聚乙二醇存在下不同合成条件对多级孔ZSM-5分子筛形貌的影响

以四丙基溴化铵（TPABr）为微孔模板剂、聚乙二醇(PEG)为介孔模板剂，在不同的水热条件下，合成不同形貌的多级孔ZSM-5分子筛，并探究其晶形及孔径分布变化。利用X射线衍射仪（XRD）、扫描电镜、N₂吸附-脱附等表征手段，研究分子筛的孔道结构和物化性能。结果表明，多级孔ZSM-5分子筛晶体尺寸随着硅/铝摩尔比(n(Si)/n(Al))的增大而减小；随着晶化温度的升高，组成晶体的晶粒由长六方板状变成正六方板状，晶化温度过高（200℃）会导致聚乙二醇的模板导向作用减弱；晶化时间延长，分子筛晶体形貌单一，只有板状晶粒穿插形成的晶体且晶体尺寸变大；随着聚乙二醇用量的增加，组成晶体的小晶粒逐渐增多，晶体从六棱明显的板状成为近球状。m(Si)/m(Al)/m(PEG)为100/0.027/20，晶化温度为180℃，晶化时间为36 h时， 多级孔ZSM-5分子筛的结晶度最高；合成的晶体大小均匀且形貌统一。

Influence of Different Synthesis Conditions in the Presence of Polyethylene Glycol on the Morphology of Hierarchical ZSM-5

A series of hierarchical ZSM-5 zeolites with different morphologies were synthesized under different hydrothermal conditions using tetrapropylammonium bromide (TPABr) as microporous templating agent and polyethylene glycol (PEG) as mesoporous templating agent. The difference of crystal shape and pore size distribution was investigated.The pore structure and physicochemical properties of molecular sieves were studied by means of X ray diffraction (XRD), scanning electron microscopy, N₂ adsorption desorption and other methods. Results show that the crystal size of hierarchical ZSM-5 zeolite is decreasing with the increase of the molar ratio of silicon and aluminum. Along with the increasing of crystallization temperature, the irregular  hexagonal plate structure of crystal grains becomes positively hexagonal. However, high crystallization temperature (200℃)  weakens the template guiding role of polyethylene glycol. When crystallization time is extended, the crystal morphology becomes much more uniform, only with the formation of plate-like grains in similar crystal  size. Moreover,  the crystal size of zeolite grains is gradually increasing as a function of the amount of polyethylene glycol,while the  morphology changes from six prismatic to nearly spherical.When the mass ratio of SiO₂, Al₂O₂ and PEG is 100∶0.027∶20, crystallization temperature is 180℃, crystallization time is 36 h, the  hierarchical ZSM-5 zeolite of the highest crystallinity is obtained,which has  the  uniform crystal size and  morphology.