PYX在DMSO中的结晶热力学

Crystallization Thermodynamics of PYX in DMSO

为了重塑2,6-二苦氨基-3,5-二硝基吡啶(PYX)的晶体形貌,改善PYX的晶体品质,采用激光动态法测定了PYX在二甲亚砜(DMSO)中的溶解度,建立了溶解度模型,估算了溶解过程的热力学参数;测定了不同条件下PYX在DMSO中的介稳区宽度,揭示了介稳区宽度的影响因素及规律,计算了成核级数;在此基础上采用降温法对PYX进行重结晶,对比分析了重结晶前后的晶体形貌和热性能。结果表明,PYX在DMSO中的溶解度随温度的升高而增大,Apelblat模型对溶解度的拟合结果较好,更适合预测溶解度;介稳区宽度随降温速率的增大而增大,随饱和浓度和搅拌速率的增大而减小,结合介稳区变化规律得到适宜的结晶条件为:饱和浓度(摩尔分数)0.016~0.022、降温速率1~2℃/min、搅拌速率250~500 r/min;当饱和浓度从0.0148增至0.0224时,受降温速率影响的成核级数(m)由3.7010增至4.7461,受搅拌速率影响的成核级数(n)由0.3601增至0.6284。PYX在DMSO中经降温重结晶能够得到表面光滑度良好、无明显缺陷的块状晶体,重结晶后PYX的DSC热分解峰温提高了11.9℃,热爆炸临界温度提高了9.8℃,说明通过重结晶能够优化PYX的热稳定性。

To reshape the crystal morphology and improve the crystal quality of 2,6-bis(picrylamino)-3,5-dinitropyridine(PYX),the solubility of PYX in DMSO was measured by laser dynamic method.The solubility models were established and the thermodynamic parameters of dissolution process were estimated.The width of metastable zone of PYX in DMSO under different conditions was measured.The influencing factors and laws affecting the width of metastable zone were revealed,and the nucleation orders were calculated.On this basis,PYX was recrystallized by cooling method,and the crystal morphology and thermal performance before and after recrystallization were analyzed.The results show that the solubility of PYX in DMSO increases with the increasing in temperature.The Apelblat model has a better fitting result for solubility and is more suitable for predicting solubility.The width of metastable zone increases with the increasing in cooling rate,and decreases with the increasing in saturation concentration and stirring rate.The optimum crystallization conditions are as follows:the saturation concentration(mole fraction)of 0.016—0.022,the cooling rate of 1—2℃/min and the stirring rate of 250—500 r/min.When the saturation concentration increases from 0.0148 to 0.0224,the nucleation order(m)affected by the cooling rate increases from 3.7010 to 4.7461,and the nucleation order(n)affected by the stirring rate increases from 0.3601 to 0.6284.The block PYX crystals with smooth surface and free of the defects can be obtained from recrystallization in DMSO after cooling.After recrystallization,the thermal decomposition peak temperature of PYX from DSC increases by 11.9℃,and the critical temperature of thermal explosion increases by 9.8℃.It is indicated that the thermal stability of PYX can be optimized by recrystallization.