郝秋凤,张敏华,余英哲.Pd/Au(100)表面上乙烯气相氧化法合成乙酸乙烯酯催化活性的密度泛函理论研究[J].分子催化编辑部,2013,(2):173-180
Pd/Au(100)表面上乙烯气相氧化法合成乙酸乙烯酯催化活性的密度泛函理论研究
DFT Study of the Catalytic Reactivity of Pd/Au(100) Alloy Surface for Vinyl Acetate Synthesis from Acetoxylation of Ethylene
投稿时间:2013-04-07  修订日期:2013-04-21
DOI:
中文关键词:  乙酸乙烯酯  Pd/Au(100)  表面活性  DFT
英文关键词:Vinyl acetate  Pd/Au(100)  surface reactivity  DFT
基金项目:
作者单位E-mail
郝秋凤 天津大学石油化工技术开发中心, 绿色合成与转化教育部重点实验室 qiufeng200820062008h@126.com 
张敏华 天津大学石油化工技术开发中心, 绿色合成与转化教育部重点实验室 mhzhang@tju.edu.cn 
余英哲 天津大学石油化工技术开发中心, 绿色合成与转化教育部重点实验室 yzhyu@tju.edu.cn 
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中文摘要:
      采用密度泛函理论方法系统地研究了乙烯气相氧化法合成乙酸乙烯酯催化剂Pd/Au(100) 表面的催化活性. 对关键反应物种在该表面的吸附、共吸附性质及耦合基元反应进行了计算和讨论. 乙烯在催化剂表面存在π-, 2σ- 两种稳定吸附构型, 为弱化学吸附; 乙酸根物种存在Pd-Au与Pd-Pd两种二位啮合(bi-dentate)构型, 为强化学吸附. 催化剂表面的吸附作用使两关键反应物种的分子轨道能量靠近. 共吸附构型中最高占据和最低未占据分子轨道的能级差(HOMO-LUMO-gap)随表面相邻Pd原子数目的增多而增大, 表明由HOMO向LUMO分子轨道发生电子转移的能力变弱. 耦合基元反应过渡态能垒的分析结果与HOMO-LUMO-gap定性分析结果一致, 说明连续相邻的表面Pd原子不利于反应的进行.
英文摘要:
      A density functional theory (DFT) study has been conducted to investigate the catalyst reactivity of Pd/Au(100) surface, which is well performed for the production of vinyl acetate (VAc) from acetoxylation of ethylene. The adsorption and co-adsorption properties of the key reagents as well as their coupling reaction were calculated and discussed. Ethylene species are weakly chemical-adsorbed on these alloy surfaces with π- and 2σ- configuration; while acetate species are strongly chemical-absorbed on the surface with Pd-Au and Pd-Pd bi-dentate configurations. As the number of first-neighbor Pd atoms decreases, the molecular orbitals of the two reagents become closer due to the adsorption of the Pd/Au catalyst. The gap between the highest occupied and the lowest unoccupied molecular orbital (HOMO-LUMO-gap) becomes larger in the co-adsorption system, which implies that the electron transfer from HOMO to LUMO becomes more difficult. Energy barrier results of the elementary reaction are in good agreement with the previous molecular orbital analysis, demonstrating that more first-neighbor Pd atoms on Pd/Au(100) surface is not favor of the VAc synthesis.
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