engleski

Seed-Induced, Structure Directing Agent-Free Crystallization of Sub-Micrometer Zeolite ZSM-5: A Population Balance Analysis

Crystallization of sub-micrometer size zeolite ZSM-5 from TPA-free reaction mixture 1.0Al2O3/100SiO2/28Na2O/4000H2O, seeded with silicalite-1 seed crystals of two different sizes (260 and 690 nm) was analyzed by population balance methodology. From this reason, measured changes of crystal size distributions and fractions of newly formed crystalline phase (ZSM-5) were compared with the calculated (simulated) data. A small disagreement between measured and simulated crystal size distributions of the crystalline end products for D ≥ 0.5 m (D is the equivalent spherical diameter as measured by laser-light scattering method) is explained by the formation of a small proportion of crystal aggregates at the end of crystallization process. However, almost perfect correlation between measured and simulated kinetics of crystallization shows that the formation of aggregates do not considerably influence the growth rate of zeolite ZSM-5 on silicalite-1 seed crystals. Analysis of the obtained results have shown that the crystallization process takes place by a linear, size-independent growth of silicalite-1 seed crystals embedded in the gel matrix and that the breeding of new nuclei during crystallization, is not favourable. Moreover, such methodology was also applied for the analysis of the alkaline-treated products. The obtained results show that the applied population balance model enables control and prediction of the particulate properties of as-synthesized and alkaline treated crystalline end products.

Sub-micrometer sized zeolite ZSM-5 ; TPA-free synthesis ; Seeding ; Mechanism of Crystallization ; Population balance ; Particulate properties

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