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Catalytic property of hetero-elements isolated in crystalline mesoporous transition metal oxides

结晶介孔过渡金属氧化物中异质元素的催化性能

基本信息

批准号：
18360385
负责人：
NOMURA Junko
金额：
$ 10.36万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2006
资助国家：
日本
起止时间：
2006 至 2007
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-18360385/
关键词：
Transition metal oxides Mesoporous Materials Hetero-elements Crystallization Isolation Catalysis

项目摘要

The evaluation of characteristic features of hetero-atoms embedded in crystallized mesoporous transition metal oxides are aimed in the present research. At the beginning as references, the catalytic performance of non-doped pure mesoporous transition metal oxides was evaluated by oxidation of olefins with hydrogen peroxide. Mesoporous tantalum oxide was found to be an efficient catalyst for oxidation of cyclohexene in cetonitrile solvent, whose activity exceeded the one expected from the surface area in comparison with non-porous materials. Ti doping to the mesoporous Ta oxide was also attempted, but no improvement was observed due to the high activity of the other material itself. In the term 2007, mesoporous Nb oxide was studied in detail.The oxidation of cyclohexene with hydrogen peroxide resulted in over 80 % selectivity for cyclohexanediol over amorphous mesoporous Nb oxide, while a similarly high selectivity was observed for epoxycyclohexane over crystalline mesporous Nb oxide. These results indicate that the selectivity of catalytic reactions can be controlled by changing the crystal structure of mesoporous transition metal oxides. By optimizing the reaction conditions, 12 % of conversion of the reactant ant 97 % of selectivity for epoxycyclohexane were obtained by the oxidation of cyclohexene with hydrogen peroxide over crystalline mesoporous Nb oxide even at 40 ℃ for 2 h.While Ti-containing zeolites are commercially utilized for the epoxidation of linear olefins, they are not effectively catalyze larger-sized molecules than zeolitic pores represented by cyclohexe. In this point of view, the present finding that mesoporous transition metal oxides can function the epoxidation of larger olefins, especially the crystalline mesoporous Nb oxide, would contribute to the practical development of catalytic systems in addition to the academic importance.

本研究的目的是评价嵌入在晶体化介孔过渡金属氧化物中的杂原子的特性。首先作为参考，用过氧化氢氧化烯烃的方法评价了未掺杂纯介孔过渡金属氧化物的催化性能。介孔氧化钽是一种有效的环己烯在鲸腈溶剂中氧化的催化剂，与非多孔材料相比，其活性超过了从表面积上预测的活性。钛掺杂到介孔氧化钛中也被尝试过，但由于其他材料本身的高活性，没有观察到任何改善。2007年，对介孔氧化铌进行了详细的研究。过氧化氢氧化环己烯导致环己二醇对非晶介孔氧化铌的选择性超过80%，而环氧环己烷对结晶介孔氧化铌的选择性也同样高。这些结果表明，可以通过改变介孔过渡金属氧化物的晶体结构来控制催化反应的选择性。通过优化反应条件，在40℃、2 h的条件下，用双氧水将环己烯在结晶型介孔氧化铌上氧化，其环氧环己烷的选择性为97%，转化率为12%。含钛沸石用于线型烯烃的环氧化反应，但其催化的分子比以环己烷为代表的沸石孔大。从这个角度来看，目前的发现介孔过渡金属氧化物可以发挥较大烯烃的环氧化作用，特别是晶体介孔氧化铌，将有助于催化体系的实际发展，除了学术上的重要性。