Abstract Ball milling modification was performed on Cs/X catalysts before or after cesium ion exchange. Multiple characterization results (such as pyridine-FTIR, XPS, and solid-state NMR) demonstrated that ball milling played a distinct role in these two different preparation procedures of the catalyst. Ball milling performed after the cesium modification has a strong influence on the Cs/X structure and acid–base properties, which results in the enhancement of the catalytic performance for side-chain methylation of toluene with methanol. Detailed studies revealed that ball milling intensified the interactions between oxides and molecular sieves, which not only increased the dispersion of the Cs species but also generated some weaker basic centers. It is proposed that the new basic centers could be Si–O–Cs and Al–O–Cs, which are produced by breaking of the Si–O–Al bonds of the zeolite framework under the synergetic effect of ball milling and alkali treatment. These new active sites may help to promote the side-chain methylation reaction. However, excessive ball milling will lead to the vanishing of zeolite micropores, thus deactivating side-chain methylation activity, which indicates that microporosity plays a key role in side-chain methylation and individual basic centers cannot catalyze this reaction.

中文翻译：

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球磨在Cs/X催化剂制备过程中的作用及对甲苯甲醇侧链烷基化催化性能的影响

摘要 在铯离子交换前后对Cs/X催化剂进行球磨改性。多项表征结果（如吡啶-FTIR、XPS 和固态核磁共振）表明，球磨在这两种不同的催化剂制备过程中发挥了独特的作用。铯修饰后的球磨对Cs/X结构和酸碱性质有很大影响，从而提高了甲苯与甲醇侧链甲基化的催化性能。详细研究表明，球磨强化了氧化物和分子筛之间的相互作用，这不仅增加了 Cs 物种的分散，而且还产生了一些较弱的碱性中心。提出新的基本中心可以是 Si-O-Cs 和 Al-O-Cs，在球磨和碱处理的协同作用下，沸石骨架的 Si-O-Al 键断裂而产生。这些新的活性位点可能有助于促进侧链甲基化反应。然而，过度球磨会导致沸石微孔消失，从而使侧链甲基化活性失活，这表明微孔在侧链甲基化中起关键作用，个别碱性中心不能催化该反应。