Improvement of oxygen uncoupling properties of copper-based composite oxygen carriers for chemical-looping air separation

To increase the oxygen concentration in the product gas of a Chemical-Looping Air Separation (CLAS) system, it is important to reduce the oxygen uncoupling temperature of the oxygen carrier (OC). In this paper, it is investigated whether and to what extent the addition of Mn2O3, Co3O4, Pb3O4 and Cr2O3, which all have oxygen uncoupling propensity according to thermodynamics, to CuO improves the oxygen uncoupling behavior of the mixed-oxide OC at lower temperatures. With thermogravimetric analyses, it is shown that the oxygen uncoupling temperature of a Cu-Mn composite OC is decreased with approximately 200 °C relative to a Cu OC. In addition, the oxygen transport capacity of this composite OC can reach up to 0.056 g O2 / g OC. Density functional theory calculations have been carried out to analyze the changes in reactivity and stability of the mixed oxide OC. When a Mn3O4 (001) surface adsorbs a Cu4O4 cluster, the average bond length of Cu-O in the Cu4O4 cluster increases from 1.983 A to 2.047 A and charge...