475338 Mechanistic, Spectroscopic and Theoretical Assessment of Porous Catalytic Materials
Porous crystalline materials such as zeolites or porous organic polymers provide a large and diverse pool of heterogeneous catalysts and catalyst supports. Thorough mechanistic investigations that employ characterization of material properties and surface structure, kinetic and isotopic studies, and computational modeling are needed in order to elucidate how these materials work as catalysts regardless of reaction or application. Further, this approach can be used in conjunction with specialized synthetic strategies in order to produce well-defined catalysts, imperative in understanding catalytic function.
One class of these materials, Brønsted acidic zeolites, catalyze a plethora of hydrocarbon and oxygenate reactions, which are mediated by ion-pair transition states. My graduate research with Prof. Enrique Iglesia investigated the factors that affect reactivity, specifically the size, shape and charge of the organic cation (derived from reactants) and anion (formed after deprotonation of the inorganic catalyst). We combined state-of-the-art theoretical methods (density functional theory) with rigorous kinetic measurements from a range of reactants and catalysts that led to a copious array of transition states and precursors. Key properties of these systems include how the anion (i) accepts the negative charge (acid strength), which results in an electrostatic interaction with the organic cation, and (ii) provides van der Waals interactions, which are dependent on the size and shape of the organic component and the surrounding pore environment (confinement). The synergy between theory and experiment exposed unprecedented mechanistic detail, such as the flexibility of zeolites to distort locally to increase van der Waals interactions with the cation. These distortions cost energy, however, and can be expensive if the transition state is too large. Thorough studies incorporating both experiment and theory can provide clarity into complex relationships, such as this one between organic moieties and inorganic zeolite catalysts.
Future plans will utilize these results and methods, along with incorporating synthetic techniques, as a framework for studying porous catalytic materials from different catalyst classes and for other reaction pathways/applications. This framework can be extended to understand effects of important catalyst properties on reactivity and selectivity in order to advance rational catalyst design.
Teaching, in the classroom and in the laboratory, is an outlet to share my zeal for science and a major driving force in my pursuit of an academic career. One benefit of research in catalysis is that multiple pillars of chemical engineering (kinetics, transport and thermodynamics) must be mastered, though I most enjoy teaching chemical reaction engineering courses. I was a graduate student instructor at UC Berkeley for the undergraduate and graduate level as well as designed and taught a new course titled “Energy and Atom Efficient Catalytic Conversions,” which covered both current and green(er), alternative industrial catalytic reactions for energy, fuel and chemical production.
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