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Theoretical studies of the alkali atoms on the Fischer-Tropsch reaction.

碱原子对费托反应的理论研究。

基本信息

批准号：
61470002
负责人：
TATEWAKI Hiroshi
金额：
$ 2.43万
依托单位：
Research Institute for catalysis, 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：
1986
资助国家：
日本
起止时间：
1986 至 1988
项目状态：
已结题

项目摘要

It is well known that alkali atoms added to transition metal catalysts promote the methanation reaction and Fischer-Tropsch syntheses. In this study we intended to clarify, a) the mechanism of the stabilization between transition metals and a alkali atom, b) that between the transition metals and the CO molecule, and c) that among the transition metals, CO, and a alkali atom, using small copper clusters as a substitute of transition metals. The method employed were ab initio SCF and CI calculations. We have completed two ((a) and (b)) of them. In a) two types of adsorption were found. One of them is a charge transfer type adsorption where a fairly large number of Na 3s electrons moves into copper clusters. The other is a non charge transfer type where the Na atom remains almost at its ground state and so do copper clusters. The former gets larger stabilization than the latter (See Ref. 1). We have some confidence that the small clusters can simulate some characteristics the bulk metals such as density of the states (See Ref. 2,3,4). We, therefore, challenged to analyzethe electron-energy-loss-spectra (EELS) observed on low-coverage Na on Cu (111) and EELS are successfully analyzed on the basis of the cluster calculation (See Ref. 5). For b), the origin of the stabilization of CO on the cu cluster was revealed. The adsorption spectra of CO on the bulk Cu were assigned by the use of the excitation energies of Cu_4CO and Cu_5CO (See Refs. 6 and 7). A study on Cu-CH_2 interaction was given in Ref. 8).

众所周知，在过渡金属催化剂中加入碱原子可以促进甲烷化反应和费托合成。在本研究中，我们打算阐明，a)过渡金属与碱原子之间的稳定机理，b)过渡金属与CO分子之间的稳定机理，以及c)过渡金属之间，CO和碱原子之间的稳定机理，使用小铜簇作为过渡金属的替代品。采用从头计算SCF和CI的方法。我们已经完成了其中的两个(a)和(b)。a)发现了两种类型的吸附。其中一种是电荷转移型吸附，其中相当多的Na 3s电子移动到铜簇中。另一种是非电荷转移类型，其中Na原子几乎保持在基态，铜簇也是如此。前者比后者具有更大的稳定性（参见参考文献1）。我们有一定的信心，小簇可以模拟大块金属的一些特性，如状态的密度（参见参考文献2,3,4）。因此，我们挑战分析在低覆盖Na on Cu（111）上观察到的电子能量损失谱（EELS），并在簇计算的基础上成功分析了EELS（参见Ref. 5）。对于b)，揭示了CO在cu簇上稳定化的原因。用Cu_4CO和Cu_5CO的激发能来分配CO在大块Cu上的吸附光谱（见参考文献6和7）。Cu-CH_2相互作用的研究见文献8)。