Acta Phys. -Chim. Sin. ›› 2016, Vol. 32 ›› Issue (4): 935-942.doi: 10.3866/PKU.WHXB201601201

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Theoretical Study of the Solvent Adsorption on Ti-Peroxo Active Center in Ti-MWW Zeolite

Jing ZOU,Zhi-Lin FAN,Li-Sha JIANG,Dan-Hong ZHOU*()   

  • Received:2015-11-24 Published:2016-04-07
  • Contact: Dan-Hong ZHOU E-mail:dhzhou@lnnu.edu.cn
  • Supported by:
    the National Natural Science Foundation of China(21343010)

Abstract:

Density functional theory is used to study the structures of the Ti-peroxide species in a Ti-MWW/H2O2 system and the influence of the coordination with solvent molecules on the geometries and electronic features. The result indicated that the framework Ti can interact with H2O2 to form two kinds of Ti-peroxide species, the five-membered ring Ti-η1-OOH and the three-membered ring Ti-η2-OOH. The framework Ti center can further interact with solvent molecules of H2O, CH3OH, and CH3CN to form 6-coordinated complexes. The adsorption energies decreased as H2O > CH3OH > CH3CN. Both Ti-peroxide species display different adsorption capacity as Ti-η1-OOH > Ti-η2-OOH. The location of Ti also has a distinct effect on the adsorption. The central Ti at T1 prefers to adsorb solvent molecule over the Ti at T3. In addition, solvent adsorption also influences the electrophilicity of the active oxygen atom. The calculated results indicate that on the Ti-η2-OOH active center with adsorbed CH3CN, the activation energy of the epoxidation of chloropropene has been reduced.

Key words: Ti-MWW zeolite, Aqueous H2O2, Ti-peroxide intermediate, Solvent effect, Density functional theory

MSC2000: 

  • O641