Editors: | F. Kongoli, F. Marquis, N. Chikhradze, T. Prikhna, M. De Campos, S. Lewis, S. Miller, S. Thomas. |
Publisher: | Flogen Star OUTREACH |
Publication Year: | 2022 |
Pages: | 290 pages |
ISBN: | 978-1-989820-68-1(CD) |
ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
The oxygen demand for medical and industrial needs grows over 6% annually from 2015, and it is estimated that the oxygen market will grow from $27.7 billion in 2019 to even $ 36.5 billion in 2030 [1]. According to The Business Research Company, this growth will be also driven by COVID-19 and the medical needs it imposes [1].
Today, most of the oxygen produced for large-scale industry needs is obtained by cryogenic distillation, which due to the high energy consumption of the liquefaction of gases from the air, is an expensive method [2]. A promising alternative to the cryogenic oxygen production technology is air separation by temperature-swing adsorption (TSA) where so-called oxygen storage materials (OSM) are used. OSMs can reversibly exchange a significant amount of oxygen between their structure and atmosphere.
In the last 2 decades, renewed interest in RMnO3+δ oxides appeared, in terms of their application as OSMs. Their main advantage (contrary to other groups of OSMs, [3]) is the ability to work in the temperature-swing mode at temperatures as low as 200-300 °C, which is promising from both, economical and construction points of view. However, until now most of those materials operated effectively only in pure O2 atmosphere, which is not applicable for oxygen production.
A significant breakthrough has come with the results of the recent research, as it was possible to design RMnO3+δ materials able to operate in air practically as effectively as in O2 atmosphere [4]. Also, some general rules were established in terms of designing such air-operating OSMs, like dependence of oxygen storage capacity (OSC) on ionic radius of R.
Nd-substituted Y1-xNdxMnO3+δ materials described in this work were synthesized via sol-gel auto-combustion method followed by several variations of annealing at elevated temperatures in different atmospheres. Crystal structure and phase composition of prepared powders were examined by means of X-ray diffractometry (XRD). Oxygen storage performance was evaluated using thermogravimetry. Structure and composition of oxidized samples were also investigated by XRD. Morphology of powders was examined by scanning electron microscopy.
It was established that proper modification of the preparation route of the Nd-substituted Y1-xNdxMnO3+δ can increase the OSC more than twice and greatly improve the rate of redox reactions. The laboratory-scale apparatus for oxygen separation from air via TSA was designed and constructed. Equipment was tested using the YMnO3+δ-based materials developed in this work.