Acta Phys. -Chim. Sin. ›› 2013, Vol. 29 ›› Issue (04): 723-730.doi: 10.3866/PKU.WHXB201302043

• THEORETICAL AND COMPUTATIONAL CHEMISTRY • Previous Articles     Next Articles

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).

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