MAS NMR studies of modified HY zeolites  

作　　者：LI Wenli WANG Yi TAN Zhongyin BAO Xinhe 

机构地区：[1]State Key Laboratory of Catalysis,Dalian Institute of Chemical Physics,Chinese Academy of Sciences,Dalian 116023,China [2]Department of Chemistry,Liaoning Normal University,Dalian 116029,China

出　　处：《Chinese Science Bulletin》2000年第4期325-330,共6页

摘　　要：The variations in structure and acidity on the internal and external surfaces of HY zeolites modified by MgO and SiO2 have been studied by MAS NMR, together with the selective adsorption of perfluorotributyl-amine. 27AI and 29Si MAS NMR spectra revealed that the modifications led to significant changes of the framework owing to the migration of some non-framework Si and Al into the framework in the course of the modifications. 1H MAS NMR spectra showed that the modifications decreased the acidity of the zeolite surfaces. With an increasing of the loading of the oxides, the acidity of the surface decreased further. Both of the two kinds of Bronsted acidity of the MgO-modified HY zeolites decreased, particularly those in the supercages, while those of the SiO2-modified HY zeolites decreased less, and this result is consistent with that of NH3-TPD. From the adsorption of perfluorotributyl-amine, it was found that the acidic sites on the external surface of the HY zeolite can be completely covered by SiO2The variations in structure and acidity on the internal and external surfaces of HY zeolites modified by MgO and SiO2 have been studied by MAS NMR, together with the selective adsorption of perfluorotributyl-amine.27Al and29Si MAS NMR spectra revealed that the modifications led to significant changes of the framework owing to the migration of some non-framework Si and Al into the framework in the course of the modifications.1H MAS NMR spectra showed that the modifications decreased the acidity of the zeolite surfaces. With an increasing of the loading of the oxides, the acidity of the surface decreased further. Both of the two kinds of Br?nsted acidity of the MgO-modified HY zeolites decreased, particularly those in the supercages, while those of the SiO2-modified HY zeolites decreased less, and this result is consistent with that of NH3-TPD. From the adsorption of perfluorotributyl-amine, it was found that the acidic sites on the external surface of the HY zeolite can be completely covered by SiO2 after being modified by the chemical liquid deposition (CLD) method.

关 键 词：HY ZEOLITE MAS NMR modification ACIDIC SITE loading. 

分 类 号：P578[天文地球—矿物学]