A study of the oxidative coupling of methane over SrO-La2O3/CaO catalysts by using CO2 as a probe

Xu, Yide; Lin, Yu Chuan; Cai, Chen; Huang, Jia-Sheng; Guo, Xiexian

doi:10.1007/bf00807178

Cited by 37 publications

(32 citation statements)

References 14 publications

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“…It is considered as one of the promising ethylene production processes (Galadima and Muraza, 2016;Taifan and Baltrusaitis, 2016). Previous publications (Le Van, 1993;Lacombe et al, 1995;Xu et al, 1995), including our recent in situ studies, indicated that La 2 O 3 is not stable in this reaction (Liu et al, 2018;Li et al, 2019;Guan et al, 2021;Pang et al, 2021;Zhou et al, 2021). In our recent studies, it was strongly suggested that a high temperature (800°C) precleaned sample surface, which is free of carbonates and hydroxyls, is enriched with a specific subsurface peroxide species (Zhou et al, 2021).…”

Section: Introductionmentioning

confidence: 74%

“…However, with high concentration (usually >10%) of CO x as the reaction byproducts, the La 2 O 3 sample is generally found forming, at least partially, surface and bulk La 2 O 2 CO 3 (Le Van, 1993). With such conditions, the reaction selectivity and activity are found to be reduced (Xu et al, 1995;Guan et al, 2021). In addition, hydroxyl is also found to be easily formed (Li et al, 2019).…”

Section: Introductionmentioning

confidence: 91%

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An In Situ Temperature-Dependent Study of La2O3 Reactivation Process

et al. 2021

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Lanthanum-containing materials are widely used in oxidative catalytic and electrocatalytic reactions such as oxidative coupling of methane (OCM) and solid oxide fuel cells (SOFCs). However, many of these materials are highly susceptible to air contamination which means ex situ characterization results generally cannot be associated with their reactivity. In this study, the activation processes of an in situ–prepared bulk La2O2CO3 sample and an ex situ as-prepared La(OH)3 sample are in situ investigated by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and online mass spectroscopy (MS). Results indicate that the La2O2CO3 sample, during linear heating to 800°C, always contains some carbonates near the surface region, which supports a two-step model of bulk carbonate decomposition through surface sites. The La(OH)3 sample structure evolution is more complex due to contaminations from air exposure. Together with TGA results, online mass analysis of water and CO2 signal loss showed that three major catalyst structure phase change steps and a preheating up to 800°C are required for the as-prepared material to be transferred to La2O3. This process is carefully investigated combining the three in situ methodologies. XPS and XRD data further reveal transformations of variety of in situ surface structures and forms including hybrid phases with hydroxyl, carbonates, and oxide as the sample heated to different temperatures within the range from 200 to 800°C. The results provide useful insights on the activation and deactivation of La-contained materials.

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Section: Introductionmentioning

confidence: 74%

Section: Introductionmentioning

confidence: 91%

An In Situ Temperature-Dependent Study of La2O3 Reactivation Process

et al. 2021

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“…57 The bands around 1550 and 1600 cm −1 can be assigned to the asymmetric stretches of bidentate carbonate. 57,58 In Figure 7b for the results obtained at 500 °C, the bands around 1400 cm −1 is assigned to monodentate carbonate with symmetric stretches and the bands around 1550 and 1600 cm −1 can be attributed to the asymmetric stretches of bidentate carbonate. 57,58 The band around 1700 cm −1 can be attributed to bridging carbonate.…”

Section: Resultsmentioning

confidence: 96%

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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“…So far, neither stability nor reactivity of supported carbonates can be comprehensively assessed from either literature data or ab initio calculations. As a matter of fact, the functions that have been attributed to carbonates in literature range from deactivation of catalysts [30,31] to promotion of catalytic activity [32]. The OCM performance data reported in literature were often obtained at the reaction conditions that varied significantly between different catalysts, i.e.…”

Section: Introductionmentioning

confidence: 99%

Oxide-supported carbonates reveal a unique descriptor for catalytic performance in the oxidative coupling of methane (OCM)

Wang

Schmack

Sokolov

et al. 2022

Preprint

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The oxidative coupling of methane (OCM) is a promising reaction for direct conversion of methane to higher hydrocarbons. The reaction can be performed over oxide-based catalysts with very diverse elemental composition. Yet, despite decades of research, no general common structure-activity relationship has been deduced. Our recent statistical meta-analysis across a wide range of catalyst compositions reported in the literature suggested that only the catalysts combining thermodynamically stable (under reaction conditions) carbonate and thermally stable oxide support exhibit good catalytic performance. Guided by these findings we explore now experimentally correlations between descriptors for structure, stability and decomposition behavior of supported metal carbonates vs. the materials’ respective performance in OCM catalysis. In this study, carbonates of Rb, Cs and Mg were supported on oxides of Sm, Y, Gd, Ce, Sr and Ba, tested in OCM and studied by IR spectroscopy and thermal analysis. From the evaluation of six proposed property-descriptors we derive a statistically robust volcano-type correlation between the onset temperature of carbonate decomposition and the C2 yield, indicating the importance of CO2 adsorption and surface carbonates in selective methane conversion. Moreover, we discuss mechanisms that can account for the observed property-performance correlation across a wide range of OCM catalysts. Carbonate species are suggested to block highly reactive sites during OCM catalysis, which reduces overoxidation and enables the formation of C2 products.

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A study of the oxidative coupling of methane over SrO-La2O3/CaO catalysts by using CO2 as a probe

Cited by 37 publications

References 14 publications

An In Situ Temperature-Dependent Study of La2O3 Reactivation Process

An In Situ Temperature-Dependent Study of La2O3 Reactivation Process

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

Oxide-supported carbonates reveal a unique descriptor for catalytic performance in the oxidative coupling of methane (OCM)

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A study of the oxidative coupling of methane over SrO-La2O3/CaO catalysts by using CO2 as a probe

Cited by 37 publications

References 14 publications

An In Situ Temperature-Dependent Study of La2O3 Reactivation Process

An In Situ Temperature-Dependent Study of La2O3 Reactivation Process

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

Oxide-supported carbonates reveal a unique descriptor for catalytic performance in the oxidative coupling of methane (OCM)

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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