聚合氯化铝制备球形拟薄水铝石和γ-Al_2O_3的研究Ⅰ——制备条件探讨

Preparation of Pseudo-boehmite and γ-Al_2O_3 Granules by Polyaluminum Chloride Ⅰ——Preparation Conditions

采用实验室自制的聚合氯化铝为原料,结合溶胶-凝胶法和油滴法制备球形拟薄水铝石及其衍生物γ-Al2O3,采用XRD,TEM和N2吸附法对样品进行了分析表征,探讨了不同pH值、不同铝形态含量的聚合氯化铝、不同煅烧温度及不同表面活性剂对产物结构性质的影响。结果表明:pH值在8.5附近合成的水合氧化铝以拟薄水铝石为主;高Alc含量的聚合氯化铝有利于形成高比表面积的球形产物;在450～750℃下煅烧产物为球形γ-Al2O3,并且随温度升高,产物比表面积下降、孔径增大,孔容变化不明显,在1000℃下煅烧产物为球形θ-Al2O3与γ-Al2O3的混合物;随着聚乙二醇表面活性剂分子量的增加,所得球形γ-Al2O3的孔容和孔径增大,聚乙二醇10000的扩孔效果最好,450℃下煅烧所得球形γ-Al2O3的比表面积、孔容分别达326m2·g-1、0.55cm3·g-1。

Pseudo-boehmite granules and their derivatives γ-Al2O3 were prepared from polyaluminum chloride by sol-gel method and oil-drop method. The samples were characterized by XRD, TEM and nitrogen adsorptiondesorption techniques. The effects of pH value, Al species content of polyaluminum chloride, calcination temperature and surfactant on the physical properties of pseudo-boehmite granules were investigated. The results show that alumina hydrate is mainly pseudo-boehmite prepared at pH value near 8.5. Polyaluminum chloride with high content of Alc enhances the surface area of granules. γ-Al2O3 granules can be obtained at 450 ℃ to 750 ℃. The surface area decreases and pore size increases while pore volume changes little with the increase of calcination temperature. At 1 000 ℃, the granules show θ-Al2O3 and γ-Al2O3 phases. With the increase of PEG molecular weight, the pore volume and pore size of γ-Al2O3 granules increase. PEG10000 is most suitable for increasing surface area of γ-Al2O3, with surface area of 326 m2·g-1 and pore volume of 0.55 cm3·g-1 obtained at 450 ℃.