Microstructure and reactivity evolution of La Fe Al oxygen carrier for syngas production via chemical looping CH4CO2 reforming

Zhu, Yanyan; Sun, Xueyan; Liu, Weiwei; Xue, Peng; Tian, Mingzhen; Wang, Xiaodong; Ma, Xiaoxun; Zhang, Tao

doi:10.1016/j.ijhydene.2017.10.037

Cited by 35 publications

(28 citation statements)

References 58 publications

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“…For the Fe−Ce oxygen carrier as can be seen in Figure 8b, CH 4 conversion declined in the first 3 min because the unselective oxygen species leading to total oxidation was depleted quickly while the selective oxygen species causing partial oxidation was not supplied timely, which decreased the rapid consumption of methane. 14,35,36 Afterward, the CH 4 conversion of Fe−Ce increased and then decreased, which resulted from more and more oxygen being released and then available lattice oxygen tending to deplete, just like the Fe@Ce oxygen carrier shown in Figure 8a. The maximum CH 4 conversion (55.60%) in the 1st cycle appeared at 1 min due to quick release of highly active unselective oxygen.…”

Section: Methodsmentioning

confidence: 97%

A Ce–Fe Oxygen Carrier with a Core–Shell Structure for Chemical Looping Steam Methane Reforming

Yin

Wang

Sun

et al. 2020

Ind. Eng. Chem. Res.

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Chemical looping steam methane reforming (CLSMR) is capable of both syngas and hydrogen generation, and an oxygen carrier is a key issue for CLSMR. In this work, a core–shell-structured Fe@Ce oxygen carrier is presented. With iron oxide nanocores covered by a ceria shell, this oxygen carrier integrates the advantages of both superior ion conductivity of ceria and high oxygen storage capacity of iron oxide. The Fe@Ce oxygen carrier was investigated for CLSRM in a fixed bed with the uniform mixing structural Fe–Ce as a reference. The test results showed that the Fe@Ce oxygen carrier exhibited a higher yield of syngas and hydrogen, CO selectivity, and methane conversion in the long-time reduction process compared with the Fe–Ce oxygen carrier. This indicates that the core–shell oxygen carrier was capable of providing more selective oxygen, resulting from the CeO2 shell that could facilitate the migration and transport of oxygen ions between the iron oxide nanocore and the shell surface. CO selectivity and methane conversion were further improved along with the redox cycles for the core–shell oxygen carrier attributed to the enhancement of the conduction of oxygen ion mainly resulting from the increase of phase proportion of CeFeO3. The average amount of carbon deposition for Fe@Ce was only 28.7% of that for Fe–Ce, which led to higher-quality syngas (H2/CO close to 2) and higher-purity hydrogen. Superior resistance toward carbon deposition is attributed to excellent oxygen ion conductivity of the ceria shell. Rapid migration and supplement of oxygen ion prevent depletion of oxygen on the surface of particles. Besides, an Fe0 metal active site, which promotes decomposition of methane, is scarce on the surface of particles due to coverage of the CeO2 shell, leading to higher resistance toward carbon deposition.

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Section: Methodsmentioning

confidence: 97%

A Ce–Fe Oxygen Carrier with a Core–Shell Structure for Chemical Looping Steam Methane Reforming

Yin

Wang

Sun

et al. 2020

Ind. Eng. Chem. Res.

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“…The improvement of Figure in the fuel stage when cofeeding an oxidant with methane could be attributed to two mechanisms: (i) simultaneous redox reactions occur in the presence of the oxidant leading to the immediate restoration of the lattice oxygen in the reduced perovskite, , (ii) oxidant addition could also ensure simultaneous gasification of the deposited carbon to CO thus eliminating its negative effect on syngas quality (H 2 /CO ratio). An additional experiment was performed by cofeeding CO 2 and CH 4 (50% molar fractions each) for more than 12 h (Figure ), which demonstrated that syngas production could be sustained continuously with only a very small drop (<5%) in the conversion of CH 4 .…”

Section: Resultsmentioning

confidence: 99%

Combined Syngas and Hydrogen Production using Gas Switching Technology

Ugwu

Zaabout

Donat

et al. 2021

Ind. Eng. Chem. Res.

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This paper focuses on the experimental demonstration of a three-stage GST (gas switching technology) process (fuel, steam/CO 2 , and air stages) for syngas production from methane in the fuel stage and H 2 /CO production in the steam/CO 2 stage using a lanthanum-based oxygen carrier (La 0.85 Sr 0.15 Fe 0.95 Al 0.05 O 3 ). Experiments were performed at temperatures between 750–950 °C and pressures up to 5 bar. The results show that the oxygen carrier exhibits high selectivity to oxidizing methane to syngas at the fuel stage with improved process performance with increasing temperature although carbon deposition could not be avoided. Co-feeding CO 2 with CH 4 at the fuel stage reduced carbon deposition significantly, thus reducing the syngas H 2 /CO molar ratio from 3.75 to 1 (at CO 2 /CH 4 ratio of 1 at 950 °C and 1 bar). The reduced carbon deposition has maximized the purity of the H 2 produced in the consecutive steam stage thus increasing the process attractiveness for the combined production of syngas and pure hydrogen. Interestingly, the cofeeding of CO 2 with CH 4 at the fuel stage showed a stable syngas production over 12 hours continuously and maintained the H 2 /CO ratio at almost unity, suggesting that the oxygen carrier was exposed to simultaneous partial oxidation of CH 4 with the lattice oxygen which was restored instantly by the incoming CO 2 . Furthermore, the addition of steam to the fuel stage could tune up the H 2 /CO ratio beyond 3 without carbon deposition at H 2 O/CH 4 ratio of 1 at 950 °C and 1 bar; making the syngas from gas switching partial oxidation suitable for different downstream processes, for example, gas-to-liquid processes. The process was also demonstrated at higher pressures with over 70% fuel conversion achieved at 5 bar and 950 °C.

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“…Interestingly, magnetoplumbite (MP) La‐hexaaluminate structure was maintained even after deeper reduction, which was quite different from the OCs reported previously where phase transformation usually occurred. For instance, the repeated phase separation occurred over Fe 2 O 3 /α‐Al 2 O 3 , and LaFe x Al 1‐x O 3 perovskites accompanied by the appearance of metallic Fe and FeAl 2 O 4 , which resulted in serious CH 4 pyrolysis [60] . On the contrary, undestroyed hexaaluminate structure favored the improvement of the CH 4 reactivity of LF3 A owing to unnecessary to overcome the energy barrier for rearrangement of La, Fe, Al, and O atoms, and the reservation of textures thus long‐term durability.…”

Section: Oxygen Carriersmentioning

confidence: 99%

Recent Advances of Oxygen Carriers for Chemical Looping Reforming of Methane

et al. 2021

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This review discussed recent advances of oxygen carriers (OCs) for chemical looping reforming (CLR) of CH4 which aims to generate high‐quality syngas, an important chemical intermediate for the synthesis of chemicals and fuels. We firstly introduced CLR and that combined with CO2 and H2O splitting as well as clarified their advantages over conventional reforming processes. Then we reviewed the latest advances of metal‐based OCs, composite OCs including perovskites and hexaaluminates, and catalytic OCs, namely oxygen‐containing materials with catalytically metal sites, during the past five years. Specific discussion focused on the influence of composition, surface, and bulk structure of these OCs on conversion, selectivity, and lattice oxygen reactivity to summarize design and optimization strategies of the tailored OCs. Finally, a brief summary and an outlook on some of the scientific challenges and suggestions for future investigations on the development of outstanding OCs for CLR of CH4 are given.

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Microstructure and reactivity evolution of La Fe Al oxygen carrier for syngas production via chemical looping CH4CO2 reforming

Cited by 35 publications

References 58 publications

A Ce–Fe Oxygen Carrier with a Core–Shell Structure for Chemical Looping Steam Methane Reforming

A Ce–Fe Oxygen Carrier with a Core–Shell Structure for Chemical Looping Steam Methane Reforming

Combined Syngas and Hydrogen Production using Gas Switching Technology

Recent Advances of Oxygen Carriers for Chemical Looping Reforming of Methane

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