The catalyst prepared by the hydrothermal synthesis of HZSM-5 zeolites and modification was utilized in the methylation of toluene and methanol,and exhibited good toluene conversion and para-selectivity to xylene.The coke behavior of the catalyst was investigated by TPO,UV-Vis,NMR and GC-MS.The results showed that oxygen in methanol did not participate in the formation of coke which consisted of carbon and hydrogen.The coke components deposited on HZSM-5 catalyst were separated into two fractions:soluble aromatics,condensed aromatics and their derivatives; insoluble ingredients containing condensed aromatics,graphitic precursors and graphites.Among them,the majority of mono or multiple methyl-substituted aromatics in the soluble fraction were attributed to the simultaneous existence of toluene and methanol as the reactants.Besides,the early-coke species over the catalyst mainly located within the pore channel of HZSM-5 zeolites.The distribution and chemical composition of coke were predominantly dependent on the pore structures and external surface acidity of the zeolites as well as the properties of the reactants and the catalytic reaction conditions.%将水热合成法制备并改性的HZSM-5分子筛催化剂应用于甲苯甲醇甲基化反应,催化剂表现出良好的甲苯转化率和二甲苯对位选择性.采用程序升温氧化法、固体紫外-可见吸收光谱、核磁共振法和气相色谱串联质谱法等研究催化剂的积炭行为.结果表明,反应介质甲醇中的氧未参与积炭形成,积炭成分较为单一,均由碳氢两种元素组成.积炭分为可溶的芳烃和稠环芳烃及其衍生物以及不可溶稠环芳烃、石墨前驱体、石墨等中的一种或几种混合物.甲苯与甲醇作为反应底物同时存在也决定了可溶性成分中单甲基或多甲基取代芳烃占大多数.早期积炭主要分布于分子筛孔道,积炭组成和分布由分子筛孔道结构和外表面酸性、反应物性质与反应条件决定.
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