高等学校化学学报 ›› 2015, Vol. 36 ›› Issue (10): 1945.doi: 10.7503/cjcu20150327

• 物理化学 • 上一篇    下一篇

碱金属阳离子对Cu+Y催化甲醇氧化羰基化性能影响的密度泛函理论研究

张艳青1,2, 郑华艳1, 章日光1, 李忠1(), 王宝俊1, 赵秋勇2   

  1. 1. 太原理工大学煤科学与技术教育部和山西省重点实验室,2. 化学化工学院, 太原 030024
  • 收稿日期:2015-04-22 出版日期:2015-10-10 发布日期:2015-10-09
  • 作者简介:联系人简介: 李 忠, 男, 博士, 教授, 主要从事催化和一碳化学研究. E-mail:lizhong@tyut.edu.cn
  • 基金资助:
    国家自然科学基金(批准号: 21276169)和山西省青年科技研究基金(批准号: 2015021030)资助

Density Functional Theory Investigation on the Effect of Alkali Metal Cations on the Catalytic Performance for Cu+Y Zeolites in Oxidative Carbonylation of Methanol

ZHANG Yanqing1,2, ZHENG Huayan1, ZHANG Riguang1, LI Zhong1,*(), WANG Baojun1, ZHAO Qiuyong2   

  1. 1. Key Laboratory of Coal Science and Technology of Ministry of Education and Shanxi Province, 2. College of Chemistry and Chemical Engineering, Taiyuan University of Technology, Taiyuan 030024, China
  • Received:2015-04-22 Online:2015-10-10 Published:2015-10-09
  • Contact: LI Zhong E-mail:lizhong@tyut.edu.cn
  • Supported by:
    † Supported by the National Natural Science Foundation of China(No.21276169) and the Natural Science Foundation for Young Scientists of Shanxi Province, China(No.2015021030)

摘要:

基于密度泛函理论方法构建并优化了CuMY(M为碱金属阳离子)分子筛的稳定构型, 采用速控步骤CO插入CH3O形成CH3OCO反应, 研究了碱金属阳离子对Cu+Y分子筛中活性中心周围电子环境及催化甲醇氧化羰基化合成碳酸二甲酯性能的影响. 计算结果表明, Li+, Na+和K+稳定落位于Y分子筛小笼中, 且随着金属离子半径的增大, CH3OH, CO, CH3O在CuMY上的吸附能和CO/CH3O的共吸附能均逐渐增加, CO插入CH3O反应的过渡态结构稳定性逐渐降低, 活化能逐渐上升, 相应的反应活性逐渐下降. 而落位在超笼中Ⅱ*位的Rb+与Cs+则随着离子半径的增大, 反应过渡态的结构稳定性提高, 克服的活化能降低, 反应活性升高. 不同CuMY分子筛上催化活性顺序为CuLiY-Ⅰ'>CuCsY-Ⅱ*>CuNaY-Ⅰ'>CuRbY-Ⅱ*>CuKY-Ⅰ'>CuCuY-Ⅰ', 其中CuLiY-Ⅰ'分子筛克服速控反应的活化能垒(52.74 kJ/mol)最低.

关键词: 碱金属阳离子, 密度泛函理论, CuY分子筛, 氧化羰基化, 碳酸二甲酯

Abstract:

On the basis of density functional theory, influence of co-cations(M=Li+, Na+, K+, Rb+)adjacenting active center Cu+ on the electronic properties and catalytic activity of Cu+Y zeolites in oxidative carbonylation of methanol to dimethyl carbonate was investigated. CuMY stable configurations were constructed, CO insertion CH3O species to CH3OCO was used to evaluate the catalytic activity of CuY zeolites, due to the fact that it was the rate-limiting step of oxidative carbonylation of methanol. The calculation results indicate that Li+, Na+, K+ cations can locate site Ⅰ' in small cages of Y zeolites surrounding the active center Cu+, the adsorption energy of CH3OH, CO, CH3O and co-adsorbed CO/CH3O on CuMY zeolite increases gradually with increase of cation size, the stability of transition states for CO insert into CH3O reaction comes to decrease, increases the activation barriers and the corresponding catalytic performance declines. Whereas, Rb+ and Cs+ cations located Ⅱ* in the supercage as increase in cation size, decreases activation energy for CO insertion reaction, improves the stability of transition states and the catalytic activity of CuY zeolites. The order of catalytic activity of CuMY zeolites is CuLiY-Ⅰ'>CuCsY-Ⅱ*>CuNaY-Ⅰ'>CuRbY-Ⅱ*>CuKY-Ⅰ'>CuCuY-Ⅰ'. The CuLiY-Ⅰ' catalyst exhibits the best catalytic performance with a lowest rate-limiting reaction activation barrier of 52.74 kJ/mol.

Key words: Alkali metal cation, Density functional theory, CuY zeolite, Oxidative carbonylation, Dimethyl carbonate

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