On the nature of active sites and catalytic activity for OCM reaction of alkaline-earth oxides-neodymia catalytic systems

Papa, Florica; Gingaşu, Dana; Patron, Luminiţa; Miyazaki, Akane; Balint, Ioan

doi:10.1016/j.apcata.2009.12.039

Cited by 43 publications

(27 citation statements)

References 29 publications

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“…It is widely accepted that the acid/base properties of the catalysts, especially the concentration of surface base sites, play an important role in the formation of C 2 hydrocarbons in the OCM reaction. Florica et al . claimed that, the higher the catalyst basicity, the better the efficiency for selectively converting methane to C 2 products.…”

Section: Resultsmentioning

confidence: 99%

Impact of Surface Composition of SrTiO₃ Catalysts for Oxidative Coupling of Methane

et al. 2019

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Oxidative coupling of methane (OCM) to C2 hydrocarbons (C2H6 and C2H4) have regained much attention due to the shale gas revolution. Perovskite catalysts have shown promising activity and selectivity to C2 hydrocarbons. Here, we investigate the effect of surface reconstruction (leading to different surface compositions) of perovskites on the OCM by using SrTiO3(STO) as a model catalyst. Different surface densities of Sr (25–96 %) were attained via various treatments of STO. Low energy ion scattering (LEIS) and UV‐Raman results are in good agreement on the surface and subsurface composition of the reconstructed STO. From H2‐TPR, the same H2 consumption of STO samples allows relating their catalytic performances with surface acid‐base properties (quantified by NH3‐/CO2‐TPD). At 600–800 °C, the surface Sr enrichment was found to enhance CH4 conversion, C2 selectivity and the ratio C2H4/C2H6 up to Sr/(Sr+Ti) of 0.66 and then levels off. Furthermore, the relative concentration of basic sites, base/(base+acid), is found as a better descriptor for STO catalytic performances. This work shows the clear correlation between surface reconstruction, relative basicity/acidity and OCM catalytic performance over perovskite catalysts. The trends here are similar to those for CH4 combustion over the reconstructed STO in our recent work. Overall, we suggest that tuning surface reconstruction/composition of perovskites can be an effective approach to control CH4 activation and conversions.

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Section: Resultsmentioning

confidence: 99%

Impact of Surface Composition of SrTiO₃ Catalysts for Oxidative Coupling of Methane

et al. 2019

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“…If the temperature is increased to 650 and 750 °C, the C2 yield reaches only 1.7 and 5.9 %, respectively (Table 5). Papa et al 7. 9 studied mixed oxides MO–Sm 2 O 3 (M=Be, Zn, Mg, Ca, and Sr) for OCM and indicated that the surface basic sites were responsible for the formation of C2+ and the acidic sites were responsible for methane combustion.…”

Section: Resultsmentioning

confidence: 99%

Effects of Polyvinylpyrrolidone on the Preparation of Supported La₂O₃ Catalysts by a Modified Impregnation Method for the Oxidative Coupling of Methane

Hou

Lin

et al. 2013

ChemCatChem

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The direct transformation of methane, such as oxidative coupling of methane (OCM), is a long‐standing challenge in methane utilization. Keeping this objective in mind, we explored the dispersion and acid–base effects of the catalysts on OCM. Herein, we prepared a series of La2O3/MgO catalysts by using a modified impregnation method with polyvinylpyrrolidone added to impregnated solutions. The BET, XRD, SEM, and TEM characterizations of the samples confirm that La2O3 dispersion on MgO increases with the addition of polyvinylpyrrolidone and the particles become smaller in size and more uniform in distribution. High catalytic performances (e.g., the C2 yield ≈16 %) of the well‐dispersed La2O3/MgO catalysts for OCM are demonstrated at a lower temperature (e.g., 550 °C) and a lower loading (e.g., 1.9 wt %). In addition, with the modification of acid–base properties of the supports, we find that base properties of the supports are responsible for C2 formation and acidic properties of the supports are responsible for COx formation. These properties establish a good correlation of the dispersion and basicity of the catalysts with the catalytic performances of the catalysts for OCM.

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“…Based on the above considerations [4], we have tried to observe the thermal decomposition of surface carbonate species of MO-Sm 2 O 3 mixed oxides and to correlate these date with the catalytic behavior in OCM reaction.…”

Section: Resultsmentioning

confidence: 99%

“…Among the best OCM catalysts are the simple or alkaline-added CeO 2 , PrO 2 , Sm 2 O 3 oxides [3]. In a recently published work, the contribution of acid and basic sites of MO-Nd 2 O 3 (M = Be, Mg, Ca, Sr) mixed to the oxidative conversion of methane was investigated in detail [4]. This is among the first attempts aiming to demonstrate that the methane conversion over oxide catalysts can be better understood if it is interpreted in the simple terms of acid-base catalysis.…”

Section: Introductionmentioning

confidence: 99%

Relevance of the basicity of MO–Sm2O3 (M = Zn, Mg, Ca, Sr) mixed oxides for the efficiency of methane conversion to C2 + hydrocarbons

Balint

Miyazaki

Gingaşu

et al. 2011

Reac Kinet Mech Cat

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This article focuses on the catalytic behavior of MO-Sm 2 O 3 (M = Zn, Mg, Ca, Sr) mixed oxides. The obtained results could be interpreted in terms of solid acid-base catalysis. The mixed oxides were prepared starting from the tartarate complexes of the constituent metals. The concentration as well as the evolution of surface carbonate species with the nature of MO and reaction temperature were analyzed by XRD and TPD methods. The amount of surface basic sites responsible for the formation of C 2 ? was determined by measuring the amount of evolved CO 2 in the 300-800°C temperature range. The catalytic behavior of the investigated mixed oxides was expressed in terms of methane yield to C 2 ? and the concentration of CO 2 in reaction mixture. The conclusion is that C 2 ? is formed on the basic sites whereas the acidic sites are responsible for nonselective oxidation of methane to CO 2 .

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On the nature of active sites and catalytic activity for OCM reaction of alkaline-earth oxides-neodymia catalytic systems

Cited by 43 publications

References 29 publications

Impact of Surface Composition of SrTiO₃ Catalysts for Oxidative Coupling of Methane

Impact of Surface Composition of SrTiO₃ Catalysts for Oxidative Coupling of Methane

Effects of Polyvinylpyrrolidone on the Preparation of Supported La₂O₃ Catalysts by a Modified Impregnation Method for the Oxidative Coupling of Methane

Relevance of the basicity of MO–Sm2O3 (M = Zn, Mg, Ca, Sr) mixed oxides for the efficiency of methane conversion to C2 + hydrocarbons

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On the nature of active sites and catalytic activity for OCM reaction of alkaline-earth oxides-neodymia catalytic systems

Cited by 43 publications

References 29 publications

Impact of Surface Composition of SrTiO3 Catalysts for Oxidative Coupling of Methane

Impact of Surface Composition of SrTiO3 Catalysts for Oxidative Coupling of Methane

Effects of Polyvinylpyrrolidone on the Preparation of Supported La2O3 Catalysts by a Modified Impregnation Method for the Oxidative Coupling of Methane

Relevance of the basicity of MO–Sm2O3 (M = Zn, Mg, Ca, Sr) mixed oxides for the efficiency of methane conversion to C2 + hydrocarbons

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Impact of Surface Composition of SrTiO₃ Catalysts for Oxidative Coupling of Methane

Impact of Surface Composition of SrTiO₃ Catalysts for Oxidative Coupling of Methane

Effects of Polyvinylpyrrolidone on the Preparation of Supported La₂O₃ Catalysts by a Modified Impregnation Method for the Oxidative Coupling of Methane