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

Abstract

Chemical looping air separation (CLAS) is a promising technology for oxygen generation with high efficiency. The key challenge for CLAS is to design robust oxygen sorbents with suitable redox properties and fast redox kinetics. In this work, perovskite-structured Sr1-xCaxFe1-yCoyO3 oxygen sorbents were investigated and demonstrated for oxygen production with tunable redox properties, high redox rate, and excellent thermal/steam stability. Cobalt doping at B site was found to be highly effective, 33% improvement in oxygen productivity was observed at 500 ◦C. Moreover, it stabilizes the perovskite structure and prevents phase segregation under pressure swing conditions in the presence of steam. Scalable synthesis of Sr0.8Ca0.2Fe0.4Co0.6O3 oxygen sorbents was carried out through solid state reaction, co-precipitation, and sol-gel methods. Both co-precipitation and sol-gel methods are capable of producing Sr0.8Ca0.2Fe0.4Co0.6O3 sorbents with satisfactory phase purity, high oxygen capacity, and fast redox kinetics. Large scale evaluation of Sr0.8Ca0.2 Fe0.4Co0.6O3, using an automated CLAS testbed with over 300 g sorbent loading, further demonstrated the effectiveness of the oxygen sorbent to produce 95% pure O2 with a satisfactory productivity of 0.04 gO2 gsorbent−1 h−1 at 600 ◦C.