甲醇制丙烯的复杂反应网络和动力学模型

Study on Complex Reaction Network and Kinetic Model of a Methanol to Propene Process

采用微型固定床反应器全面研究了甲醇制丙烯(MTP)反应过程,考察了甲醇单独进料、不同烯烃单独进料、甲醇和烯烃混合进料三种条件下的反应规律。结果表明,在工业H-ZSM-5催化剂上甲醇主要发生甲基化和裂解反应,C_2~C_5烯烃主要发生叠合-裂化反应,C_6和C_7烯烃主要发生裂解反应,甲醇通过一系列甲基化和烯烃裂化路径转化为丙烯,生成丙烯的反应步骤都是快反应,而甲醇裂化、乙烯转化和生成烷烃及芳烃的副反应都是慢反应。提出了MTP的复杂反应网络与动力学模型,通过实验数据的拟合获得了各步反应的动力学参数,其中甲醇甲基化和裂解反应的表观活化能大于零,烯烃叠合-裂化的表观活化能小于零,是裂化吸热反应与表面吸附放热耦合作用的结果。

A methanol to propene（MTP） process was studied experimentally in a miniature fixed bed reactor. Effects of feeding conditions, i.e. methanol feeding, olefin feeding, and methanol/olefin co-feeding were investigated respectively. The results show that the key reactions of MTP on H-ZSM-5 zeolite include methylation of methanol, oligomerization–cracking of olefins（C2～C5） and cracking of olefins（C6～C7）. Methanol to propene is happened through a complex reaction network in which all steps are fast reactions, while methanol cracking, ethylene conversion, aromatic and paraffin formation are slow reactions. A comprehensive MTP reaction network with kinetic model is developed. Kinetic parameters are obtained by data fitting with the Levenberg–Marquardt method. The results show that the apparent activation energies of methanol cracking and methylation, and olefin cracking are positive, while the apparent activation energies of oligomerization–cracking are negative, which is the result of endothermic cracking reactions coupled with exothermic adsorption of olefins.