高硅分子筛ZSM-22的动态合成及表征

Dynamic Synthesis and Characterization of ZSM-22 Zeolite with High Silica

以 1,6 己二胺 (DAH)为模板剂 ,采用水热条件下的动态合成方法 ,合成出结晶度良好的ZSM 2 2晶体 .研究表明 ,合成的关键是避免ZSM 5分子筛的生长 ,当n(Si) /n(Al) =2 5～ 6 5 ,n(H2 O) /n(SiO2 ) =16 3～ 40 3,n(DAH) /n(Si) =0 1～ 0 6和T=42 8～ 44 8K时 ,都能稳定合成出ZSM 2 2分子筛 .采用TEM ,XRD ,TG DTA和NH3 TPD等方法 ,对ZSM 2 2晶体的形貌 ,生长动力学 ,模板剂的作用以及硅铝比对分子筛酸性的影响等进行了较详细的研究 .实验结果和理论计算证实 ,1,6 己二胺分子以首尾相连的方式 ,线性排列并完全充满ZSM 2 2的十元环孔道 ,同时起到结构导向和骨架电荷平衡的作用 .

There has been an increasing interest in isomerizationof n-butene to isobutene over ZSM-22 with high silica, for its unique unidirectional pore structure and accompanying high Si/Al ratio. Using I 6-diaminohexane (DAH) as a template, the ZSM-22 was synthesized as a unique phase under dynamic condition. Under the conditions of n(Si)/n(Al)=25similar to65, n(H2O)/n(SiO2) = 16.3similar to40.3 and n(DAH)/n(SiO2) = 0.1similar to0.6, the ZSM-22 was obtained as a pure phase and with good yield in a relatively broad range of temperature (428-448 K). The crystallization kinetics and morphology of ZSM-22, and the role of template and the effect of Si/Al ratios on acid property of ZSM-22 were studied by XRD, TEM, TG-DTA and NH3-TPD techniques. Based on the experimental results and the theoretical calculation, it can be considered that the DAH molecules are in a line by end-to-end configuration and fill the total volume of the straight ten-membered ring pores.