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Molecular Design and Structural Controlling of Heterogeneous Reaction Sites by Ship-in-bottle Synthesis

瓶中合成异质反应位点的分子设计和结构控制

基本信息

批准号：
03453001
负责人：
ICHIKAWA Masaru
金额：
$ 4.35万
依托单位：
Hokkaido University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1991
资助国家：
日本
起止时间：
1991 至 1992
项目状态：
已结题

项目摘要

Metal carbonyl clusters grafted on supports such as oxides and zeolites offer a great advantage in the rational preparation of metal/bimetal ensemble sites for activation of small molecules such as CH_4,CO_2 and H_2O to be effectively converted into useful chemicals. Metal clusters entrapped in zeolite micro-pores are ideal objects for the study of collective behavior and heteronuclear two-site promotion in stoichiometric and catalytic reactions of chemically modest small molecules such as CH_4,CO and CO_2.We have extended works to synthesize Rh_<6-x>Ir_x(CO)_<16>(x=0-6) and Rh_4Fe_2(CO)_<15>^<2-> inside NaY zeolite by the "ship-in-bottle" technique, and characterized the H_2-reduced bimetal ensembles by EXAFS, FTIR, and Mossbauer in CO and CH_4 atmosphere. NaY-entrapped RhIr ensembles provide selectively C_2H_6 via central C-C bond-scission in the butane hydrogenolysis, while NaY-entrapped RhFe ensembles selective towards CH_4+C_3H_8 via terminal C-C bond scission. Recently, we have succeeded to synthesize the series of Chini-type Pt clusters such as [Pt_3(CO)_6]_n^<2-> (n=3,4,5) inside NaY cages, which are characterized by FTIR, EXAFS and UV-vis. They are catalytically active for NO reaction with CO and the water gas shift reaction (CO+H_2O=CO_2+H_2) at lower temperatures, and exhibited effective photocatalysis for the latter reaction with a marked enhancement under the illumination of a Xe lamp compared with the dark reduction. The results suggest that H_2O is activated with anionic Pt carbonyl clusters inside the cages to promote the H (or OH) formation under the photo-illumination.

接枝在氧化物和沸石等载体上的金属羰基簇在合理制备金属/双金属系综位点以活化CH_4、CO_2和H_2O等小分子以有效转化为有用化学品方面具有巨大优势。沸石微孔中的金属团簇是研究CH_4、CO和CO_2等化学计量和催化反应中的集体行为和异核二位点促进的理想对象。我们已经扩展了合成Rh_<6-x>Ir_x(CO)_<16>(x=0-6)和采用“瓶中船”技术将Rh_4Fe_2(CO)_<15>^<2->置于NaY沸石内部，并在CO和CH_4气氛中通过EXAFS、FTIR和Mossbauer对H_2还原双金属系簇进行了表征。 NaY包埋的RhIr系综在丁烷氢解中通过中心C-C键断裂选择性地提供C_2H_6，而NaY包埋的RhFe系综通过末端C-C键断裂选择性地提供CH_4+C_3H_8。最近，我们成功合成了NaY笼内的[Pt_3(CO)_6]_n^<2-> (n=3,4,5)等一系列Chini型Pt团簇，并通过FTIR、EXAFS和UV-vis对其进行了表征。它们在较低温度下对NO与CO的反应以及水煤气变换反应(CO+H_2O=CO_2+H_2)具有催化活性，并且对后一种反应表现出有效的光催化作用，与暗还原相比，在氙灯照射下有明显增强。结果表明，H_2O 被笼内的阴离子 Pt 羰基簇激活，促进光照射下 H（或 OH）的形成。