离子液体作用下溶胶-凝胶法合成介孔氧化铝的研究

Synthesis of Mesoporous Al_2O_3 with an Ionic Liquid-Assisted Sol-Gel Method

采用溶胶-凝胶法,以离子液体1-丁基-3-甲基咪唑六氟磷酸盐([Bmim]PF_6)为模板、异丙醇铝为铝源合成介孔氧化铝,重点考察了离子液体用量和煅烧温度对氧化铝介孔结构的影响,用X射线衍射仪(XRD)、场发射透射电子显微镜(TEM)、氮气物理吸脱附仪、傅里叶红外分析仪(FT-IR)等手段对合成样品进行了表征。研究结果表明,离子液体对氧化铝的介孔构建起到了模板调控的作用,适量的离子液体有助于有序介孔的构建;煅烧温度影响孔道参数,温度过高导致孔道坍塌会造成比表面积、孔径、孔容的减小。当离子液体与异丙醇铝的摩尔比为0.018、煅烧温度为500℃下可获得相对有序的介孔γ-Al_2O_3,其比表面积最大为447 m^2×g^(-1),最大孔容1.17 cm^3×g^(-1),平均孔径7.6 nm。此外还对离子液体合成介孔氧化铝的微观机理进行了探讨。

Mesoporous alumina was synthesized from aluminum isopropoxide by an ionic liquid-assisted sol-gel method using 1-butyl-3-methylimidazolium hexafluorophosphate（[Bmim]PF6） as a template. The effects of ionic liquid [Bmim][PF6] amount and calcination temperature on the mesostructures of alumina were studied. The obtained products were characterized by X-ray diffraction（XRD）, transmission electron microscopy（TEM）, N2 adsorption-desorption technique and Fourier transform infrared spectroscopy（FT-IR）. The results indicated that the ionic liquid can act as a template to control the mesostructure of alumina. Proper amount of ionic liquid helped the construction of ordered mesopores, while the calnation temperature affected pore parameters. Temperatures over certain degree can cause the collapse of pore channels and lead to the decrease of specific surface area, pore size and pore volume. Ordered mesoporous γ-Al2O3 with the highest specific surface area of 447 m^2×g^-1, the biggest pore volume of 1.17 cm^3×g^-1, and the widest pore diameter of 7.6 nm was prepared at the [Bmim]PF6 / aluminum mole ratio of 0.018 and the calcination temperature of 500℃. Additionally, the formation mechanism of mesoporous alumina using the ionic liquid was also investigated.