Hu Sufang, Song Guoqiang, Xue Da, Li Fuxiang
Research Institute of Special Chemicals, Taiyuan University of Technology Taiyuan 030024 China.
RSC Adv. 2019 Jan 21;9(5):2551-2558. doi: 10.1039/c8ra08952c. eCollection 2019 Jan 18.
The mechanism of formation of hierarchical LTA zeolite involved the methoxyl groups of bridged polysilsesquioxane hydrolyzing into hydroxyl groups. The covalent Si-O-Si bond between silicon hydroxyl in the above solution and other silica sources forms by dehydration, avoiding phase separation. The influence of alkalinity on the synthesis of hierarchical LTA zeolites was investigated by using bridged polysilsesquioxane. XRD patterns indicate the synthesis of sodalite at the same molar composition of the hierarchical LTA zeolites without bridged polysilsesquioxane. The characterization results from TG and DTG revealed that bridged polysilsesquioxane was successfully incorporated into the as-synthesized hierarchical LTA zeolite. N-adsorption/desorption results proved that mesopores and the porosities of the hierarchical LTA zeolites are adjustable by a change of alkalinity. SEM images indicated that the morphologies of the hierarchical LTA zeolites changed with increasing alkalinity. The hierarchical LTA zeolites showed faster initial exchange rates of Na to Mg compared with conventional LTA.
分级LTA沸石的形成机制涉及桥连聚倍半硅氧烷的甲氧基水解为羟基。上述溶液中硅羟基之间的共价Si-O-Si键通过脱水形成，避免了相分离。利用桥连聚倍半硅氧烷研究了碱度对分级LTA沸石合成的影响。XRD图谱表明，在相同摩尔组成下，没有桥连聚倍半硅氧烷时会合成方钠石。TG和DTG的表征结果表明，桥连聚倍半硅氧烷已成功掺入合成的分级LTA沸石中。N吸附/脱附结果证明，分级LTA沸石的介孔和孔隙率可通过改变碱度进行调节。SEM图像表明，分级LTA沸石的形态随碱度增加而变化。与传统LTA相比，分级LTA沸石显示出更快的Na到Mg的初始交换速率。
