波谱学杂志 ›› 2007, Vol. 24 ›› Issue (4): 501-509.

• 祝贺邬学文先生八十华诞(专辑) • 上一篇    下一篇

NMR探针分子表征分子筛酸性的理论研究

邬忠琴1,2,  郑安民1,  杨俊1, 邓风1*   

  1. 1.波谱与原子分子物理国家重点实验室(中国科学院 武汉物理与数学研究所), 湖北武汉430071;
    2.中国科学院 研究生院, 北京100049
  • 收稿日期:2007-05-15 修回日期:2007-05-21 出版日期:2007-12-05 发布日期:2007-12-05
  • 作者简介:邬忠琴(1982-),女,湖北荆门人,硕士研究生,无线电物理专业.*通讯联系人:邓风,电话:027-87198820,E-mail:dengf@wipm.ac.cn.
  • 基金资助:

    国家自然科学基金资助项目(20425311).

Characterization of Acidity of Zeolites by NMR Probe Molecules:A Theoretical Investigation

WU Zhong-qin1,2, ZHENG An-min1, YANG Jun1, DENG Feng1*   

  1. 1.State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics (Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences), Wuhan 430071, China; 
    2.Graduate School of the Chinese Academy Sciences, Beijing 100049, China
  • Received:2007-05-15 Revised:2007-05-21 Online:2007-12-05 Published:2007-12-05
  • About author:*Corresponding author:Deng Feng,Tel:027-87198820,E-mail:dengf@wipm.ac.cn.
  • Supported by:

    国家自然科学基金资助项目(20425311).

摘要:

用量子化学计算的方法,采用三甲基氧膦(TMPO)、吡啶和三甲基膦(TMP)3种探针分子,研究了工业上常用的3种分子筛H-Y、H-ZSM5、H-MOR的Bronsted酸强度,讨论了这3种探针分子化学位移与Bronsted相对酸强度的相关性,揭示了各种探针分子在表征Bronsted酸性上的适用性.

关键词: 核磁共振, 化学位移, 探针分子, 量化计算, 分子筛, 吸附能

Abstract:

In this contribution, trimethylphosphine oxide (TMPO), pyridine and trimethylphosphine (TMP) were selected as NMR probe molecules to study the acid strength of several industrially used zeolites (H-Y, H-ZSM5 and H-MOR) theoretically. The relationship between chemical shifts of these probe molecules and acid strength of zeolites was revealed. In the meanwhile, the applicability of probe molecules on the characterization of Bronsted acidity was discussed. Since the 1H, 15N and 31P chemical shift ranges of adsorbed D5-pyridine and TMP on the Bronsted acid sites in zeolites were relatively very smaller (i.e., δ 18.2 ~ 18.7,  δ  -191.0~-186.9, δ  -8.7~-3.5 for 1H, 15N and 31P, respectively), they were only used to detect the existence of acidic protons in the zeolites. However, the 31P chemical shift range of adsorbed TMPO ranges from δ 62.8 to δ 90.5, and it may be expected that the adsorbed TMPO were very sensitive to measure solid acid strengths of the zeolites catalysts, compared with the 31P NMR of adsorbed TMPO.

Key words: NMR, chemical shifts, probe molecule, quantum chemical calculation, zeolite, adsorption energy

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