Effect of coal ash on the performance of CuO@TiO2-Al2O3 in chemical looping with oxygen uncoupling

For the chemical looping with oxygen uncoupling (CLOU) process that fueled with coal, the release of the gaseous O2 or the mobility of the lattice oxygen can be suppressed by coal ash deposition on the surface of the oxygen carrier (OC) or weakened by the interaction between the active phase of the OC and coal ash. In this work, we aim to identify the potential effects of coal ash on the performance of CuO@TiO2-Al2O3 OC in CLOU. Over 50 redox cycles, the CO2 yield was attained in the range of 92.1%–99.6%, indicating the stable redox reactivity of the CuO@TiO2-Al2O3 OC. According to the XRD results, Ca was found to be deposited on the surface of the OC in the form of Ca2Al2SiO7. However, a close-grained ash shell was avoided to cover the surface of OC due to the continuously gaseous O2 by CuO. In addition, stable active phases (CuO and CuAl2O4) were detected in both of the fresh and used samples. Moreover, the consumption of CuO was avoided by the formation of CaSO4 and Ca2Al2SiO7. At last, the uniform distribution of Fe2O3 was detected and accumulated on the OC, which also act as the active phase of the OC.