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题名: Amorphous features of working catalysts: XAFS and XPS characterization of Mn/Na2WO4/SiO2 as used for the oxidative coupling of methane
作者: Kou, Y;  Zhang, B;  Niu, JZ;  Li, SB;  Wang, HL;  Tanaka, T;  Yoshida, S
刊名: JOURNAL OF CATALYSIS
发表日期: 1998-01-25
卷: 173, 期:2, 页:399-408
收录类别: SCI
文章类型: Article
WOS标题词: Science & Technology ;  Physical Sciences ;  Technology
类目[WOS]: Chemistry, Physical ;  Engineering, Chemical
研究领域[WOS]: Chemistry ;  Engineering
英文摘要: Mn/Na2WO4/SiO2 catalyst for the oxidative coupling of methane has been investigated by using the L-edge and the K-edge XAFS and XPS, The surface of the fresh catalyst is found to be dominated by oxygen-enriched amorphous phases consisting of discretely distributed tetrahedral WO4 and octahedral MnO6 groups, The average bond lengths, which is 1.77 Angstrom for W-O and 2.00 Angstrom for Mn-O, are fully identical to those in pure Na2WO4 and Mn2O3. However, on the used catalyst after a 450 h run, almost no tungsten species is detectable. Instead, tetrahedral manganese sites are observed, The surface of the used catalyst is dominated by highly dispersed MnO4 groups consisting of tetrahedral and coordinatively unsaturated octahedral sites. The average Mn-O bond length increases to 2.09 Angstrom while the Mn 2P(3/2) binding energy increases from 641.4 eV (Mn3+) to 641.7 eV (Mn2+), These results suggest that the combination of tetrahedral and octahedral metallic cores with different oxidation states from each other is responsible for the catalysis in the oxidative coupling of methane, and that the high activity of the manganese-tungsten catalyst is due to the surface oxygen species, which are pre-activated from lattice oxygens to "the nearest oxygens" by the surface in an amorphous state. (C) 1998 Academic Press.
关键词[WOS]: RAY ABSORPTION-SPECTROSCOPY ;  COORDINATE GEOMETRY ;  EDGE SPECTROSCOPY ;  SILVER SURFACE ;  IRON CATALYST ;  OXIDE ;  EXAFS ;  COMPLEXES ;  XANES ;  ETHYLENE
语种: 英语
WOS记录号: WOS:000071846200015
Citation statistics: 
内容类型: 期刊论文
URI标识: http://cas-ir.dicp.ac.cn/handle/321008/138509
Appears in Collections:中国科学院大连化学物理研究所_期刊论文

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作者单位: 1.Chinese Acad Sci, Lanzhou Inst Chem Phys, State Key Lab Oxo Synth & Select Oxidat, Lanzhou 730000, Peoples R China
2.Chinese Acad Sci, Dalian Inst Chem Phys, State Key Lab Catalysis, Dalian 116023, Peoples R China
3.Kyoto Univ, Dept Mol Engn, Kyoto 60601, Japan

Recommended Citation:
Kou, Y,Zhang, B,Niu, JZ,et al. Amorphous features of working catalysts: XAFS and XPS characterization of Mn/Na2WO4/SiO2 as used for the oxidative coupling of methane[J]. JOURNAL OF CATALYSIS,1998,173(2):399-408.
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