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通过精细调整控制合成条件,在SiO2-TPAOH-H2O-NH4F(TPAOH:四丙基氢氧化铵)体系中制备出了厚度可控的薄板型Silicalite-1分子筛材料,并利用扫描电镜(SEM)、高分辨透射电镜(HRTEM)、粉末X射线衍射(XRD)及差热-热重分析(TG-DTA)对样品的结构信息、样品形貌及物理化学性质进行了表征.研究表明,NH4F浓度和反应体系pH值对Silicalite-1分子筛的形貌起着重要的导向作用.随着NH4F/SiO2的摩尔比(n(NH4F)/n(SiO2))由0增加到0.18,分子筛形貌由交互生长的椭圆形变为板形,其厚度也逐渐变薄;当n(NH4F)/n(SiO2)=0.4时,厚度达到最薄.继续增加NH4F/SiO2的摩尔比,其厚度增加,这是由于F-提高了样品结晶度.HRTEM研究表明b轴垂直于平面,由于在MFI结构的材料中,b轴方向是其直孔道方向,这种材料有利于客体分子的进出.还研究了样品的热稳性,所有样品在1100°C焙烧2h后,其形貌和结构不发生变化.
By controlling the synthesis conditions finely, the thin-shaped Silicalite-1 molecular sieve material with controlled thickness was prepared in the system of SiO2-TPAOH-H2O-NH4F (TPAOH: Tetrapropylammonium hydroxide) The structure, sample morphology and physico-chemical properties of the samples were characterized by HRTEM, XRD and TG-DTA.The results showed that the concentration of NH4F and The pH value of the reaction system plays an important guiding role on the morphology of Silicalite-1 zeolite.With the increase of the NH4F / SiO2 molar ratio (n (NH4F) / n (SiO2)) from 0 to 0.18, The thickness becomes thinner, and the thickness reaches the thinnest when n (NH4F) / n (SiO2) = 0.4, and the thickness of NH4F / SiO2 increases with the increase of the NH4F / SiO2 molar ratio because F - increased the crystallinity of the sample.HRTEM study shows that the b-axis is perpendicular to the plane, because the material in the MFI structure, the b-axis direction is the direction of its straight hole, this material is conducive to the guest molecules in and out. All samples were calcined at 1100 ° C for 2 h, their morphology and structure did not change.