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Effects of Activation Atmospheres on Structure and Activity of Mo-based Catalyst for Synthesis of Higher Alcohols
Ji-long Zhou,Wei Xie,Song Sun,Li-li Ji,Li-rong Zheng,Chen Gao,Jun Bao
Author NameAffiliationE-mail
Ji-long Zhou National Synchrotron Radiation Laboratory, Collaborative Innovation Center of Chemistry for Energy Materials, University of Science and Technology of China, Hefei 230029, China  
Wei Xie National Synchrotron Radiation Laboratory, Collaborative Innovation Center of Chemistry for Energy Materials, University of Science and Technology of China, Hefei 230029, China  
Song Sun National Synchrotron Radiation Laboratory, Collaborative Innovation Center of Chemistry for Energy Materials, University of Science and Technology of China, Hefei 230029, China baoj@ustc.edu.cn 
Li-li Ji National Synchrotron Radiation Laboratory, Collaborative Innovation Center of Chemistry for Energy Materials, University of Science and Technology of China, Hefei 230029, China  
Li-rong Zheng Institute of High Energy Physics, Chinese Academy of Science, Beijing 100039, China  
Chen Gao National Synchrotron Radiation Laboratory, Collaborative Innovation Center of Chemistry for Energy Materials, University of Science and Technology of China, Hefei 230029, China;CAS Key Laboratory of Materials for Energy Conversion, Department of Materials Science and Engineering, University of Science and Technology of China, Hefei 230026, China  
Jun Bao National Synchrotron Radiation Laboratory, Collaborative Innovation Center of Chemistry for Energy Materials, University of Science and Technology of China, Hefei 230029, China;CAS Key Laboratory of Materials for Energy Conversion, Department of Materials Science and Engineering, University of Science and Technology of China, Hefei 230026, China suns@ustc.edu.cn 
Abstract:
Activated carbon supported Mo-based catalysts were prepared and reduced under different activation atmospheres, including pure H2, syngas (H2/CO=2/1), and pure CO. The catalysts structures were characterized by X-ray diffraction, X-ray absorption fine structure, and in situ diffuse reflectance infrared Fourier transform spectroscopy. The catalytic performance for the higher alcohol synthesis from syngas was tested. The pure H2 treatment showed a high reduction capacity. The presence of a large amount of metallic Co0. and low valence state Moφ+ (0<φ<2) on the surface suggested a super activity for the CO dissociation and hydrogenation, which promoted hydrocarbons formation and reduced the alcohol selectivity. In contrast, the pure CO-reduced catalyst had a low reduction degree. The Mo and Co species at the catalyst mainly existed in the form of Mo4+ and Co2+. The syngas-reduced catalyst showed the highest activity and selectivity for the higher alcohols synthesis. We suggest that the syngas treatment had an appropriate reduction capacity that is between those of pure H2 and pure CO and led to the coexistence of multivalent Co species as well as the enrichment of Moδ+ on the catalyst's surface. The synergistic effects between these active species provided a better cooperativity and equilibrium between the CO dissociation, hydrogenation and CO insertion and thus contributed beneficially to the formation of higher alcohols.
Key words:  Higher alcohol synthesis  Activation mechanism  in situ diffuse reflectance infrared Fourier transform spectroscopy  Mo-based catalyst  Syngas
FundProject:This work was supported by the National Natu-ral Science Foundation of China (No.11179034 and No.11205159), the National Basic Research Program of China (No.2012CB922004).
活化气氛对钼基合成醇催化剂的结构和性能的影响
周纪龙,谢威,孙松,姬丽丽,郑黎荣,高琛,鲍骏
摘要:
制备了活性炭担载的钼基催化剂,采用三种不同的活化气氛对催化剂进行还原. 还原气包括纯氢,合成气(H2/CO=2/1),纯CO. 催化剂结构利用X射线衍射(XRD)、X射线吸收的精细结构光谱(XAFS) 和原位的漫反射傅里叶变换红外光谱(in-situ DRIFTS)表征. 活化后催化剂低碳醇合成性能经过测试. 纯氢具有最强的还原能力,导致催化表面生成更多的低价态的Moφ+(0<φ<2)物种和Co金属,CO的解离和氢化活性过高,促进了烃的生成而降低了醇的选择性. 相比之下,CO还原的催化剂的还原程度相对弱,Mo、Co物种主要以Mo4+和Co2+形式存在. 合成气还原的催化剂表现最佳的低碳醇合成活性和选择性. 这说明合成气具有介于H2和CO之间的合适还原能力,导致催化剂表面丰富的Moδ+物种和多种价态的Co物种共存. 这些物种之间的协同作用,平衡了CO解离、加氢和CO插入反应活性,因而促进了低碳醇的生成.
关键词:  低碳醇合成  活化机理  原位漫反射傅里叶变换红外光谱  钼基催化剂  合成气
DOI:10.1063/1674-0068/29/cjcp1603038
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