Abstract:

Alkylation of toluene with methanol is a promising technology for p-xylene?production. However, this process is exothermic and the easier coke deposition will cause a relatively quick catalyst deactivation. Accordingly, the fluidized bed should be an appropriate reactor due to the excellent heat transfer performance and easy realization of continuous catalyst regeneration. In this paper, the discrete particle model was applied for a numerical study on alkylation of toluene with methanol in a fluidized bed reactor. And some conclusions were as follows for a given flow rate of toluene. If the toluene/methanol feed molar ratio reduced, the p-xylene yield and selectivity would increase, while the mole ratio of p-xylene to olefin had a sharp decrease. Both of the toluene conversion and methanol conversion can be well improved at elevated pressures, following with a reduction in p-xylene selectivity. Staged methanol feeding can not only improve the toluene conversion, but also adjust the product distribution. Gas backmixing in fluidized bed reactors would lower the p-xylene selectivity. And the change of the flow pattern under different operating conditions followed with different gas-solid contact efficiency and local partial pressure of the reactants, which would also influence the product distribution. These results can give some guidance for the optimization and scale-up of the fluidized bed reactor.

Key words: alkylation of toluene with methanol, fluidized bed reactor, discrete particle model

摘要：

利用甲醇甲苯烷基化工艺生产对二甲苯具有良好的应用前景。甲醇甲苯烷基化催化剂较易积炭失活，且反应存在明显热效应。流化床因传热传质性能好、易实现催化剂连续再生，适合用作甲醇甲苯烷基化反应器。本文采用离散颗粒模型，对甲醇甲苯烷基化流化床反应器进行了数值模拟研究，重点考察了进料比、反应压力、分段进料对反应特性的影响。结果表明，当甲苯进料量给定时：降低反应物中甲苯甲醇比可有效提升对二甲苯产率和选择性，但产物中对二甲苯和烯烃摩尔比值较低；提高反应压力可显著提升甲醇和甲苯转化率，但会降低对二甲苯选择性；在低苯醇比基础上采用甲醇分段进料方式不仅可有效提高甲苯利用率，还可灵活调节产物中对二甲苯和烯烃比率；流化床反应器气体返混不利于获得高对二甲苯选择性，且操作条件变化会造成流化床反应器内气固流动改变，导致气固接触效率或反应物局部分压发生改变，这亦将对反应转化特性造成显著影响。这些结果对于流化床反应器优化和放大具有一定的指导意义。

关键词: 甲醇甲苯烷基化, 流化床反应器, 离散颗粒模型