Isomerization of xylene and methylation of toluene on zeolite H-ZSM-5. Compound kinetics and selectivity
Isomerization of xylene and methylation of toluene on zeolite H-ZSM-5. Compound kinetics and selectivity
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DOI：
10.1006/jcat.1993.1163
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发表时间：
1993-06
影响因子：
7.3
通讯作者：
K. Beschmann;L. Riekert
中科院分区：
文献类型：
--
作者：
K. Beschmann;L. Riekert
以H-ZSM-5分子筛为催化剂，分别对甲苯与甲醇的烷基化反应和二甲苯的异构化反应进行了详细的研究。在573和723 K温度下，在无梯度间歇反应器中研究了沸石中两种硅铝比下，晶体尺寸对反应速率和产物分布的影响。由甲苯甲基化产生的二甲苯中的异构体分布在化学计量混合物中从零到至少50%的甲醇转化率是恒定的，H-ZSM-5总是对位选择性的。当晶粒尺寸、温度或沸石中Al含量增加时，产物中对二甲苯占主导地位;用未改性的H-ZSM-5作为催化剂可以在极限下获得基本上纯的对二甲苯。二甲苯单独异构化的异构体的平衡混合物的速率被发现是大致成比例的沸石晶体的（外）表面的程度，异构化的三角形方案中的不同反应的速率的比率几乎独立于晶体尺寸。这些观察结果可以理解为是晶体体积中反应和扩散相互作用的结果。参考文献34篇，图11，4个标签。
The alkylation of toluene with methanol and the isomerization of xylene were investigated separately and in detail on zeolite H-ZSM-5 as catalyst. The influence of crystal size alone on rates and product distributions was studied for two Si/Al ratios in the zeolite at 573 and 723 K in a gradientless batch-reactor. The isomer distribution in the xylene resulting from toluene methylation is constant from zero up to at least 50% conversion of the methanol in a stoichiometric mixture, H-ZSM-5 being always para-selective. para-Xylene prevails increasingly in the products when either crystal size, temperature, or Al content in the zeolite increase; essentially pure p-xylene can be obtained in the limit with unmodified H-ZSM-5 as catalyst. The rate of isomerization of xylene alone to an equilibrium mixture of isomers was found to be roughly proportional to the extent of the (external) surface of the zeolite crystals, the ratios of the rates of different reactions in the triangular scheme of isomerization being nearly independent of crystal size. The observations can be understood as resulting from the interaction of reaction an diffusion in the volume of the crystals. 34 refs., 11 figs., 4 tabs.