SrCo_xFe_1–xO_3−δ Oxygen Sorbent Usable for High-Temperature Pressure-Swing Adsorption Process Operating at Approximately 300 °C

Abstract

Oxygen sorption/desorption properties of SrCo x Fe1–x O3−δ were examined as an oxygen sorbent for a high-temperature pressure-swing adsorption (HT-PSA) process. Perovskite-type structure of the SrCo x Fe1–x O3−δ powder samples was observed in the composition range of 0 ≤ x ≤ 0.85, by using XRD measurements. A temperature-programmed-desorption (TPD) measurement revealed that the oxygen desorption temperature in N2 for the perovskite-type SrCo x Fe1–x O3−δ samples was lowered with increasing x. Consequently, the oxygen desorption temperature of the SrCo0.85Fe0.15O3−δ sample exhibited around 300 °C, which was the lowest of those of the examined samples. A high-temperature X-ray diffraction (HT-XRD) measurement suggested that the oxygen desorption of SrCo0.85Fe0.15O3−δ in N2 occurred, accompanying the phase transition from perovskite-type structure to brownmillerite structure. Isothermal oxygen sorption/desorption behavior of the SrCo x Fe1–x O3−δ samples was examined by means of thermogravimetric analysis (TGA). As a result, it was confirmed that the amount of sorbed oxygen for the SrCo0.85Fe0.15O3−δ sample gave 11.7 cm3 g–1 at 300 °C, which was larger than that (8.6 cm3 g–1) for a benchmark oxygen sorbent (La0.1Sr0.9Co0.9­Fe0.1O3−δ). In order to obtain oxygen-enriched air by using the SrCo0.85­Fe0.15O3−δ pellet sample as the oxygen sorbent, the oxygen separation from synthetic air was carried out by using a small-scale PSA apparatus equipped with a vacuum pump. It was confirmed that the 45 vol % oxygen-enriched air was obtained even at 300 °C, by using this apparatus.

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

“…Recently, SrFeO 3 based oxygen sorbents have received many research interests, owing to its large oxygen capacity and low operating temperature [40][41][42]. 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].…”

Structural and thermodynamic study of Ca A- or Co B-site substituted SrFeO3−δ perovskites for low temperature chemical looping applications

“…In fact, perovskite-type materials have been studied intensively in the past years for a wide range of applications, including thermochemical water splitting, SOFC and high temperature pressure swing adsorption (HT-PSA). [27][28][29][30][31] The basic crystal structure of perovskites is cubic (Pm% 3m), although deviations in their composition (e.g. by cation substitution) can generate distortions of the ideal cubic lattice structure.…”

“…27 When the complete reduction of the perovskite ABO 3 occurs, it transforms to its defect-ordered variant brownmillerite (ABO 2.5 ), with an orthorhombic basic crystal structure (Ibm2). 27 29,32 For example, Mishra et al 33 performed DFT studies on the effect of dopants such as Sr and Fe in CaMnO 3 and found that the dopants enhance the O 2 donation properties of the material through a distortion of the lattice structure and changes in the oxygen coordination.…”

“…28 In addition, substitution of the B-site of SrFeO 3 with Co was investigated by Ikeda et al and they found that the substitution of 85% of Fe with Co allows the release of O 2 at temperatures as low as 300 1C instead of 600 1C for the unsubstituted SrFeO 3Àd . 29 Dou et al 38 recently showed that the A-and B-site co-substitution in SrFeO 3 of Sr and Fe by Ca and Co, respectively, lowers the activation energy of oxygen diffusion and surface oxygen exchange i.e. faster redox kinetics compared to the unsubstituted perovskite.…”

“…Motivated by the promising results reported by Miura et al 28 and Ikeda et al, 29 we focused in our study on the thermodynamic and structural analysis of Ca A-site or Co B-site substituted SrFeO 3 (Sr 1Àx Ca x FeO 3Àd and SrFe 1Àx Co x O 3Àd , 0 r x r 1) aiming at elucidating changes in the chemical-physical properties (i.e. OSC, thermodynamics, structural stability) upon substitution.…”