Dissertation > Mathematical sciences and chemical > Crystallography > Crystal growth > Crystal growth process

Study on the Morphology Control of Solution Crystallization Processes for Organic Compound

Author ZhangYing
Tutor WangJingKang
School Tianjin University
Course Chemical Engineering
Keywords Molecular modeling Crystal habit prediction Solvent effect Additive effects Polymorph Control
CLC O782
Type PhD thesis
Year 2005
Downloads 892
Quotes 7
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In addition to the solid product purity and yield indicators, the crystalline form of the crystal, the crystal habit and particle size distribution is also affecting product quality, process design and technical and economic indicators of important factors. Through the selection of suitable solvents or additives to optimize the crystallization process, control of the crystal habit and the polymorph of the crystalline product is the main component of the crystalline engineering. In this paper, the methods of molecular modeling, solvent additives on the crystal habit and polymorph. Molecular modeling has also been referred to as the computer experimental methods, molecular modeling software provides powerful computing capabilities, by quantifying the interaction energy between the atoms, molecules, from the molecular level to understand the interaction of crystalline internal structure and crystal - liquid interface, the study crystal The key issues in the nucleation and growth process. Through its powerful graphics processing capabilities, can be more intuitive observations to the internal structure of the crystal, the atomic arrangement of the crystal plane, also gives the decision by the relative growth rate and the growth shape. The microscopic world of the original visual visual ideas to better research. Interface layer model, were constructed crystal layer and solvent layer, using molecular mechanics and molecular dynamics method to calculate the solvent layer and the crystal layer between the interaction energy of the interaction can be investigated solvent layer with the same crystal different crystal faces. Crystal growth theory, the new model is used to describe the impact of the solvent on the crystal habit. The model takes into account not only the solvent molecules - molecules of crystal surface interactions can also consider the solvent molecules, closer to the actual situation than the previous model. The new model introduces the area correction factor S can reflect the characteristics of the crystal surface and the volume effect of the solvent molecules, which is before the model does not have. Can be applied to different type of solvent, different proportions) under the conditions of the mixed solvent (organic crystal crystal habit prediction. The crystal habit of the applied α-glutamic acid, β-glutamic acid and urea in the aqueous solution, it can be well described solvent effects. The solution structure around the solute molecules studied by molecular dynamics simulations, the results show that the allocation of different solvent molecules around the solute molecules of different solubility and conformation, mainly due to the impact. The the grand canonical Monto Carlo method to simulate the physical adsorption of the additive molecules in the crystal surface. Effects of additive molecule adsorption equilibrium, adsorption energy, adsorbed molecules density of adsorbed molecules pitch, the results show that you can take advantage of the Langmuir equation to describe the impurity concentration on the relative growth rate, the model parameters are determined by the size of the adsorption energy. Using the model to verify the role of additives on the the glutamate and 6APA crystal habit. The crystalline environment factors polymorph were discussed. Glutamate example, the use of the lattice to be able to judge the relative stability of different polymorphs. Investigated the ratio of solute in conformational changes in the environment of a solvent and different conformation of the different temperatures, and to explain different temperatures different polymorph. Of additives on polymorph selection control, the use of different additives molecule can be different in different polymorphs of the interaction of the respective crystal plane, the selection of suitable additives can inhibit the growth of the undesired polymorph, thereby promoting the desired polymorph. growth obtain a specified crystal form.

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