通过优化水热陈化条件制备纳米L沸石,再采用水热合成结合原位二次晶化法,合成具有微-介复合孔结构的高效ZSM-5-L二元复合分子筛.考察了体系pH、二次晶化温度等因素对ZSM-5-L复合分子筛合成的影响,采用X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)和傅里叶变换红外光谱(FTIR)等技术对复合分子筛进行表征,确定了最佳复合条件:pH=10.5-11.5,晶化温度170℃,晶化时间24 h.ZSM-5-L复合分子筛具有不同于ZSM-5沸石、L沸石及两者机械混合物的物性特征,且具有微-介复合孔结构.以正戊烷催化转化为探针反应,评价了ZSM-5-L复合分子筛轻烃芳构化反应性能.在相同反应条件下,ZSM-5-L复合分子筛具有优于2种单分子筛及二者机械混合物的正戊烷芳构化催化性能.
Nano-sized L zeolite was synthesized via an improved hydrothermal synthesis method. On this basis, efficiently ZSM-5-L molecular sieves with micro-mesoporous hierarchically structure were obtained through the way of hydrothermal treatment incorporated with in situ recrystallization. X-Ray diffraction ( XRD), scanning electron microscopy ( SEM), transmission electron microscopy ( TEM ), Fourier transform infrared spectroscopy(FTIR) were applied to characterize the effect of pH value and recrystallize temperature on the manufacture of the composite ZSM-5-L molecular sieves, and optimum synthesis conditions ( pH = 10.5-11.5, crystallization temperature 170 ℃, crystallization time 24 h) were confirmed. The structure of the as-synthesized composite ZSM-5-L molecular sieves was micro-mesoporous hierarchically, which was different from that of pure L zeolite, ZSM-5 zeolite and their mechanical mixture zeolite. The light hydrocarbon aromatization properties of the composite ZSM-5-L molecular sieves were evaluated via a n-pentane probe reaction. Compared with the properties of L zeolite, ZSM-5 zeolite and their mechanical mixture zeolite catalyst, the composite ZSM-5-L molecular sieves show superior catalytic performances in aromatization, and exhibit potentially applications as a catalyst in light hydrocarbon aromatization field.