【作者】 张宇；

【导师】 车黎明； 刘明久；

【作者基本信息】 厦门大学 ， 化学工程， 2022， 硕士

【摘要】 SSZ-13分子筛具有优异的脱硝性能,在汽车尾气处理等领域具有广泛应用。在SSZ-13分子筛合成方法中,分子筛转晶法作为水热合成法的替代方法,具有成本低和用时短的优点,因而倍受关注。目前已有Y型(FAU骨架结构)、β型(*BEA骨架结构)、ZSM-5(MFI骨架结构)型等多种分子筛在N,N,N-三甲基-1-金刚烷铵(TMAdaOH)的结构导向作用下转晶制备SSZ-13分子筛(CHA骨架结构)的报道。但是现有的转晶机理无法解释ZSM-5分子筛向SSZ-13分子筛的转化过程。基于此,本论文致力于研究ZSM-5分子筛转晶制备SSZ-13分子筛的机理,并在此基础上寻找合成SSZ-13分子筛的新路径。具体研究内容和结果如下:首先,运用分子力学和动力学模拟的方法,对有机结构导向剂TMAdaOH与MFI、*BEA、FAU和CHA分子筛骨架的相互作用进行了研究,计算了有机结构导向剂与分子筛骨架的匹配性和稳定能。结果表明,TMAdaOH在MFI、*BEA、FAU和CHA分子筛骨架中的最佳吸附位点分别是十元环扭曲孔道、十二元环直孔道、t-fau笼以及t-cha笼;TMAdaOH与CHA分子筛骨架的匹配性最好,其次是MFI和*BEA分子筛骨架,与FAU分子筛骨架匹配性最差;TMAdaOH在MFI、*BEA、FAU分子筛骨架中的稳定能高于其在CHA分子筛骨架中的稳定能。据此可认为,有机结构导向剂可促使高稳定能分子筛转晶为低稳定能分子筛。其次,运用分子力学和动力学模拟的方法,研究了四乙基氢氧化铵(TEAOH)与MFI和CHA分子筛骨架的相互作用。结果表明,TEAOH在MFI和CHA分子筛骨架中的最佳吸附位点分别是十元环扭曲孔道和t-cha笼;TEAOH在MFI分子筛骨架中的稳定能高于其在CHA分子筛骨架中的稳定能。据此可推测,以TEAOH为有机结构导向剂,ZSM-5分子筛可转晶制备成SSZ-13分子筛。最后,以TEAOH为有机结构导向剂,ZSM-5分子筛在160℃的水热条件下转晶制备成SSZ-13分子筛,并对所制得的分子筛进行了结构和功能特性表征。结果表明,无机碱、有机结构导向剂和晶种对ZSM-5分子筛向SSZ-13分子筛的转化都有重要影响;所制备的SSZ-13分子筛具有一定的介孔结构,酸性适中。更多还原

【Abstract】 SSZ-13 zeolite has excellent denitration performance and is thus used widely to treat automobile exhaust.As an alternative to hydrothermal method to synthesize SSZ13 zeolite,interzeolite conversion method attracts more and more attention due to its low-cost and simplicity.So far,Y-type zeolite(FAU framework),β-type zeolite(*BEA framework)and ZSM-5 zeolite(MFI framework)have been converted into SSZ-13 zeolite(CHA framework)with the help of N,N,N-Trimethyl-1-ammonium adamantane(TMAdaOH).However,the micromechanism of interzeolite conversion from ZSM-5 to SSZ-13 is still not clear.The aim of this thesis is therefore to explore such mechanism and look for a new path to synthesize SSZ-13 zeolite.The specific research contents and results are as follows:Firstly,the interactions between organic structure-directing agent TMAdaOH and MFI,*BEA,FAU or CHA frameworks were investigated by using molecular mechanics and dynamics simulation in terms of structure matching index and stablization energy.Simulation results show that the best adsorption sites of TMAdaOH in the frameworks of MFI,*BEA,FAU and CHA are twisted 10-MR channel,straight 12-MR channel,tfau cage and t-cha cage,respectively.TMAdaOH matches CHA framework best,followed by MFI and*BEA frameworks,and then FAU framework.The stablization energies of TMAdaOH in the framworks of MFI,*BEA and FAU are higher than that in CHA framework.It implies that interzeolite conversion from high stablization energy to low one is favourable in the presence of organic structure-directing agent.Secondly,the interactions between tetraethylammonium hydroxide(TEAOH)and MFI or CHA frameworks were investigated by using molecular mechanics and dynamics simulation.Simulation results show that the best adsorption sites of TEAOH in MFI and CHA frameworks are twisted 10-MR channel and t-cha cage,respectively.The stablization energy of TEAOH in MFI framework is higher than that in CHA framework.It implies that ZSM-5 zeolite might be converted to SSZ-13 zeolite in the presence of TEAOH.Finally,ZSM-5 zeolite was converted to SSZ-13 zeolite in the presence of TEAOH under hydrothermal conditions at 160℃.The structural and properties of resultant SSZ-13 zeolite were characterized comprehensively.The results show that inorganic base,organic structure-directing agent and crystalline seed are all vital to interzelite conversion from ZSM-5 to SSZ-13.The SSZ-13 zeolite obtained has moderate acidity with mesoporous structure.更多还原