制备条件对拟薄水铝石晶粒度与孔结构的影响

采用反应结晶法，以偏铝酸钠、硫酸铝为原料，制备了一系列拟薄水铝石样品．用X射线衍射、氮吸附脱附、扫描电镜等方法分析了制备条件对拟薄水铝石晶粒度与孔结构的影响．实验结果表明：拟薄水铝石的平均晶粒度随pH值、温度及老化时间的增加而增加；较低pH值或温度下生成无定形凝胶，较高的pH值或温度下生成了薄水铝石或β-三水铝石；温度升高与老化时间增加可分别有利于大孔的形成与整体孔数量的增加；晶粒度较大的单一拟薄水铝石样品，其表面积与孔容也较大．在 pH 值为8.6、反应温度75,℃及老化时间2,h 的优化制备条件下，拟薄水铝石具有单一晶相，平均晶粒度为4.58,nm，比表面积为342,m2/g，孔容为0.533,cm3/g，平均孔径约为3,nm，形貌如绒毛球状．

Effect of Preparation Conditions on Crystal Size and Pore Structure of Pseudoboehmite

Pseudoboehmite can be prepared by the reaction-crystallization of sodium metaaluminate and aluminum sulfate under suitable reaction conditions. The effects of preparation conditions on the mean crystal size and pore structure of pseudoboehmite were investigated by X-ray diffraction （XRD）, nitrogen adsorption/desorption and scan-ning electron microscope （SEM）. The mean crystal size, which was used to distinguish pseudoboehmite from boeh-mite, was figured out by Debye-Scherrer method. The results indicate that the mean crystal size of products increases with the increment of pH, temperature and aging time. Amorphous hydroxide will be formed at low pH or temperature, while boehmite or β-gibbsite exists at high pH or temperature. Increase of temperature or aging time is helpful for forming big pores or increasing pore number. Single crystalline phase pseudoboehmite with a bigger mean crystal size has a higher specific surface area and pore volume. Under the optimum condition （pH 8.6, reaction temperature 75℃and aging time 2 h）, single crystalline phase pseudoboehmite was obtained, with the mean crystal size of 4.58 nm, specific surface area of 342 m2/g, pore volume of 0.533 cm3/g, average pore diameter of 3 nm, and an appearance of fluffy ball.