Enhanced C-H Bond Activation by a Concerted Mechanism: A Comparative Microkinetic Analysis of Propane Dehydrogenation over Single-Pt-Doped θ- and γ-Al2O3 Catalysts

Alumina is among the most widely used supports in the field of heterogeneous catalysis. In this work, DFT calculations and microkinetic analysis have been combined to examine the catalytic behaviors of theta- and gamma-Al2O3-supported Pt single atom catalysts in propane dehydrogenation (PDH). Calculated results indicate oxygen vacancies may weaken the Lewis acid-base interactions between a pair of coadsorbed amphoteric species at the Al-O sites. Although the coadsorption cannot be strengthened at the Pt-O sites, the reaction intermediates involved are bound most tightly at the Pt sites. A concerted mechanism in which two C-H bonds are simultaneously activated is proposed on Pt-doped theta-Al2O3, which dominates the stepwise mechanism and gives rise to a high activity. In contrast, PDH cannot take place along the concerned pathway on Pt-doped gamma-Al2O3 because of the large surface distortion induced. These results provide a rational interpretation of the superior PDH performance of the theta-Al2O3-supported Pt catalyst