Catalytic Interplay of Ga, Pt, and Ce on the Alumina Surface Enabling High Activity, Selectivity, and Stability in Propane Dehydrogenation

Abstract

Pt-based bimetallic catalysts have been widely investigated in propane dehydrogenation (PDH) owing to their high activity in C-H cleavage and propylene selectivity. However, upon repeated coke oxidation for catalyst regeneration, they suffer from significant metal sintering and dealloying. Recently, gamma-Al2O3 doped with Ga, Pt, and Ce was reported to exhibit superior catalytic activity, selectivity, and stability in PDH, but the catalytic role of each element has not been clearly understood because of the complexity of this system. In this study, we rigorously investigated the reaction mechanism and catalytic interplay of each component (Ga, Pt, and Ce). Selective poisoning, in situ diffuse reflectance infrared Fourier transform spectroscopy, and H-2-D-2 exchange revealed that Ga3+ is responsible for the heterolytic dissociation of the C- H bond of propane, while Pt-0 facilitates the sluggish H recombination into H-2 via reverse spillover. Catalyst deactivation during repeated reactionregeneration cycles is mainly due to the irreversible sintering of Pt-0. Notably, optimal Ce doping (similar to 2 wt %) selectively generated atomically dispersed Ce3+ sites on the gamma-Al2O3 surface, which greatly suppressed the sintering of Pt-0 particles by increasing the metal-support interactions. In contrast, excessive Ce loading generated discrete CeO2 domains, which stabilized the Pt species in the form of Pt2+ inactive for H recombination. Thus, excessive Ce loading led to an even more severe loss of catalytic activity and selectivity. The present results demonstrate that the selective generation of atomically dispersed Ce3+ on the gamma-Al2O3 surface is important for stabilizing Pt-0 species, which is essential for simultaneously achieving high catalytic activity, selectivity, and longevity in PDH.