乙醇为溶剂制备超细高氯酸铵的GAS研究

Recrystallization of Ammonium Perchlorate from Ethanol Using Supercritical Carbon Dioxide as Antisolvent

在测定CO2-乙醇系统膨胀度和气液平衡计算的基础上,以乙醇为溶剂测试了超临界二氧化碳气体抗溶剂法(gas anti-solvent,GAS)重结晶高氯酸铵(AP)过程中压力、温度、溶液初始浓度及升压速率、静置时间等对产品晶粒大小、晶形的影响规律。试验结果表明:在GAS细化过程中,AP颗粒的平均粒度随温度升高而增大。在25℃时,平均粒度随初始浓度的增大而减小,但在31℃和40℃时,影响趋势相反。升压速率越大,越易得到粒度均匀的小颗粒AP。终点压力越大,平均粒度越小,但终点压力大于9MPa后,影响不再明显。终点压力为6MPa时,静置时间延长,粒度明显增大,且分布较宽;但终点压力达到9MPa时,粒度变化变小,晶形略有改变。综合分析表明,升压操作引起的液相湍动强度和溶剂本身的物化性质是影响样品粒径、晶型的关键性因素。最后,在温度25℃,终点压力9MPa,升压速率35kg.h-1,初始浓度1.0g.(100mL)-1时,得到60nm多面体形状的AP微细颗粒,其边缘不规则,晶体有断裂现象。

The recrystallization of ammonium perchlorate（AP）was carried out using supercritical CO2 as the anti-solvent and ethanol as solvent.The volumetric expansion curves of CO2-ethanol were measured and the vapor-liquid equilibrium of CO2-ethanol system was calculated with Peng-Robinson equation.The effects of the main operation parameters on the result of the gas anti-solvent（GAS）recrystallization process were studied experimentally,such as the initial concentration of the solution,the final pressure and hold time after the pressurization.It is shown that the average grain size increases when the temperature rises.And the average grain size decreases when the initial concentration increases at 25 ℃ and by contraries at 31 ℃ and 40 ℃.Meanwhile the faster the pressure raising,the more uniform little AP grain could be produced.If the final pressure is more than 9 MPa,the increase of pressure has little effect on average size of AP particle.When the pressure is 6 MPa,the increase of hold time leads to a significant increase of the average grain size with a wide distribution.But when the final pressure is 9 MPa,there is a little change in size,only a slight change in its morphology.The effect of the intensity of liquid flow and the physical and chemical properties of the solvent itself were prevailing when compared to the effects of the other operation parameters.Finally,AP particles（60 nm,polyhedron）with narrow size distribution were obtained at 9 MPa,25 ℃ and 35 kg·h-1,and the phenomenon of intercrystalline fracture was found in AP particle.