Propane dehydroaromatization (PDA) to high value-added aromatic hydrocarbons, such as benzene, toluene, and xylene (BTX), is an attractive but challenging process. The traditional Zn/H-ZSM-5 or Ga/H-ZSM-5 catalysts can offer considerable PDA performances but still suffer from low activity and poor stability because of harsh reaction conditions. Here, we report a multifunctional Pt–Zn@H-ZSM-5 catalyst that exhibits a significantly improved performance in the PDA reaction at 550 °C, with a single-pass propane conversion of 74%, aromatics selectivity of 56%, and CH₄ selectivity of only 4.7%. The yield of aromatics is twice as much as those of Zn/H-ZSM-5 and Ga/H-ZSM-5 catalysts. We have demonstrated that the Pt–Zn alloy nanoparticles with an average size of 2.4 nm are uniformly confined within H-ZSM-5 crystals, providing atomic-scale proximity between metal and zeolite acid sites. This unique structure enhances not only the dehydrogenation of the propane feedstock in the initial reaction stage but also the dehydrogenation of cyclic C₆₊ hydrocarbons by the recombinative desorption of surface hydrogen species in the last stage while suppressing the side hydrogenolysis and hydrogen-transfer reactions. Furthermore, the Si/Al ratio of H-ZSM-5, the synergistic effect between platinum and zinc, and the location of Pt–Zn nanoparticles over composite catalysts have also been discussed. These findings suggest that via bimetallic alloying and rational arrangements of functional sites at the nanoscale, the multistep PDA reaction can be greatly intensified.

中文翻译：

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通过将 PtZn 合金纳米粒子限制在 H-ZSM-5 晶体中促进丙烷脱氢芳构化

丙烷脱氢芳构化 (PDA) 制取高附加值的芳烃，如苯、甲苯和二甲苯 (BTX)，是一个有吸引力但具有挑战性的工艺。传统的 Zn/H-ZSM-5 或 Ga/H-ZSM-5 催化剂可以提供可观的 PDA 性能，但由于反应条件苛刻，仍然存在活性低和稳定性差的问题。在这里，我们报道了一种多功能 Pt-Zn@H-ZSM-5 催化剂，该催化剂在 550 °C 下的 PDA 反应中表现出显着提高的性能，单程丙烷转化率为 74%，芳烃选择性为 56%，CH ₄选择性仅为 4.7%。芳烃的收率是 Zn/H-ZSM-5 和 Ga/H-ZSM-5 催化剂的两倍。我们已经证明，平均尺寸为 2.4 nm 的 Pt-Zn 合金纳米粒子均匀地限制在 H-ZSM-5 晶体中，在金属和沸石酸位之间提供原子级接近。这种独特的结构不仅增强了丙烷原料在初始反应阶段的脱氢，而且还增强了环状 C _6+的脱氢通过在最后阶段表面氢物种的重组解吸同时抑制副氢解和氢转移反应来制备碳氢化合物。此外，还讨论了 H-ZSM-5 的 Si/Al 比、铂和锌之间的协同效应以及 Pt-Zn 纳米粒子在复合催化剂上的位置。这些发现表明，通过双金属合金化和纳米级功能位点的合理排列，可以大大加强多步 PDA 反应。