The Ostwald Ratio, Kinetic Phase Diagrams, and Polymorph Maps
The Ostwald Ratio, Kinetic Phase Diagrams, and Polymorph Maps
复制标题
DOI：
10.1021/acs.cgd.9b00815
复制
发表时间：
2019-10-01
影响因子：
3.8
通讯作者：
Davey, Roger J.
中科院分区：
文献类型：
--
作者：
Cardew, Peter T.;Davey, Roger J.
从多晶系间歇结晶的一般公式出发，证明了Ostwald比的概念为理解和计算晶型组成随时间、温度和过饱和度的变化提供了一个基本参数。特别是，根据广为人知的奥斯特瓦尔德阶段法则，它定义了系统将呈现多态的顺序发展的条件，反之，当只产生稳定的多态或当形式同时出现导致伴随的多态时。Ostwald比不是一个常数，而是随温度、初始过饱和度、晶体形状和密度而变化。结果表明，它的评估可以得到一个基于动力学的相图，从而能够在成分和温度空间中构造多晶型映射。对现有相关动力学数据的回顾表明，缺乏关于多晶相的相对形核和生长速度的信息。以孕二烯为例，展示了该方法在多晶型体系间歇结晶过程稳健设计中的意义和潜力。
From a general formulation of batch crystallization in a polymorphic system, it is shown that the concept of an Ostwald ratio provides a fundamental parameter with which to understand and compute the variation in polymorph composition with time, temperature, and supersaturation. In particular, it defines the conditions under which a system will exhibit sequential development of polymorphs, as per the widely known Ostwald's Rule of Stages and conversely when either only the stable polymorph will result or when forms appear simultaneously resulting in concomitant polymorphism. The Ostwald ratio is not a constant but varies with temperature, the initial supersaturation, crystal shape, and density. It is shown that its evaluation can lead to a kinetically based phase diagram enabling the construction of polymorph maps in compositional and temperature space. A review of relevant existing kinetic data reveals a lack of information concerning both the relative nucleation and growth rates of polymorphic phases. The specific case of gestodene is used as a means of demonstrating the significance and potential of this approach to the robust design of batch crystallization processes in polymorphic systems.