(387c) The Multifunctional Role of Zinc on Zeolite Growth

Zeolites are aluminosilicate materials used across a wide range of fields such as catalysis, ion-exchange, and separations, due to their diverse structural and chemical properties. Because of their importance in the chemical industry, zeolites have been extensively studied in an effort to gain control of structure and functionality during synthesis. Cationic species are often used as inorganic structure-directing agents during zeolite synthesis and can play a key role in the final zeolite product, as well as stabilize charges in the framework. In our recent work we have investigated the impact of cations on the initial oligomerization steps of zeolite growth^[1]. In this current work, we closely examine the effects of zinc on zeolite growth and stability using first principles calculations and multiscale quantum mechanics/molecular mechanics (QM/MM) approaches. Specifically, we investigate the reaction profiles of early zeolite oligomerization steps in the presence of zinc, as well as the feasibility of zinc to be substituted into the FAU zeolite framework. Additionally, we address the behavior of hydrated zinc ions in a zeolite cell. Our results indicate that zinc decreases the exothermicity of oligomerization, in contrast to other cations (e.g. Na⁺ and Ca²⁺) which exhibit increased exothermicity. Our hydration calculations suggest that in a solvated environment zinc strongly coordinates with water, which may affect zinc’s propensity to be incorporated into the framework and the overall stability of the GIS zeolite. Overall, this work provides insights into the impact of zinc on zeolite growth and final framework stability.

[1] Freeman, E.E., Neeway, J.J., Motkuri, R.K., Rimer, J.D., Mpourmpakis, G. Understanding Initial Zeolite Oligomerization Steps with First Principles Calculations. AIChE Journal. (Under Review). 2020.