(516g) Developing Data-Driven Methods to Enable Computationally Efficient First-Principles Kinetic Models in Nanoporous Catalysts

Crystalline nanoporous solids such as zeolites are employed in a wide range of chemical processes due in part to their tunable micro-environments. Kinetics at internal zeolite acid sites can be modified by changing pore size, pore architecture, or polarity.^1,2 These environments impart shape-selectivity that preferentially stabilizes transition states, but the large design space including pore architecture, polarity, and catalytic active site identity precludes comprehensive kinetic studies. Density functional theory (DFT) describes the electronic states of reactive intermediates and transition states but cannot access the longer length scales necessary to quantify adsorbate entropy and the fluxionality of coadsorbed species or solvents. Force field-based simulations can accurately capture these conformational changes but require parameterized values. Machine learning interatomic potentials have emerged as a technique to derive parameterized models from DFT data, and thereby link DFT and force field-based observables.

We used zeolite-catalyzed lactic acid dehydration to acrylic acid³ and ethanol-to-olefins⁴ as probe reactions to interrogate the relative importance of intrinsic kinetic barriers and mass transfer on product selectivity. We then developed machine learning strategies to accelerate the quantification of hopping rate constants and quasi-harmonic adsorbate entropies under reaction conditions and demonstrated their relevance for predicting turnover frequencies, reaction orders, and product selectivities using microkinetic models. These methods are scalable for larger reaction pathways allowing for the development of ab-initio microkinetic models that account for quasi-harmonic interactions and improved predictions of reaction kinetics.

1. Bukowski, B. C. et al. “Defect-Mediated Ordering of Condensed Water Structures in Microporous Zeolites”. Chem. Int. Ed. 2019.
2. Bregante, D. T. et al. “Cooperative Effects between Hydrophilic Pores and Solvents: Catalytic Consequences of Hydrogen Bonding on Alkene Epoxidation in Zeolites”. Am. Chem. Soc. 2019.
3. Yan, B. et al. “Acrylic Acid Production by Gas-Phase Dehydration of Lactic Acid over K+-Exchanged ZSM-5: Reaction Variable Effects, Kinetics, and New Evidence for Cooperative Acid–Base Bifunctional Catalysis”. Eng. Chem. Res. 2020.
4. Zhang, J. et al. “Isolated Metal Sites in Cu–Zn–Y/Beta for Direct and Selective Butene-Rich C3+ Olefin Formation from Ethanol”. ACS Catal. 2021.