Hybrid catalysts containing Ba, Ti, Mn, Na, and W for the low-temperature oxidative coupling of methane

Thi, Lien; Choi, Ji‐Won; Suh, Dong Jin; Yoo, Chun‐Jae; Lee, Hyunjoo; Ha, Jeong‐Myeong

doi:10.1016/j.apcatb.2021.120553

Cited by 17 publications

(8 citation statements)

References 69 publications

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“…In conclusion, surface oxygen vacancies play a key role in catalyzing the OCM reaction. 18 O are produced by the reaction of methyl groups with molecular dioxygen 18 O 2 in the gas phase. 73 The results also show that the oxygen present in the La 2 Ce 2−x Ca x O 7−δ catalyst can be exchanged into the final products.…”

Section: Results Of In Situ Driftsmentioning

confidence: 99%

“…The catalyst was then heated from 50 to 800 °C at a ramp rate of 10 °C min −1 under a CH 4 / 18 O 2 /Ar (4/1/ 5) flow (30 mL min −1 ). Isotopically labeled products were measured by a mass spectrometer based on the following massto-charge ratio: 18 O 2 (36), CH 4 (16), C 18 O (30), C 16 O (28), C 16 O 2 (44), C 18 O 2 (48), and C 16 O 18 O (46).…”

Section: Experimental Sectionsmentioning

confidence: 99%

“…It was also found that the cations in metal oxide catalysts partially substituted by lanthanide, alkaline, and alkaline earth metals can increase the number of oxygen vacancies. , The increasing oxygen vacancies in the catalysts can improve the activation of O 2 molecules into active oxygen species, which improves the catalytic activity of the OCM reaction at a low temperature (<650 °C). Nowadays, the effects of alkaline earth metals (Mg, Ca, and Ba) substitution on active oxygen species in some metal oxide catalysts have been reported. − It is of great significance to further investigate the promoting effect on the catalytic activity of the OCM reaction by the substitution of the A site or B site in A 2 B 2 O 7 compounds. Thus, the design and synthesis of La 2 Ce 2– x Ca x O 7−δ oxide catalysts with a high density of oxygen vacancies are promising for the enhancement of the low-temperature catalytic activity during the OCM reaction.…”

Section: Introductionmentioning

confidence: 99%

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Surface Oxygen Vacancies Induced by Calcium Substitution in Macroporous La₂Ce_2–xCa_xO_7−δ Catalysts for Boosting Low-Temperature Oxidative Coupling of Methane

Wu,

Zhang,

Wei

et al. 2024

ACS Catal.

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Surface oxygen vacancies in the catalysts play a key role in improving the catalytic performances for low-temperature oxidative coupling of methane (OCM). Herein, macroporous La 2 Ce 2−x Ca x O 7−δ (A 2 B 2 O 7 -type) catalysts with a disordered defective cubic fluorite phased structure were prepared by a citric acid sol−gel method. The macroporous structure improved the accessibility of the reactants (O 2 and CH 4 ) to the active sites. The partial substitution of the B site (Ce) with low-valence calcium (Ca) ions in La 2 Ce 2−x Ca x O 7−δ catalysts induced the formation of surface oxygen vacancies, which facilitated the adsorption and activation of O 2 molecules to generate the active oxygen species (O 2 − species). The O 2 − species can boost the activation of CH 4 and govern the following step of the oxidative dehydrogenation of C 2 H 6 to C 2 H 4 . La 2 Ce 2−x Ca x O 7−δ catalysts have high catalytic activity for low-temperature OCM, and the La 2 Ce 1.3 Ca 0.7 O 7−δ catalyst with the highest density of O 2− species exhibits the highest catalytic activity during low-temperature OCM into C 2 H 4 and C 2 H 6 (C 2 ) products, i.e., its CH 4 conversion, selectivity, and yield of C 2 products at 600 °C are 31.0, 65.6, and 20.3%, respectively. Based on the results of multiple experimental characterizations and density functional theory calculations, the mechanism of La 2 Ce 2−x Ca x O 7−δ catalysts for the OCM reaction is proposed: surface oxygen vacancies induced by the substitution of the Ce site with Ca ions significantly promote the critical steps of C−H bond breaking and C−C bond coupling during the low-temperature OCM reaction. It is important for the design of low-temperature and high-efficiency catalysts for practical applications.

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Section: Results Of In Situ Driftsmentioning

confidence: 99%

Section: Experimental Sectionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Surface Oxygen Vacancies Induced by Calcium Substitution in Macroporous La₂Ce_2–xCa_xO_7−δ Catalysts for Boosting Low-Temperature Oxidative Coupling of Methane

Wu,

Zhang,

Wei

et al. 2024

ACS Catal.

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“…TiO 2 was used as an alternative carrier for SiO 2 to provide more oxygen species in the Mn/Na 2 WO 4 ‐based catalyst to promote CH 4 conversion 26 . The OCM performance with 66.3% C 2+ (olefins and paraffins) selectivity and 25.9% C 2+ yield at 700°C was obtained by using a mixture of BaTiO 3 perovskite and Mn‐Na 2 WO 4 27 . However, the active sites and catalytic mechanism of this catalyst are still controversial due to its complex composition and structure.…”

Section: Introductionmentioning

confidence: 99%

“…26 The OCM performance with 66.3% C 2+ (olefins and paraffins) selectivity and 25.9% C 2+ yield at 700 C was obtained by using a mixture of BaTiO 3 perovskite and Mn-Na 2 WO 4 . 27 However, the active sites and catalytic mechanism of this catalyst are still controversial due to its complex composition and structure. Additionally, Li/MgO is one of the most frequently studied catalysts for OCM reaction.…”

Section: Introductionmentioning

confidence: 99%

Perovskite catalysts for oxidative coupling of methane improved by Y‐doping

Wang

Cai

Cao

et al. 2022

Asia-Pacific J Chem Eng

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Oxidative coupling of methane (OCM) is an effective route for methane direct conversion to ethylene. Perovskite oxides (ABO 3 ) with variable properties are potential catalysts for OCM by adjusting the compositions. In this study, four perovskite catalysts, BaMO 3-δ and BaM 1-x Y x O 3-δ (M = Zr, Ce; x = 0.2), were prepared by the sol-gel method to explore their catalytic performance of OCM.All catalysts are active toward OCM and reach the highest catalytic performance at 800 C. The OCM performance of Ce-based catalysts is higher than that of Zr-based catalysts. The selectivity of C 2 compounds is significantly improved by Y-doping. At CH 4 /O 2 mol ratio of 8, a C 2 selectivity of 67% was achieved on BaCe 0.8 Y 0.2 O 3-δ . Compared with Zr-based catalysts, more amounts of active oxygen species, which are beneficial to OCM, were observed on BaCeO 3-δ and BaCe 0.8 Y 0.2 O 3-δ . Meanwhile, higher contents of moderate and strong basic sites, which are beneficial to OCM, were found on the Y-doped catalysts. This is attributed to the generation of oxygen vacancies caused by Ydoping in the B-site. Therefore, BaCe 0.8 Y 0.2 O 3-δ with more active oxygen species and stronger basicity exhibits the highest performance among the four catalysts.

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Layered Perovskite La₂Ti₂O₇ Nanostructures for Photocatalytic Degradation of Congo Red Dye Pollutant

Bhagwat,

Maridevaru,

Al Souwaileh

et al. 2024

ChemistrySelect

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In photocatalytic innovation, there has been a lot of interest in creating broad spectral responsive photocatalysts to get superior catalytic performance. In this study, we synthesized highly visible‐light responsive La2Ti2O7 perovskite photocatalysts by the probe ultrasonication procedure followed by high‐temperature calcination. Such materials are characterized using UV‐vis diffuse reflectance spectra, powder X‐ray diffraction, X‐ray photoelectron spectroscopy, and scanning electron microscopy to illustrate the optical absorption activities, crystalline properties, chemical composition, and microscopic features. La2Ti2O7 extends optical absorption towards the visible light spectrum and narrows the band gap. The photocatalytic efficacy of the resulting La2Ti2O7 nanostructures was investigated by performing photocatalytic degradation of persistent Congo red (CR) dye while subjected to visible photon illumination using three Osram 150 W tungsten halogen lamp ((λ≥400 nm), 5000 lm nominal luminous flux, 80,600 lx radiation intensity. With effective efficiency, the optimum degradation of the 10 ppm CR dye with a percentage of 95.9 was achieved after 90 min during exposure to the La2Ti2O7 perovskite with a catalyst dosage of 30 mg/100 mL at pH 6. Consequently, La2Ti2O7 nanostructures alone depicted 19.8 % adsorption efficiency for CR dye. In addition, OH⋅ and holes were important in degrading CR dye, which included many different reaction pathways. The treated solution can also demonstrate the environment's safety for accepting water. In summary, under natural visible light irradiation, the synthesized La2Ti2O7 showed enormous promise for eliminating different organic contaminants using photocatalytic methodology.

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Hybrid catalysts containing Ba, Ti, Mn, Na, and W for the low-temperature oxidative coupling of methane

Cited by 17 publications

References 69 publications

Surface Oxygen Vacancies Induced by Calcium Substitution in Macroporous La₂Ce_2–xCa_xO_7−δ Catalysts for Boosting Low-Temperature Oxidative Coupling of Methane

Surface Oxygen Vacancies Induced by Calcium Substitution in Macroporous La₂Ce_2–xCa_xO_7−δ Catalysts for Boosting Low-Temperature Oxidative Coupling of Methane

Perovskite catalysts for oxidative coupling of methane improved by Y‐doping

Layered Perovskite La₂Ti₂O₇ Nanostructures for Photocatalytic Degradation of Congo Red Dye Pollutant

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Hybrid catalysts containing Ba, Ti, Mn, Na, and W for the low-temperature oxidative coupling of methane

Cited by 17 publications

References 69 publications

Surface Oxygen Vacancies Induced by Calcium Substitution in Macroporous La2Ce2–xCaxO7−δ Catalysts for Boosting Low-Temperature Oxidative Coupling of Methane

Surface Oxygen Vacancies Induced by Calcium Substitution in Macroporous La2Ce2–xCaxO7−δ Catalysts for Boosting Low-Temperature Oxidative Coupling of Methane

Perovskite catalysts for oxidative coupling of methane improved by Y‐doping

Layered Perovskite La2Ti2O7 Nanostructures for Photocatalytic Degradation of Congo Red Dye Pollutant

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Product

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Surface Oxygen Vacancies Induced by Calcium Substitution in Macroporous La₂Ce_2–xCa_xO_7−δ Catalysts for Boosting Low-Temperature Oxidative Coupling of Methane

Surface Oxygen Vacancies Induced by Calcium Substitution in Macroporous La₂Ce_2–xCa_xO_7−δ Catalysts for Boosting Low-Temperature Oxidative Coupling of Methane

Layered Perovskite La₂Ti₂O₇ Nanostructures for Photocatalytic Degradation of Congo Red Dye Pollutant