Isolated Pt Species Anchored by Hierarchical-like Heteroatomic Fe-Silicalite-1 Catalyze Propane Dehydrogenation near the Thermodynamic Limit

Abstract

The atomic dispersion of precious metals accompanied by maximum atom utilization can provide specific chemical properties compared to nanoparticles and clusters that have attracted widespread interest. The selection of a suitable carrier to stabilize platinum atoms while maintaining high stability and propylene selectivity is of great challenge for propane dehydrogenation reactions operating at extremely high temperatures. Here, we report a conceptually designed catalyst comprising isolated Pt atoms stably bonded through skeleton O in a hierarchical-like heteroatomic ferrosilicate zeolite (H-Fe-S-1–3; denoted as “Fe-3”), capable of achieving high propane conversions at different temperatures and atmospheres close to the thermodynamic limit. No significant deactivation was observed for 3 days in a pure propane atmosphere at 580 °C, outperforming most of the cutting-edge Pt-based catalysts. The moderate acidity of Fe-3 and anchoring of hydroxyl species other than silanol nests were responsible for maintaining a suitable C–H break rather than an excessive C–C cleavage capacity and a high degree of Pt dispersion, respectively. X-ray absorption spectra and atomically resolved high-angle annular dark-field electron microscopy demonstrated major atomic dispersion of Pt species, along with complementary density functional theory calculations to determine the structure of ≡Si–O–Pt–O–Fe≡ corresponding to the T4 location as the key active site. Pt anchoring by sites other than the T4 site with analogous energies, such as T6, could be accountable for the observation that “cluster-like Pt species” are essentially composed of isolated Pt atoms not interacting with each other.