OSDA-free synthesis of FeZSM-22 zeolite from natural minerals for n-octane hydroisomerization

A seed-directed approach to synthesizing Fe ZSM-22 zeolite without organic structure directing agent(OSDA)was developed by using Fe-rich diatomite as all aluminum and iron sources.The Fe ZSM-22zeolite with optimal crystallinity and purity can be obtained by systematically adjusting feed composition and synthesis conditions.Characterizations show that Fe ZSM-22 zeolite synthesized with OSDA-free owns high crystallinity,obvious thin needle-shaped morphology and high Bronsted/Lewis acid ratio.Significantly,when used for n-octane hydroisomerization reaction,its derived catalyst exhibits the best catalytic performance reflected by the highest selectivity to C_(8)isomers compared to the two reference catalysts prepared based on a Fe-containing and a Fe-free ZSM-22 synthesized through an OSDA-directed route from natural diatomite and conventional chemicals,respectively.This work provides an alternative route to sustainably synthesizing heteroatomic zeolites with high performance.

异相晶种诱导快速合成低硅菱沸石分子筛

在不含有机模板剂体系(OSDAs)中,利用异相晶种(T型分子筛)诱导快速合成出纯相的低硅菱沸石分子筛。采用XRD、SEM、TEM、27Al MAS NMR和紫外拉曼等手段表征分子筛的结构属性和形貌特点。详细研究了菱沸石分子筛的晶化过程以及晶种添加量、nAl2O3/nSi O2、nH2O/nSiO2和碱度对菱沸石分子筛晶化的影响,并探讨T型分子筛晶种诱导合成菱沸石分子筛的晶化机理。原位合成体系中仅形成L型分子筛晶相,而一定量T型分子筛异相晶种的加入诱导溶胶快速制备出纯相的菱沸石分子筛。T型分子筛晶体在一定的水热条件下不断溶解而释放的六元环(6R)和四元环(4R)迅速形成菱沸石分子筛特征笼(CHA笼),抑制了L型分子筛特征单元和特征笼(不含四元环的CAN笼)的形成。

含氟体系中无模板剂合成SSZ⁃13分子筛

本实验以玻璃纤维为硅源,在不添加有机模板剂的条件下通过水热合成法合成了SSZ⁃13分子筛。通过X射线衍射(XRD)、扫描电镜(SEM)、傅里叶红外光谱(FT⁃IR)等表征手段,探讨原料投料比中硅源的含量、SiO2/Al2 O3比、体系碱度及晶化时间对SSZ⁃13分子筛形成的影响。结果表明,在120℃下,晶化反应24 h,且初始混合物的物质的量之比n(Na2O)∶n(Al2O3)∶n(SiO2)∶n(H2O)∶n(NH4F)=3∶1∶3.5∶250∶1时,制备得到了纯相的SSZ⁃13分子筛。该合成过程中不添加任何有机模板剂,降低了生产成本,且无需煅烧去除有机模板剂,减少了有害气体的排放。