Enhancement of La2O3 to Li-Mn/WO3/TiO2 for oxidative coupling of methane

Cheng, Fei; Yang, Jian; Yan, Liang; Zhao, Jing‐Tai; Zhao, Huahua; Song, Huanling; Chou, Ling Jun

doi:10.1016/j.jre.2019.03.023

Cited by 25 publications

(14 citation statements)

References 41 publications

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“…According to the C 1s spectra in Figure S4, a typical peak of carbonate species at 289.6 eV is evidently detected on the spectra of all the catalysts. Moreover, compared to LiNbO 3 and KNbO 3 , an extra O 1s peak located at 533.4 eV is evidently observed on NaNbO 3 , which is assignable to the electrophilic O 2 – species. − On the basis of these facts, three peaks respective to various oxygen anions, such as O 2– (∼529.5 eV), surface hydroxyl group −OH or CO 3 2– (∼531.5 eV), and O 2 – (∼533.4 eV) are deconvoluted and quantified in Table . − The surface lattice O 2– content of the A +1 Nb 5+ O 3 catalysts follows the order of LiNbO 3 > KNbO 3 > NaNbO 3 , which shows an opposite trend to their C 2 selectivity, implying that it may contribute to the deep oxidation reactions. Notably, the evident presence of the active superoxide O 2 – anions on NaNbO 3 catalysts could be one of the reasons to explain its optimal reaction performance.…”

Section: Resultssupporting

confidence: 64%

A⁺¹Nb⁵⁺O₃ (A = Li, Na, K) Perovskites with Different Fine Structures for Oxidative Coupling of Methane: Tracing the Crystalline Phase Effect on the Surface Active Sites

Gong

Zhang

et al. 2021

J. Phys. Chem. C

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Targeting to unravel the catalytic sites of some specific perovskites for OCM reaction, and elucidate the influences of crystal phase changes on the active sites, three A +1 Nb 5+ O 3 (A = Li, Na, K) complex oxides were synthesized in the pure phase. The reaction performance is ranked as NaNbO 3 > KNbO 3 > LiNbO 3 for the catalysts. It is revealed that LiNbO 3 possesses a hexagonal ilmenite-type phase, and NaNbO 3 and KNbO 3 possess orthorhombic and tetragonal perovskite phases, respectively. Due to the fine structure difference, NaNbO 3 and KNbO 3 have higher oxygen mobility than LiNbO 3 , as testified by the electric conductivity measurements. Moreover, the Nb−O bond strength of NaNbO 3 and KNbO 3 is much weaker than that of LiNbO 3 , which promotes also the oxygen mobility and phase transformation of the two samples, especially in the high temperature OCM process. As a result, more oxygen vacancies/defects are generated on NaNbO 3 and KNbO 3 , which facilitates the efficient formation of OCM active and selective surface O 2 − species and basic sites. Subsequently, the OCM performance of NaNbO 3 and KNbO 3 can be evidently improved. Combining the above advantages, NaNbO 3 exhibits the optimal OCM performance in all the samples.

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Section: Resultssupporting

confidence: 64%

A⁺¹Nb⁵⁺O₃ (A = Li, Na, K) Perovskites with Different Fine Structures for Oxidative Coupling of Methane: Tracing the Crystalline Phase Effect on the Surface Active Sites

Gong

Zhang

et al. 2021

J. Phys. Chem. C

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“…The NWTM‐CP sample possessed a much larger integrated peak area and a higher total basic sites amount (Table 1) for CO 2 desorption relative to the other samples. Several studies have suggested that a strong basic site can promote a high C 2+ selectivity and C 2+ yield 55‐57 . This is because a strong basic site is associated with active O 2− species that convert CH 4 into radical species.…”

Section: Resultsmentioning

confidence: 99%

“…Several studies have suggested that a strong basic site can promote a high C 2+ selectivity and C 2+ yield. [55][56][57] This is because a strong basic site is associated with active O 2− species that convert CH 4 into radical species. Therefore, it is possible that the NWTM-CP catalyst could produce a high C 2+ yield; this will be discussed later in the activity results.…”

Section: Resultsmentioning

confidence: 99%

Effect of surface treatment technique on properties and performance of Na₂WO₄‐TiO₂‐MnO_x/SiO₂ for oxidative coupling of methane

Chuntalap

Panchan

Junsomboon³

et al. 2021

J of Chemical Tech & Biotech

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BACKGROUND Oxidative coupling of methane (OCM) is a promising catalytic process for the conversion of methane to higher‐valued hydrocarbons (C2+). In this study, Na2WO4‐TiO2‐MnOx/SiO2 (NWTM) catalysts were obtained by various treatment techniques, including conventional calcine (CC, 800 °C), cold plasma (CP, 7 kV, 1 Hz), microwave radiation (MW, 800 °C), and electron beam radiation (EB, 4000 kGy), with no surface treatment (WT) as a benchmark method. RESULTS The results showed substantial differences in catalytic performance. The catalyst prepared by the cold plasma method provided the highest performance in the activity (20.91% C2+ yield with 48.04% C2+ selectivity and 43.52% CH4 conversion) at the early stage of testing (1–4 h). CONCLUSION However, the catalyst prepared by microwave radiation achieved the most stable active phases for the 24‐h testing period and yielded the highest C2+ for a five‐cycle reusability test. The catalyst prepared by electron beam radiation was found to have the lowest C2+ activity due to the poor distribution of the active elements. © 2021 Society of Chemical Industry (SCI).

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“…The adsorption of oxygen vacancies on oxygen could be detected by O 2 -TPD (Figure 7g). The absorption peaks of WO 2.9 , WO 2.72 , and WO 2 MVMOs at 360, 359, and 371 °C, respectively, could be attributed to the adsorption of lattice oxygen, 51 which indicated the conversion of nonchemometric tungsten oxide to WO 3 at high temperatures. However, the peaks of WO 3−x MVMOs between 79 and 121 °C belonged to the adsorption of oxygen.…”

Section: Anticorrosion Mechanismmentioning

confidence: 97%

Gradient Design of Vacancies and Their Positive Correlation with Electrochemical Anticorrosion Protection

et al. 2022

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The contribution of defects to electrochemistry is a controversial but practically applicable subject. Meanwhile, it is challenging to obtain precisely a certain nonchemometric single phase in mixed-valence compounds. The precise design of nonchemometric single-phase WO3–x (x = 0, 0.1, 0.28, and 1) mixed-valence metal oxides (MVMOs) was achieved by the gradient intrinsic reduction method, and the correlation between oxygen vacancies and electrochemical anticorrosion protection was explored systematically. Then, the decisive role of periodic oxygen vacancies in electrochemical anticorrosion was confirmed. And the origin was the synergistic reaction of oxygen vacancy-upgraded photocathodic protection, vacancy-induced passivation, and mixed-valence reductive protection, which were brought about by the high oxygen vacancy concentration. Integrating the above three aspects, the WO2.72 MVMO showed the best electrochemical anticorrosion performance by increasing the resistance value to 7.67 times that of the epoxy resin coating. The establishment of a positive correlation between oxygen vacancy and corrosion protection in WO3–x (x = 0, 0.1, 0.28, and 1) materials can not only guide the design of MVMOs but also make an important contribution to the rapid precorrosion performance of the materials.

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Enhancement of La2O3 to Li-Mn/WO3/TiO2 for oxidative coupling of methane

Cited by 25 publications

References 41 publications

A⁺¹Nb⁵⁺O₃ (A = Li, Na, K) Perovskites with Different Fine Structures for Oxidative Coupling of Methane: Tracing the Crystalline Phase Effect on the Surface Active Sites

A⁺¹Nb⁵⁺O₃ (A = Li, Na, K) Perovskites with Different Fine Structures for Oxidative Coupling of Methane: Tracing the Crystalline Phase Effect on the Surface Active Sites

Effect of surface treatment technique on properties and performance of Na₂WO₄‐TiO₂‐MnO_x/SiO₂ for oxidative coupling of methane

Gradient Design of Vacancies and Their Positive Correlation with Electrochemical Anticorrosion Protection

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Enhancement of La2O3 to Li-Mn/WO3/TiO2 for oxidative coupling of methane

Cited by 25 publications

References 41 publications

A+1Nb5+O3 (A = Li, Na, K) Perovskites with Different Fine Structures for Oxidative Coupling of Methane: Tracing the Crystalline Phase Effect on the Surface Active Sites

A+1Nb5+O3 (A = Li, Na, K) Perovskites with Different Fine Structures for Oxidative Coupling of Methane: Tracing the Crystalline Phase Effect on the Surface Active Sites

Effect of surface treatment technique on properties and performance of Na2WO4‐TiO2‐MnOx/SiO2 for oxidative coupling of methane

Gradient Design of Vacancies and Their Positive Correlation with Electrochemical Anticorrosion Protection

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A⁺¹Nb⁵⁺O₃ (A = Li, Na, K) Perovskites with Different Fine Structures for Oxidative Coupling of Methane: Tracing the Crystalline Phase Effect on the Surface Active Sites

A⁺¹Nb⁵⁺O₃ (A = Li, Na, K) Perovskites with Different Fine Structures for Oxidative Coupling of Methane: Tracing the Crystalline Phase Effect on the Surface Active Sites

Effect of surface treatment technique on properties and performance of Na₂WO₄‐TiO₂‐MnO_x/SiO₂ for oxidative coupling of methane