CJCU

Chem. J. Chinese Universities ›› 2009, Vol. 30 ›› Issue (11): 2252.

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Density Functional Theory Study on Interaction of CO2 with Metal Surface Carbon Species in Synthesis of Acetic Acid from CH4/CO2 on Co-Pd Catalysts

ZHANG Ri-Guang, HUANG Wei*, WANG Bao-Jun   

  1. Key Laboratory of Coal Science and Technology, Ministry of Education and Shanxi Province, Taiyuan University of Technolgy, Taiyuan 030024, China
  • Received:2008-12-02 Online:2009-11-10 Published:2009-11-10
  • Contact: HUANG Wei. E-mail: huangwei@tyut.edu.cn
  • Supported by:

    国家自然科学基金(批准号: 20471040, 20906066, 20776093)、国家“九七三”计划(批准号: 2005CB221204)、教育部重点基金(批准号: 207016)和教育部博士点基金(批准号: 20060112014)资助.

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Abstract:

The insertion reactions of CO2 with M—H(M=Co, Pd) and Pd—CH3 were systematically investigated by the first-principle DFT-GGA calculations. The mechanisms of CO2 reacting with M—H and Pd—CH3 were obtained for the direct synthesis of acetic acid from CH4/CO2 by a two-step reaction sequence on Co—Pd catalysts. The calculation result showed that the pathway that CO2 inserts into Co—H bonds forming HCOO—Co was the most advantageous in dynamics for all four designed reaction paths. However, HCOO was linked with Co in bi-dentate form, whose binding energy was very large, so the desorption of HCOO hardly taken place and formic acid was little produced. Meanwhile, the pathway that CO2 inserts into Pd—CH3 bonds forming H3CCOO—Pd was secondly preferential pathway favored in dynamics. The binding energy between H3CCOO and Pd was small, and desorption of H3CCOO easily occurred, so the main product was acetic acid. While methyl formate was inhibited by dynamics. The calculated result was in accordance with the experimental facts.

Key words: Carbon dioxide; Acetic acid; Reaction mechanism; Cobalt; Palladium; Density functional theory; General gradient approtimationry(GGA)

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