Highly Dispersed Single-Atom Pt and Pt Clusters in the Fe-Modified KL Zeolite with Enhanced Selectivity for n-Heptane Aromatization.

Conversion of straight-chain paraffins into aromatics is particularly attractive but extremely challenging in the oil refining industry. Constructing the Pt-supported catalysts with high aromatic selectivity is vital. Here, we report a strategy to use Fe-modified KL zeolites to improve the Pt atom utilization efficiency and anchor them inside KL zeolite channels via atomic-layer deposition technique. A combination of highly dispersed single-atom Pt and electron-rich Pt clusters is fabricated on the KL zeolite through the creation of proper nucleation sites. The resulted catalyst (PtFe-1/KL) exhibits excellent performance for the n-heptane aromatization (90.1% aromatic selectivity) with an apparent activation energy of 131 kJ/mol and much enhanced stability at a relatively lower temperature (420 °C). Experimental analysis and density functional theory calculation demonstrate that the single-atom Pt might play a key role in the initial dehydrogenation of n-heptane to 1-heptene, and the superior stable Pt clusters encapsulated inside Fe-decorated KL zeolite channels accelerate the 1-heptene dehydrocyclization to aromatics. The synergetic interaction between single-atom Pt and Pt clusters enables the PtFe-1/KL catalyst to be one of the most effective n-heptane aromatization catalysts reported to date.