La2O2CO3-Induced phase composition oscillation in La–Cu mixed oxides during repeated catalytic soot combustion

Abstract

La–Cu mixed oxides, denoted as LaCuO-x (x = 500, 650 and 800), were prepared by calcination at 500, 650 and 800 °C, respectively, with the same precursor. It was found that fresh LaCuO-x catalysts exhibit various phase compositions, and different phase evolutions occur in LaCuO-x during the repeated soot combustion tests. In particular, an interesting reversible phase evolution, i.e., La₂O₂CO₃ + CuO ↔ La₂CuO₄ + CO₂, was observed in LaCuO-500 or -650. Various characterization methods including XRD, XPS, soot/CO/H₂-TPR, and thermal analysis, together with verification tests were designed and conducted to unveil the reasons behind the phase oscillation. A plausible mechanism was further proposed, emphasizing the vital role of La₂O₂CO₃-catalyzed CO formation in the phase oscillation in the repeated soot combustion tests.