物理化学学报 >> 2014, Vol. 30 >> Issue (10): 1847-1854.doi: 10.3866/PKU.WHXB201407141

理论与计算化学 上一篇    下一篇

Au/Pd(111)双金属表面催化噻吩加氢脱硫的反应机理

张连阳, 施炜, 夏盛杰, 倪哲明   

  1. 浙江工业大学化学工程学院, 先进催化材料实验室, 杭州 310032
  • 收稿日期:2014-06-03 修回日期:2014-07-11 发布日期:2014-09-30
  • 通讯作者: 倪哲明 E-mail:jchx@zjut.edu.cn

Hydrodesulfurization Mechanisms of Thiophene Catalyzed by Au/Pd(111) Bimetallic Surfa

ZHANG Lian-Yang, SHI Wei, XIA Sheng-Jie, NI Zhe-Ming   

  1. Laboratory of Advanced Catalytic Materials, College of Chemical Engineering, Zhejiang University of Technology, Hangzhou 310032, P. R. China
  • Received:2014-06-03 Revised:2014-07-11 Published:2014-09-30
  • Contact: NI Zhe-Ming E-mail:jchx@zjut.edu.cn

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摘要：

采用密度泛函理论（DFT）计算了Pd（111）表面含有N（N=1-4）个Au原子数目时的表面形成能，选取最优构型进一步研究了噻吩在Au/Pd（111）双金属表面的吸附模式及加氢脱硫反应过程. 结果表明：当Pd（111）表面含有1个Au原子时，其形成能最低. 在Au/Pd（111）双金属表面噻吩初始吸附于Pd-Hcp-30°位时，其构型最稳定. 在各加氢脱硫过程中，反应总体均放出热量. 对于直接脱硫机理，其所需活化能较低，但脱硫产物较难控制；对于间接脱硫机理，反应最有可能按照顺式加氢方式进行，C―S键断裂开环时所需活化能最高，是反应的限速步骤. 此外，与单一Au（111）面及Pd（111）面相比，Au/Pd（111）双金属表面限速步骤的反应能垒最低，表明AuPd双金属催化剂比Au、Pd单金属催化剂更有利于噻吩加氢脱硫反应的进行.

关键词: 密度泛函理论, 噻吩, Au/Pd(111)双金属表面, 吸附, 加氢脱硫

Abstract:

The formation energy of different ensembles on Pd(111) surfaces containing N (N=1-4) Au atoms were investigated using a density functional theory model. The best model for exploring the adsorption of thiophene was selected, and the mechanism of competitive hydrodesulfurization on a Au/Pd(111) bimetallic surface was investigated. The results showed that Au/Pd(111) has the lowest formation energy, and adsorption at the hexagonal close-packed site is most stable when the thiophene plane is tilted at 30° to the Au/Pd(111) bimetallic surface with S atom. The reactions are exothermic, and desulfurization can be either direct or indirect. The direct desulfurization pathway has a low activation energy, but it is difficult to control the products. The indirect desulfurization pathway is the best fit for the cis-hydrogenation process; C―S cleavage has the highest reaction energy barrier, and is the rate-determining step. The activation energy barrier of the rate-determining step on Au/Pd(111) is lower than those on Au(111) and Pd(111). This indicates that bimetallic AuPd is more active than single Au and Pd in the hydrodesulfurization of thiophene.

Key words: Density functional theory, Thiophene, Au/Pd(111) bimetallic surface, Adsorption, Hydrodesulfurization