Controllable deposition of Pt nanoparticles into a KL zeolite by atomic layer deposition for highly efficient reforming of n-heptane to aromatics

Abstract

Atomic layer deposition (ALD) was applied to deposit Pt into KL zeolite channels. The location of Pt deposition and the interaction between Pt and the KL zeolite have been investigated by various characterization methods as well as DFT simulations. It has been demonstrated that Pt nanoparticles (NPs) with precisely controlled size (∼0.8 nm) and high dispersion have been successfully deposited into the micropores of the KL zeolite. The produced Pt/KL catalysts exhibited highly efficient performance for n-heptane reforming to aromatics with a high toluene selectivity up to 67.3% (toluene/total aromatics = 97.8%) and a low methane selectivity (0.9%), in spite of an ultralow Pt loading (0.21 wt%). It was revealed that the strong interaction between Pt and the KL zeolite resulting in the electron-enriched state of Pt and the confinement of Pt in the micropores of the KL zeolite facilitated the aromatization of n-heptane. The small size and high dispersion of Pt NPs contributed to inhibition of the hydrogenolysis reaction. Prevention of agglomeration of Pt NPs due to confinement inside the micropores of the KL zeolite and the strong interaction led to the high stability of the Pt/KL catalysts.