高等学校化学学报 ›› 2020, Vol. 41 ›› Issue (12): 2681-2689.doi: 10.7503/cjcu20200474

• 庆祝《高等学校化学学报》复刊40周年专栏 • 上一篇    下一篇

Ga改性Ga/ZSM-5分子筛的结构、 性质及其催化丙烷芳构化的固体核磁共振波谱研究

赵星岭1,2, 齐国栋1, 王强1, 褚月英1, 高伟1,2, 李申慧1, 徐君1,3(), 邓风1   

  1. 1.中国科学院精密测量科学与技术创新研究院, 武汉物理与数学研究所, 波谱与原子分子物理国家重点实验室, 武汉 430071
    2.中国科学院大学, 北京 100049
    3.华中科技大学, 武汉国家光电研究中心, 武汉 430074
  • 收稿日期:2020-07-20 出版日期:2020-12-10 发布日期:2020-12-09
  • 通讯作者: 徐君 E-mail:xujun@wipm.ac.cn
  • 基金资助:
    国家自然科学基金(批准号(U1932218);21872170 , 21733013)、 中国科学院前沿科学重点项目(QYZDB-SSW-SLH027);湖北省自然科学基金(2017CFA032)

Structure, Nature and Activity of Ga Species for Propane Aromatization in Ga/ZSM-5 Revealed by Solid-state NMR Spectroscopy

ZHAO Xingling1,2, QI Guodong1, WANG Qiang1, CHU Yueying1, GAO Wei1,2, LI Shenhui1, XU Jun1,3(), DENG Feng1   

  1. 1.State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics,Wuhan Institute of Physics and Mathematics,Innovation Academy for Precision Measurement Science and Technology,Chinese Academy of Sciences,Wuhan 430071,China
    2.University of Chinese Academy of Sciences,Beijing 100049,China
    3.Wuhan National Laboratory for Optoelectronics,Huazhong University of Science and Technology,Wuhan 430074,China
  • Received:2020-07-20 Online:2020-12-10 Published:2020-12-09
  • Contact: XU Jun E-mail:xujun@wipm.ac.cn

摘要:

采用不同的方法制备了一系列Ga改性的ZSM-5分子筛催化剂, 通过固体核磁共振波谱(ssNMR)技术对催化剂的结构和酸性进行了表征, 并考察了其催化丙烷芳构化的性能. 结合71Ga NMR、 吸附三甲基磷(TMP)探针分子的一维31P 和二维(2D)1H-31P HETCOR NMR实验, 发现物理混合法制备的Ga2O3/ZSM-5样品只含有具有较弱Lewis酸性的Ga2O3物种, 浸渍法制备的Ga/ZSM-5-ox和浸渍后还原再氧化法制备的Ga/ZSM-5-redo 2种样品上主要以高分散的氧化镓和阳离子Ga物种为主, 而离子交换法制备的Ga/ZSM-5-IE样品上Ga主要以阳离子Ga物种的形式存在, 高分散的氧化镓和阳离子Ga物种都具有更强的Lewis酸性. Ga/ZSM-5分子筛催化丙烷芳构化反应的结果表明, Ga物种与酸性明显影响催化剂的芳构化性能, 丙烷的转化率和芳烃的选择性顺序为 Ga/ZSM-5-IE>Ga/ZSM-5-redox>Ga/ZSM-5-ox>Ga2O3/ZSM-5>H-ZSM-5. 2D 1H-31P HETCOR NMR实验结果表明, Ga/ZSM-5催化剂上产生的Br?nsted酸和Lewis酸(阳离子以及高分散Ga物种)的协同作用提高了分子筛的催化反应活性.

关键词: 金属改性分子筛, 活性位, 结构表征, 丙烷芳构化, 固体核磁共振

Abstract:

A series of Ga-modified ZSM-5 zeolites were prepared by different methods. The structure and aci-dity of these catalysts were characterized by solid-state NMR(ssNMR). The catalytic reactions for propane aromatization were also investigated. With the help of 71Ga NMR and trimethylphosphine(TMP) probe 1D 31P and 2D 1H-31P HETCOR NMR, it was found that the Ga2O3/ZSM-5 sample prepared by physical mixing only contains Ga2O3 species with weak Lewis acidity, and the samples prepared by impregnation(Ga/ZSM-5-ox) and impregnation followed by reduction-oxidation treatment(Ga/ZSM-5-redox) contain both highly dispersed ga- llium clusters and cationic Ga species. Cationic Ga species was favored on Ga/ZSM-5-IE prepared by ion exchange. Both dispersed gallium clusters and cationic Ga exhibited stronger Lewis acidity. The results of propane aromatization over Ga-modified ZSM-5 showed that the speciation and acidity of Ga have significant effect on the propane conversion. The conversion and selectivity to aromatics followed the order of Ga/ZSM-5-IE > Ga/ZSM-5-redox > Ga/ZSM-5-ox > Ga2O3/ZSM-5 > H-ZSM-5. The synergic active sites composed of Br?nsted acid site(BAS) and Lewis acid sites(cationic Ga and dispersed Ga species) on Ga/ZSM-5 zeolite were identified by 2D 1H-31P HETCOR NMR spectroscopy, which were correlated to the catalytic activity.

Key words: Metal-modified zeolite, Active site, Structural characterization, Propane aromatization, Solid-state NMR

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