红辉沸石两步水热法合成A型分子筛机理研究

以红辉沸石为原料，采用两步水热法将其转化为A型分子筛，系统地探讨A型分子筛的转化机理。对不同晶化时间的样品进行系统表征，深入解析天然红辉沸石转化A型分子筛的成核机制、生长控制、晶型稳定转化等结构基础问题。研究表明，A型分子筛的生长可分为3个阶段：在成核诱导期（晶化时间≤0.5 h），凝胶中的β笼通过双四元环构筑成α笼，生成较多晶核及少量1 μm小晶体；此后为快速生长期（晶化时间1~4 h），大量晶核通过聚集生长形成2 μm大晶体；在生长稳定期（晶化时间5~8 h），通过二次成核凝胶将会转化为更多的分子筛晶体。A型分子筛的形成遵循：铝硅酸盐凝胶→四元环、六元环→双四元环、β笼→α笼的晶化过程，因而其转化过程符合液相转化机理。

Study on mechanism of zeolite A synthesized from stellerite zeolite by two-step hydrothermal method

Stellerite zeolite was used as raw material to convert into zeolite A by the two-step hydrothermal method，and the conversion mechanism of zeolite A was systematically investigated.The samples with different crystallization times were systematically characterized.The basic structural problems such as the nucleation mechanism，growth control and stable conversion of crystal form of natural stellerite zeolite into zeolite A were analyzed in depth.The results indicated that the growth process of zeolite A could be divided into three stages.When it was in the nucleation induction stage（crystallition time≤0.5 h），the β cages in gel was constructed by double four-membered rings to form α cages and many crystal nuclei and a few 1 μm small crystal were formed.When it was in the rapid growth（crystallition time of 1~4 h），a large number of nuclei were grown by aggregation to form large crystals with 2 μm.Finally，when it was in the stable growth（crystallition time of 5~8 h），the gel was converted into more zeolite crystals by secondary nucleation.The formation of zeolite A was followed：aluminosilicate gel→four-membered rings and six-membered rings→double four-membered rings and β cages→α cages.Therefore，the process of stellerite zeolite conversion to zeolite A was belonged to a liquid phase conversion mechanism.