(513cc) Improving Alkane Dehydrogenation Activity on ?-Al2O3 through Doping

Light olefins are one of the most valuable compounds in the chemical industry due to their use as building blocks in the synthesis of polymers, plastics, and petrochemicals. Taking advantage of the low cost of light alkanes, and their abundance in shale reserves, nonoxidative alkane dehydrogenation (ADH) on metal oxides is an attractive route to produce olefins. Several metal oxides, including γ-Al₂O₃ and β-Ga₂O₃, have shown promise as ADH catalysts due to their surface Lewis acid-base properties. However, there is still no systematic approach to screen catalysts for ADH, and this process is achieved mainly by experimental “trial and error”. To address this problem, we use density functional theory (DFT) calculations to investigate mechanisms (concerted and stepwise) of ethane, propane, and isobutane dehydrogenation on different surface sites of (100) undoped and Ga-doped γ-Al₂O₃. Our calculations reveal that doping γ-Al₂O₃ with Ga atoms significantly improves the catalytic activity by decreasing the C-H activation of the kinetically favored concerted mechanism. An alkane dehydrogenation model (prediction of C-H activation energies) was developed that accurately captures the effect of reactant substitution (through carbenium ion stability)¹, and catalyst acid-base properties (through dissociative H₂ binding energy)^2,3. Furthermore, with the dissociative H₂ binding energy being a descriptor for C-H activation, we demonstrate that it can be extended to predict the overall ADH turnover frequencies. Taken together, our developed methodology accelerates the screening of metal oxides toward ADH and introduces new routes (doping) to enhance catalytic activity.

1. Kostetskyy P., Nolan C., Dixit M., Mpourmpakis G. Industrial & Engineering Chemistry Research 57, 16657-16663 (2018)

2. Dixit M., Kostetskyy P., Mpourmpakis G. ACS Catalysis 8, 11570-11578 (2018)

3. Cholewinski M., Dixit M., Mpourmpakis G. ACS Omega 3, 18242-18250 (2018)