(47g) Designing New Platforms to Control the Properties of Zeolite Catalysts

The ability to selectively control zeolite crystallization in organic-free syntheses without inducing the formation of unwanted crystal polymorphs is often a challenging task. In order to tailor material properties, such as zeolite size, shape, and composition, without sacrificing crystal purity, we constructed ternary diagrams at varying synthesis conditions [1]. These kinetic phase diagrams revealed regions of pure and mixed phases of more than eight zeolite framework types synthesized from colloidal silica and sodium aluminate. Increasing temperature and/or crystallization time revealed phase transformations following the Ostwald rule of stages, wherein metastable structures dissolve and recrystallize into more thermodynamically stable (higher density) framework types. We explored the fundamental mechanisms of zeolite structural transformations to identify synthetic routes capable of modifying material properties most critical for catalytic applications. This generalized platform serves as a basis for parameter selection to achieve phase-pure zeolites and provides systemic insight into the effect of synthesis parameters on phase behavior and the rational design of zeolite catalysts with optimal physicochemical properties.

[1] Maldonado, M., Oleksiak, M.D., Chinta, S., Rimer, J.D., J. Am. Chem. Soc. 135 (2013) 2641-2652.