Vanadium oxide monolayer catalysts. 3. A Raman spectroscopic and temperature-programmed reduction study of monolayer and crystal-type vanadia on various supports
Vanadium oxide monolayer catalysts. 3. A Raman spectroscopic and temperature-programmed reduction study of monolayer and crystal-type vanadia on various supports
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DOI：
10.1021/j100458a023
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发表时间：
1980-10
期刊：
影响因子：
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通讯作者：
F. Roozeboom;Mc Mittelmeijer-Hazeleger;J. Moulijn;J. Medema;V. D. Beer;P. Gellings
中科院分区：
文献类型：
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作者：
F. Roozeboom;Mc Mittelmeijer-Hazeleger;J. Moulijn;J. Medema;V. D. Beer;P. Gellings
通过X-射线荧光、X-射线衍射、特别是结合拉曼光谱和程序升温还原（TPR）分别对7-Al 2 O3、GO 2、Cr 2 O3、SiO 2、TiO 2和ZrO 2负载的氧化钒（V）进行了定性和定量结构分析。通过离子交换和湿浸渍法制备催化剂。的V含量范围从-1至40重量%V。在低表面浓度下，只有表面钒酸盐相的二维字符观察到所有载体。根据拉曼和TPR数据，这些表面钒酸盐物种的结构是独立的制备技术。在中等和高表面浓度下，网状浸渍的样品已经含有结晶V2 Ob。在相同的表面浓度下，离子交换的催化剂不含V2 O 5微晶。例外的是SiO2，在这两种制备技术中在其上也形成结晶V2 O 6。对于热处理的单层稳定性以AZO>3 TiO 2> CeO 2的顺序降低，其中在加热离子交换的V/SiO2时，结晶V2 O 6在二氧化硅表面上展开。用TPR法测定的离子交换催化剂的还原性可作为氧化钒与载体氧化物之间接触相互作用的量度。在500-800 K的温度下，这种相互作用的范围从与二氧化钛的强到与作为载体的二氧化硅的弱。
Vanadium(V) oxide supported on 7-A1203, GO2, Cr2O3, Si02, Ti02, and Zr02 was studied by X-ray fluorescence, by X-ray diffraction, and especially by the combination of Raman spectroscopy and temperature-programmed reduction (TPR) for qualitative and quantitative structural analysis, respectively. Catalysts were prepared via ion-exchange and wet-impregnation methods. The V contents ranged from - 1 to 40 wt % V. At low surface concentrations only surface vanadate phases of two-dimensional character are observed for all carriers. According to Raman and TPR data the structure of these surface vanadate species is independent of the preparation technique. At medium and high surface concentrations, the webimpregnated samples already contain crystalline V20b At equal surface concentrations the ion-exchanged catalysts contain no V205 crystallites. An exception is Si02 on which also crystalline V206 is formed in both preparation techniques. Monolayer stability toward thermal treatment decreases in the order AZO>3 Ti02> Ce02,w hereas on heating ion-exchanged V/Si02 the crystalline V206 spreads out over the silica surface. The reducibilities of the ion-exchanged catalyats, as measured by TPR, can be used as a measure for the contact interaction between vanadia and the carrier oxides. At temperatures of 500-800 K, this interaction ranges from strong with titania to weak with silica as a carrier.