一步合成核壳结构ZSM-5/EU-1复合分子筛及其表征

在添加适量柠檬酸的条件下采用双模板剂一步法, 一次晶化合成ZSM-5/EU-1核壳共生复合分子筛, 对其物理化学性质进行表征, 结果显示: 核壳分子筛中存在ZSM-5和EU-1两种分子筛晶相, 且EU-1分子筛在ZSM-5分子筛表面缺陷处外延生长; 复合以后核壳分子筛为微孔-介孔多级孔道结构, 且其微孔孔径达到0.94 nm; 相比于单一分子筛, 核壳分子筛的强酸量相对提高, 酸性质有所改善。通过对柠檬酸加入量、晶化时间影响因素的分析, 得到合成核壳共生结构的最佳条件为: n(citrate)/n(Al₂O₃)=0.8~1.2, 晶化时间为72~96 h, 并推测核壳分子筛可能的生长过程。

Synthesis and Characterization of ZSM-5/EU-1 Composite Zeolite with ore-shell Structure by One Step

ZSM-5/EU-1 core-shell intergrowth composite zeolite was synthesized by one-step crystallization method based on dual-template and appropriate citric acid addition. The properties of core-shell zeolite were characterized by XRD, TEM, FT-IR, NH₃-TPD, etc. The results showed that there were ZSM-5 and EU-1 zeolite crystalline phases formed in the core-shell zeolite, as EU-1 overgrowing around ZSM-5 surface defects. The synthetic sample composed of microporous and mesoporous multiple porous composite zeolite, with micropore diameter of 0.94 nm. The core-shell structure increased strong acid content and improved its acidity as compared with the single zeolite. Based on the investigation of citric acid addition and crystallization time influence on the structure and Zeta potential of core-shell zeolite, the optimum condition of core-shell intergrowth was as follows, i.e. n(citrate)/n(Al₂O₃)=0.8-1.2 and crystallization time of 72-96 h. And the possible growth process of core-shell zeolite was proposed.