水蒸气诱导自组装制备介-微孔ZSM-5分子筛的研究

Synthesis of Meso-microporous ZSM-5 Zeolite by Steam-Assisted Post-Crystallization

软模板剂方法可以合成介-微孔分子筛,但有些模板剂与硅铝酸盐之间弱的化学结合力导致晶化过程模板剂与合成体系的相分离,结果形成了无定型的介孔材料和微孔分子筛的混合物。采用新的技术路线:通过使用四丙基氢氧化铵(TPAOH)作模板剂,以三嵌段共聚物P123原位植入介孔结构,采用水蒸气诱导干凝胶自组装晶化的方法制备介-微孔ZSM-5分子筛。优点是:大大减少了模板剂的使用量,省去了产品与母液分离的繁琐步骤,无大量废液产生,对环境友好。采用X射线衍射(XRD)、傅立叶变换红外光谱(FT-IR)、N2吸附-脱附比表面分析(BET)、扫描电镜(SEM)、高倍透射电镜(TEM)系列表征方法对介-微孔ZSM-5分子筛进行表征,可知样品具有典型的ZSM-5分子筛的骨架结构和明显地介孔孔道。在800℃,100%水蒸气条件下经15h水热老化后,分子筛的比表面积保留率73.44%,孔容保留率74.35%,表明分子筛的水热稳定性良好。

Soft templates can be used in the synthesis of meso-microporous zeolite,much attention is being paid to the weak interaction between the templates and the silicate species.As a result,during the crystallization and growth process of zeolite particles,phase separation between surfactant and zeolite crystals would inevitably took place,and a mixture of amorphous mesoporous materials and pure zeolite crystals could be obtained.In the present work,using conventional block copolymers P123 as soft templates,a direct synthetic route of mesoporous zeolites has been developed with the assistance of post-steaming and the mesopore size and pore volume are tuned by changing the amount of meso templates.The advantages of the method are that greatly reduce the dosages of the templates and avoid phase separation between the conducts and the mother solution.At the same time,this method is very environmental saving,such as it will not produce lots of waste liquids.XRD,N 2 adsorption-desorption,FT-IR,SEM,TEM,27Al MAS NMR and 29Si MAS NMR techniques are employed to characterize the resulting samples.This novel product exhibits both the clear mesostructure.After 800℃100%steaming treatment 12 h,remain fractions of BET surface and pore volume were 73.44%and 74.35%,the zeolites shows high hydrothermal stability.