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Population Balance of Seed-induced, SDA-free crystallization of Sub-micrometer Zeolite ZSM-5

Crystallization of sub-micrometer zeolite ZSM-5 from TPA-free reaction mixture1.0Al2O3/100SiO2/28Na2O/4000H2O, seeded with silicalite-1 seed crystals of different size (90 - 690 nm) was analyzed by population balance methodology. From this reason, mesured 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 micrometers (D is the spherical equivalent diameter measured by laser-light scattering method) is explained by formation of small proportion of crystal aggregates during crystallization. However, almost perfect correlation between measured and simulated kinetics of crystallization shows that the formation of aggregates do not considerably influences the growth rate of zeolite ZSM-5 on silicalite-1 seed crystals. Thus, population balance analysis of the crystallization process and particulate properties of the crystalline end products show that crystallization takes place by a linear, size-independent growth of silicalite-1 seed crystals embedded in the gel matrix and that there is not formation of new nuclei during crystallization. The obtained results also show that the developed population balance model enables control and prediction of the particulate properties of the crystalline end products.

Zeolite ZSM-5; Synthesis; SDA-free; Seed-induced; Population balance

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