中空ZSM-5分子筛的制备及其在2-甲基萘烷基化合成2,6-二甲基萘中的应用

通过在溶胶-凝胶过程中添加适量成核促进剂NaH_2PO_4进行凝胶控制,经一步水热晶化法合成出具有中空结构小晶粒ZSM-5分子筛,并通过XRD、FTIR、SEM、TEM、激光粒度分析和N_2吸附-脱附等手段对其结构进行了表征。表征结果显示,成核促进剂的添加使得合成的ZSM-5分子筛形貌更加规则,晶粒大小更为均一,晶粒出现中空结构。在2-甲基萘烷基化合成2,6-二甲基萘的过程中,制得的中空ZSM-5分子筛表现出较好的稳定性、活性和选择性。在反应温度400℃、2-甲基萘重时空速0.5 h~(-1)的条件下,2-甲基萘初始转化率大于28%;反应12h后仍保持在25%以上,2,6-二甲基萘收率最高可达10.5%。

Preparation of Hollow ZSM-5 and Its Application in Methylation of 2-Methylnaphthalene to 2, 6-Dimethylnaphthalene

Hollow ZSM-5 zeolite was prepared through a one-step hydrothermal crystallization method with NaH_2PO_4 as the nucleation promoter in the sol-gel process.The prepared zeolite was characterized by means of XRD,FTIR,SEM,TEM,DLS,and N_2 adsorption/desorption,and used in the methylation of 2-methylnaphthalene(2-MN) with methanol to 2,6-dimethylnaphthalene (2,6-DMN).The characterizations show that the addition of the NaH_2PO_4 promoter leads to larger crystal,more regular crystal morphology and more uniform crystal size of the ZSM-5 zeolite with hollow crystalline structure.The hollow zeolite exhibits the high selectivity to 2,6-DMN and catalytic stability in the methylation.The initial 2-MN conversion is 28%under the conditions of 400℃ and 0.5 h~(-1) of 2-MN WHSV and still more than 25%after the reaction for 12 h.The highest yield of 2,6-DMN is 10.5%.