铝铂掺杂团簇及羰基钼化合物催化CO氧化的密度泛函理论研究
发布时间：2019-05-16 12:33
【摘要】：近年来过渡金属合金团簇因具有特殊的光学性能、催化活性和磁性等性质使其在一氧化碳催化氧化方面备受关注。研究发现相比纯团簇,掺杂团簇在催化性能上有所增加而其成本却大大减低。因此,本着高效低廉的原则,我们探究了Al-Pt团簇催化一氧化碳氧化反应。虽然目前相关Al-Pt团簇的研究已经报道Al_(12)Pt团簇在催化一氧化碳氧化方面显示了较好的催化活性,但是团簇尺寸的大小也会对团簇的催化性能产生一定的影响。所以,本章中我们采用密度泛函理论探讨了Al_nPt(n=1-11)团簇催化一氧化碳氧化反应。对Al_nPt团簇的基态结构以及小分子CO和O_2在团簇表面的吸附行为分析发现:掺杂Pt原子会破坏合金团簇的对称性,结构发生畸变;O_2分子相比CO分子更容易吸附到团簇表面而参与反应。与此同时,为了阐明反应机理,我们研究了Al_nPt(n=1-11)团簇催化CO氧化反应通过(Langmuir-Hinshelwood)LH路径。对比相关Al-Pt研究结果,发现Pt原子的掺杂可以有效提高合金团簇对CO的催化性能,并且Al_(11)Pt团簇表现出最好的催化性能。在氢氧燃料电池和工业应用中,水煤气转化反应因其能够较好的除去甲烷重整气过程中的副产物CO而成为一个重要的工业反应。目前,大量有关水煤气转换反应的催化剂研究主要集中在闭壳的过渡金属面上、金属氧化物负载以及团簇表面。相比这些形式的催化剂,过渡金属羰基催化剂不仅能够有效的催化水煤气反应持续进行而且容易制取。因此,本章采用密度泛函理论系统地研究了Mo(CO)_6催化水煤气转化反应的四种机理,并分别在气相和甲醇溶液中进行反应以寻找最优反应路径和合适的反应条件。计算结果显示Torrent机理中OH~-脱去的一步需要较高的能量使得反应难以进行。而Barrows机理虽然避免了这一步,但却忽略了实验中观察到的重要中间体。与此同时,Rozanska和Zhang机理则对Torrent机理做了修改,很好的解决了Torrent机理中的难题。我们计算过程中发现在气相和甲醇溶液中Zhang机理是最合适的,其对应的反应路径为:Mo(CO)_6+OH~-→Mo(CO)_5(COOH)~-→Mo(CO)_5H~-+H_2O→Mo(CO)_4H_2(COOH)~-→Mo(CO)_4(COOH)~-+CO→Mo(CO)_5(COOH)~-。介于近年来催化剂中金属间协同作用在水煤气转化反应中的应用,我们设计了Mo的双核催化剂。通过计算单核Mo(CO)_6和双核Mo_2(CO)_(10)的反应势能面和Energy Span Model(ESM)模型的Turnover Frequency(TOF)值分析得到Mo_2(CO)_(10)的能垒较Mo(CO)_6低并且其TOF值较Mo(CO)_6大,表现了较好的催化性能。因此,我们认为双核Mo_2(CO)_(10)是一种好的水煤气反应催化剂。
[Abstract]:In recent years, transition metal alloy clusters have attracted much attention in catalytic oxidation of carbon monoxide because of their special optical properties, catalytic activity and magnetic properties. It is found that compared with pure clusters, the catalytic performance of dopant clusters is increased, but its cost is greatly reduced. Therefore, based on the principle of high efficiency and low cost, we investigated the oxidation of carbon monoxide catalyzed by Al-Pt clusters. Although the related Al-Pt clusters have been reported to have good catalytic activity in the catalytic oxidation of carbon monoxide, the size of the clusters will also have a certain effect on the catalytic performance of the clusters. Therefore, in this chapter, we use density functional theory to investigate the oxidation of carbon monoxide catalyzed by Al_nPt (n 鈮，
本文编号：2478279
[Abstract]:In recent years, transition metal alloy clusters have attracted much attention in catalytic oxidation of carbon monoxide because of their special optical properties, catalytic activity and magnetic properties. It is found that compared with pure clusters, the catalytic performance of dopant clusters is increased, but its cost is greatly reduced. Therefore, based on the principle of high efficiency and low cost, we investigated the oxidation of carbon monoxide catalyzed by Al-Pt clusters. Although the related Al-Pt clusters have been reported to have good catalytic activity in the catalytic oxidation of carbon monoxide, the size of the clusters will also have a certain effect on the catalytic performance of the clusters. Therefore, in this chapter, we use density functional theory to investigate the oxidation of carbon monoxide catalyzed by Al_nPt (n 鈮，
本文编号：2478279
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