In recent years, ZSM-5 aggregates fabricated by nanocrystals have attracted great attentions to overcome the problem of separation and meanwhile retain the shorter diffusion path length of nanocrystals. But, to the knowledge of our best, aggregates prepared by present strategies are always of non-uniform sizes and coupled with isolated nanocrystals. These small particles are either initially synthesized or peeled from aggregates afterwards, which would be still very difficult for separation and recovery. Therefore, ZSM-5 aggregates with a more concrete structure are needed for industrial application.<br/>Here, we report a one-step hydrothermal synthesis of ZSM-5 s with a compact shell (named AZ) in very dense gels with a single organic amine template. The resultant materials are like a core-shell aggregate structure. The shell is formed by the intergrowth of twin crystals as a whole, which gives the material strong mechanic strength and facile collection through filtration (Fig. 1A). The broken crystal (Fig. 1B) shows the core is composed of aggregates with stacked primary particles (about 100nm). Moreover, the adopted dense gels with low H2O/SiO2 (&lt;9) could enhance product yield and reduce the usage of SDA and discharge of waste. N2 sorption analysis (Fig. 1C) shows the total and external surface areas of AZ are larger than the conventional nanocrystals (named NZ, 300nm) because of the smaller size of primary particles. Applied to hexane catalytic cracking (Fig. 1D), the longer lifetime of AZ than NZ benefits from improved diffusion properties due to its smaller primary particles and inter-crystalline mesopores. These above characters of AZ make it very potential for practical industrial application.

Hierarchical ZSM-5 aggregates with a compact shell synthesized in extremely dense gels

255th National Meeting (2018)

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