高等学校化学学报 ›› 1999, Vol. 20 ›› Issue (9): 1429.

• 论文 • 上一篇    下一篇

过渡金属改性MCM-41的结构及对苯催化氧化的研究

徐文萍, 何静, 孙鹏, 段雪   

  1. 北京化工大学应用化学系, 北京 100029
  • 收稿日期:1998-12-25 出版日期:1999-09-24 发布日期:1999-09-24
  • 通讯作者: 段雪
  • 作者简介:徐文萍,女,28岁,硕士研究生.
  • 基金资助:

    中国石油化工集团总公司资助

Studies on the Structures of Transition Metal-substituted MCM-41 Materials and Their Catalysis for Hydroxylation of Benzene

XU Wen-Ping, HE Jing, SUN Peng, DUAN Xue   

  1. Department of Applied Chemistry, Beijing University of Chemical Technology, Beijing 100029, China
  • Received:1998-12-25 Online:1999-09-24 Published:1999-09-24

摘要: 制备了Ti,Fe,Cr,Ni改性的MCM-41,采用XRD、低温N2吸附及TPD手段研究了改性MCM-41的结构特征和表面性质.过渡金属可同品取代骨架Si,同品取代的能力与过渡金属离子半径有关.过渡金属改性MCM-41均具有较好的长程有序结构、均一的孔径分布和较高的比表面积.引入不同的过渡金属可以改变MCM-41表面酸性和亲水/憎水性.考察了改性MCM-41对苯氧化的催化性能.

关键词: 过渡金属, 改性MCM-41, 表面性质, 苯羟基化

Abstract: Taking advantage of the substitutability of the framework and the modifiability of the surface, the structural characteristics and the surface properties of MCM-41 were adjusted and controlled by transition-metal substitution.Owing to the accessibility of active site.and lower diffusion resistance, transition-metal substituted MCM-41 materials were chosen as catalysts for the hydroxylation of aromatics.Isomorphous substituted MCM-41 materials with well-ordered structrues were hydrothermally synthesized by adding Al or Ti, Fe, Cr and Ni compounds to the reaction mixtrue.Not only do the long-range characterisitcs and local structures vary with the nature and amount of the heteroatom, but the characteristics of the pore structure can also be adjusted to some extent by isomorphous substitution.Meanwhile, the surface acidity and the surface hydrophilicity of MCM-41 increased after inserting Al or transition metal elements into the framework, while the results of benzene and methanol-TPDshow that the surface hydrophobicity of MCM-41 decreased.Transition-metal substituted MCM-41 materials were used as catalysts for the liquidphase hydroxylation of aromatics.The catalytic activities of substituted MCM-41 are influenced by both the redox properties of the transition elements and the surface hydrophilicity/hydrohobicity.owing to its Lewis acid nature and the hydrophobic surface, Ti-MCM-41gives high conversion of benzene and high chemical selectivity to the intermediate productphenol.The chemical selectivity can be controlled by matching the hydrophilicity/hydrophobicity of the MCM-41 catalyst, and the polarity of the solvent to the polarities of the reacantbenzene and intermediate product-phenol.MCM-41 exhitits some geometrical selectivity because of the narrow distribution of pore diameters.The accessible active sites, lower diffusio n resistance and unique surface properties result in a better catalytic performance than microporous TS-1 in the hydroxylation of benzene.The MCM-41 catalysts can be reactived by calcination.

Key words: Transition metal substitutied, MCM-41, Surface properties, Hydroxylation of benzene

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