Disproportionation and Methylation of Toluene with Methanol Over Zeolite Catalysts
Disproportionation and Methylation of Toluene with Methanol Over Zeolite Catalysts
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DOI：
10.1007/s11244-010-9605-6
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发表时间：
2010-09
影响因子：
3.6
通讯作者：
A. Baduraig;T. Odedairo;S. Al-Khattaf
中科院分区：
文献类型：
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作者：
A. Baduraig;T. Odedairo;S. Al-Khattaf
考察了沸石分子筛TNU-9、SSZ-33、丝光沸石(MOR)和ZSM-5在甲苯歧化和甲苯甲基化反应中的活性。与SSZ-33、丝光沸石和ZSM-5催化剂相比，中孔分子筛TNU-9具有最高的甲苯歧化转化率。在甲苯甲基化反应中，硅铝比最高为135.9(活性中心浓度最低)的丝光沸石具有最高的甲苯转化率和最高的二甲苯产率。在丝光沸石上，通道交叉点的存在为大体积中间体和/或产物的形成提供了更大的反应空间，另一方面，12环通道的存在允许扩散而不会捕获，因为通道直径足够大。在甲苯甲基化反应中，相同转化率水平的二甲苯选择性遵循如下顺序：ZSM-5、TNU-9、MOR、SSZ-33，这意味着二甲苯选择性与中孔到大孔沸石的孔道大小直接相关。具有10环孔道的中孔分子筛ZSM-5对二甲苯的进一步烷基化反应活性最低，而具有12环孔道的丝光沸石对二甲苯进一步烷基化反应的活性最高。
Zeolites TNU-9, SSZ-33, mordenite (MOR) and ZSM-5 were evaluated for their activities in toluene disproportionation and methylation reaction of toluene with methanol. The medium-pore zeolite TNU-9 was found to possess the highest conversion in toluene disproportionation as compared with SSZ-33, mordenite and ZSM-5 based catalyst. Zeolite mordenite with the highest Si/Al ratio of 135.9 (the lowest concentration of active sites) exhibited the highest toluene conversion and maximum xylene yield in toluene methylation. On mordenite, the presence of channel intersections allows more reaction space for the formation of bulky intermediates and/or products and the 12-ring channels on the other hand, allow diffusion without trapping, since the channel diameter is large enough. In toluene methylation, xylene selectivity at the same conversion level follows the order: ZSM-5 > TNU-9 > MOR > SSZ-33, which implies that xylene selectivity is directly related to the size of channels from medium to large pore zeolites. The medium-pore zeolite ZSM-5, with 10-ring channels, shows the lowest reactivity for further alkylation of xylene, while mordenite with 12-ring channel shows the highest reactivity for further alkylation of xylene.