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

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

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%。

Hollow ZSM-5 zeolite was prepared through a one-step hydrothermal crystallization method with NaH2PO4 as the nucleation promoter in the sol-gel process. The prepared zeolite was characterized by means of XRD, FTIR, SEM, TEM, DLS, and N2 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 NaH2PO4 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 of2-MN WHSV and still more than 25% after the reaction for 12 h. The highest yield of 2, 6-DMN is 10.5%.