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  

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

作　　者：赵星岭 齐国栋 王强 褚月英 高伟 李申慧 徐君 邓风[1] ZHAO Xingling;QI Guodong;WANG Qiang;CHU Yueying;GAO Wei;LI Shenhui;XU Jun;DENG Feng(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;University of Chinese Academy of Sciences,Beijing 100049,China;Wuhan National Laboratory for Optoelectronics,Huazhong University of Science and Technology,Wuhan 430074,China)

机构地区：[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

出　　处：《高等学校化学学报》2020年第12期2681-2689,共9页Chemical Journal of Chinese Universities

基　　金：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(批准号:QYZDB-SSWSLH027);湖北省自然科学基金(批准号:2017CFA032)资助。

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Brønsted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.A series of Ga-modified ZSM-5 zeolites were prepared by different methods.The structure and acidity of these catalysts were characterized by solid-state NMR(ssNMR).The catalytic reactions for propane aro⁃matization 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 con⁃tains 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 gallium clusters and cationic Ga species.Cationic Ga species was favored on Ga/ZSM-5-IE prepared by ion ex⁃change.Both dispersed gallium clusters and cationic Ga exhibited stronger Lewis acidity.The results of pro⁃pane 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 Brønsted 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.

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 

分 类 号：O643[理学—物理化学]