Efficient Dehydrogenation of Propane to Propene over PtIn Nanoclusters Encapsulated in Hollow-Structured Silicalite-1

Pt-based catalysts have been widely used for propane dehydrogenation to propene. However, the high reaction temperature generally induces serious sintering and agglomeration of metal species, thus leading to rapid deactivation of the catalysts. Herein, PtIn nanoclusters (NCs) encapsulated in hollow-structured silicalite-1 (designated as PtIn@S1–H) was prepared using recrystallization method. This material shows high catalytic performance in propane dehydrogenation. The propane conversion and propene selectivity reach ∼45–47.5% and ∼99%, respectively, at 547 °C at least within 167.6 h. As a result, it displays a significantly higher specific activity for C3H6 formation (0.37–0.59 s–1) than Pt@S1, Pt@S1–H, and other reported Pt-based catalysts. Notably, its catalytic performance is well maintained for more than 3600 h, with propane conversion of ∼31–34% and propene selectivity of ∼91–95%, when pure propane is fed. More interestingly, this catalyst can be reused through regeneration. EXAFS, HAADF-STEM and DFT calculation, and AIMD simulation results show that hollow-structured silicalite-1 crystal morphology not only facilitates the formation of Pt5In3 alloy NCs but also inhibits NC aggregation and growth. PtIn@S1–H showed a TON ≥ 38996 in contrast to 5367, 4928, 798, and 542 obtained on PtIn@S1, PtSn@S1, PtSn/Al2O3, and PtIn/Al2O3, respectively, if the catalysts were considered to be deactivated when the propane conversion was decreased by 15%. This is because alloying of In into Pt NCs weakens the interaction of C3H7* intermediates with metallic Pt NCs and the adsorption of C3H6 on the catalyst surface, thus suppressing the C3H7* cleavage reaction and enhancing propane activation and propene selectivity.