methane.…”

Section: Introductionmentioning

confidence: 99%

“…7,14 Because of this, supported palladium oxides have been widely studied. [3][4][5][6][7][8][9][10][11][12][13] The oxidation state, dispersion, oxide nature and the morphology of the particles are dependent on the preparation method and on the nature of the support, which complicates the characterization efforts to elucidate the nature of the active site for methane oxidation. Experimental studies confirmed that the cleavage of the strong C-H bond in CH 4 is the rate-determining step for the catalytic o xidation of methane.…”

Section: Introductionmentioning

confidence: 99%

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Oxidation of Methane to Methanol over Single Site Palladium Oxide Species on Silica: A Mechanistic view from DFT

et al. 2017

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Abstract:A theoretical analysis was carried out on the mechanism of methane oxidation to methanol occurring on single site palladium oxide species [PdO] 2+ supported on a model of Al-MCM-41 silica. Both 6 and 8-membered ring structures were considered to represent the support.The energy profile for each elementary reaction was determined from density functional theory calculations with the OPBE functional. The calculated overall activation energies are close to the experimental values. Our calculations confirm that spin inversion can play a significant role in decreasing the barrier heights for the pathways. Indeed, in this type of reactions we could show a crossing between singlet and triplet reaction paths. We showed that the mechanism for the C-H bond cleavage and for the formation of methanol has a radical nature. According to our results, the [PdO] 2+ species located on a 8-membered ring of silica is more active than that deposited on a 6-membered ring. The calculated activation energies to cleave the methane C-H bond are 35 and 84 kJ/mol for the radical and ionic pathways, respectively. The activation barrier and the transition state geometry of this H-abstraction step are directly correlated with the optimal angle at which the substrate should approach the [Pd=O] 2+ moiety, with the elongation of the Pd-O oxo bond and finally with the energy of the π* acceptor orbital.2

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Oxidation of Methane to Methanol over Single Site Palladium Oxide Species on Silica: A Mechanistic view from DFT

et al. 2017

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“…Afterwards, the catalyst redox center (Pd 0 ) is oxidized by the stream O 2 to recover [Pd 2+ O 2− ] through adsorption and dissociation of O 2 (step b). Many researchers testified that the oxidation state of Pd particles is significantly dependent on the acidic and basic properties of support [50,51]. Namely, Pd particles loaded on acidic supports were more easily oxidized than supported on the neutral or basic support as the acidic supports with electrophilic character resulted in the electron deficient on Pd atoms, thus the Pd surface was easily oxidized, which was directly testified by Okumura et al via EXAFS study [50].…”

Section: Catalytic Performance and Textural Properties Of Catalystsmentioning

confidence: 99%

“…There are many factors that influence the toluene oxidation efficiency, such as active phase dispersion and valence state, support acidity and material textural properties [9,16,49,50]. Table 2 lists the related textural data of all synthesized catalysts.…”

Section: Catalytic Performance and Textural Properties Of Catalystsmentioning

confidence: 99%

“…For example, the Pd/SC-10 has the lowest S BET (552.8 m 2 /g), while it possesses the best Pd dispersion (D c = 1.75 nm). Okumura et al proposed that the support acid property has significant influence on the dispersion of Pd, and the Brønsted acid sites are responsible for the generation of dispersed Pd species [9,50,51]. As is known, only the tetrahedral Al species contribute to the Brønsted acidity of materials [21].…”

Section: Catalytic Performance and Textural Properties Of Catalystsmentioning

confidence: 99%

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Nanometric palladium confined in mesoporous silica as efficient catalysts for toluene oxidation at low temperature

He¹,

Zhang²,

Yue³

et al. 2012

Applied Catalysis B: Environmental

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a b s t r a c tShort column SBA-15 supported Pd mesoporous catalysts with controllable acidity and expanded microporosity were firstly prepared through a simple "two-solvents" approach. The catalytic performances of the synthesized catalysts were evaluated for toluene oxidation. The characterization results reveal that Al atoms prefer to be tetrahedrally coordinated in the framework of the synthesized materials, and the acid sites can significantly promote Pd particle dispersion and metallic Pd oxidation due to their electrophilic characters. The Pd-confined catalysts possess high toluene turnover frequencies and toluene can be totally converted to CO 2 and H 2 O below 210 • C. The oxidation reaction can be suppressed by water vapor due to the formation of inactive Pd-hydroxides, and the synthesized catalyst has a good hydrothermal stability and high tolerance to moisture. Both the specific surface area and the toluene adsorption/desorption property are not the main factors determining the catalytic activity. Overall, the toluene oxidation performance is closely related to the support microporosity and acidity, the Pd dispersion and the CO 2 desorption capability.

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Dynamic Structural Change of Pd Induced by Interaction with Zeolites Studied by Means of Dispersive and Quick XAFS

Okumura

2009

Molecular Nano Dynamics

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Support effect of zeolite on the methane combustion activity of palladium

Cited by 132 publications

References 18 publications

Oxidation of Methane to Methanol over Single Site Palladium Oxide Species on Silica: A Mechanistic view from DFT

Oxidation of Methane to Methanol over Single Site Palladium Oxide Species on Silica: A Mechanistic view from DFT

Nanometric palladium confined in mesoporous silica as efficient catalysts for toluene oxidation at low temperature

Dynamic Structural Change of Pd Induced by Interaction with Zeolites Studied by Means of Dispersive and Quick XAFS

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