Evolution of Pd catalyst structure and activity during catalytic oxidation of methane and ethane

Bychkov, V. Yu.; Tyulenin, Yu. P.; Gorenberg, A. Ya.; Sokolov, Sergey; Корчак, В. Н.

doi:10.1016/j.apcata.2014.07.028

Cited by 26 publications

(27 citation statements)

References 25 publications

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“…XPS did not show any peak for elemental Pd, thereby confirming the absence of metallic palladium in the catalyst. This result is in contrast to previous research reports on the presence of metallic Pd in Pd/γ-Al2O3 catalysts [18][19][20]26]. In addition to metallic Pd and stoichiometric PdO, palladium surfaces exhibit non-stoichiometric native oxides.…”

Section: X-ray Photoelectron Spectroscopy (Xps)contrasting

confidence: 56%

“…This confirms the supposition that the γ-Al 2 O 3 support facilitated oxygen migration from the support to the stoichiometric PdO to form Pd native oxide (PdO x ). Other researchers reported the presence of Pd and/or PdO in Pd/γ-Al 2 O 3 catalysts [2,6,7,9,18,19]. Miller et al [20] and Schwartz et al [22] suggested that the support could facilitate oxygen mobility and affect composition of the surface catalytic sites at temperatures <400 • C. In order to identify the active phases in the catalytic combustion process, we did XPS of the catalyst after reaction with 2% CH4/4% O2 at 450 °C for 20 min.…”

Section: Active Phase Of the Catalyst And Proposed Mechanismmentioning

confidence: 99%

“…The nature and identity of the active phase in Pd catalysts during methane combustion is currently under dispute [2,6,7,9,[18][19][20][21]. Several researchers recognize PdO as the active phase [2,6,7,9]; some advocate for Pd [18,19], and others for the Pd to PdO ratio [20,21].…”

Section: Introductionmentioning

confidence: 99%

“…Several researchers recognize PdO as the active phase [2,6,7,9]; some advocate for Pd [18,19], and others for the Pd to PdO ratio [20,21]. Another consideration is the possibility of the support lending its constituents to the catalytic active site during the course of the reaction [20].…”

Section: Introductionmentioning

confidence: 99%

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Low-Temperature Activity and PdO-PdOx Transition in Methane Combustion by a PdO-PdOx/γ-Al2O3 Catalyst

et al. 2018

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Abstract:The search to discover a suitable catalyst for complete combustion of methane at low temperature continues to be an active area of research. We prepared a 5 wt % PdO-PdO x /γ-Al 2 O 3 catalyst by a modified Vortex-assisted Incipient Wetness Method. X-ray Photoelectron Spectroscopy showed that the original catalyst contained PdO (38%) and PdO x (62%) on the surface and indicated that PdO x originated from the interaction of PdO with the support. Scanning Transmission Electron Microscopy confirmed the catalyst had an average particle size of 10 nm and was well-dispersed in the support. The catalyst exhibited exceptional low-temperature activities with 90-94% methane conversion at 300-320 • C. The catalyst was active and stable after several catalytic runs with no signs of deactivation by steam in this narrow temperature range. However, the conversion decreased in the temperature range 325-400 • C. The surface composition changed to some extent after the reaction at 325 • C. A tentative mechanism proposes PdO x (Pd native oxide) as the active phase and migration of oxide ions from the support to PdO and then to PdO x during the catalytic oxidation. The high methane conversion at low temperature is attributed to the vortex method providing better dispersion, and to catalyst-support interaction producing the active phase of PdO x .

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Section: X-ray Photoelectron Spectroscopy (Xps)contrasting

confidence: 56%

Section: Active Phase Of the Catalyst And Proposed Mechanismmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Low-Temperature Activity and PdO-PdOx Transition in Methane Combustion by a PdO-PdOx/γ-Al2O3 Catalyst

et al. 2018

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“…As cited earlier, multiple research teams reported oscillatory behaviors of palladium-or platinum-loaded catalysts in different processes. Some attributed their occurrence to the oxidation of carbonaceous compounds adsorbed at the catalyst surface while others correlated their observations with a change in the oxidation state of palladium [21,26,27,31]. Therefore, this work focused on identifying the implication of both hypotheses in the oscillatory behavior seen in Figure 1.…”

Section: Discussionmentioning

confidence: 99%

Oscillatory Behavior of Pd-Au Catalysts in Toluene Total Oxidation

et al. 2018

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In this work, the activity of bimetallic Pd-Au doped hierarchically structured titania catalysts has been investigated in the total oxidation of toluene. In earlier works, doping titania with group Vb metal oxides ensured an increased catalytic performance in the elimination of VOC molecules. A synergy between gold and palladium loaded at the surface of titania supports provided better performances in VOC oxidation reactions. Therefore, the main focus in this work was to investigate the durability of the prepared catalysts under long time-on-stream periods. Vanadium-doped catalysts showed a stable activity throughout the whole 110 h test, whereas, surprisingly, niobium-doped catalysts presented a cycle-like activity while nevertheless maintaining a high performance in toluene elimination. Operando Diffuse Reflectance Infrared Fourrier Transform spectroscopy (DRIFT) experiments revealed that variations in the presence of OH radicals and the presence of carbonaceous compounds adsorbed at the surface of spent catalysts varies with the occurrence of oscillations. X-ray Photoelectron Spectroscopy (XPS) results show that interactions between the material and the active phase provided extra amounts of mobile oxygen species and participated in easing the reduction of palladium. An enhanced redox reaction scheme is thus obtained and allows the occurrence of the cyclic-like performance of the catalyst.

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Synthesis of Hierarchically Porous SiCN Materials and Pd Catalysts based on it for the Oxidation of Methane

Schwarz

Friedrich

Motz

et al. 2015

Zeitschrift anorg allge chemie

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Polymer derived silicon carbon nitride (SiCN) ceramics are versatile materials with broad potential applications in industry and technology. Their high stability towards thermomechanical and chemical stress makes them a promising support material in heterogeneous catalysis. Due to the challenging process of synthesizing high-surfacearea porous SiCN only a few examples of porous SiCN based catalysts are reported. Herein, we present a simple and efficient route to obtain 2266 mesoporous SiCN containing materials by impregnation of activated carbon with a polymeric silazane precursor. Oxidative removal of the template yields high-surface-area SiCN materials with a BET surface area from 200-470 m 2 ·g -1 and high content of mesopores from 70-99 %. By incipient wetness impregnation with palladium, efficient catalysts for the total oxidation of methane were obtained.

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Evolution of Pd catalyst structure and activity during catalytic oxidation of methane and ethane

Cited by 26 publications

References 25 publications

Low-Temperature Activity and PdO-PdOx Transition in Methane Combustion by a PdO-PdOx/γ-Al2O3 Catalyst

Low-Temperature Activity and PdO-PdOx Transition in Methane Combustion by a PdO-PdOx/γ-Al2O3 Catalyst

Oscillatory Behavior of Pd-Au Catalysts in Toluene Total Oxidation

Synthesis of Hierarchically Porous SiCN Materials and Pd Catalysts based on it for the Oxidation of Methane

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