期刊
CHEMISTRY OF MATERIALS
卷 21, 期 4, 页码 641-654出版社
AMER CHEMICAL SOC
DOI: 10.1021/cm801951a
关键词
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资金
- Secretaria General de Politica Cientifica y Tecnologica
- Ministerio de Educacion y Ciencia in Spain [CTQ2005-09078, CTQ200502375]
- Ministerio de Educacion y Ciencia [PR2006-0078]
- U.S. Department of Energy, Office of Basic Energy Sciences, Catalysis Sciences [DE-FG02-03ER15467]
- USARO [W911NF-05-1-0085]
- NSF [DMR 05-20415]
Surface-passivating silanization of protozeolitic units has been shown to be an effective strategy for the preparation of ZSM-5 nanocrystals, showing a controlled aggregation degree and a hierarchical porosity. ZSM-5 zeolite materials are thus obtained with adjustable and relatively uniform mesoporosities that have a strong influence on resulting macroscopic reaction properties, especially for macromolecular reagents. The mean sizes of the nanounits and, therefore, the textural and accessibility of these materials can be varied by changing the precrystallization conditions and the concentration of the seed-silanization agent. In addition to conventional characterization techniques, solid-state two-dimensional (21)) nuclear magnetic resonance (NMR) spectroscopy measurements and the application of the NLDFT model to the argon adsorption isotherms have allowed both the local and the mesoscopic compositions, as well as the structures of the hierarchically porous ZSM-5 materials, to be established. The resulting combination of mesopore sizes and exterior-nanocrystal surface properties of the hierarchically structured ZSM-5 zeolites is shown to catalyze reactions that are otherwise limited by steric and/or diffusional limitations, as demonstrated by their enhanced activity for polyethylene cracking.
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