Density functional theory (DFT) is used to model reaction pathways of the oxidation of n-butane to 1-butanol over metal alloy and pure metal catalysts under steric constraints, and the implications on designing MOF-encapsulated catalysts are discussed. MOFs are porous crystalline solids comprised of metal-based nodes connected by organic "linker" molecules. Recently, they have been successfully grown around metal nanoparticles, creating porous networks at the MOF/catalyst interface, which have been shown to promote the regioselective hydrogenation of trans-1,3-hexadiene to 3-hexene. In this work, we explore the use of sterically constrained MOF-encapsulated catalysts for selective alkane oxidation. We are specifically interested in n-butane oxidation to 1-butanol, which is important in the pharmaceuticals, energy, and specialty chemicals industries. It is a useful reaction for studying regioselectivity since 2-butanol is thermodynamically more stable than 1-butanol. In this work, we investigate n-butane oxidation to 1-butanol and 1-butanal on the (111) facets of Cu, Cu3Pd, Pd, Ag3Pd, and PdZn. We use a "surrogate pore" comprised of helium atoms to model the MOF pores. We compute the energies of reaction intermediates and transition states involved in the mechanism using DFT, and we develop scaling relationships linking these energies to simpler "descriptors" of catalytic activity. We use these scaling relationships in microkinetic modeling to identify the optimal descriptor values, which maximize the rate and selectivity to 1-butanol. Further, we perform degree of rate control analysis in order to reveal the catalytic intermediates and transition states that have the greatest control on the rate. The results reveal design criteria for n-butane selective oxidation to 1-butanol.

Selective oxidation of n-butane to 1-butanol over transition metal catalysts encapsulated by metal-organic frameworks

255th National Meeting (2018)

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