An operando Raman study of structure and reactivity of alumina-supported molybdenum oxide catalysts for the oxidative dehydrogenation of ethane

被引:104
作者
Christodoulakis, A.
Heracleous, E.
Lemonidou, A. A.
Boghosian, S. [1 ]
机构
[1] Univ Patras, Dept Chem Engn, Patras 26500, Greece
[2] FORTH, ICE, HT, Patras 26500, Greece
[3] Univ Thessaloniki, Dept Chem Engn, GR-54006 Thessaloniki, Greece
[4] CPERI, CERTH, GR-54006 Thessaloniki, Greece
关键词
in situ Raman spectra; ethane ODH; molecular structure; molybdena active sites; MoO3/Al2O3; catalysts; anchoring bonds;
D O I
10.1016/j.jcat.2006.05.024
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
The structural and catalytic properties of supported MoO3/Al2O3 catalysts with Mo surface densities, n(s), in the range 1.1-12.5 Mo/nm(2) were studied for the oxidative dehydrogenation of ethane by in situ Raman spectroscopy with simultaneous catalytic measurements at temperatures of 400-550 degrees C. Isolated mono-molybdates (MoO4) and polymolybdates are formed at various proportions (depending on the loading) on the catalyst surface under dehydrated conditions; bulk Al-2(MoO4)(3) crystals are formed at ns exceeding the monolayer. Under reactive environment (C2H6/O-2), the Raman features attributed to Mo=O and Mo-O-Mo modes appear to be perturbed, indicating that surface MoOx species are reduced to lower valence states. The combined information on catalyst structure under reaction conditions and catalytic data shows a concurrence between the trends for activity per Mo (turnover frequency [TOF]) and for the number of Mo-O-Al bonds per Mo as a function of ns. The catalytic activity is related to the anchoring Mo-O-support bonds. Structure-activity/selectivity relations are derived and discussed. (c) 2006 Elsevier Inc. All rights reserved.
引用
收藏
页码:16 / 25
页数:10
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