Preparation of MnOx–CeO2–Al2O3 mixed oxides for NOx-assisted soot oxidation: Activity, structure and thermal stability
Preparation of MnOx–CeO2–Al2O3 mixed oxides for NOx-assisted soot oxidation: Activity, structure and thermal stability
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DOI：
10.1016/j.cej.2013.04.006
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发表时间：
2013-06
影响因子：
15.1
通讯作者：
Fangjian Lin;Xiaodong Wu;Shuang Liu;D. Weng;Yuying（黄宇营） Huang
中科院分区：
文献类型：
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作者：
Fangjian Lin;Xiaodong Wu;Shuang Liu;D. Weng;Yuying（黄宇营） Huang
通过在溶胶-凝胶法的不同阶段将 Al2O3 引入到 MnOx-CeO2 中，制备了三种 MnOx-CeO2-Al2O3 混合氧化物。通过将硝酸铝和氧化铝粉末分别添加到 Mn-Ce 前驱体溶液中得到 MnCeAl 和 MnCe/Al，而通过机械混合溶胶凝胶合成的 MnOx-CeO2 和 Al2O3 粉末得到 MnCe + Al。将催化剂在空气中于800℃下煅烧20小时，得到热老化样品。通过烟灰和NO程序升温氧化（烟灰-TPO和NO-TPO）、X射线衍射（XRD）、Brunauer-Emmett-Teller（BET）、扩展X射线吸收精细结构（EXAFS）、能量色散光谱（EDS）和H2程序升温还原（TPR）对催化剂进行了表征。与MnOx-CeO2混合氧化物相比，Al2O3的引入降低了新鲜催化剂的烟灰氧化活性，但在严格的老化处理后有助于保持相对较高的催化剂表面积和较高的MnOx分散度。在所制备的催化剂中，MnCe/Al表现出最高的热稳定性，老化后的烟灰氧化Tm小幅增加17°C。活性表面积是指MnOx在催化剂上的暴露面积，建议用于确定老化催化剂的NO氧化和烟灰氧化活性。
Three kinds of MnOx–CeO2–Al2O3mixed oxides were prepared by introducing Al2O3to MnOx–CeO2at different stages of a sol–gel method. MnCeAl and MnCe/Al were received by adding aluminum nitrate and alumina powders to the Mn–Ce precursor solution, respectively, while MnCe + Al was obtained by mixing the sol–gel-synthesized MnOx–CeO2and Al2O3powders mechanically. The catalysts were calcined in air at 800 °C for 20 h to obtain the thermally aged samples. The catalysts were characterized by soot and NO temperature-programmed oxidation (soot-TPO and NO-TPO), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), extended X-ray absorption fine structure (EXAFS), energy dispersive spectroscopy (EDS) and H2temperature-programmed reduction (TPR). The introduction of Al2O3degrades the soot oxidation activity of the fresh catalysts compared with MnOx–CeO2mixed oxides, but it helps to maintain relatively high catalyst surface area and high MnOxdispersion after the rigorous aging treatment. Among the catalysts prepared, MnCe/Al exhibits the highest thermal stability with a small increase ofTmby 17 °C for soot oxidation after aging. The active surface area, which refers to the exposure area of MnOxon the catalyst, is suggested to determine the NO oxidation and soot oxidation activities of the aged catalysts.