Evaluation of Copper–Aluminum Oxides as Sorbents for High-Temperature Air Separation

Abstract

Oxygen production in an economic way is critical to oxy-firing combustion, a carbon capture technology. Oxygen-deficient oxides have been used for absorption of oxygen from air and desorption of oxygen in recycled flue gas for oxy-firing combustion. Cuprous/cupric oxide equilibrium with alumina can be used as an alternative for oxygen production and absorption. In this work, the effect of the spinel phase (CuAl2O4) content on oxygen sorptive/desorptive properties of CuO–CuAl2O4 sorbents has been investigated using thermogravimetric analysis. The desorption rate and oxygen sorption capacity were shown to be dependent upon the amount of alumina addition. The effect of SO2 and H2O in flue gas was investigated using FACTSage over a range of conditions. It was found that, at temperatures above 750 °C, CuO is inert to these species, making it a proper choice for oxygen carrier. Cyclic stability was also investigated using the same instrument. The molar CuAl2O4 content of 20% was observed to have the most positive cyclic stability effect. A stable morphology was observed in the scanning electron microscopy microstructure of the sorbent with this CuAl2O4 content. Sintering at a lower CuAl2O4 content and attrition because of second-phase agglomeration can destabilize the sorbents.