Oxygen Storage Capability of Brownmillerite-type Ca₂AlMnO_5+δ and Its Application to Oxygen Enrichment

The oxygen storage capability was investigated for Ca₂(Al_<i>x</i>Mn_1–<i>x</i>)₂O_5+δ (0.50 ≤ <i>x</i> ≤ 0.67) with a Brownmillerite-type structure. This oxide can store/release a large amount of excess oxygen (∼3.0 wt %) topotactically in response to variations in temperature and the surrounding atmosphere in a highly reversible manner. The capacity and response of oxygen storage are remarkable only in the vicinity of <i>x</i> = 0.50, that is, Ca₂AlMnO_5+δ, and rapidly deteriorated as the Al content increases. Owing to the high sensitivity in terms of oxygen nonstoichiometry, Ca₂AlMnO_5+δ exhibits oxygen intake/release ability when temperature swing between 500 and 700 °C is applied. With this characteristic feature of this oxide, a facile method for oxygen enrichment is demonstrated

Ultrafast Continuous-Flow Synthesis of Crystalline Microporous Aluminophosphate AlPO₄‑5

Crystalline microporous materials have been typically synthesized by long-time hydrothermal treatment in a batch reactor, which suffers from drawbacks like frequent start-up and shut-down operations and low energy efficiency. The development of a continuous flow process for the synthesis of crystalline microporous materials is extremely challenging due to the slow crystallization of the microporous materials. In this work, we demonstrate the continuous flow synthesis of an important crystalline microporous aluminophosphate material, AlPO₄-5. The continuous synthesis of AlPO₄-5 was achieved by combining the seed-assisted method with a continuous flow reactor that could provide a much higher heating rate. The results showed that single phase AlPO₄-5 was obtained after one-minute synthesis in the continuous flow reactor. A stable continuous process was maintained, because any hydrodynamic failure from the precipitation of the solid product could be minimized thanks to the ultrafast synthesis and the small particle size of the AlPO₄-5 product. In addition, the reuse of the product from the continuous flow synthesis as a seed is demonstrated. This easily designed, efficient route can result in the significant cost and energy savings and thus has huge potential for the industrial-level production of AlPO₄-5 crystals in the future