Combination of Hollow Capsule Structure and Zn Uniform\nLoad for the Conversion of Methanol to Aromatics over Zn/ZSM‑5\nZeolites

As an important nonoil route for\nacquiring aromatics, the highly\nefficient conversion of methanol to aromatics over Zn/ZSM-5 zeolites\nremains an ongoing challenge. In this work, we developed a uniform\nloading approach of zinc and further combined it with a hollow capsule\nstructure to design the high-performance Zn/ZSM-5 catalyst. The electrostatic\nassembly among EDTA<sup>3–</sup>, <i>n</i>-butylamine<sup>+</sup> and negative silica–alumina gel gave rise to an “Inorganic–Organic\nHybrid Sphere” in form of Na<sub>(<i>l</i>+<i>m</i>+<i>n</i>+3<i>x</i>)–(<i>y</i>+<i>z</i>)</sub>·{[(SiO)<sub>4</sub>Al<sup>–</sup>]<sub>l</sub>/(SiO<sup>–</sup>)<sub><i>m</i></sub>(<i>n</i>-butylamine<sup>+</sup>)<sub><i>y</i></sub>(EDTA<sup>3–</sup>)<sub><i>x</i></sub>(<i>n</i>-butylamine<sup>+</sup>)<sub><i>z</i></sub>(SiO<sup>–</sup>)<sub><i>n</i></sub>, which\nfurther transformed into mesoporous aluminosilicates sphere (MASS)\nthrough calcination. The characteristic of abundant mesopore guaranteed\nMASS fantastic ability to evenly incorporate Zn ingredient inside,\nand the resultant Zn/MASS further served as a “hard template”\nfor the direct synthesis of Hollow Zn/ZSM-5 capsules, rather than\nafter impregnation. When tested in the methanol-to-aromatics (MTA)\nprocess, the direct synthesis method not only facilitated the homogeneous\ndispersion of the Zn ingredient, but also benefited for the generation\nof more (ZnOH)<sup>+</sup> sites and strengthened their synergism\nwith zeolite acid for the superior aromatics selectivity (50.63%).\nMeanwhile, the hollow capsule structure increased the contact time\nof MTA intermediate products with the Zn/ZSM-5 shell, and it increased\nthe coke-admitting capacity and suppressed the coke rate, which maintained\nquite an excellent stability (131 h). Therefore, the above combination\nof hollow capsule structure and uniform load of Zn ingredient brings\nforward a wide prospect to develop zeolite materials with excellent\nproperties in catalysis.