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 cry...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.展开更多
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...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。展开更多
The use of an organic structure-directing agent(OSDA)makes zeolite synthesis expensive and environmentally non-friendly.Seeded zeolite synthesis offers an environmentally benign alternative that avoids using an OSDA w...The use of an organic structure-directing agent(OSDA)makes zeolite synthesis expensive and environmentally non-friendly.Seeded zeolite synthesis offers an environmentally benign alternative that avoids using an OSDA while providing a high purity,crystallinity,and yield in the product.In this study,we report using embryonic zeolites(EZs)as efficient seeds to obtain industrially important zeolites such as ZSM-34 and SSZ-13 in an OSDA-free synthesis system.Our results showed that zeolites ZSM-34,SSZ-13 and LTL could be obtained depending on the Al/Si ratio in the synthesis system.The synthesis time was considerably shorter than other ZSM-34 and SSZ-13 syntheses methods reported in the literature,achieving more than 90%crystallinity.The physicochemical analysis showed that highly crystalline zeolites with characteristics similar to the OSDA synthesized counterparts were obtained.Furthermore,the EZs seeding approach is facile,low cost,and environmentally friendly,pro-vided the synthesis is OSDA-free.In addition,the EZs seeds can be obtained under hydrothermal synthesis conditions.The method can be potentially applied to the synthesis of other zeolite types.展开更多
基金the financial supports from the National Natural Science Foundation of China(22322803,22178059,22208054,22221005,22072019)Key Technologies Innovation and Industrialization Projects of Fujian Province(2022G031)Qingyuan Innovation Laboratory(00121002,00523005)。
文摘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.
文摘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。
文摘The use of an organic structure-directing agent(OSDA)makes zeolite synthesis expensive and environmentally non-friendly.Seeded zeolite synthesis offers an environmentally benign alternative that avoids using an OSDA while providing a high purity,crystallinity,and yield in the product.In this study,we report using embryonic zeolites(EZs)as efficient seeds to obtain industrially important zeolites such as ZSM-34 and SSZ-13 in an OSDA-free synthesis system.Our results showed that zeolites ZSM-34,SSZ-13 and LTL could be obtained depending on the Al/Si ratio in the synthesis system.The synthesis time was considerably shorter than other ZSM-34 and SSZ-13 syntheses methods reported in the literature,achieving more than 90%crystallinity.The physicochemical analysis showed that highly crystalline zeolites with characteristics similar to the OSDA synthesized counterparts were obtained.Furthermore,the EZs seeding approach is facile,low cost,and environmentally friendly,pro-vided the synthesis is OSDA-free.In addition,the EZs seeds can be obtained under hydrothermal synthesis conditions.The method can be potentially applied to the synthesis of other zeolite types.
