【摘要】 采用 pH摆动法 ,以硫酸铝为铝源 ,以氢氧化钠为碱沉淀剂 ,考察了添加SiO2 对沉淀氧化铝物性的影响 .通过孔结构分析、粒度测定和电镜观察等证实 ,加入少量SiO2 可使沉淀粒子分散、变小 ,颗粒相对均匀 ,从而提高了氧化铝的比表面积和孔集中的程度 .当加入 2 5 %的SiO2 时 ,pH仅摆动 2次 ,即可使氧化铝粉体的孔体积高达 1 2 ml/ g,比表面积达 380m2 / g.这类氧化铝的孔结构适宜 ,粒子小 ,易直接成型为孔径集中和耐压强度好的载体 ,故用于重油高压加氢脱氮反应具有较好的性能 .沉淀时酸侧 pH值降低 ,尽管沉淀氧化铝的孔径向较小的方面集中 ,但此时沉淀粒子呈紧密堆积 ,颗粒变大 ,比表面积下降 ,氧化铝沉淀粒子的结构发生改变 .不同结构的氧化铝表现出不同的催化活性更多还原

【Abstract】 The effects of silica on physical properties of precipitated alumina were examined by pH swing method, using Al 2(SO 4) 3 as feed and using NaOH as precipitant. The investigation results of pore structure, particle size, TEM and SEM showed that the addition of small quantity of SiO 2 can increase the dispersity and decrease the size of precipitated particles and make the particles more homogeneous. Therefore, high specific surface area and more narrow pore size distribution can be obtained. The Al 2O 3 powder with bulk density 0.24 g/ml, specific surface area 380 m 2/g and pore volume 1.2 ml/g can be obtained only by pH swing two times when 2.5%SiO 2 was added. This kind of Al 2O 3 has proper pore structure, smaller particles and narrow pore size distribution, it can be easily extruded to catalyst support with better strength, thus the catalyst exhibits good performance for HDN of heavy oil. The better pore size distribution of precipitated Al 2O 3 can be reached by decreasing pH value on acid-side, but the precipitated particles become bigger and denser, and the specific surface area decreases. The structure of precipitated Al 2O 3 particles changed in different acid environments and the catalytic activity is related to the structure of Al-2O-3.更多还原