负压条件强化拟薄水铝石晶种分解过程

对负压条件下从铝酸钠溶液中析出拟薄水铝石的晶种分解(简称种分)过程进行了研究，考察了水热时间、分子比(Na2O/Al2O3摩尔比)、晶种比(晶种与铝酸钠溶液中Al2O3质量比)、晶种循环使用次数和负压值对铝酸钠溶液分解率及种分产物结构与织构性质的影响. 结果表明，负压条件可以在不改变种分产物拟薄水铝石基本结构的前提下，显著强化铝酸钠溶液的种分过程，但种分产物的比表面积和孔容较晶种有所降低. 在铝酸钠溶液Al2O3浓度120 g/L、晶种比1.0、分子比1.3和125℃下，通过改变负压值(0.01~0.09 MPa)，水热0.5 h后溶液分解率可达46.0%，而常压下仅为33.4%. 晶种循环使用1~3次溶液分解率为41.0%~44.0%，基本保持稳定.

Precipitation Enhancement of Pseudoboehmite from Seeded Sodium Aluminate Solution under Subpressure Condition

Based on decomposition of seeded sodium aluminate solution under certain subpressure for preparing pseudoboehmite, the effects of hydrothermal time, caustic ratio (molar ratio of Na_2O to Al_2O_3), seed ratio (mass ratio of seed to Al_2O_3 in sodium aluminate solution), precipitation cycle number and degree of subpressure on the precipitation yield of Al_2O_3, and crystal structure and textural properties were studied. The results showed that subpressure condition could remarkably intensify precipitation of pseudoboehmite from seeded sodium aluminate solution without changing its basic crystal structure. However, the obtained pseudoboehmite had lower pore volume and specific surface area than seed. Under the conditions of 120 g/L Al_2O_3, seed ratio of 1.0, caustic ratio of 1.3 and 125℃, about 46.0% precipitation yield of Al_2O_3 was obtained with hydrothermal time of 0.5 h by changing degree of subpressure from 0.01 to 0.09 Mpa, while it was only about 33.4% under atmospheric pressure. Furthermore, the precipitation yield of Al_2O_3 ranged from 41.0% to 44.0% during the 1st to 3rd precipitation cycle, indicating that the precipitation activity of the seed was stable.