Diffusion limitations and monofunctional acidity of ZSM-5 molecular sieves affect the catalyst stability and aromatic yield in the reaction of methanol to aromatics (MTA). In this study, based on ZSM-5 nanosheets as parent molecular sieves, Zn-modified hollow ZSM-5 nanosheets were obtained after hydrothermal treatment by adding ZIF-8 or zinc nitrate as a source of Zn while treating with different types and concentrations of alkali solutions. The physical and chemical properties of the fabricated samples and their catalytic performance of methanol aromatization were systematically investigated by a combination of XRD, TEM, N₂ adsorption–desorption, NH₃-TPD, Py-IR, ²⁷Al MAS NMR, ²⁹Si MAS NMR, XPS, and TG characterization analyses and MTA experimental evaluation. The results indicated that a hollow structure emerged in the samples after alkaline treatment, with a significant increase in the proportion of mesopores, which further increased with the concentration of the alkaline solution. Both alkaline treatment and the introduction of Zn led to changes in the acidity of the catalyst. The increase in tetrahedrally coordinated aluminum during the alkaline treatment resulted in a higher content of B acid sites, while the introduction of Zn formed Zn-Lewis acid sites. Among the prepared samples, the catalyst obtained using ZIF-8 as the Zn source and treated with a mixed alkaline solution of 0.15 M sodium hydroxide and tetrapropylammonium hydroxide (Zn_Z8(N+T)/Z5) exhibited higher relative crystallinity, more appropriate micromesopore ratio, a greater amount of Zn(OH)⁺, and a suitable B/L ratio (0.74). Under the same conditions (450 °C, atmospheric pressure, weight hourly space velocity (WHSV) = 5 h^–1), the aromatic product yield of Zn_Z8(N+T)/Z5 reached 26.2%, which is 14 percentage points higher than that of the parent ZSM-5 and 4 percentage points higher than that of Zn_ZN(N+T)/Z5 modified with zinc nitrate as the Zn source. After 8 h of reaction, the aromatic yield over Zn_Z8(N+T)/Z5 could still be maintained above 18.5% with good catalyst stability.

中文翻译：

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以 ZIF-8 作为 Zn 源通过不同碱处理合成空心 Zn/ZSM-5 纳米片用于甲醇的高效芳构化


ZSM-5 分子筛的扩散限制和单功能酸性会影响甲醇与芳烃 （MTA） 反应中的催化剂稳定性和芳烃产率。本研究以 ZSM-5 纳米片为母体分子筛，在用不同类型和浓度的碱溶液处理的同时，加入 ZIF-8 或硝酸锌作为 Zn 的来源，经过水热处理后得到 Zn 修饰的空心 ZSM-5 纳米片。采用 XRD、TEM、N₂ 吸附-脱附、NH 3-TPD、Py-IR、²⁷Al MAS NMR、²⁹Si MAS NMR、XPS 和 TG 表征分析以及 MTA 实验评价，系统研究了制备样品的物理化学性质及其甲醇芳构化催化性能。结果表明，碱处理后样品中出现中空结构，介孔比例显著增加，随着碱性溶液浓度的增加，介孔比例进一步增加。碱处理和 Zn 的引入都导致了催化剂酸度的变化。在碱性处理过程中，四面体配位铝的增加导致 B 酸位点的含量更高，而 Zn 的引入形成了 Zn-Lewis 酸位点。在制备的样品中，以 ZIF-8 为 Zn 源，经 0.15 M 氢氧化钠和四丙基氢氧化铵 （Zn_Z8（N+T）/Z5） 混合碱性溶液处理获得的催化剂表现出更高的相对结晶度、更合适的微中孔比、更大的 Zn（OH）⁺ 用量和合适的 B/L 比 （0.74）。 在相同条件下（450 °C，大气压，重量小时空速 （WHSV） = 5 h^–1），_{Zn Z8}（N+T）/Z5 的芳烃产物收率达到 26.2%，比母体 ZSM-5 高 14 个百分点，比以硝酸锌为 Zn 源改性的_{Zn ZN}（N+T）/Z5 高 4 个百分点。反应 8 h 后，Zn_Z8（N+T）/Z5 的芳烃产率仍能保持在 18.5% 以上，催化剂稳定性好。