Chemical-looping steam methane reforming over macroporous CeO_2-ZrO_2 solid solution: Effect of calcination temperature

摘要

Chemical-looping steam methane reforming (CL-SMR) is a novel process for the co-production of pure hydrogen and syngas without purification processes. A series of CeO_2-ZrO_2 mixed oxides were prepared by colloidal crystal templating method with calcination temperature increasing from 450 to 850℃. The structural characteristic and reducibility of CeO_2-ZrO_2 oxygen carriers were investigated by SEM, XRD and TPR techniques and correlated to their reactivity for CL-SMR. The CeO_2-ZrO_2 mixed oxides calcined at low temperatures (e.g., 450℃) exhibit a better uniform and three-dimensionally ordered macroporous structure, which enhance the mobility of oxygen species, improving the reducibility of CeO_2-ZrO_2 oxygen carriers. The ordered macroporous structure can lead to a high reactivity for CL-SMR, especially for the hydrogen production in water splitting reaction. It was found that the Ce-Zr-450 sample showed the best performance for H_2 production. After ten redox CL-SMR cycles at 800℃, the Ce-Zr-450 sample still maintained relatively high hydrogen yield and the three-dimensionally ordered macroporous structure remained in good condition, indicating high reactivity and structural stability.