Experimental Study of Transition Metal-Doped Cu-Based Oxygen Carrier for Chemical Looping with Oxygen Uncoupling

The Cu-based oxygen carrier exhibits promising potential in the chemical looping with oxygen uncoupling (CLOU) process, wherein its performance is significantly influenced by the characteristics of oxygen release and cyclic reaction stability. In this work, a series of Cu-based oxygen carriers doped with transition metals (Ti, Y, Zr, and Ce) were synthesized by using the sol-gel combustion method and impregnation method. The microstructure, phase structure, O₂ desorption, and cyclic reaction of Cu-based oxygen carriers were studied by experiments. The results show that (1) the doped element loading rate, specific surface area, average pore size, and pore volume of the oxygen carrier prepared by the sol-gel combustion method surpass those achieved through the impregnation method; (2) Ce doping formed a solid solution with CuO and CuAl₂O₄ without altering the main crystal phases, while Zr, Ti, and Y doping resulted in the formation of distinct phases; (3) the doped samples exhibit superior oxygen release performance compared to the undoped ones, with Ce-doped carriers demonstrating the highest level of performance; and (4) the cycling stability of Cu-based oxygen carriers is significantly enhanced by Ce doping. The aforementioned results collectively demonstrate the remarkable efficacy of Ce doping as a highly effective modification technique for Cu-based oxygen carriers. Furthermore, the sol-gel combustion method emerges as a superior method for preparing doped oxygen carriers.