制备条件对氧化铝前驱体形貌及孔径分布的影响

Effects of preparation conditions on morphology of Al_2O_3 precursor and pore size distribution of Al_2O_3

以硝酸铝溶液为原料,NH4HCO3为沉淀剂,采用共沉淀-溶胶工艺,制备了一系列前驱物Al(OH)3,通过正交实验考察前驱物生成条件对氧化铝孔径分布的影响.利用比表面孔径测试仪和TEM分别对氧化铝孔径分布和前驱物的形貌及聚集状态进行表征.结果表明,制备高分散度的前驱体是制备孔径分布集中的氧化铝的前提;前驱体生成条件对氧化铝孔径分布的影响从大到小依次为:陈化时间,过量系数(pH值),反应温度,加料方式,Al3+浓度.通过正交实验考察成型压力、黏结剂浓度和煅烧温度对氧化铝孔径分布的影响.高压下成型使Al2O3颗粒形成缺陷孔,孔径分布出现双峰结构,说明高压不利于形成孔径集中分布的Al2O3颗粒.成型条件对孔径分布的影响顺序为:成型压力,其次是煅烧温度和黏结剂.Al2O3孔径分布集中在5～10 nm.

A series of Al（OH）3were prepared by a coprecipitation-sol technology from Al2（SO4）3and NH4HCO3precipitates.The effects of preparation conditions of Al2O3 precursor on pore size distribution of Al2O3 were studied by orthogonal tests.The alumina and the precursor were characterized by surface area and pore size analyzer and TEM,respectively.The results show that the preparation of precursor with high dispersion is of great significance in preparing Al2O3 with concentrated pore distribution.The order of effects of precursor formation condition on the pore distribution of Al2O3 is as follows： aging timeexcess coefficient（pH）reaction temperaturefeeding wayAl3＋ concentration.The effects of the molding pressure,calcining temperature and binder on pore size distribution of Al2O3 were researched by orthogonal tests as well.The surface area and pore size test suggest that the high pressure results in the formation of defective pores,and the pore size distribution is of double-structure,which indicate that the high pressure is not of benefit to the formation of Al2O3 particles with concentrated pore size distribution.The order of effects on pore size distribution is as follow： molding pressurecalcining temperaturebinder.According to the conditions defined by the orthogonal tests,the Al2O3 with the concentrated pore size distribution from 5 to 10 nm was prepared.