Modeling spontaneous formation of precursor nanoparticles in clear-solution zeolite synthesis

Jorge, M and Auerbach, S M and Monson, P A (2005) Modeling spontaneous formation of precursor nanoparticles in clear-solution zeolite synthesis. Journal of the American Chemical Society, 127 (41). pp. 14388-14400. ISSN 0002-7863

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    Abstract

    We present a lattice model describing the formation of silica nanoparticles in the early stages of the clear-solution templated synthesis of silicalite-1 zeolite. Silica condensation/hydrolysis is modeled by a nearest-neighbor attraction, while the electrostatics are represented by an orientation-dependent, short-range interaction. Using this simplified model, we show excellent qualitative agreement with published experimental observations. The nanoparticles are identified as a metastable state, stabilized by electrostatic interactions between the negatively charged silica surface and a layer of organic cations. Nanoparticle size is controlled mainly by the solution pH, through nanoparticle surface charge. The size and concentration of the charge-balancing cation are found to have a negligible effect on nanoparticle size. Increasing the temperature allows for further particle growth by Ostwald ripening. We suggest that this mechanism may play a role in the growth of zeolite crystals.