Chinese Journal of Magnetic Resonance ›› 2021, Vol. 38 ›› Issue (4): 514-522.doi: 10.11938/cjmr20212927

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The Effects of Ammonium Hexafluorosilicate Post-Treatment on the Acidity of H-ZSM-5 Zeolite Studied by Solid-State NMR Spectroscopy

Yong-xiang WANG1,2,Qiang WANG2,*(),Jun XU2,Qing-hua XIA1,*(),Feng DENG2,*()   

  1. 1. Ministry-of-Education Key Laboratory for the Synthesis and Application of Organic Functional Molecules, Collaborative Innovation Center for Advanced Organic Chemical Materials Co-constructed by the Province and Ministry, Hubei University, Wuhan 430062, China
    2. State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Innovation Academy for Precision, National Centre for Magnetic Resonance in Wuhan, Wuhan 430071, China
  • Received:2021-06-29 Online:2021-12-05 Published:2021-08-18
  • Contact: Qiang WANG,Qing-hua XIA,Feng DENG E-mail:qiangwang@wipm.ac.cn;xiaqh518@aliyun.com;dengf@wipm.ac.cn

Abstract:

In this study, solid-state nuclear magnetic resonance (NMR) spectroscopy was used to probe the changes of acidity of H-ZSM-5 zeolite caused by ammonium hexafluorosilicate (AHFS) washing-related changes of aluminium species. It was observed that the four-coordinate framework aluminum species with Brønsted acidity were partially reduced, while the tri-coordinated framework aluminum with Lewis acidity was slightly decreased after the AHFS treatment. However, AHFS washing was also found to induce mild dealumination and a significant reduction of aluminum species with Lewis acidity containing Al-OH group on zeolites, thus resulting in a remarkable change in the overall acidity of the zeolites.

Key words: ammonium hexafluorosilicate (AHFS), trimethylphosphine oxide (TMPO) probe molecules, acidity, solid-state nuclear magnetic resonance

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