(504a) Examination of Brønsted and Lewis Acid-Catalyzed Alkane Reactions in MFI Zeolites Using a Hybrid QM/MM Scheme

Mansoor, E., University of California-Berkeley
Head-Gordon, M., University of California - Berkeley
Bell, A. T., University of California
MFI Zeolites are particularly well-suited for the valorization of light alkanes as aromatic compounds, due to their shape selectivity to Benzene, Toluene and Xylene (BTX) products and resistance to coke formation [1]. Both H-MFI and metal-exchanged H-MFI zeolites, such as Ga/H-MFI, Zn/H-MFI, etc. are capable of alkane aromatization. However, Brønsted Acid sites present in these zeolite catalysts are known to be less effective for catalyzing alkane dehydrogenation chemistry [2, 3]. Using QM/MM computations which accurately capture molecular adsorption in the MFI Framework, we predict the role of Lewis Acid sites in zeolite-catalyzed alkane transformations; with the help of both experimental and computational efforts, we demonstrate how Lewis Acidic Gallium Hydrides provide effective electronic stabilization to rate determining C-H Cleavage bottlenecks. We additionally investigate alkane reactions and zeolites which were not investigated in our earlier work [4].

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[2] T. F. Narbeshuber, H. Vinek, J. A. Lercher, Monomolecular Conversion of Light Alkanes over H-ZSM-5. J. Catal. 157, 388–395 (1995).

[3] A. Bhan, W. Nicholas Delgass, Propane Aromatization over HZSM-5 and Ga/HZSM-5 Catalysts. Catal. Rev. 50, 19–151 (2008).

[4] E. Mansoor, M. Head-Gordon, A.T. Bell, Computational Modeling of the Nature and Role of Ga Species for Light Alkane Dehydrogenation in Ga/H-MFI, Submitted. (2018).