论文部分内容阅读
采用水热法合成了系列Ce1-XMnXO2-a-T(X=0.0,0.1,0.2,0.3,0.5,0.7,0.9,1.0;T表示焙烧温度),T=500,650,800℃)复合氧化物催化剂用于甲烷的催化燃烧。通过XRD、N2吸/脱附、TG-DSC、UV-Vis-DRS和TPR表征手段研究了不同组成催化剂的物理化学性质及其对甲烷催化燃烧活性。结果表明,在500℃焙烧的情况下Mn进入CeO2晶格形成均相固溶体催化剂的最大取代值为0.7,而当Mn继续增加时则出现Mn2O3晶相偏析,同时各催化剂具有较高的比表面积;随着焙烧温度的升高,进入CeO2晶格的Mn最大取代值逐渐减少,650和800℃时分别为0.5和0.3,且比表面积相应降低。Ce1-XMnXO2-a-800催化剂的还原行为大致呈现三阶段,即为Mn2O3→Mn3O4的还原(340～420℃),Mn3O4→MnO的还原(420～480℃)和体相氧化铈的还原(700～900℃),且Mn的引入整体上提高了催化剂的可还原能力。甲烷催化燃烧活性评价结果表明,比表面积并非影响催化剂活性的主要因素,影响催化剂甲烷催化活性的主要因素为催化剂的组成、可还原能力和焙烧温度;而其中以Ce0.3Mn0.7O2-a-800催化剂表现出较高的甲烷催化燃烧活性,在甲烷转化率为10%和90%时的温度分别为430和613℃。进一步考察Ce0.3Mn0.7O2-a在不同温度(500、650、800和1000℃)焙烧后的催化活性表明,随着焙烧温度的提高催化剂催化活性降低。
A series of Ce1-XMnXO2-aT (X = 0.0,0.1,0.2,0.3,0.5,0.7,0.9,1.0; T represents calcination temperature), T = 500,650,800 ℃ were synthesized by hydrothermal method. Catalytic combustion. The physicochemical properties of the catalysts with different compositions and their catalytic activities for methane combustion were studied by means of XRD, N2 adsorption / desorption, TG-DSC, UV-Vis-DRS and TPR characterization. The results show that the maximum substitution of Mn into CeO2 lattice is about 0.7 when calcined at 500 ℃ and the Mn2O3 phase segregation occurs when Mn continues to increase. Meanwhile, each catalyst has high specific surface area. With the increase of the calcination temperature, the maximum substitution of Mn into the CeO2 lattice decreased gradually, which were 0.5 and 0.3 at 650 and 800 ℃ respectively, and the specific surface area decreased accordingly. The reduction behavior of Ce1-XMnXO2-a-800 catalyst shows roughly three stages: the reduction of Mn2O3 → Mn3O4 (340-420 ℃), the reduction of Mn3O4 → MnO (420-480 ℃) and the reduction of bulk cerium oxide ~ 900 ℃), and the introduction of Mn improves the catalytic reducibility as a whole. The results of methane catalytic combustion showed that the specific surface area was not the main factor affecting the catalyst activity. The main factors influencing the catalytic activity of methane were catalytic composition, reducibility and calcination temperature. Among them, Ce0.3Mn0.7O2-a-800 The catalysts showed higher methane catalytic combustion activity at temperatures of 430 and 613 ° C at methane conversion of 10% and 90%, respectively. Further investigation of the catalytic activity of Ce0.3Mn0.7O2-a calcined at different temperatures (500, 650, 800 and 1000 ° C) showed that the catalytic activity of the catalyst decreased as the calcination temperature increased.