Preparation of pseudo-boehmite and γ-Al₂O₃ granules by polyaluminum chloride i -preparation conditions

Pseudo-boehmite granules and their derivatives γ-Al₂O ₃ 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 AL enhances the surface area of granules. γ-Al₂O₃ granules can be obtained at 450 °C to 750 °C. The surface area decreases and pore size increases while pore volume changes little with the increase of calcination temperature. At 1000 °C, 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 °C.