ZrO2-Supported CuO Oxygen Carriers for Chemical-Looping with Oxygen Uncoupling (CLOU)

The chemical-looping combustion (CLC) and chemical-looping with oxygen uncoupling (CLOU) processes are novel solutions for efficient combustion with inherent separation of carbon dioxide. In this work, oxygen carriers based on CuO supported by zirconia (ZrO2) and stabilized by calcia (CaO), magnesia (MgO) and ceria (CeO2) are investigated. The oxygen carriers were produced by freeze-granulation and calcined at 950 and 1050 °C. Their chemical-looping performance was evaluated in a laboratory-scale fluidized-bed reactor at 900 and 925 °C under cyclic oxidizing, inert (N2) and reducing (CH4) conditions. Five out of six oxygen carriers exhibited rapid release of oxygen in the inert environment (CLOU). Also, complete conversion of methane was obtained for three out of the six oxygen carriers. However, only in the case of MgO-stabilized ZrO2 as support and calcined at 950 °C, the oxygen carrier exhibited intact active CuO phase; agglomeration and particle fragmentation were also not observed. Thus, the use of this material could be suggested as a suitable oxygen carrier for the CLOU process.