【作者】 刘宝树；

【导师】 王静康；

【作者基本信息】 天津大学 ， 化学工程， 2007， 博士

【摘要】 5’-鸟苷酸二钠是一种重要的食品添加剂及医药用品,属于第二代鲜味剂。5’-鸟苷酸二钠以无定形体和晶体两种固体状态存在。针对目前国内生产5’-鸟苷酸二钠基本为无定形体,且产品纯度低、水含量不稳定等问题,本文对5’-鸟苷酸二钠的结晶过程进行了系统的研究,提出了新型精制结晶工艺,解决了制备高质量的I型5’-鸟苷酸二钠晶体的问题。具体研究内容如下:利用聚焦光束反射测量仪(FBRM)、颗粒图像测量仪(PVM)和X射线粉末衍射仪(powder-XRD)等测试手段对5’-鸟苷酸二钠由无定形体转化为晶体的过程进行了研究,推断出其过程机理为溶液过渡转化。考察了pH值、添加剂量、溶剂配比、转化温度和原料粒度等因素对转化速率和转化程度的影响。利用X-射线单晶衍射仪测定了I型5’-鸟苷酸二钠晶体结构。同时测定了溶析结晶所得晶体产品的powder-XRD图谱,经与单晶结构分析结果对比,证明溶析结晶产品为I型5’-鸟苷酸二钠晶体。应用Cerius2分子设计软件分析了真空中的BFDH模型和AE模型晶习,并考察了生长环境对晶习的影响。利用热重分析技术对5’-鸟苷酸二钠加热脱水过程进行研究。采用微分法和积分法对实验数据进行处理,推断出5’-鸟苷酸二钠脱水过程机理为三维扩散机理,机理函数为Z-L-T方程。并算得脱水动力学参数E和A。采用动态法测定了5’-鸟苷酸二钠在不同温度和溶剂配比下的溶解度,利用经验方程、λh方程和CNIBS/Redlich-Kister方程对溶解度数据进行关联;测定了溶液pH值和添加剂含量对5’-鸟苷酸二钠溶解度的影响,并分别利用两性化合物电离平衡原理和多项式模型对实验结果进行关联;测定了5’-鸟苷酸二钠的结晶介稳区和结晶诱导期,利用初级成核理论计算了固液表面张力。采用间歇动态法测定了5’-鸟苷酸二钠溶析结晶过程中的动力学行为。利用矩量变换法按体积无关生长-体积无关多元等体积破碎模型求解粒数衡算方程。采用非线性最小二乘法建立了实验范围内的晶体生长速率、二次成核速率、破碎速率常数以及破碎分布函数的数学模型。在结晶热力学、结晶动力学以及结晶过程分析的基础上,建立了5’-鸟苷酸二钠结晶过程数学模型。实验考察了各种操作参数对结晶过程及最终晶体产品质量的影响,得到5’-鸟苷酸二钠优化结晶工艺条件。制得了高质量的I型5’-鸟苷酸二钠结晶。本文研究成果尚未见国内外文献报道。更多还原

【Abstract】 Disodium 5’-guanylate heptahydrate (5’-GMPNa2) is an important food additive and medicine material, which belongs to the second-generation fresh reagents. 5’-GMPNa2 exists in two solid forms: amorphism and crystal. In order to overcome the fault of 5’-GMPNa2 product quality, such as amorphic state, lower purity and inconstant water content, a systematical study on the crystallization process of 5’-GMPNa2 had been presented in this thesis. A new crystallization process has been developed, with which the high quality crystals of 5’-GMPNa2 (formⅠ) can be obtained. The main contents in this thesis go as follows.The polymorphic transition process of 5’-GMPNa2 from amorphism to crystal (formⅠ) was investigated by in-situ monitoring technique( FBRM and PVM) and ex-situ monitoring technique(powder-XRD). The transition mechanism was deduced to be solution mediated transition (SMT). The effects of pH, additive, solvent ratio, temperature and particle size of raw materials on transition rate and transition degree were studied.By the use of X-ray single crystal diffraction technique, the crystal structure of 5’-GMPNa2 was determined. In addition, the powder X-ray diffraction pattern of 5’-GMPNa2 from dilution crystallization was measured. By comparing the single crystal diffraction data and the powder-XRD pattern, it can be concluded that the dilution crystallization product is form I of 5’-GMPNa2. With commercial software Cerius2, the crystal morphology in the vacuum was calculated based on BFDH and AE principles. The factors that may affect the crystal habit were discussed.The non-isothermal dehydration behavior of 5’-GMPNa2 was investigated by thermogravimetry /differential thermal analysis (TG-DTA). The dehydration kinetics were achieved from the TG-DTA curves by both the differential method and the integral method. The dynamic dehydration processes for all four steps are best expressed by the Z-L-T equation, suggesting a three-dimensional diffusion-controlled mechanism. The dehydration kinetics parameters, E and A, were calculated.The solubilities of 5’-GMPNa2 at different temperature and solvents were measured with dynamic method, and correlated by empirical equation,λh equation and CNIBS/Redlich-Kister equation, respectively. The dependence of solubility on pH and additive were studied, and results were correlated by the principle of ionization equilibrium and polynomial model respectively. The metastable zone and induction period for crystallization of 5’-GMPNa2 were also measured. The solid-liquid surface tension was estimated from primary nucleation theory.The dilution crystallization kinetic behaviors of 5’-GMPNa2 were measured with batch dynamic method. By moment transformation method, and basing on particle size independent growth– particle size independent multi equal volume breakage model, the population balance equation was solved. By non-linear least square method, the mathematical models for crystal growth rate, secondary nucleation rate, breakage rate constant and daughter distribution were established.On the basis of population balance equations and crystallization thermodynamics, kinetics, as well as mass balance equations, the mathematical model for dilution crystallization process of 5’-GMPNa2 was established. The effects of operation conditions on the crystallization process and the quality of product were studied in detail by both experiments and model simulation, on the basis of which the optimal operation strategy was established. And the high quality crystals of 5’-GMPNa2 (formⅠ) were obtained.No same report to above study results has been published in literature up to date.更多还原