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

Abstract

Crystallization of sub-micrometer sized zeolite ZSM-5 from a TPA-free (TPA = tetrapropyl ammonium) reaction mixture 1.0Al 2 O 3 /100SiO 2 /28Na 2 O/4000H 2 O, seeded with silicalite-1 seed crystals of two different sizes (260 and 690 nm), was analyzed by population balance methodology. Changes in crystal size distributions and fractions of the newly formed crystalline phase (ZSM-5) were measured and compared with the calculated (simulated) data. For the crystalline end products having D ≥ 0.5 μm (D is the equivalent spherical diameter as measured by a laser-light scattering method), a small disagreement between measured and simulated crystal size distributions is observed and explained by the formation of a small proportion of crystal aggregates at the end of the crystallization process. However, an 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 has also shown that the crystallization process takes place only by a linear, size-independent growth of silicalite-1 seed crystals embedded in the gel matrix and thus that the process of crystallization is consistent with the absence of extra nucleation in the presence of seed crystals. Moreover, such methodology was also applied for the analysis of the alkaline-treated products. The obtained results show that the applied population balance methodology enables control and prediction of the particulate properties of as-synthesized and alkaline-treated crystalline end products, which is of great significance for their further applications.

Anti-cancer activity of hierarchical ZSM-5 zeolites synthesized from rice-based waste materials

“…9,10 However, the organic templates needed for the synthesis are toxic and highly expensive as well as these organic species enclosed within zeolitic structures can be removed by calcination at high temperatures; this inevitably leads to both energy consumption and environmental pollution. 11,12 Therefore, organic template-free synthesis of zeolites is strongly desirable since it is more ideal, cheaper, and less toxic. 13,14 Silica is the second most abundant element on the earth surface, which accounts for approximately 32% of the total weight of it.…”

Precise control of the size of zeolite B-ZSM-5 based on seed surface crystallization

“…Based on seed surface crystallization mechanism, N. Ren et al proposed a method for facile, rapid, controllable and low-cost synthesis of ZSM-5 zeolite with submicron-size. [40][41][42][43] Furthermore, crystal growth kinetics, crystalline yield, and physicochemical properties of zeolite nanoparticles as a function of the seed concentration and synthesis temperature were addressed by V. Valtchev et al 44 However, most reports focused on the study of the seed role under a single system. Few studies have revealed the effect of the synthesis system on the particle size of ZSM-5 in the presence of seed crystals.…”

Operating Strategy for Continuous Multistage Mixed Suspension and Mixed Product Removal (MSMPR) Crystallization Processes Depending on Crystallization Kinetic Parameters

“…19,20 The PBE have been applied for estimating and modeling various crystallization systems. 11,12,[21][22][23][24] However, PBE containing breakage and agglomeration terms, which are commonly expressed as integral functions, are so complex that analytic solution of the PBE could not be obtained. 18 Although solutions of the PBE could be obtained by several numerical methods, such as the method of moments, 25,26 the method of characteristics, 27 discretized population balances, [28][29][30] and weighted residuals, 31 the computation time for model solving is significantly long and it is too difficult to estimate the parameters required for expressing the breakage and agglomeration phenomena.…”