Quantitatively Mapping the Distribution of Intrinsic Acid Sites in Mordenite Zeolite by High-Field 23Na Solid-State Nuclear Magnetic Resonance

Benhan Fan; Wenna Zhang; Pan Gao; Guangjin Hou; Rongsheng Liu; Shutao Xu; Yingxu Wei; Zhongmin Liu

doi:10.1021/acs.jpclett.2c00932

Quantitatively Mapping the Distribution of Intrinsic Acid Sites in Mordenite Zeolite by High-Field ²³Na Solid-State Nuclear Magnetic Resonance

J Phys Chem Lett. 2022 Jun 6:5186-5194. doi: 10.1021/acs.jpclett.2c00932. Online ahead of print.

Authors

Benhan Fan^{1

2}, Wenna Zhang¹, Pan Gao³, Guangjin Hou³, Rongsheng Liu^{1

2}, Shutao Xu¹, Yingxu Wei¹, Zhongmin Liu^{1

3

2}

Affiliations

¹ National Engineering Research Center of Lower-Carbon Catalysis Technology, Dalian National Laboratory for Clean Energy, iChEM (Collaborative Innovation Center of Chemistry for Energy Materials), Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China.
² University of Chinese Academy of Sciences, Beijing 100049, P. R. China.
³ State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, P.R. China.

PMID: 35666100
DOI: 10.1021/acs.jpclett.2c00932

Abstract

It is of great significance to accurately quantify the Brønsted acid sites (BASs) at different positions of mordenite (MOR) zeolite. However, H-MOR obtained from Na-MOR can hardly avoid dealumination under hydrothermal conditions, which causes difficulty in the acid characterization. Herein, ²³Na-²⁷Al D-HMQC was performed combined with high-field ²³Na MQ MAS NMR and DFT calculation, which provided an unambiguous attribution of the ²³Na chemical shifts and further helped to improve the resolution of ²⁷Al MAS NMR. By fitting the ²³Na and ¹H MAS NMR spectra of Na/H-MOR, the intrinsic BAS contents in different T-sites were measured by characterizing the location and content of sodium ions. These Na/H-MOR zeolites with various acid distributions were used for DME carbonylation and showed that the amount of BASs in the T3 site was proportional to the activity of carbonylation. This study provides a new method for investigating the intrinsic acid properties of zeolites.