PtFe@S‑1\nCoupling with ZSM‑5 for the\nPropane Dehydro-Aromatization Reaction: The Effect of Acidity and <i>b</i>‑Axis Diffusion Distance

A series of ZSM-5 zeolites with different\nacidities and <i>b</i>-axis diffusion distances were synthesized\nunder hydrothermal\nconditions using the seed-induced method and characterized by X-ray\ndiffraction (XRD), scanning electron microscopy (SEM), transmission\nelectron microscopy (TEM), ammonia temperature-programmed desorption\n(NH<sub>3</sub>-TPD), and infrared spectroscopic analysis of the adsorption\nof pyridine (Py-IR). The structure–activity relationships of\nPtFe@S-1&ZSM-5 tandem catalysts in the propane dehydro-aromatization\nreaction (PDA) were investigated, especially focusing on the impact\nof ZSM-5 acidity and <i>b</i>-axis diffusion distance. The\nresults indicate that the ZSM-5 zeolite with a low Si/Al ratio (∼25)\nand suitable <i>b</i>-axis diffusion distance (∼100\nnm) coupled with PtFe@S-1 is more conducive on improving the PDA catalytic\nperformance. When the mass ratio of PtFe@S-1/ZSM-5 was 1:1, the propane\nconversion and aromatics selectivity of PtFe@S-1&ZSM-5–25\nremained above 78.9% and 40.5% within 500 min on stream, respectively.