以四丙基溴化铵为模板剂、硅质量分数为5%的晶种为硅源,采用水热合成法制备了ZSM-5分子筛,利用XRD、SEM、N₂物理吸附-脱附、NH₃-TPD等方法对催化剂进行表征;将ZSM-5与具有不同拓扑结构的β、HY、丝光沸石催化偏三甲苯裂解制苯、甲苯、二甲苯(BTX)。结果表明,ZSM-5分子筛具有较强的酸强度和较多的酸量,使其更适用于偏三甲苯裂解反应;在反应过程中,随着反应温度的升高,偏三甲苯先发生异构化反应,再发生裂解脱烷基反应;脱烷基程度随温度升高逐渐加深,且反应按照偏三甲苯、异构化三甲苯、二甲苯、甲苯为反应物逐级发生;当反应温度为500℃时,偏三甲苯转化率接近100%,同时发生苯环开环裂解反应。

ZSM-5 molecular sieve is prepared via a hydrothermal method by using tetrapropylammonium bromide as a template agent and a crystal species with a silicon content of 5wt% as a silicon source,and characterized by means of XRD,SEM,N₂-adsorption,NH₃-TPD and other methods.The prepared ZSM-5 molecular sieve,β-zeolite,HY-zeolite and mordenite,each with a different topological structure,are respectively applied to catalyze 1,2,4-trimethylbenzene to crack to make benzene,toluene,and xylene.It is verified that the prepared ZSM-5 molecular sieve is more suitable for catalyzing 1,2,4-trimethylbenzene cracking reaction because it has stronger acid strength and larger amount of acid content.During the reaction process,as the reaction temperature rises,1,2,4-trimethylbenzene undergoes firstly isomerization reaction,and then dealkylation cracking reaction.The degree of dealkylation reaction deepens gradually as the temperature rises,and the reaction occurs step by step in the order with trimethylbenzene,isomerized trimethylbenzene,xylene,and toluene as reactants.At a reaction temperature of 500℃,the conversion rate of 1,2,4-trimethylbenzene approaches 100%,and the benzene ring cracking reaction occurs.