物理化学学报 >> 2009, Vol. 25 >> Issue (05): 876-882.doi: 10.3866/PKU.WHXB20090507

研究论文 上一篇    下一篇

Pd催化甲醇裂解制氢的反应机理

倪哲明 毛江洪 潘国祥 胥倩 李小年   

  1. 浙江工业大学化学工程与材料学院, 杭州 310032
  • 收稿日期:2008-12-05 修回日期:2009-01-25 发布日期:2009-05-04
  • 通讯作者: 倪哲明 E-mail:jchx@zjut.edu.cn

Mechanism of Palladium-Catalyzed Methanol Decomposition for Hydrogen Production

NI Zhe-Ming, MAO Jiang-Hong, PAN Guo-Xiang, XU Qian, LI Xiao-Nian   

  1. College of Chemical Engineering and Materials Science, Zhejiang University of Technology, Hangzhou 310032, P. R. China
  • Received:2008-12-05 Revised:2009-01-25 Published:2009-05-04
  • Contact: NI Zhe-Ming E-mail:jchx@zjut.edu.cn

摘要:

基于密度泛函理论(DFT), 研究了甲醇在Pd(111)面上首先发生O—H键断裂的反应历程(CH3OH(s)→CH3O(s)+H(s)→CH2O(s)+2H(s)→CHO(s)+3H(s)→CO(s)+4H(s)). 优化了裂解过程中各反应物、中间体、过渡态和产物的几何构型, 获得了反应路径上各物种的吸附能及各基元反应的活化能数据. 另外, 对甲醇发生C—O键断裂生成CH3(s)和OH(s)的分解过程也进行了模拟计算. 计算结果表明, O—H键的断裂(活化能为103.1 kJ·mol-1)比C—O键的断裂(活化能为249.3 kJ·mol-1)更容易; 甲醇在Pd(111)面上裂解的主要反应历程是: 甲醇首先发生O—H键的断裂, 生成甲氧基中间体(CH3O(s)), 然后甲氧基中间体再逐步脱氢生成CO(s)和H(s). 甲醇发生O—H键断裂的活化能为103.1 kJ·mol-1, 甲氧基上脱氢的活化能为106.7 kJ·mol-1, 两者均有可能是整个裂解反应的速控步骤.

关键词: 甲醇裂解, 反应机理, 密度泛函理论, 过渡态

Abstract:

The reaction pathway of methanol decomposition (CH3OH(s)→CH3O(s)+H(s)→CH2O(s)+2H(s)→CHO(s)+3H(s)→CO(s)+4H(s)) on Pd(111) surfaces was studied using density functional theory (DFT). Geometries of reactants, intermediates, transition states and products were calculated. Adsorption energies of possible species and activation energy barriers of possible elementary reactions involved in the mechanism were obtained in this work. In addition, we studied the reaction mechanism for C—O bond scission in methanol decomposition, which led to the formation of CH3(s) and OH(s). Results show that O—H bond scission (with an activation energy barrier of 103.1 kJ·mol-1) requires less energy than C—O bond scission (with an activation energy barrier of 249.3 kJ·mol-1). The major reaction pathway on Pd(111) surfaces involves O—H bond scission in CH3OH and then a further decomposition of the resultant methoxy intermediate to CO(s) and H(s) via sequential hydrogen abstraction from CH3O(s). O—H bond scission in methanol and hydrogen abstraction from the methoxy group are possible rate-determining steps for this decomposition with activation energy barriers of 103.1 and 106.7 kJ·mol-1, respectively.

Key words: Methanol decomposition, Reaction mechanism, Density functional theory, Transition state

MSC2000: 

  • O641