动态条件下ZSM-12分子筛的合成

Dynamic Synthesis of ZSM-12 Zeolite

采用动态晶化法,系统考察了硅源、硅铝比、模板剂含量以及水含量对ZSM-12分子筛合成的影响,得到合成纯相ZSM-12分子筛的最佳条件为：硅溶胶为硅源,n（Si）/n（Al）=45～70,n（四乙基氢氧化铵,TEAOH）/n（SiO_2）=0.14,n（H2O）/n（SiO_2）=13。通过XRD、SEM、BET、NH3-TPD对所合成的产物进行了表征。体系中的硅铝比对所合成产物的晶相和晶化动力学有显著影响：当硅铝比（Si/Al摩尔比,下同）过低时,容易导致MFI和BEA结构的杂晶相的生成;硅铝比较高时,动态晶化比静态晶化更有利于提高分子筛的合成效率;体系中的n（TEAOH）/n（SiO_2）和n（H_2O）/n（SiO_2）会在很大程度上影响所合成产物的晶相和形貌。

Effects of the silica source,the Si / Al ratio,and the content of template agent and H2 O on the synthesis of ZSM-12 zeolite were studied.The optimal conditions for synthesis of pure ZSM-12 were determined as n（Si） / n（Al） = 45 ～ 70,n（TEAOH） / n（SiO_2） = 0.14 and n（H2O） / n（SiO_2） = 13 under conditions in this investigation.The physical properties of the products were characterized by means of X-ray diffraction,field emission scanning electron microscopy,N2 adsorption,and NH3-temperature programmed desorption.The results showed that colloidal silica was the best silica source and the Si / Al ratio had major effects on the crystalline phase of the product and the crystalline dynamics under the conditions studied.More specifically,the MFI-type and BEA-type zeolites appeared in product with low Si / Al ratio,and the dynamic crystallization was more effective than the static crystallization in the synthesis with high Si / Al ratio.Both of n（TEAOH） / n（SiO_2） and n（H2O） /n（SiO_2） had strong effect on the phase and morphology of the as-synthesized products.