Designed oxygen carriers from macroporous LaFeO3 supported CeO2 for chemical-looping reforming of methane

Abstract

Chemical-looping reforming of methane (CLRM) offers an effective approach for coproducing syngas and pure hydrogen. In this work, CeO2 nano particles (2–3nm) are well dispersed on the wall surface of three-dimensional ordered macroporous (3DOM) LaFeO3, obtaining a highly efficient oxygen carrier for the CLRM technology. The physical and chemical properties of the oxygen carriers were characterized by SEM, TEM, H2-TPR, XPS, XRD, CH4-TPR and CH4-TPD techniques. It is found that the presence of CeO2 on LaFeO3 results in the formation of Ce3+ and Fe2+ due to the CeO2-LaFeO3 interaction. The coexistence of Ce3+ and Fe2+ irons induces abundant oxygen vacancies on the mixed oxides, which strongly improves the reducibility, oxygen mobility and reactivity for methane oxidation. The presence of CeO2 also improves the resistance towards carbon deposition formation, and this allows the CeO2/LaFeO3 materials own high available oxygen storage capacity (available OSC, the maximum amount of oxygen consumed by methane reduction without the formation of carbon deposition). It is also noted that the agglomeration of CeO2 nano particles would reduce the reactivity of oxygen carriers. Among all the obtained samples, the 10% CeO2/LaFeO3 sample exhibits the highest yields of syngas (9.94mmolg−1) and pure hydrogen (3.38mmolg−1) without the formation of carbon deposition, which are much higher than that over the pure LaFeO3 sample (5.73mmolg−1 for syngas yield and 2.00mmolg−1 for hydrogen yield). In addition, the CeO2/LaFeO3 oxygen carrier also showed high stability during the successive CLRM testing either in the activity (yields of syngas and pure hydrogen) or structure (macroporous frameworks) aspect.