Methanol-to-olefin (MTO) conversion on zeolites has encountered severe coke deposition and rapid deactivation. Creating different levels of porosity is essential to mitigate such issues. Herein, we demonstrate a facile and green strategy to synthesize uniform and hierarchically macro/mesoporous ZSM-5 microspheres by combining spray-freeze drying and steaming-assisted crystallization (SAC). The structure, crystallinity, and porosity of the zeolite microspheres are controlled by adjusting the water/gel mass ratio and time in the SAC process. The structure evolution during the SAC process is revealed. In the catalytic MTO reaction, the representative hierarchically porous ZSM-5 catalyst exhibits superior catalytic performance. At a very high weight hourly space velocity of 18 h⁻¹, it shows a dramatically prolonged lifetime (47 h at >99% conversion) and much-improved selectivity to ethylene and propylene compared with the conventional microporous ZSM-5 and nano-sized ZSM-5. The enhanced performance is originated from the hierarchical structure and suitable acidity of the ZSM-5 microspheres.

中文翻译：

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具有优异催化甲醇制烯烃转化性能的多级 ZSM-5 微球的合成

沸石上的甲醇到烯烃 (MTO) 转化遇到严重的焦炭沉积和快速失活。创建不同级别的孔隙率对于缓解此类问题至关重要。在此，我们展示了一种简便且绿色的策略，通过结合喷雾冷冻干燥和蒸汽辅助结晶 (SAC) 来合成均匀且分层的宏观/介孔 ZSM-5 微球。沸石微球的结构、结晶度和孔隙率通过调节 SAC 过程中的水/凝胶质量比和时间来控制。揭示了 SAC 过程中的结构演变。在催化MTO反应中，具有代表性的分级多孔ZSM-5催化剂表现出优异的催化性能。^{在 18 h −1}的非常高的重时空速下，与传统的微孔 ZSM-5 和纳米尺寸的 ZSM-5 相比，它显示出显着延长的寿命（>99% 的转化率为 47 小时）和对乙烯和丙烯的选择性大大提高。性能的增强源于ZSM-5微球的层次结构和合适的酸度。