Acta Chimica Sinica ›› 2022, Vol. 80 ›› Issue (5): 590-597.DOI: 10.6023/A22010014 Previous Articles     Next Articles

Special Issue: 中国科学院青年创新促进会合辑



张瑾a,c, 丁湘浓a, 刘红超a, 樊栋a, 徐舒涛a,*(), 魏迎旭a, 刘中民a,b,c   

  1. a 中国科学院大连化学物理研究所 甲醇制烯烃国家工程实验室 辽宁大连 116023
    b 中国科学院大连化学物理研究所 催化基础国家重点实验室 辽宁大连 116023
    c 中国科学院大学化学工程学院 北京 100049
  • 投稿日期:2022-01-09 发布日期:2022-05-31
  • 通讯作者: 徐舒涛
  • 作者简介:
  • 基金资助:
    国家自然科学基金(21972142); 国家自然科学基金(22022202); 国家自然科学基金(21991092); 国家自然科学基金(21991090); 大连市杰出青年基金项目(2021RJ01); 中国科学院前沿科学重点研究计划(QYZDY-SSW-JSC024); 中国科学院国际合作(121421KYSB20180007)

Study on the Framework Aluminum Distributions of HMOR Zeolite and Identification of Active Sites for Dimethyl Ether Carbonylation Reaction

Jin Zhanga,c, Xiangnong Dinga, Hongchao Liua, Dong Fana, Shutao Xua(), Yingxu Weia, Zhongmin Liua,b,c   

  1. a National Engineering Laboratory for Methanol to Olefins, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning 116023
    b State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning 116023
    c School of Chemical Engineering, University of Chinese Academy of Sciences, Beijing 100049
  • Received:2022-01-09 Published:2022-05-31
  • Contact: Shutao Xu
  • About author:
    Dedicated to the 10th anniversary of the Youth Innovation Promotion Association, CAS.
  • Supported by:
    National Natural Science Foundation of China(21972142); National Natural Science Foundation of China(22022202); National Natural Science Foundation of China(21991092); National Natural Science Foundation of China(21991090); Dalian Outstanding Young Scientist Foundation(2021RJ01); Key Research Program of Frontier Sciences, Chinese Academy of Sciences(QYZDY-SSW-JSC024); International Partnership Program of Chinese Academy of Sciences(121421KYSB20180007)

HMOR zeolites has an excellent performance similar to enzyme catalysis in the carbonylation of dimethyl ether (DME). The distribution of framework aluminum and the identification of the active site of the reaction are the key issues in the study of the reaction mechanism. The early work was based on theoretical calculation to study the active site of DME carbonylation, but lacked direct experimental evidence. In this work, a series of HMOR catalysts were prepared by calcination of NH4MOR at various temperatures. The stability and location of framework aluminum were studied by a variety of spectroscopic characterization methods. Moreover, the evidence of reaction mechanism was obtained by the carbonylation reaction activity of dimethyl ether related to the acidity of MOR zeolite and aluminum distribution. Firstly, it was found that the crystallinity and morphology of MOR zeolites did not change significantly after calcination at different temperatures by XRD (X-Ray diffraction) and SEM (Scanning electron microscope). However, it was found by 29Si, 27Al and 1H Magic angle spinning (MAS) solid-state nuclear magnetic resonance (NMR) that the local environment of HMORs was dealuminated, which resulted in obvious defect hydroxyl groups and the decrease of Brönsted acid sites (BASs) content. In addition, the calcination temperature has a great influence on the stability of framework Al of HMORs. Increase of calcination temperature will accelerate the occurrence of dealumination. Quantitative 1H MAS NMR combined with Fourier transform infrared spectra (FTIR) provided the distribution of BASs content in different channels of HMOR zeolites. By using 2D 27Al multiple quantum (MQ) MAS NMR method combined with the representative slices parallel to the F2 dimension of MQMAS NMR spectra at selected F1 chemical shift to distinguish the framework Al sites, it was found that when the temperature was lower than 600 ℃, framework Al atoms located in the different T-sites had the similar dealumination rate. But when the calcination temperature was increased to 600 ℃, the removal rate of Al atom at T3 site was accelerated. Furthermore, the relationship between the carbonylation performance of dimethyl ether and the distribution of Brønsted acid and aluminum was studied, and the definitive spectral evidence of the carbonylation activity center was obtained, that is, the Al site at T3-O33 was the active site of the carbonylation reaction.

Key words: HMOR, acidity, aluminum distribution, solid-state NMR, DME carbonylation