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学科主题: 物理化学
题名: Effects of redox property and morphology of nanostructure MnxCe1-xO2 mixed oxides on soot oxidation
作者: Sun SM(孙淑敏) ;  Chu WL(楚文玲) ;  Yang WS(杨维慎)
会议名称: A Pre-conference of the 14th International Congress on Catalysis
会议日期: 2008-7-9
出版日期: 2008-07-09
会议地点: 中国
通讯作者: Weishen Yang
主办者: 大连化学物理研究所
摘要: Particulate matter(mainly soot) is the main pollutant in diesel engine emission, one of the most effective methods to eliminate the particulate matter is to use an oxidation catalyst which promotes soot catalytic combustion at the rather low temperature (below 400oC ). For this purpose, a series of MnxCe1-xO2 (x=0.01, 0.03, 0.05, 0.1, 0.2, 0.3, 0.5, 1) catalysts for soot combustion were prepared using citric acid combustion method (CA). The catalysts were characterized with XRD, BET, H2-TPR, XPS, SEM and TEM. Potential catalyst in the soot oxidation is evaluated by temperature-programmed oxidation under tight contact in the fixed bed reactor with a fed gas containing O2. The results revealed that all the mixed oxides show better catalytic activity for the soot combustion reaction than the individual oxides. Furthermore, it can be found that the mixed oxides of x=0.05-0.3 exhibited the best catalytic activity, in which the maximum soot combustion rate is obtained at 312 oC. Especially, the soot can be burned completely before 378oC and a nearly 100% selectivity to CO2 production was observed if the ratio of soot/catalyst=1/9. The XRD diffraction patterns of all mixed oxides showed only the signals of the CeO2 cubic fluorite structure and no diffraction peaks of Mn2O3 are detected. And the shrinkage of lattice of CeO2 further identified that the Mn3+ had been dissolved into the lattice of CeO2. The results of H2-TPR showed that the reduction of Mn2O3 and surface CeO2 in the mixed oxides is modified, which is thought to be beneficial to the soot combustion because the redox property has been improved in the low temperature. Thus, it is evident that the catalytic activity for the soot combustion is related to the reducibility of the mixed oxides due to the synergetic effect between CeO2 and Mn2O3, and the presence of high-valance Mn species in the mixed oxides are beneficial to the synergetic effect. As noted above, the soot combustion is a complicated solid-solid-gas reaction and the intrinsic redox property of the catalyst play a key role in the reaction, while good contact between soot particles and catalyst is an indispensable condition for an active catalyst in soot combustion. In order to investigate the effect of morphology on the catalytic activity, the other Mn0.05Ce0.95O2 catalyst was synthesized by coprecipitation method (CP). Mn0.05Ce0.95O2 catalyst prepared by CA was found to be more active than its counter part though the results of XRD and TEM show the two samples prepared by CA and CP had the similar crystal size about 10nm. In particular, H2-TPR also revealed that no obvious difference was observed for the reduction characters. But from the SEM pictures, it can be seen that the sample prepared by CA is more spongy and owns more pores than the sample prepared by CP, which are due to the large amount of gaseous species emitted during the synthesis. Because the microstructure (pores and foam of nano-sized crystal) is particularly suitable for maximizing the number of contact points between the soot particles and the catalysts, the catalyst prepared by CA have more active points to catalyze the soot combustion and exhibited higher catalytic activity.
语种: 中文
内容类型: 会议论文
URI标识: http://cas-ir.dicp.ac.cn/handle/321008/112986
Appears in Collections:中国科学院大连化学物理研究所_会议论文

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Recommended Citation:
Sun SM,Chu WL,Yang WS. Effects of redox property and morphology of nanostructure MnxCe1-xO2 mixed oxides on soot oxidation[C]. 见:A Pre-conference of the 14th International Congress on Catalysis. 中国. 2008-7-9.
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