水热法制备薄水铝石粉体及其脱水动力学分析

Preparation and Kinetics of Dehydration of Boehmite by Hydrothermal Treatment

以铝直接水解法获得的氢氧化铝粉末为原料,采用水热法制备薄水铝石粉体.利用X射线衍射、扫描电子显微镜、透射电子显微镜和热重-差示扫描量热仪等检测方法对粉体样品的物相结构、微观形貌及热分解过程进行表征.结果表明:水热产物均为斜方相薄水铝石,粉体粒径在300 nm左右,经600℃煅烧后得到相似形貌的γ-Al_2O_3粉体.使用Popescu法对粉体的脱水动力学进行分析.经计算得,粉体脱水过程的机理函数为g(α)=(1-2α/3)-(1-α)^(2/3),属于D4模型,是三维扩散过程,该过程的活化能Ea=160.34 k J·mol^(-1),指前因子A=9.75×10~9 min^(-1),相关系数R_2=0.9916.

Boehmite powder was synthesized by hydrothermal method using aluminum hydroxide as raw material. The phase structure,microstructure and thermal decomposition process of the obtained powder were investigated by X-ray diffraction,scanning electron microscopy,transmission electron microscopy and thermogravimetric-differential scanning calorimetry,respectively. The results show that all the hydrothermal products are pure orthorhombic phase boehmite with particle size about 300 nm. After calcined at 600 ℃,the obtained γ-Al2O3 powder had the similar morphology. The dehydration kinetics of the powder was analyzed by Popescu method（ constant conversion rate method）. The analysis results demonstrate that the mechanism functions of the sample dehydration process is g（ α） =（ 1-2α/3）-（ 1-α）2/3,which belonged to D4 model and threedimensional diffusion process. The activation energy of the process is Ea = 160. 34 k J·mol^（-1）,the pre-exponential factor is A = 9. 75 × 10~9 min^（-1）,and the correlation coefficient is R2= 0. 991 6.