CAREER: Cation and Nanoparticle Interconversion in Metal-Exchanged Zeolites

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Small pore, microcrystalline zeolite materials are widely used in the chemicals and fuels industries for processes where molecular-scale capture, separation, or catalytic reaction is needed. In the case of catalysis, zeolites are often used in conjunction with extremely small particles of catalytic metals – or even individual atoms – dispersed throughout the nanoscale pores and voids in the zeolite structure. The resulting catalysts are highly effective for promoting specific catalytic reactions, while efficiently utilizing small amounts of expensive metals such as platinum or palladium. Nevertheless, the harsh conditions associated with many catalytic reactions results in metal particle agglomeration and concomitant loss of catalyst efficiency. The project develops computational molecular models and theory predicting the dynamics of agglomeration and redispersion of metals supported by zeolites. In addition, the models include design and synthesis features that deter the agglomeration of metal atoms and particles under reaction conditions, thus improving the energy efficiency of catalysts widely used for petrochemical and emissions related applications. The project is integrated with efforts that address retention of underrepresented communities at multiple points in the STEM pipeline, through collaboration with local organizations that emphasize coding for girls in K-12, and by organizing events that address social and professional development challenges faced by both international and domestic undergraduate and graduate engineering students. The project develops atomistic models that describe how zeolite composition, gas conditions, and nanoparticle size and distribution affect the thermodynamics and kinetics of cation and nanoparticle interconversion in zeolites. The main objectives are to 1) model the thermodynamics of zeolite-supported platinum and palladium cation and nanoparticle interconversion, 2) predict how catalytically relevant reactant gases promote or impede interconversion, 3) determine how zeolite encapsulation modulates the structure and energy of nanoparticles, and 4) determine the fundamental processes that govern the kinetics of interconversion between cations and nanoparticles. These objectives will be fulfilled by using molecular modeling tools that include density functional theory, wave function theory, classical forcefields, and Monte Carlo simulations. This project will provide guidance on the engineering of deactivation resistant zeolites, a challenge at the frontiers of catalysis and zeolite synthesis. Further, the project will enable transformative predictions of zeolite compositions and synthetic strategies that stabilize catalyst performance in the reaction environment.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.