Influence of surface composition of perovskite-type complex oxides on methane oxidative coupling

Ding, Weiping; Chen, Yi; Fu, Xiancai

doi:10.1016/0926-860x(93)80210-h

Cited by 25 publications

(21 citation statements)

References 27 publications

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“…As previously reported, the OCM reaction performance on perovskites is influenced by surface A/B-site molar ratios, preparation methods, heterovalent cation doping, and modification with metal oxides and halides. ,− Ding et al found that the surface enrichment by A-site elements on the ABO 3 compounds can improve the OCM performance, but the enrichment of the B-site elements leads to the complete oxidation of methane . Wu et al adjusted the surface chemical compositions of SrTiO 3 and found that the surface enrichment of Sr increased the methane conversion and C 2 product selectivity.…”

Section: Introductionmentioning

confidence: 91%

“…found that the surface enrichment by A-site elements on the ABO 3 compounds can improve the OCM performance, but the enrichment of the B-site elements leads to the complete oxidation of methane. 23 Wu et al adjusted the surface chemical compositions of SrTiO 3 and found that the surface enrichment of Sr increased the methane conversion and C 2 product selectivity. The reaction performance is positively correlated to the basic sites/acid sites ratio.…”

Section: Introductionmentioning

confidence: 99%

“…For perovskite catalysts with alkaline earth metals as the A-site cations, the chemisorbed O 2 − , O 2 2− and O − are regarded as the OCM reactive oxygen species. 16,18,23 Nevertheless, Jung et al have studied perovskite catalysts for OCM reaction. 14,32−37 They found that the oxygen ion conductivity is intimately related to its methane conversion for a perovskite catalyst, which is determined by the structure factors, including the tolerance factor and the cell free volume.…”

Section: Introductionmentioning

confidence: 99%

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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

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: Introductionmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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

Gong

Zhang

et al. 2021

J. Phys. Chem. C

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“…The data indicate that these perovskite‐type titanates have basicity and weak Lewis acidity. In addition, the acid–base properties of perovskite‐type titanates can be controlled by the counter cations . The controllable acid–base properties are expected to be useful towards the tailoring of finely tuned acid–base catalysts.…”

Section: Introductionmentioning

confidence: 99%

“…The controllable acid–base properties are expected to be useful towards the tailoring of finely tuned acid–base catalysts. However, to our knowledge, titanates have been seldom applied to acid–base reactions . Moreover, various metallates have been developed as acid–base catalysts.…”

Section: Introductionmentioning

confidence: 99%

Glucose Isomerization Using Alkali Metal and Alkaline Earth Metal Titanates

et al. 2017

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Glucose isomerization was performed using various titanate catalysts, which include SrTiO3, BaTiO3, CaTiO3, Na2Ti6O13, K2Ti6O13, and Sr3Ti2O7, prepared using a conventional solid‐phase method. Among the titanates, SrTiO3, CaTiO3, and Na2Ti6O13 offered a relatively high fructose yield (32 %) with a high selectivity (68–78 %). The yields are comparable to yields reported previously using a Sn‐modified BEA zeolite, which shows a high efficiency for glucose isomerization as a Lewis acid catalyst. A study of the mechanism of glucose isomerization on a SrTiO3 catalyst surface by using 1H NMR spectroscopy suggested that the titanates catalyze the isomerization as base catalysts. Thus, the effect of the basicity of the titanates on glucose isomerization was investigated in terms of the base quantity and strength. The analysis was performed by using an acid–base titration method and FTIR spectroscopy with CHCl3 as a probe molecule. It is proposed that glucose isomerization on the titanates depends not only on the base amount but also on the base strength.

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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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Influence of surface composition of perovskite-type complex oxides on methane oxidative coupling

Cited by 25 publications

References 27 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

Glucose Isomerization Using Alkali Metal and Alkaline Earth Metal Titanates

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

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Influence of surface composition of perovskite-type complex oxides on methane oxidative coupling

Cited by 25 publications

References 27 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

Glucose Isomerization Using Alkali Metal and Alkaline Earth Metal Titanates

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

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Product

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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

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