A new approach to study the gas-phase oxidation of toluene:: probing active sites in vanadia-based catalysts under working conditions

被引:33
作者
Brückner, A [1 ]
机构
[1] Inst Angew Chem Berlin Adlershof eV, D-12489 Berlin, Germany
关键词
selective oxidation; toluene; benzaldehyde; vanadyl pyrophosphate; vanadia; potassium doping; in situ-EPR; in situ-UV-VIS-DRS; in situ-XRD; in situ-XPS;
D O I
10.1016/S0926-860X(00)00639-6
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
Differently prepared vanadyl pyrophosphate and potassium-doped vanadia catalysts have been studied during the selective oxidation of toluene and p-methoxy toluene to the corresponding benzaldehydes using a portfolio of various in situ-methods (EPR, UV-VIS-DRS, XRD and XPS). The poor catalytic performance of (VO)(2)P2O7 is mainly due to strong product adsorption which is favoured by surface OH-groups formed under reaction conditions. This process can be partially suppressed by adding competitive adsorbates to the feed, in K-V2O5 catalysts, a potassium vanadate phase is formed on the surface in which about 25% of the vanadium ions are tetravalent. This leads to lower acidity and oxidation potential of the surface and, thus, to improved benzaldehyde selectivities. (C) 2000 Elsevier Science B.V. All rights reserved.
引用
收藏
页码:287 / 297
页数:11
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