CeO_2-MnO_x催化剂形貌对低浓度甲烷催化燃烧反应性能的影响

Morphological effect of CeO_2-MnO_x catalyst on their catalytic performance in lean methane combustion

采用水热合成法制备了船形、扁球形及纳米片CeO_2-MnO_x复合氧化物。并运用低温N2吸脱附、XRD、SEM、TEM、H2-TPR、拉曼光谱、XPS等表征技术对不同形貌CeO_2-MnO_x复合氧化物的结构与其低浓度CH4催化燃烧反应性能之间的关系进行了关联。结果表明,CeO_2-MnO_x复合氧化物的形貌与其催化性能密切相关。其中,扁球形CeO_2-MnO_x复合氧化物的氧空位、Ce3+含量及表面吸附活性氧物种最多,其CH4催化燃烧反应活性最高,540℃时,可将CH4完全转化;其次是船形CeO_2-MnO_x复合氧化物催化剂,540℃时其CH4转化率为94.05%;与前两者相比,纳米片CeO_2-MnO_x复合氧化物催化剂的氧空位及表面吸附活性氧物种较少,活性较差,相同反应温度下,其CH4转化率仅为89.68%。

Ship-like,oblate spheroid and nano sheet CeO2-MnOxmixed oxides were prepared by hydrothermal method and characterized by N2 sorption, XRD, SEM, TEM, H2-TPR, Raman spectra and XPS. The relationship between the structure of CeO2-MnOxand their catalytic performance in lean methane combustion were then investigated. The results reveal that the catalytic performance of the mixed CeO2-MnOxoxide was greatly depended on its morphology. Among all of the samples,the mixed oblate spheroid CeO2-MnOxoxides with most oxygen vacancies,Ce3＋content and surface active oxygen exhibited the highest activity in lean methane combustion,with a complete CH4 conversion at 540 ℃. Following it,the mixed ship-like CeO2-MnOx oxides catalyst had 94.05% of the CH4 conversion at 540 ℃. On the contrast,the mixed nano sheet CeO2-MnOx oxides catalyst presented the lowest catalytic activity with only 89. 68% CH4 conversion at the same reaction temprature owing to its lower oxygen vacancies and surface active oxygen.