An A- and B-Site Substitutional Study of SrFeO3-δ Perovskites for Solar Thermochemical Air Separation.

Tyler P Farr,Peter G Loutzenhiser,H Evan Bush,Andrea Ambrosini,Nhu Pailes Nguyen

doi:10.3390/ma13225123

Tyler P Farr, Peter G Loutzenhiser + Show 3 more

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https://doi.org/10.3390/ma13225123

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Abstract

An A‑ and B‑site substitutional study of SrFeO3−δ perovskites (A’xA1−xB’yB1−yO3−δ, where A = Sr and B = Fe) was performed for a two‑step solar thermochemical air separation cycle. The cycle steps encompass (1) the thermal reduction of A’xSr1−xB’yFe1−yO3−δ driven by concentrated solar irradiation and (2) the oxidation of A’xSr1−xB’yFe1−yO3−δ in air to remove O2, leaving N2. The oxidized A’xSr1−xB’yFe1−yO3−δ is recycled back to the first step to complete the cycle, resulting in the separation of N2 from air and concentrated solar irradiation. A-site substitution fractions between 0 ≤ x ≤ 0.2 were examined for A’ = Ba, Ca, and La. B-site substitution fractions between 0 ≤ y ≤ 0.2 were examined for B’ = Cr, Cu, Co, and Mn. Samples were prepared with a modified Pechini method and characterized with X-ray diffractometry. The mass changes and deviations from stoichiometry were evaluated with thermogravimetry in three screenings with temperature- and O2 pressure-swings between 573 and 1473 K and 20% O2/Ar and 100% Ar at 1 bar, respectively. A’ = Ba or La and B’ = Co resulted in the most improved redox capacities amongst temperature- and O2 pressure-swing experiments.

Highlights

N2 is an industrial gas with a wide array of chemical and medical applications, including in the production of ammonia via the Haber–Bosch process [1]
Current practice to obtain N2 employs cryogenic air separation to compress and liquefy the air followed by distillation to separate O2 and
The best cryogenic separation processes operate with energy demands three times higher than the thermodynamic minimum energy required for N2 /O2 separation [2]

Summary

Introduction

N2 is an industrial gas with a wide array of chemical and medical applications, including in the production of ammonia via the Haber–Bosch process [1]. Current practice to obtain N2 employs cryogenic air separation to compress and liquefy the air followed by distillation to separate O2 and. Pressure-swing adsorption is another air separation process utilizing activated carbon, but with the limitation of not producing high-purity N2 [3,4]. Inorganic membranes provide energy-efficient and scalable means of gas separation but are often tailored towards CO2 , with little effectiveness for air separation [5]. Chemical looping air separation relies on reversible reduction/oxidation (redox) reactions to cyclically adsorb O2 from the air to produce high-purity N2 [6]

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