FTIR study of CO interaction with Ru/TiO2 catalysts
FTIR study of CO interaction with Ru/TiO2 catalysts
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DOI：
10.1006/jcat.1998.2038
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发表时间：
1998-06-10
影响因子：
7.3
通讯作者：
Che, M
中科院分区：
文献类型：
--
作者：
Hadjiivanov, K;Lavalley, JC;Che, M
通过 TPR 和 FTIR 光谱研究了离子交换法制备的 Ru/TiO2（锐钛矿）样品在不同温度下吸附的 CO。样品表面存在两种还原性不同的 Run+ 物质。样品和吸附的 CO 的红外光谱表明存在 RuO2 类相和 Run+（1 小于或等于 n 小于或等于 3）阳离子。负载的钌在 523 K 下用氢气处理后完全还原为 Ru-0。同时，大部分初始锐钛矿位点被释放用于交换。因此，Ru/TiO2 的第二次离子交换是可能的，这使得钌浓度加倍。还原后的 Ru/TiO2 催化剂上的低温 CO 吸附揭示了 Ru-0 位点以及裸露二氧化钛典型的不同位点的存在。在接近环境温度的情况下，CO 与 RuO 团簇相互作用，导致一些 Ru-Ru 键断裂并增加钌颗粒的分散度。在较高温度下，CO 在特定的 RuO 位点上解离，从而将一些 Ru-0 原子氧化为 Run+ 离子。随后，在这些后一种物质上吸附额外的CO分子后，形成Run+(CO)(3)物质。同时，在还原过程中释放的二氧化钛位点被重新占据。在通过 CO 接触改变分散体的 Ru/TiO2 催化剂上，在 523 K 下用氢气进一步还原导致金属分散体出现新的下降（类似于新还原的催化剂），表明金属烧结/分散体增加是可逆效应。当在氧化催化剂上进行CO吸附时，表面上会形成Run+(CO)(3)和Rum+(CO)(2)物质。所有这些现象在通过浸渍制备的Ru/TiO2（锐钛矿）催化剂上也观察到。结果仅在某些定量值上有所不同。 (C) 1998 年学术出版社。
A Ru/TiO2 (anatase) sample prepared by ion-exchange was studied by TPR and FTIR spectroscopy of CO adsorbed at different temperatures. Two kinds of Run+ species, differing in their reducibility, are present on the sample surface. The IR spectra of the sample and of CO adsorbed reveal the existence of a RuO2-like phase and Run+ (1 less than or equal to n less than or equal to 3) cations. The supported ruthenium is completely reduced to Ru-0 after treatment with hydrogen at 523 K. Simultaneously, a large part of the initial anatase sites are liberated for exchange. Therefore, a second ion-exchange of Ru/TiO2 is possible which allows to double ruthenium concentration. Low-temperature CO adsorption on the reduced Ru/TiO2 catalyst reveals the existence of Ru-0 sites as well as different sites typical of the bare titania. At temperatures close to the ambient one, CO interacts with the RuO clusters causing disruption of some Ru-Ru bonds and increase in dispersion of ruthenium particles. At higher temperatures, CO dissociates on particular RuO sites, thus oxidizing some Ru-0 atoms to Run+ ions. Subsequently, Run+(CO)(3) species are formed after adsorption of additional CO molecules on these latter species. Simultaneously, the titania sites that have been liberated during the reduction are re-occupied. On the Ru/TiO2 catalyst whose dispersion has been modified by CO contact, further reduction with hydrogen at 523 K leads to a new drop of the metal dispersion (similar to that of freshly reduced catalyst) showing that the metal sintering/increase in dispersion are reversible effects. When CO adsorption is performed on an oxidized catalyst, both Run+(CO)(3) and Rum+(CO)(2) species are formed on the surface. All these phenomena are also observed on the Ru/TiO2 (anatase) catalyst prepared by impregnation. The results differ only in some quantitative values. (C) 1998 Academic Press.