ZSM-5分子筛结晶度及晶粒大小的影响因素

以硅溶胶为硅源,偏铝酸钠为铝源,用晶种法制备ZSM-5分子筛.考察了物料混合方式、陈化时间、晶化时间、晶化温度、碱度和水量等对ZSM-5分子筛相对结晶度和晶粒大小的影响.用X射线衍射仪(XRD)、扫描电子显微镜(SEM)和激光粒度分析等对所合成样品进行了表征.结果表明:在一定的高碱度条件下形成高浓度的硅铝酸盐凝胶,才能合成出晶化良好的样品,ZSM-5分子筛是按固相机理形成的;合成ZSM-5分子筛的相对结晶度和平均颗粒度均随晶化温度的升高及硅铝酸盐凝胶浓度的增加而增大,在室温陈化24 h、180℃晶化12～24 h时相对结晶度最高,平均颗粒度基本上与陈化时间无关.

The Influence Factors of the Crystallinity and Crystal Size of ZSM-5 Zeolite

ZSM-5 zeolite was synthesized by seeding technique using silica sol and aluminum sulfate as raw materials.The effects of key factors,such as the mixing modes of material,aging time,crystallization temperature,crystallization time,alkalinity and dosage of H2O on the crystallinity and crystal size were investigated.The samples were characterized by XRD,SEM and LPSA etc.The result indicated that the high crystallinity ZSM-5 zeolite can only be synthesized with the high concentration aluminosilicate gel formed in the condition of certain high alkalinity.ZSM-5 zeolite crystallization proceeds is based on the solid-solid transformations mechanism.The higher of the crystallization temperature and the concentration of aluminosilicate gel,the higher of the relative crystallinity and average particle size,the sample of the highest crystallinity can be synthesized with the aging time of 24 h at room temperature and the crystallization time of 12~24 h at 180 ℃.The aging time have a small influence on the crystal size.