CuxCeMgAlO mixed oxide catalysts derived from multicationic LDH precursors for methane total oxidation

Al-Aani, Hussein Mahdi S.; Iro, Emmanuel; Chirra, Pramodh; Fechete, Ioana; Badea, Mihaela; Negrilă, Cătălin; Popescu, Ionel; Olea, Maria; Marcu, Ioan–Cezar

doi:10.1016/j.apcata.2019.117215

Cited by 15 publications

(14 citation statements)

References 59 publications

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“…Table compares the activities of the most active Al-rich Cu-*BEA with supported and oxidelike Cu catalysts, Ce-, Co-, Fe-, and Mn-based catalysts of various structures and compositions, and supported Pd catalysts found in the literature. The T 50 value for the Al-rich Cu-*BEA is 407 °C, while for the supported and mixed Cu-oxo catalyst, it is typically in the 450–550 °C − range. The supported and mixed Cu-oxo catalysts generally exhibit lower activity than the Al-rich Cu-*BEA.…”

Section: Resultsmentioning

confidence: 99%

Effect of the Nuclearity and Coordination of Cu and Fe Sites in β Zeolites on the Oxidation of Hydrocarbons

et al. 2020

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Cu and Fe zeolites can activate oxygen for oxidative reactions of methane and stable hydrocarbon molecules. Here, we analyzed the activity of Cu and Fe sites with various nuclearities and coordinations in *BEA zeolites toward complete oxidation of methane, toluene, and ethanol by molecular oxygen. Spectral analysis of the interaction of methane with the individual Cu and Fe sites and a kinetic study show that the oxidation of methane is catalyzed by different active sites with different activation energies. In the low-temperature region (225–325 °C), the activity is primarily caused by reactive bridging oxygen atoms in dimeric Cu and Fe clusters. Isolated Fe3+-oxo ions in the octahedral coordination and Cu2+ partially charge-balanced by the framework with less rigid redox states contribute to the activity at higher temperatures of ≥350 °C. The isolated Fe3+-oxo ions tetrahedrally coordinated to the framework oxygen and the bare Cu2+ ions charge-balanced exclusively by the framework are strongly stabilized and cannot act as active sites. Oxidation of the hydrocarbons over both the dimeric and isolated Cu and Fe active sites is nonspecific with practically barrierless consecutive reactions of already activated molecules and therefore fully CO2-selective for all of the hydrocarbons in an excess of oxygen.

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Section: Resultsmentioning

confidence: 99%

Effect of the Nuclearity and Coordination of Cu and Fe Sites in β Zeolites on the Oxidation of Hydrocarbons

et al. 2020

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“…An interesting approach to combine multiple cations besides ceria into some materials has sought to achieve competitive and active catalysts for complete methane combustion as alternative for noble metal catalysts. The synthesis of mixed oxides derived from LDH via the co-precipitation method and calcination at 750 • C in air afforded a series of Cu-Ce-MgAlO catalysts with fixed 10 at.% Ce, Mg/Al atomic ratio of 3 and different Cu content ranging from 6% to 18 at.%, with respect to cations [183].…”

Section: Multimetallic Modified Ceria Catalystsmentioning

confidence: 99%

Total Oxidation of Methane on Oxide and Mixed Oxide Ceria-Containing Catalysts

et al. 2021

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Methane, discovered in 1766 by Alessandro Volta, is an attractive energy source because of its high heat of combustion per mole of carbon dioxide. However, methane is the most abundant hydrocarbon in the atmosphere and is an important greenhouse gas, with a 21-fold greater relative radiative effectiveness than CO2 on a per-molecule basis. To avoid or limit the formation of pollutants that are dangerous for both human health and the atmospheric environment, the catalytic combustion of methane appears to be one of the most promising alternatives to thermal combustion. Total oxidation of methane, which is environmentally friendly at much lower temperatures, is believed to be an efficient and economically feasible way to eliminate pollutants. This work presents a literature review, a statu quo, on catalytic methane oxidation on transition metal oxide-modified ceria catalysts (MOx/CeO2). Methane was used for this study since it is of great interest as a model compound for understanding the mechanisms of oxidation and catalytic combustion on metal oxides. The objective was to evaluate the conceptual ideas of oxygen vacancy formation through doping to increase the catalytic activity for methane oxidation over CeO2. Oxygen vacancies were created through the formation of solid solutions, and their catalytic activities were compared to the catalytic activity of an undoped CeO2 sample. The reaction conditions, the type of catalysts, the morphology and crystallographic facets exposing the role of oxygen vacancies, the deactivation mechanism, the stability of the catalysts, the reaction mechanism and kinetic characteristics are summarized.

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“…Catalysts 2020, 10, x FOR PEER REVIEW 7 of 23 the lateral structure, respectively [31]. The oxygen in the lateral structure was associated to hydroxyl and/or carbonate species [32] and also to subsurface oxygen ions with particular coordination and lower electron density than the lattice oxygen probably located at the interface of the crystalline CuO and CeO2 phases [21,31].…”

Section: Catalysts Characterizationmentioning

confidence: 99%

“…Recently, it has been shown [21] that Ce-containing Cu-based LDH-derived mixed oxide catalysts are quite active in the total oxidation of methane, the optimum composition corresponding to a CuCeMgAlO system with 15% Cu, 10% Ce (at.%, with respect to cations), and Mg/Al atomic ratio of 3. For this, an excellent dispersion of Cu in the CeMgAlO matrix was observed favoring a strong synergistic effect between Cu and Ce and, hence, an enhanced catalytic activity.…”

Section: Introductionmentioning

confidence: 99%

Highly Active Transition Metal-Promoted CuCeMgAlO Mixed Oxide Catalysts Obtained from Multicationic LDH Precursors for the Total Oxidation of Methane

Al-Aani

Trandafir

Fechete³

et al. 2020

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To improve the catalytic performance of an active layered double hydroxide (LDH)-derived CuCeMgAlO mixed oxide catalyst in the total oxidation of methane, it was promoted with different transition-metal cations. Thus, two series of multicationic mixed oxides were prepared by the thermal decomposition at 750 °C of their corresponding LDH precursors synthesized by coprecipitation at constant pH of 10 under ambient atmosphere. The first series of catalysts consisted of four M(3)CuCeMgAlO mixed oxides containing 3 at.% M (M = Mn, Fe, Co, Ni), 15 at.% Cu, 10 at.% Ce (at.% with respect to cations), and with Mg/Al atomic ratio fixed to 3. The second series consisted of four Co(x)CuCeMgAlO mixed oxides with x = 1, 3, 6, and 9 at.% Co, while keeping constant the Cu and Ce contents and the Mg/Al atomic ratio. All the mixed oxides were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) coupled with X-ray energy dispersion analysis (EDX), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption-desorption at −196 °C, temperature-programmed reduction under hydrogen (H2-TPR), and diffuse reflectance UV-VIS spectroscopy (DR UV-VIS), while thermogravimetric and differential thermal analyses (TG-DTG-DTA) together with XRD were used for the LDH precursors. The catalysts were evaluated in the total oxidation of methane, a test reaction for volatile organic compounds (VOC) abatement. Their catalytic performance was explained in correlation with their physicochemical properties and was compared with that of a reference Pd/Al2O3 catalyst. Among the mixed oxides studied, Co(3)CuCeMgAlO was found to be the most active catalyst, with a temperature corresponding to 50% methane conversion (T50) of 438 °C, which was only 19 °C higher than that of a reference Pd/Al2O3 catalyst. On the other hand, this T50 value was ca. 25 °C lower than that observed for the unpromoted CuCeMgAlO system, accounting for the improved performance of the Co-promoted catalyst, which also showed a good stability on stream.

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CuxCeMgAlO mixed oxide catalysts derived from multicationic LDH precursors for methane total oxidation

Cited by 15 publications

References 59 publications

Effect of the Nuclearity and Coordination of Cu and Fe Sites in β Zeolites on the Oxidation of Hydrocarbons

Effect of the Nuclearity and Coordination of Cu and Fe Sites in β Zeolites on the Oxidation of Hydrocarbons

Total Oxidation of Methane on Oxide and Mixed Oxide Ceria-Containing Catalysts

Highly Active Transition Metal-Promoted CuCeMgAlO Mixed Oxide Catalysts Obtained from Multicationic LDH Precursors for the Total Oxidation of Methane

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