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Preparation of catalysts based on unique valence and coordination state in mesoporous titania with extremely high surface area

基于极高比表面积介孔二氧化钛独特价态和配位态的催化剂的制备

基本信息

批准号：
15560666
负责人：
YOSHITAKE Hideaki
金额：
$ 2.69万
依托单位：
Yokohama National University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2005
项目状态：
已结题

项目摘要

With the aid of dodecylamine as a mesostructure-directing agent, novel catalysts consisting of V, Ce, Mo and W supported on mesoporous titania were synthesized by the direct co-condensation of the alkoxides, X-meso TiO_2, or by the post-modification technique, X/meso TiO_2, where X=V, Ce, Mo and W. We investigated the phases of the support titania, the local structure of X as well as the ethanol-oxygen reaction on these catalysts. Calcination at 673 K induced a new mesophase in both catalysts, with a larger pore size (3.2-4.6 nm) than was originally presented (2.0-2.1 nm). This phase is not similar to any mesoporous titania ever reported previously. X-ray diffraction and Raman spectroscopy revealed that the phase transitions that occur at 573 K and 673 K in Mo/meso TiO_2 are from the amorphous to rutile and from the rutile to anatase phases, respectively. Changes from the rutile to the anatase phase with increasing temperature have rarely been observed before. In contrast, it was shown that Mo-meso TiO_2 is transformed from the amorphous to the anatase phase at 573 K, and that the size of the crystallites increased at 673 K. The intensity of pre-edge peak of the Mo K-edge was measured in vacuum and in air. These mesoporous titania-supported Mo catalysts in the newly-observed mesophase were then used to the catalyst for ethanol-oxygen reactions. Although acetaldehyde was almost exclusively formed on a 4.0 wt% Mo/P-25 catalyst (which agrees with the result in the literature) ethylene was selectively formed on 3.9 wt% Mo-meso TiO_2 and on 4.0 wt% Mo/meso TiO_2.

以十二烷基胺为介孔导向剂，通过X-介孔TiO_2直接共缩合或X/介孔TiO_2后修饰技术（X=V, Ce， Mo和W）合成了V、Ce、Mo和W负载在介孔二氧化钛上的新型催化剂，研究了载体二氧化钛的物相、X的局部结构以及在这些催化剂上的乙醇-氧反应。在673 K下煅烧，两种催化剂都形成了一个新的中间相，其孔径（3.2-4.6 nm）比原来的孔径（2.0-2.1 nm）更大。这一阶段与以往报道的任何介孔二氧化钛都不相似。x射线衍射和拉曼光谱分析表明，在573 K和673 K时，Mo/meso TiO_2的相变分别是从无定形相到金红石相和从金红石相到锐钛矿相。从金红石相到锐钛矿相随温度升高的变化是以前很少观察到的。结果表明，在573 K时，Mo-meso TiO_2由非晶态向锐钛矿相转变，晶粒尺寸增大。分别在真空和空气中测量了钼k边的前边峰强度。这些介孔钛载体Mo催化剂在新观察到的中间相中被用于乙醇-氧反应的催化剂。虽然乙醛几乎完全在4.0 wt% Mo/P-25催化剂上形成（这与文献中的结果一致），但乙烯在3.9 wt% Mo-meso TiO_2和4.0 wt% Mo/meso TiO_2上选择性地形成。