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题名	溶液中维生素C晶体生长过程与模拟计算
作者	陈慧萍
学位类别	博士
答辩日期	2002
授予单位	中国科学院过程工程研究所
授予地点	中国科学院过程工程研究所
导师	邵曼君
关键词	单晶 生长动力学 维生素C 生长机理 晶体结构 原子-原子势能近似
其他题名	Modeling Prediction and Crystal Growth Process from Solution for Vitamin C
学位专业	生物化工
中文摘要	该研究主要测定不同生长环境下晶体[010]、[001]、[100]方向的生长速率,考察各因素的影响,多元线性回归单晶生长动力学,分析晶体生长机理.结合晶体结构数据,采用原子-原子势能近似方法计算分子相互作用,探讨晶体结构对面相对生长速率和晶体形态的影响.在实验中采用单晶研究法直接显微观察晶体形态变化,测定了静止水溶液中维生素C晶体[010]、[001]、[100]的生长速率,回归出单晶生长动力学方程.显著性检验以及生长速率的计算值和实验值比较表明回归结果可靠性较好.维生素C晶体各面线性生长速率G存在差G<[010]>>G<[001]>>G<[100]>,在低过饱和度下则为G<[001]>>G<[100]>>G<[010]>,其相对大小也随温度、过饱和度而变化.根据扩散-反应理论可以认为在静止溶液中[010]的生长为扩散和表面反应综合控制,而(001)面与(100)面则为扩散控制.维生素C的工业生产中常采用水/乙醇的混合溶剂,该研究也考察了混合溶剂对维生素C单晶生长动力学的影响,同样得到动力学方程.
英文摘要	Crystallization is a process in which the solid substances were separated at the state of crystal from vapors, solutions or melts, and which is a complex multi-phase multi-component transfer process of heat and mass with surface reaction. Up to now, its application area has been successfully expanded from traditional drug and food industries to fields of material, electronics, life science and so on. Growth kinetics, playing an important role in crystallization, is the base of process analysis, design, operation and optimization. Vitamin C is an essential nutriment, but few literatures discussed its crystal growth kinetics. This study emphasized on single crystal growth from solution. The experimental setup was designed to observe the morphology change of single crystals with inverted microscope. The growth process of vitamin C crystals in stagnant aqueous solution was studied and the growth rates of [010], [001], [100] were obtained. The significance test and comparison of growth rates show that the regressed kinetic parameters have good reliability. The growth of crystal faces behaved differently, the relative value of growth rates changed with temperature and supersaturation. At the above circumstance, the growth of [010] was controlled by the combination of solute diffusion and surface integration, while face (001) and (100) just by solute diffusion. The mixture solvent of water/ethanol is often used in industrial production of vitamin C, so the effect of mixture solvent on growth kinetics was also investigated. We can see that the growth rates of [010] and [100] in water/ethanol were slower than those in pure water, while [001] is more sensitive to supersaturation and lead a faster growth rate than in water. The comparison of regressed activation energy demonstrates that ethanol molecules may hinder the formation of hydrogen bond between vitamin C and water molecules, and accelerate the growth of [001]. In water/ethanol solution the growths of main crystal faces were controlled by diffusion and surface integration. So the change of solvent component not only affected the impact of temperature and supersaturation on growth rates, but changed controlling step of growth process and crystal form of product. In flowing solution, the orthogonal test can be used to analyze the effect of factors. The orthogonal table L4(23) was selected, and presented that supersaturation is the most important factor by maximum difference analysis. The growth kinetics was studied experimentally. In this case, the effect of diffusion can be neglected and crystal growth was controlled by surface interaction. Comparing the experimental data with existing theories of growth kinetics, we can analyze the crystal growth mechanism. The relationship between crystal growth and size was investigated with environmental scanning electron microscope (ESEM). For small crystals of vitamin C, the phenomenon of size-dependent growth was confirmed and the growth dispersion may exist. Crystal structure often causes different faces to grow at different rates. According to the theory of attachment energy, we can predict the structural effect on face growth rate. In the program, crystal data were input to calculate the interaction between molecules with atom-atom potential approximation, and the lattice energy, slice energies and attachment energies of face (hkl) were obtained. With the increase of limiting sphere radius, the sum of intermolecular actions augments, tends to a constant value, but the number of included molecules sharply increased. The potential function of Lennard-Jones 6-12 was shown good accuracy by the value of lattice energy. The different attachment energies declared that face (100), (010) and (001) should grow at different rates. In a whole, research on single crystal growth can provide accurate growth information of vitamin C crystals. The effects of growth environment and crystal structure on directional growth rates were realized to a more detail extent and the growth mechanism can be analyzed with the experimental data.
语种	中文
公开日期	2013-09-16
页码	60
内容类型	学位论文
源URL	[http://ir.ipe.ac.cn/handle/122111/1347]
专题	过程工程研究所_研究所（批量导入）
推荐引用方式 GB/T 7714	陈慧萍. 溶液中维生素C晶体生长过程与模拟计算[D]. 中国科学院过程工程研究所. 中国科学院过程工程研究所. 2002.

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