物理化学学报 >> 2013, Vol. 29 >> Issue (04): 723723-730.doi: 10.3866/PKU.WHXB201302043

理论与计算化学 上一篇    下一篇

苯乙烯在Ag(111)和Ag(110)表面环氧化反应结构敏感性的理论研究

王晨1, 魏子章2, 吕永康1, 邢斌3, 王贵昌3   

  1. 1 太原理工大学教育部和山西省共建煤科学与技术重点实验室, 太原 030024;
    2 天津环境工程评估中心, 天津 300191;
    3 南开大学化学学院和天津市分子--金属基重点实验室, 天津 300071
  • 收稿日期:2012-11-07 修回日期:2013-01-30 发布日期:2013-03-25
  • 通讯作者: 吕永康, 王贵昌 E-mail:wangguichang@nankai.edu.cn; lykang@tyut.edu.cn
  • 基金资助:

    国家自然科学基金(21078252)资助项目

Theoretical Investigation of Structure-Sensitivity of Styrene Epoxidation on Ag(111) and Ag(110) Surfaces

WANG Chen1, WEI Zi-Zhang2, LÜ Yong-Kang1, XING Bin3, WANG Gui-Chang3   

  1. 1 Key Laboratory of Coal Science and Technology, Ministry of Education and Shanxi Province, Taiyuan University of Technology, Taiyuan 030024, P. R. China;
    2 Tianjin Enviromental Engineering Assessment Center, Tianjin 300191, P. R. China;
    3 Department of Chemistry and the Tianjin Key Laboratory of Metal and Molecule-based Material Chemistry, Nankai University, Tianjin 300071, P. R. China
  • Received:2012-11-07 Revised:2013-01-30 Published:2013-03-25
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (21078252).

摘要:

采用密度泛函理论(DFT)对苯乙烯在Ag(110)表面和Ag(111)表面的环氧化反应进行了计算研究. 经计算, 在Ag(110)表面预吸附氧原子更易吸附在3 重穴位(3h), 吸附能为-3.59 eV; 在Ag(111)表面预吸附氧原子的最稳定吸附位是fcc 位, 吸附能为-3.69 eV. 苯乙烯的环氧化反应过程首先经过一个金属中间体, 然后再进一步反应变为产物, 其中经过直链中间体较支链中间体更加有利. Ag(110)面的反应活化能一般大于Ag(111)面的, 并且微观动力学模拟结果表明, Ag(111)表面生成环氧苯乙烷的选择性要明显高于Ag(110)表面(0.38 与 0.003), 原因是Ag(111)面环氧化反应活化能小于苯乙醛及燃烧中间体的活化能, 而在Ag(110)上正相反.

关键词: 苯乙烯, 选择性氧化, 结构敏感, 银催化剂, 密度泛函理论计算

Abstract:

The selective oxidation of styrene on oxygen-covered Ag(110) and Ag(111) surfaces is studied by density functional theory (DFT) calculations with the periodic slab model. On the Ag(110) surface, a pre-adsorbed oxygen atom prefers the 3-fold hollow site (3h) with an adsorption energy of -3.59 eV. On the Ag(111) surface, the most stable adsorption site for a pre-adsorbed oxygen atom is the fcc site, and the adsorption energy is -3.69 eV. The reaction process of the selective oxidation of styrene includes two steps: the formation of surface intermediates (branched oxametallacycle and linear oxametallacycle) and the subsequent formation of different products. The calculated results show that the formation of styrene oxide via the linear oxametallacycle (i.e., the pre-adsorbed atomic oxygen bound to the methylene group in styrene) is the favorable reaction mechanism on both Ag(110) and Ag(111) surfaces. The reaction barriers for the different reaction steps of styrene epoxidation on the Ag(110) surface are generally higher than those on the Ag(111) surface. Moreover, the micro-kinetic simulation results indicate that the relative selectivity towards the formation of styrene oxide on the Ag(111) surface is much higher than that on the Ag(110) surface (0.38 vs 0.003) because the energy barrier for the styrene epoxidation is smaller than that for the formation of phenyl acetaldehyde and its combustion intermediate on Ag(111) surface. The reverse trends occurred on the Ag(110) surface.

Key words: Styrene, Selective oxidation, Structure sensitivity, Ag catalyst, Density functional theory calculation

MSC2000: 

  • O641