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学科主题: 物理化学
题名: Influence of reducing atmosphere on nano-structure and activity of Mo-V-Te-Nb-O catalysts for propane selective oxidation
作者: Deng ZH(邓忠华) ;  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
部门归属: 五室
主办者: 大连化学物理研究所
摘要: Due to the abundance and low cost, the light alkanes are widely used as starting materials for the industrial production of many oxygenates by oxidation processes. Recently discovered Mo-V-Te-Nb-O has received a great attention because of high activity and selectivity in the selective oxidation to acrylic acid. And it is well known that two phases, so-called orthorhombic M1 and hexagonal M2 phases, are indispensable for a highly effective catalyst. However, there are ongoing debates about the origin of the high catalytic performance of Mo-V-Te-Nb-O catalysts. For this reason, in this study, the reductant, namely ammonium chloride, was added to the solution containing Mo-V-Te-Nb-O to adjust the proportion between M1 and M2 phase. Further, catalysts with different reductant concentrations were characterized by XRD, XPS, XRF, H2-TPR, SEM and BET and their catalytic behavior for propane selective oxidation to acrylic acid were investigated. Our findings indicate that only the M1 phase was observed for the catalyst without reductant; with an increase in reductant/Mo ratio to 0.05, the M2 phase began to appear and especially Mo8O23 was also observed when the ratio was further increased to 0.2, supporting the conclusion that the existence of the reductant is responsible for the transformation of phase structure of the catalysts. It was found that,with the addition of the reductant, M1 phase would be transformed into M2 phase during calcination by reacted with α-TeVO4,which could be formed in the precursor by adding NH4Cl to the solution. In addition, results of XPS and XRF showed that the addition of reductant has no obvious influence on the composition of elements in the bulk of catalysts, but the slight enrichment of surface Nb element was observed. Especially, it was found that the existence of reductant led to the sharp decrease in the ratio of surface V5+/V4+, which has been confirmed to have an important influence on the catalytic activity of propane oxidation. Furthermore, H2-TPR results revealed that, upon the addition of the reductant, consumption peaks of H2 raised from 892K to 936K, showing the obvious weaken on the reactivity of lattice oxygen Finally, according to our results obtained from the propane oxidation to acrylic acid, it can concluded that M1 phase content has direct relation with activity of catalysts, the more is the M1 phase content, the more active are the catalysts. And the ratio of V5+/V4+ on the surface and reactivity of lattice oxygen are also found to be important factors that can affect the activity of catalysts.
语种: 中文
内容类型: 会议论文
URI标识: http://cas-ir.dicp.ac.cn/handle/321008/112990
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:
Deng ZH,Chu WL,Yang WS. Influence of reducing atmosphere on nano-structure and activity of Mo-V-Te-Nb-O catalysts for propane selective oxidation[C]. 见:A Pre-conference of the 14th International Congress on Catalysis. 中国. 2008-7-9.
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