A‐ and B‐site Codoped SrFeO3 Oxygen Sorbents for Enhanced Chemical Looping Air Separation

Dou, Henri; Krzystowczyk, Emily; Wang, Xijun; Robbins, Thomas R.; Ma, Liang; Liu, Xingbo; Li, Fanxing

doi:10.1002/cssc.201902698

Cited by 60 publications

(91 citation statements)

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“…SCFC7391-CP) only leads to decrease in oxygen capacity ( figure 1 and table 1). Doping of Ca causes distortion of perovskite structure and creates oxygen vacancies even in the presence of 20% O 2 , which possibly leads to smaller oxygen capacity observed [46]. The effect of cobalt is also examined by comparing the oxygen capacity at 400 • C-700 • C. As illustrated in figure 2, all the oxygen sorbents with various cobalt loading demonstrate a similar volcano shaped trend with respect to operating temperature.…”

Section: Resultsmentioning

confidence: 95%

“…The sample was denoted as SCFC8246-SSR. The procedure of preparing sol-gel sample was similar as previously reported [46].…”

Section: Introductionmentioning

confidence: 99%

“…The versatile structure of SrFeO 3 offers many opportunities to introduce dopants at A and/or B site to further tuning the redox property [43][44][45]. By co-doping of Ca and Co at A and B sites respectively, oxygen partial pressure swing can be operated between 0.05 and 0.2 atm to achieve 1 wt% oxygen capacity at 400 • C-500 • C based on our recent study [46]. The SCFC sorbent is very robust and stable for up to 2000 cycles in the presence of 1% H 2 O.…”

Section: Introductionmentioning

confidence: 99%

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Sr_1-xCa_xFe_1-yCo_yO_3-δ as facile and tunable oxygen sorbents for chemical looping air separation

et al. 2020

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Chemical looping air separation (CLAS) is a promising technology for oxygen generation with high efficiency. The key challenge for CLAS is to design robust oxygen sorbents with suitable redox properties and fast redox kinetics. In this work, perovskite-structured Sr 1-x Ca x Fe 1-y Co y O 3 oxygen sorbents were investigated and demonstrated for oxygen production with tunable redox properties, high redox rate, and excellent thermal/steam stability. Cobalt doping at B site was found to be highly effective, 33% improvement in oxygen productivity was observed at 500 • C. Moreover, it stabilizes the perovskite structure and prevents phase segregation under pressure swing conditions in the presence of steam. Scalable synthesis of Sr 0.8 Ca 0.2 Fe 0.4 Co 0.6 O 3 oxygen sorbents was carried out through solid state reaction, co-precipitation, and sol-gel methods. Both co-precipitation and sol-gel methods are capable of producing Sr 0.8 Ca 0.2 Fe 0.4 Co 0.6 O 3 sorbents with satisfactory phase purity, high oxygen capacity, and fast redox kinetics. Large scale evaluation of Sr 0.8 Ca 0.2 Fe 0.4 Co 0.6 O 3 , using an automated CLAS testbed with over 300 g sorbent loading, further demonstrated the effectiveness of the oxygen sorbent to produce 95% pure O 2 with a satisfactory productivity of 0.04 g O2 g sorbent −1 h −1 at 600 • C.

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Section: Resultsmentioning

confidence: 95%

“…The sample was denoted as SCFC8246-SSR. The procedure of preparing sol-gel sample was similar as previously reported [46].…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Sr_1-xCa_xFe_1-yCo_yO_3-δ as facile and tunable oxygen sorbents for chemical looping air separation

et al. 2020

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“…Perovskite‐based ABO 3 oxygen carriers have garnered much attention in the past decade for their rapid kinetics and resilience during repeated uptake/release cycling due to the limited structural rearrangement that occurs during oxygen gain/loss [1–24] . The efficacy of a perovskite oxygen carrier is dependent upon the identity of both the A‐ and B‐site elements chosen, with common options of Ba, Sr, Ca, and La on the A‐site, and Fe, Co, and Mn on the B‐site [1–8] .…”

Section: Introductionmentioning

confidence: 99%

Investigation of Sr_0.7Ca_0.3FeO₃ Oxygen Carriers with Variable Cobalt B‐Site Substitution

et al. 2021

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A‐site and B‐site substitutions are effective methods towards improving well‐studied oxygen carrier materials that are vital for emerging gasification technologies. Such materials include SrFeO3, which greatly benefits from the inclusion of calcium and/or cobalt, and Sr0.8Ca0.2Fe0.4Co0.6O3 has been regarded as the best‐performing composition. In this study, systems with higher calcium and lower cobalt contents are investigated with a view to lessening the societal and economic burdens of these dual‐doped carriers. Density functional theory calculations are performed to illustrate the Fe−O bonding and relaxation contributions to the oxygen vacancy formation energy in Sr1‐xCaxFe1‐yCoyO3 systems (x=0.1875, 0.25, 0.3125; y=0.125, 0.25, 0.375, 0.5) and determine that increased calcium A‐site substitution requires the use of less cobalt B‐site doping to reach the same oxygen vacancy formation. These findings are experimentally validated in situ and ex situ characterization of bulk Sr0.7Ca0.3Fe1‐yCoyO3 materials. Sr0.7Ca0.3Fe0.7Co0.3O3 is found to have similar O2 adsorption/desorption rates and storage capacity to Sr0.8Ca0.2Fe0.4Co0.6O3 in air/N2 cycling experiments. Additionally, both materials are outperformed by Sr0.7Ca0.3Fe1‐yCoyO3 systems with y=0–0.10 at 400–500 °C, which cycle 1.5 wt% O2 in under ten minutes.

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“…2MxOy-1 + O2 → 2MxOy (2) For most oxygen carrier materials, reaction (2) is exothermic except for a few perovskite-type oxides. [2,3] The overall enthalpy change of the CLC process is equal to that of the conventional combustion process, but the use of a solid oxygen carrier to transfer oxygen from air to the fuel avoids the direct contact between air and the fuel. Consequently, the costs associated with the cryogenic separation of oxygen from air (conventional oxy-combustion process) or CO 2 from the flue gas (post-combustion CO2 capture processes) are avoided in CLC, thereby significantly lowering the overall CO2 capture costs.…”

Section: Introductionmentioning

confidence: 99%

Preventing Agglomeration of CuO-Based Oxygen Carriers for Chemical Looping Applications

Imtiaz¹,

Armutlulu²,

Donat³

et al. 2021

Preprint

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Chemical looping combustion (CLC) is a promising alternative to the conventional combustion-based, fossil fuel conversion processes. In CLC, a solid oxygen carrier is used to transfer oxygen from air to a carbonaceous fuel. This indirect combustion route allows for effective CO2 capture since a sequestrable stream of CO2 is inherently produced without any need for energy-intensive CO2 separation. From a thermodynamic point of view, CuO is arguably one of the most promising oxygen carrier candidates for CLC. However, the main challenge associated with the use of CuO for CLC is its structural instability at the typical operating temperatures of chemical looping processes, leading to severe thermal sintering and agglomeration. To minimize irreversible microstructural changes during CLC operation, CuO is commonly stabilized by a high Tammann temperature ceramic, e.g., Al2O3, MgAl2O4, etc. However, it has been observed that a high Tammann temperature support does not always provide a high resistance to agglomeration. This work aims at identifying descriptors that can be used to characterize accurately the agglomeration tendency of CuO-based oxygen carriers. CuO-based oxygen carriers supported on different metal oxides were synthesized using a Pechini method. The cyclic redox stability and agglomeration tendency of the synthesized materials was evaluated using both a thermo-gravimetric analyser and a lab-scale fluidized bed reactor at 900 °C using 10 vol. % H2 in N2 as the fuel and air for re-oxidation. In order to study the diffusion of Cu(O) during redox reactions, well-defined model surfaces comprising thin films of Cu/CuO and two different supports, viz. ZrO2 or MgO, were prepared via magnetron sputtering. Energy dispersive X-ray (EDX) spectroscopy on focused ion beam (FIB)-cut cross-sections of the thin films revealed that Cu atoms have a tendency to diffuse outward through most of the films of the support material under redox conditions. The support that inhibits the outward movement of Cu(O), i.e. avoiding the presence of low melting Cu on the oxygen carrier surface, is found to provide the highest agglomeration resistance. The support MgO was found to possesses such diffusion characteristics.

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A‐ and B‐site Codoped SrFeO₃ Oxygen Sorbents for Enhanced Chemical Looping Air Separation

Abstract: Supporting Information and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

Cited by 60 publications

References 50 publications

Sr_1-xCa_xFe_1-yCo_yO_3-δ as facile and tunable oxygen sorbents for chemical looping air separation

Sr_1-xCa_xFe_1-yCo_yO_3-δ as facile and tunable oxygen sorbents for chemical looping air separation

Investigation of Sr_0.7Ca_0.3FeO₃ Oxygen Carriers with Variable Cobalt B‐Site Substitution

Preventing Agglomeration of CuO-Based Oxygen Carriers for Chemical Looping Applications

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A‐ and B‐site Codoped SrFeO3 Oxygen Sorbents for Enhanced Chemical Looping Air Separation

Abstract: Supporting Information and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

Cited by 60 publications

References 50 publications

Sr1-xCaxFe1-yCoyO3-δ as facile and tunable oxygen sorbents for chemical looping air separation

Sr1-xCaxFe1-yCoyO3-δ as facile and tunable oxygen sorbents for chemical looping air separation

Investigation of Sr0.7Ca0.3FeO3 Oxygen Carriers with Variable Cobalt B‐Site Substitution

Preventing Agglomeration of CuO-Based Oxygen Carriers for Chemical Looping Applications

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Product

Resources

About

A‐ and B‐site Codoped SrFeO₃ Oxygen Sorbents for Enhanced Chemical Looping Air Separation

Sr_1-xCa_xFe_1-yCo_yO_3-δ as facile and tunable oxygen sorbents for chemical looping air separation

Sr_1-xCa_xFe_1-yCo_yO_3-δ as facile and tunable oxygen sorbents for chemical looping air separation

Investigation of Sr_0.7Ca_0.3FeO₃ Oxygen Carriers with Variable Cobalt B‐Site Substitution