SSZ-39分子筛的合成及晶化机理研究

Synthesis of SSZ-39 zeolite and its crystallization mechanism

SSZ-39分子筛是化学催化领域的新型催化剂。文中以自主设计、合成的N,N-二乙基-2,6-二甲基哌啶碱(DEDMP+OH-)为结构导向剂、硅溶胶为补加硅源,Y型分子筛提供铝源,采用低温老化、高温晶化的水热法成功地合成出SSZ-39分子筛。通过XRD,TG-DSC,NH 3-TPD等手段对合成样品进行了表征,对n(SiO 2)/n(Al 2 O 3)、老化温度、补加硅源与Y型分子筛的加入顺序进行考察。由表征可知:n(SiO 2)/n(Al 2 O 3)=10~20,老化温度为25—45℃,晶化温度为180℃,可合成具有AEI拓扑结构的SSZ-39分子筛。最后对Y沸石转化合成SSZ-39分子筛的晶化机理进行了研究。结果表明,补加硅源与Y分子筛先形成无定形硅铝凝胶,随着晶化中间相ANA沸石生成,在结构导向剂的作用下,生成的ANA沸石转变为SSZ-39分子筛。

SSZ-39 zeolite is a new type of the catalyst in chemical industry field.SSZ-39 zeolite was prepared by hydrothermal process with low temperature aging and high temperature crystallization period using the silica sol as adding silicon source,Y zeolite as aluminum source,and designed synthesis N,N-diethyl-2,6-dimethylpiperidinium hydroxide(DEDMP+OH-)as organic template.SSZ-39 zeolite was characterized by XRD,TG-DSC,NH 3-TPD and other methods,and the effects of the aging temperature,molar ratio of SiO 2 to Al 2 O 3,the addition sequence of silicon source and Y molecular sieve on the crystallization of SSZ-39 zeolite were investigated.The characterization shows that SSZ-39 with the topological structure of AEI are obtained within a ratio range of gel SiO 2/Al 2 O 3 of 10-20,aging temperature of 25-45℃,and crystallization temperature of 180℃.Finally,the transformation of Y zeolite to SSZ-39 molecular sieve was studied.The result shows that amorphous silica-alumina gel first forms with the supplemented silicon source and Y molecular sieve,the intermediate phase is crystallized gradually into SSZ-39 crystals in N,N-diethyl-2,6-dimethyl piperidinium hydroxide,and finally the formed SSZ-39 crystals induces the initial ANA to transform into SSZ-39 zeolite.