Methylation of aromatic compounds is a key reaction step in various industrial processes such as the aromatic cycle of methanol-to-hydrocarbon chemistry. The study of isolated methylation reactions and of the influence of catalyst acidity on their kinetics is a challenging task. Herein, we have studied unidirectional metal-substituted H-MeAlPO-5 materials to evaluate the effect of acid strength on the kinetics of benzene methylation with DME. First-principle simulations showed a direct correlation between the methylation barrier and acid site strength, which depends on the metal substituent. Three H-MeAlPO-5 catalysts with high (Me = Mg), moderate (Me = Si) and low acidity (Me = Zr) were experimentally tested, confirming a linear relationship between the methylation activation energy and acid strength. The effects of temperature and reactant partial pressure were evaluated, showing significant differences in the byproduct distribution between H-MgAlPO-5 and H-SAPO-5. Comparison with propene methylation suggested that the Mg substituted catalyst is also the most active for the selective methylation of alkenes.

芳香化合物的甲基化是各种工业过程中的关键反应步骤，例如甲醇到烃化学的芳香循环。研究孤立的甲基化反应和催化剂酸度对其动力学的影响是一项具有挑战性的任务。在此，我们研究了单向金属取代的 H-MeAlPO-5 材料，以评估酸强度对 DME 苯甲基化动力学的影响。第一性原理模拟显示甲基化势垒和酸位强度之间存在直接相关性，这取决于金属取代基。实验测试了三种具有高 (Me = Mg)、中等 (Me = Si) 和低酸度 (Me = Zr) 的 H-MeAlPO-5 催化剂，证实了甲基化活化能与酸强度之间的线性关系。评估了温度和反应物分压的影响，显示 H-MgAlPO-5 和 H-SAPO-5 之间的副产物分布存在显着差异。与丙烯甲基化的比较表明，Mg 取代的催化剂对于烯烃的选择性甲基化也是最活跃的。