Density functional theory (DFT) is used to analyze both desired and undesired reaction pathways for the regioselective oxidation of n-butane to 1-butanol over a silver/palladium alloy catalyst under steric constraints, and the implications on the design of MOF-encapsulated catalysts are discussed. MOFs are porous crystalline solids comprised of metal nodes linked by organic molecules. Recently, they have been successfully grown around metal nanoparticles, creating porous networks at the MOF/catalyst interface. These networks have been shown to promote regioselective reactions such as hydrogenation of <i>trans</i>-1,3-hexadiene to 3-hexene, presumably by forcing the linear alkene to stand “upright” on the catalyst surface and allowing only the terminal C-H bonds to be activated. In this work, we study computationally the extension of this design concept to alkane oxidation. In our simulations, we provide similar steric constraints using a surrogate pore made of chemically inert atoms on an Ag<sub>3</sub>Pd(111) surface. We demonstrate several possible reaction pathways from n-butane to the desired 1-butanol product as well as to the undesired side products butanal and 1-butene oxide (which are both representative of the first steps of over-dehydrogenation). We find that the desired n-butane to 1-butanol reaction proceeds through an oxygen-assisted pathway leading to several side products that directly compete with 1-butanol formation. Microkinetic modeling results indicate that butanal formation is particularly favorable, suggesting that future work in the design of MOF-encapsulated catalysts for n-butane oxidation to 1-butanol should aim to tune the catalyst composition to inhibit this side reaction. Based on sensitivity analysis, i.e., the degrees of rate control, in our microkinetic model, we predict ways to tune the catalyst composition to improve the selectivity toward 1-butanol.

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

251st National Meeting (2016)

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