【作者】 张缨；

【导师】 王静康；

【作者基本信息】 天津大学 ， 化学工程， 2005， 博士

【摘要】 除了固态产品的纯度和收率指标外,晶体的晶型、晶习和粒度分布也是影响产品质量、过程设计和技术经济指标的重要因素。通过选择适合的溶剂或添加剂来优化结晶过程、控制结晶产品的晶习和晶型是结晶工程的主要组成部分。本文利用分子模拟的方法,研究了溶剂、添加剂对晶习和晶型的影响。分子模拟也被称为计算机实验方法,分子模拟软件提供了强大的计算功能,通过量化原子、分子间相互作用能,可以从分子水平来认识晶体内部结构和晶-液界面相互作用,研究晶体成核和生长过程中的关键问题。通过其强大的图形处理功能,可以较直观地观测到晶体的内部结构,晶面的原子排布,还可给出由相对生长速率决定的生长外形。可以使原来不可视的微观世界可视化,从而更好地提供思路进行研究。建立了界面层模型,分别构建晶体层和溶剂层,利用分子力学和分子动力学方法计算溶剂层和晶体层相互作用能,考察溶剂层与同一晶体不同晶面间的相互作用能。结合晶体生长理论,建立了用于描述溶剂对晶习影响的新模型。该模型不仅考虑了溶剂分子-晶面分子相互作用能,还考虑了溶剂分子之间的作用能,比之前的模型更接近实际情况。新模型引入了面积校正因子S,可反映晶面特性和溶剂分子的体积效应,这是之前模型中没有具备的。可以应用到不同溶剂种类、混合溶剂(不同配比)条件下有机晶体的晶习预测。应用于α-谷氨酸、β-谷氨酸和尿素在水溶液中的晶习,可以很好地描述溶剂效应。通过分子动力学模拟对溶质分子周围的溶液结构进行研究,结果表明不同溶剂分子在溶质分子周围的分配不同是溶解度和构象等产生影响的主要原因。利用巨正则蒙托卡洛方法模拟了添加剂分子在晶面上的物理吸附过程。考察了添加剂分子的吸附平衡、吸附能量、吸附分子密度、吸附分子间距,结果表明可以利用Langmuir方程描述杂质浓度对相对生长速率的影响,其模型参数由吸附能大小确定。利用该模型验证了添加剂对谷氨酸和6APA晶习的作用。对结晶环境因素对多晶型的影响进行了讨论。以谷氨酸为例,利用晶格能判断不同多晶型之间的相对稳定性。考察不同温度下溶质在溶剂环境中的构象变化和不同构象的比例,解释不同温度下获得不同的多晶型。研究了添加剂对多晶型的选择控制,利用不同添加剂分子在不同多晶型的各个晶面上的相互作用能不同,选择合适的添加剂可以抑制非期望晶型的生长,从而促进期望晶型的生长,获得指定的晶型。更多还原

【Abstract】 As well as the purity and yield, polymorphism, habit and crystal size distribution ofthe solid state are of specific importance. Both have a pronounced influence on theproduct quality and production index of economic and technology. Controlling thepolymorphism and habit by selecting proper solvent or additives and optimizing thesolution crystallization process are the main parts of the crystal engineering.In order to control the morphology of solid product, the molecular modeling methodwas used to study the effects of solvent and additives on the crystal habit andpolymorphism in this thesis.Molecular modeling is also known as computer experiment method, its softwareprovides functions to calculate and optimize the interaction energy between atoms andmolecules, which made it possible to study the crystal structure, crystal-liquidinterface interaction and the key problems of crystal nucleation and growth on thescale of atoms or molecules. By the advantages of the powerful graph interface, theinternal crystal structure, the atom arrangement on the surface, and even the outsideappearance derived by the relative growth rate can be observed directly. Themicrostructure can be visualized, providing better ideas for research.The interface layer model, which composed by crystal layer and solvent layer, wasestablished. The interaction between two layers was estimated by molecular methodand molecular dynamic method, and was also used to estimate the interaction betweensolvent and different surfaces of crystal. Combined with the crystal growth theory, anew model was developed to describe the influence of solvent on habit. In this model,both the interaction of solvent -crystal surface and interaction of solvent-solvent wereconsidered. Compared with the single molecule model, this new model is closer to theactual situation. Area factor S is used to describe the volume effect of solventmolecule. This model can be applied to crystal habit prediction under several ofsolvents and solvent mixtures (with various ratios). It has been verified when it wasused to analyze the habit of α L-glutamic acid、β L-glutamic acid and urea grownfrom solution crystallization.The solution structure near the solute molecule was studied by means of molecularmodeling. The results should the difference distribution of solvents are main influencefactor for the change on solubility and conformation of the solute molecules.Grand Canonical Monte Carlo simulations have been performed to model theadsorption of additives on the crystal surface. The study results of equilibriumadsorption amount, potential adsorbed sites, adsorption energy, density and distanceof adsorbed additive molecules showed that the contribution of additives at differentconcentration can be estimated by the Langmuir equation, in which the coefficient isdepended on adsorption energy. It was applied to calculate the modified habit ofL-glutamic acid with different additives and the habit of 6APA in present of phenylacetic acid (PAA ) as impurity at a series concentration.The environment effects on the polymorph have been discussed. Taking L-glutamicacid as an example compound, lattice energy was used to determine the relativestability. Molecular dynamic method was applied to study the conformation of thesolute molecule in the solution at different temperature. It was shown that the ratio ofdifferent conformations varied with temperature, and elucidated why L-glutamic acidcrystalline being different polymorph at different temperature. The additive effects onpolymorph selection in solution crystallization have also been studied in detail. It hasbeen proved that using proper additives, which could restrain the existence ofunexpected polymorph or accelerate phase transformation into desired polymorph.更多还原