Crystallization and precipitation: chiral compounds and metals powders

结晶和沉淀是在工业中广泛用于大量应用的两个过程。这些应用可以分为两大类。第一个也是最常见的应用是基于溶液中组分的溶解度分离组分以进行回收或纯化。另一种是通过气相或液相均相反应生产固体颗粒。结晶/沉淀操作中最重要的考虑因素是控制固体产物的纯度、粒度分布以及通常所产生晶体的形态和习性。例如，在药物应用中，晶体形态和晶体结构可以影响药物在接受生物体中的可用性。建议的研究计划包括两个项目都密切相关的结晶和沉淀。第一个项目涉及对映体的结晶，这是一组在制药和食品工业中极其重要的化合物。对映异构体是一对互为镜像的分子。由于它们除了在空间中的构型之外是相似的，因此它们的物理性质如溶解度、熔点和沸点是相同的，但它们的化学性质可以不同。例如，尽管大量药物是手性分子，但只有一种对映体作为药物是有活性的。其他的可能活性较低，甚至有毒。 从经济、医学和环境的观点来看，能够分离感兴趣的对映异构体的有用性是显而易见的。第二个项目与银粉的生产有关。高纯度银粉末用作玻璃和陶瓷的催化剂、透明涂层和颜料，并且它们广泛用于微电子元件的生产。粉末在此类应用中的适用性取决于形状、尺寸和尺寸分布。因此，重要的是预测和控制沉淀或结晶反应的行为，以获得所需的粉末性能。这两个项目的总体目标是建立条件，使所得产品在纯度、尺寸、尺寸分布和形态方面具有所需的性能。

Crystallization and precipitation are two processes that are widely used in the industry for a vast array of applications. These applications can be classified into two broad groups. The first and most common application is in separating components in solution based on their solubility for recovery or purification. The other is in the production of solid particles via either gas or liquid phase homogenous reactions. The most important consideration in crystallization /precipitation operation is the control of the solid product with respect to its purity, particle size distribution and very often morphology and habit of the produced crystal. For example, in pharmaceutical applications, the crystal morphology and crystal structure can influence the availability of the drug in the receiving organism. The proposed research program consists of two projects both intimately related to crystallization and precipitation. The first project is concerned with the crystallization of enantiomers, a group of compounds which are extremely important in the pharmaceutical and food industries. Enantiomers are pairs of molecules that are mirror images of each other. Since they are similar except for their configuration in space, their physical properties such as solubility, melting and boiling point are identical but their chemical properties can differ. For example, although a large number of drugs are chiral molecules, only one enantiomer is active as a drug. The others may be less active, or even toxic.  The usefulness of being able to isolate the enantiomer of interest is obvious both from economical, medical and environmental points of view. The second project is related to the production of silver powder. High purity silver powders are used as catalysts, transparent coatings, and pigments for glasses and ceramics and they are widely used in the production of microelectronic components. The suitability of the powder for use in such applications depends on the shape, size and size distribution. Thus it is important to predict and control the behavior of the precipitation or crystallization reaction for the attainment of the desired powder properties. The general objective of both projects is to establish the conditions at which the resulting products have the desired properties in terms of their purity size, size distribution and morphology.