Stabilization of Brownmillerite-Type SrCoO_2.5 by a Cost-Effective Quenching Method for Oxygen-Scavenging Applications

Abstract

Brownmillerite (BM)-type oxide sorbents have gained attention recently for producing oxygen-enriched streams. Herein, a cost-effective method of quenching with the use of an Al foil pad is adapted for the synthesis of brownmillerite SrCoO 2.5 . The oxygen storage capacity of this oxide has been investigated using a simple home-built volumetric setup. The oxygen-rich phase was formed by a pressurized heat-treatment of a BM sample. The oxygen storage capacity of the sample has been calculated from the pressure change during desorption. The effect of oxygen pressure on the amount of oxygen stored inside the sample has also been evaluated. Furthermore, selective absorption of oxygen is confirmed by performing the absorption in compressed air. The results indicate that 15.28 cm 3 O 2 g −1 can be stored in the sample at STP. The change in oxygen content in SrCoO 2.5+δ varied reversibly up to a δ value of 0.26, which is confirmed by iodometric titration. It is shown that the new method of quenching proposed does not deteriorate the oxygen storage property of the material.

Rare earth barium cobaltites: potential candidates for low-temperature oxygen separation

“…The oxygen intake/release properties of the samples were measured using a home-built volumetric setup (3) reported elsewhere [14]. The temperatures of absorption/ desorption obtained from TGA were used as reference in the intake/release measurements with volumetric setup.…”

“…It was held isothermal for 1 hour at 723 K to make sure that desorption was complete. The pressure change due to oxygen evolution was converted to volume of oxygen which can be reversibly incorporated into the material [14]. Representative desorption curves of the absorbed samples are given in Fig.…”

“…A number of new oxygen storage materials have been discovered in recent years [6,[9][10][11][12][13][14][15][16][17][18][19][20]. The oxygen intake/ release in these non-stoichiometric oxygen storage oxides takes place through the following steps [21], (1) oxygen molecules are diffused to the surface, (2) dissociative adsorption through electron transfer, (3) diffusion of the oxide ions from surface to the lattice through an activated hopping mechanism.…”

“…A reversible oxygen intake/release was observed for DyBaCo 2 O 6−x at 873 K [28] by switching the atmosphere O 2 ∕N 2 , while for YBaCo 2 O 6−x it is 673 K by switching the atmosphere O 2 ∕H 2 [16]. Third is the easiness in synthesis of the rare earth barium cobaltites, it does not need special reduction treatments or quenching to stabilize the required phase compared to other oxygen storage materials explored [9,14,17,18]. Also, the intake/ release observed with a switching of atmosphere O 2 ∕N 2 rather than O 2 ∕H 2 emphasizes the use of these materials for enriched oxygen stream production.…”

“…In this study, relationship between the size of rare earth cation and oxygen intake temperature has been established on the three above mentioned samples synthesized through solid state reaction. Oxygenation/deoxygenation of the samples were characterized using a home-built volumetric setup reported elsewhere [14], thermogravimetric analysis, room temperature X-ray diffraction experiments and iodometric titration. Linear thermal expansion and morphology of the samples before and after the oxygen intake/release were measured to know the changes in the sample, if any, brought about by the redox reactions.…”