(378f) Identifying Alkane Dehydrogenation Metal-Oxide Catalysts through Lewis Acid-Base Strengths

Non-oxidative dehydrogenation of alkanes (DH) on metal oxides is a promising route to satisfy the increasing global demand of olefin production.^[1-3]Metal oxides are attractive DH catalysts owing to their surface Lewis acid-base functionalities.^[1,2] Due to high degree of surface heterogeneity of metal oxides, the identification of structure activity relationships is highly desirable to facilitate designing and screening of active catalysts. Recent computational work revealed the dissociated H₂ binding energy (H₂BE) as an activity descriptor for alkane DH on pristine and Ga-doped γ-Al₂O₃, accounting for the Lewis acidity and basicity of the active sites.^[1,2] Importantly, a volcano-shape relationship was identified between DH activity and H₂BE on different γ-Al₂O₃ facets.¹ Herein we systematically computationally screen 20 catalysts of group IIA, IIIA, and IVA metal oxides as potential candidates for alkane DH. We apply Density Functional Theory to calculate the H₂BE on the most thermodynamically stable facet of each oxide. We then investigate the stepwise and concerted pathways of propane DH on oxide catalysts with varying H₂BE. We identify CaO that exhibits H₂BE corresponding to a catalytic optimum (top of the volcano plot), thus revealing a potential catalyst for alkane DH to olefins. We demonstrate that the H₂BE descriptor can be used as a DH activity descriptor on oxides that follow a concerted C-H activation mechanism (i.e. simultaneous cleavage of two C–H bonds to directly form the olefin). Furthermore, we probe the Lewis acidity and basicity of oxides by identifying the location of the unoccupied and occupied band centers, respectively. We demonstrate a quantitative relationship between band centers, Lewis acidy/basicity, and DH activity, thus connecting electronic properties of metal oxides with the overall catalytic behavior. Our developed relationships find application on alkane dehydrogenation chemistries and general C-H activation processes.