Synthesis and characterization of LTA zeolite with uniform intracrystal mesopores directed by bridged polysilsesquioxane monomer |
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Authors: | Guoqiang Song Hongtao Liu Fuxiang Li Zhiping Lv Jianwei Xue |
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Affiliation: | 1. Institute of Special Chemicals, Taiyuan University of Technology, 79# West Yingze Street, Taiyuan, 030024, People’s Republic of China
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Abstract: | An ordered mesoporous LTA zeolites (MLTA) have been synthesized in presence of the bridged polysilsesquioxane monomer (BS-1) as mesoporogen. The relatively well-defined small-angle X-ray diffraction peaks and nitrogen sorption isotherms with narrow pore size distribution centered at around 2.2 nm both indicated the presence of uniformly mesopores in MLTA samples. The scanning electron microscopy and transmission electron microscopy observations further confirmed that the uniform and partially interconnected intracrystal mesopores were randomly distributed throughout the globular particles with rugged surfaces. Interestingly, removal of the BS-1 resulted in uniform mesopore diameters that are nearly consistent with the molecular size of BS-1 (1.8 nm). 29Si MAS NMR revealed that the BS-1 was linked to MLTA zeolite crystal surface through 2 Si–O bonds and 3 Si–O bonds before calcinations. Nitrogen sorption analysis showed that the mesoporosity in MLTA samples could be adjusted by adding different amounts of BS-1 in starting gels. Relative to conventional mesoporous materials, one obvious feature of MLTA is that the resultant mesopores were structured by the bridged polysilsesquioxane monomer instead of commercial polymers or micelles, which broad the routes in synthesizing of various mesoporous materials with controllable pore size distribution, adjustable mesopore volume, and large surface area. |
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