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Keywords:

  • crystal growth;
  • heterogeneous catalysis;
  • mesoporous materials;
  • microporous materials;
  • zeolites

Abstract

Preparation and characterization of well-organized zeolitic nanocrystal aggregates with an interconnected hierarchically micro–meso–macro porous system are described. Amorphous nanoparticles in bimodal aluminosilicates were directly transformed into highly crystalline nanosized zeolites, as well as acting as scaffold template. All pores on three length scales incorporated in one solid body are interconnected with each other. These zeolitic nanocrystal aggregates with hierarchically micro–meso–macroporous structure were thoroughly characterized. TEM images and 29Si NMR spectra showed that the amorphous phase of the initial material had been completely replaced by nanocrystals to give a micro–meso–macroporous crystalline zeolitic structure. Catalytic testing demonstrated their superiority due to the highly active sites and the presence of interconnected micro–meso–macroporosity in the cracking of bulky 1,3,5-triisopropylbenzene (TIPB) compared to traditional zeolite catalysts. This synthesis strategy was extended to prepare various zeolitic nanocrystal aggregates (ZSM-5, Beta, TS-1, etc.) with well-organized hierarchical micro–meso–macroporous structures.