干胶-水蒸汽辅助晶化法合成多级孔ZSM-5分子筛

Synthesis of hierarchical ZSM-5 zeolites by xerogel-steam assisted hydrothermal method

采用干胶-水蒸汽辅助晶化法,通过优化制备条件,合成了粒径约80 nm的表面多孔纳米球形ZSM-5.考察了结构导向剂质量分数、硅源、铝源、沉淀剂种类、晶核形成时间及老化温度对纳米ZSM-5晶体形貌的影响.采用X射线衍射(XRD)、傅里叶变换红外光谱(FT-IR)、N_2物理吸附-脱附及透射电子显微镜(TEM)等表征手段对合成的分子筛进行了表征.结果表明:结构导向剂的质量分数、铝源的类型和晶核形成时间均能明显影响分子筛晶体形貌;结构导向剂质量分数的降低有助于提高ZSM-5微孔结构的长程有序性;优化合成条件可制备出具有约介孔2 nm、比表面积357.1 m^2/g、由80 nm的晶粒堆积形成的多级孔ZSM-5分子筛材料.

The nano-spherical ZSM-5 with a surface porous structure and particle diameter of 80 nm was synthesized by xerogel-steam assisted hydrothermal method under optimized preparation conditions. The effect of the concentration of structure-directed agent, silicon source, aluminum source, precipitant, the nucleation time, and aging time on the morphology of ZSM-5 were studied. The zeolite material was characterized by using XRD, FT-IR, N2 adsorption-desorption, and TEM. The results demonstrated that the morphology of the ZSM-5 crystallites was significantly affected by the concentration of structure-directed agent, the type of aluminum source and nucleation time. Decreasing the concentration of structure-directing agent helped to improve the long-range order of the microporous structured ZSM-5. The hierarchical ZSM-5 with mesopores of 2 nm, specific surface area of 357.1 m2/g and particle size centered at 80 nm was obtained under optimized conditions.