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张梦婷, 颜婷婷, 戴卫理, 关乃佳, 李兰冬   

  1. 材料科学与工程学院 & 国家先进材料研究院 南开大学 天津 300350
  • 发布日期:2020-09-18
  • 通讯作者: 李兰冬
  • 基金资助:

Zeolite stabilized isolated molybdenum species for catalytic oxidative desulfurization

Mengting Zhang, Tingting Yan, Weili Dai, Naijia Guan, Landong Li   

  1. School of Materials Science and Engineering & National Institute for Advanced Materials, Nankai University, Tianjin 300350, PR China
  • Published:2020-09-18
  • Supported by:
    Project supported by Municipal Natural Science Foundation of Tianjin (18JCJQJC47400, 18JCZDJC37400), Fundamental Research Funds for the Central Universities, Nankai University.

A series of Mo/beta zeolite samples with different Mo loadings were prepared via a two-step post-synthesis strategy using dealuminated Si-beta and bis (cyclopentadienyl) molybdenum dichloride (Cp2MoCl2) as precursors. The as-prepared samples were thoroughly characterized by a series of techniques including X-ray diffraction (XRD), the diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), temperature-programmed reduction by hydrogen (H2-TPR), high-resolution transmission electron microscopy (HR-TEM) and scanning transmission electron microscopy (STEM), Mo the K-edge X-ray absorption near edge structure (XANES), the extended X-ray absorption fine structure (EXAFS) and Raman spectroscopy. Dioxo (Si-O)2Mo(=O)2 species were determined to be the dominant Mo species confined and stabilized in structure of beta zeolite. The as-prepared Mo/beta samples were applied as potential catalysts in the reaction of oxidative desulfurization (ODS) from model fuel. The effects of catalyst supports, molybdenum loadings, reaction temperature, and sulfur substrates on the ODS performance were investigated in detail, and typical kinetic analyses of DBT oxidation were conducted, giving an apparent activation energy value of 50.2 kJ/mol. Owing to the structure confinement, Mo species can be well stabilized within the pores and cages of beta zeolite, and the distribution of which can be regulated by controlling the anchoring sites in the zeolite support to derive well-defined isolated dioxo Mo species. 1% Mo/beta exhibited remarkable oxidative desulfurization efficiency in the removal of heterocyclic sulfur compounds like DBT from the model fuel among all the catalysts tested. Typically, 99.3% of DBT could be oxidized to the corresponding sulfone within 120 min at 333 K. Moreover, 1% Mo/beta showed good recyclability and no obvious activity loss could be observed in five recycles, in significant contrast to poor cyclic stability of traditional Mo/SiO2 catalyst caused by the significant loss of Mo species during desulfurization reaction. Therefore, Mo/beta might be developed as efficient and stable ODS catalysts for future applications under mild reaction conditions.

Key words: molybdenum species, zeolite, oxidative desulfurization