利用钾长石粉体水热合成13X沸石分子筛的晶化过程

实验研究了以钾长石粉体为原料水热合成13X沸石分子筛的晶化过程,确定了晶化过程的诱导期、晶化期和沸石晶体的平均生长速率。以钾长石焙烧熟料为前驱物合成13X沸石,反应混合物首先转变为铝硅酸钠(钾)凝胶,再逐步水热晶化为13X沸石;在反应物未完全转变为铝硅酸钠(钾)凝胶之前,13X沸石已开始结晶。13X沸石晶体的生成主要发生在凝胶相内部,是凝胶结构逐步趋于有序化的过程。13X沸石晶体生成是由凝胶相内的TO4]四面体相互连接,互套构成笼状结构。推测13X沸石形成机理为:硅酸根离子和铝酸根(+铁酸根)离子发生聚合反应,生成次级结构单元双六元环;双六元环进一步缩合,生成方钠石型笼;最后,方钠石型笼进一步相互联结,生成13X型沸石分子筛的硅铝骨架结构。

Reaction Mechanism of 13X Zeolite Crystallization with K-feldspar Powder as Raw Materials

The synthesis of 13X zeolite with K-feldspar powder as raw materials is characterized by XRD,SEM,IR,chemical analysis and Raman spectroscopy.The investigation discovers the inducement period,the crystal period of the crystallizing process and the average growth speed of 13X zeolite grains.The experimental results demonstrate that the reactive mixture is firstly transformed into aluminosilicate gels,and then the gels is transformed into 13X zeolite crystal grains while synthesizing 13X zeolite from the aluminosilicate precursor prepared by baking the K-feldspar powder.13X zeolite has already appeared before the mixture all transforming into the aluminosilicate gels.The growth of 13X zeolite is mainly in the aluminosilicate gels,which is a process of putting the aluminosilicate gels structure in order while the liquid participates in the formation of 13X zeolite. tetrahedrons of the aluminosilicate gels connect each other to form the framework of 13X zeolite.A model for the formation of 13X zeolite is proposed,which involves that silicate ions and aluminate(or ferrite) ions polymerize to double six-membered rings,the secondary building unit,then the double six-membered rings interconnecting to SOD cages,and then SOD cages further interconnecting to form the framework of 13X zeolite.