【作者】 李玲；

【导师】 李希；

【作者基本信息】 浙江大学 ， 化学工程， 2008， 硕士

【摘要】 精对苯二甲酸(Purified Terephthalic acid,PTA)是聚酯工业的原料,其生产过程包括对二甲苯(para-Xylene,PX)催化氧化生成粗对苯二甲酸(CrudeTerephthalic acid,CTA)和CTA精制两大工序。本文以PTA生产工艺的国产化技术开发为背景,以CTA熟化过程为研究对象,采用实验与模型方法,获得了TA体系液固平衡数据、CTA颗粒熟化动力学和产物纯化动力学等一系列新的研究成果。论文内容包括以下三个方面:1.TA体系在模拟工业母液中的液固平衡TA体系的液固平衡数据是深入研究TA结晶与熟化过程必需的热力学基础数据。本文实验测定了TA在工业生产条件范围的溶解度,考察了液相杂质对TA溶解度的影响。在氧化与非氧化条件下分别考察了主要杂质对羧基苯甲醛(4-Carboxybenzaldehyde,4-CBA)在液固两相中的分配规律,发现4-CBA很难通过分子扩散达到液固分配平衡,而氧化能够显著降低固体中4-CBA的含量;晶体结构影响4-CBA在液固两相中的分配。2.CTA颗粒熟化动力学采用分批式实验技术,详细考察了180℃～230℃熟化温度下CTA晶体的粒径演变规律,分析了熟化机理,获取了CTA熟化过程中粒径变化的动力学模型与参数。研究结果表明:CTA颗粒的高温熟化过程遵从Ostwald熟化机理,根据这一机理建立的动力学模型能够较好地描述晶体粒径随时间的变化规律。高温熟化能明显改善CTA晶体的粒度分布,增大粒径;温度越高,熟化速率越快。3.CTA熟化纯化动力学详细考察了180℃～230℃熟化温度下CTA晶体中杂质4-CBA含量随时间的变化规律,建立了描述CTA熟化纯化的内扩散-表面反应模型,确定了模型参数。研究结果表明:氧化条件下的熟化能够显著降低CTA晶体中杂质4-CBA的含量,温度越高,4-CBA的浓度下降越快。所提出的内扩散-表面反应模型能够较好地解释各种实验现象,模型计算结果与实验结果相符。更多还原

【Abstract】 PTA (Purified Terephthalic acid), one of the most important raw material of polyester, is produced by two steps: catalytic oxidation of PX (para-Xylene) to CTA (Crude Terephthalic acid) and latter purification. With the domestic technology development of PTA as background, this thesis focuses on the aging process of CTA. By experiments and modeling, some novel results in crystallization thermodynamics, aging kinetics of CTA particles and purification kinetics were obtained. The work included the following three parts:1. Solid-liquid equilibrium of TA system in simulated mother liquorThe solid-liquid equilibrium data of TA system is a kind of prerequisite thermodynamics data for the further research of TA production and purification. Solubilities of TA were experimental determined in the industrial operated temperature and solvent compositions. The effect of impurities in liquid phase was examined. The partition of main impurity 4-CBA (4-Carboxybenzaldehyde) between solid and liquid phase was studied respectively with and without oxygen. The results showed that it was very hard for 4-CBA to achieve solid-liquid equilibrium by molecule diffusion, however oxidation can decrease the concentration of 4-CBA in solid phase remarkably. Crystal structure affected the partition of 4-CBA between solid and liquid pahse.2. Aging kinetics of CTA particlesBased on a series of batch experiments, the evolution of CTA crystal size was carefully studied over a temperature range from 180°C to 230°C. According to the experimental results, the aging mechanism and kinetics of crystal size were developed. The results indicated that aging of CTA obeyed Ostwald ripening theory and the kinetics model can describe the crystal size evolution well. Aging of CTA at elevated temperature can improve the crystal size distribution remarkably and increase the crystal size. The velocity of aging increased with the increase of temperature.3. Aging kinetics of CTA purification The concentration of impurity 4-CBA in CTA crystals was carefully studied by batch experiments over a temperature range from 180°C to 230°C. Diffusion-surface reaction kinetics model of CTA purification was developed and the model parameters were experimentally determined. The results indicated that aging of CTA with oxygen can decline the concentration of 4-CBA efficiently in CTA crystals. The higher the temperature was, the faster decreasing of impurity 4-CBA. The diffusion-surface reaction model can illustrate the concentration of 4-CBA in CTA crystals.更多还原