酯化反应精馏的微波场强化机理与过程研究

The emergence of new technology of Microwave distillation process intensification is promoting the new exploration and cognition about the motion of the vapor-liquid interface, transfer and separation process at microscopic molecular level in the microwave field. This project will reveal the mechanism of the thermal motion of molecules and transfer at vapor-liquid interface and the separation principle of esterification distillation under the conditions of microwave outfield. To clarify the transfer law of vapor-liquid interface and reveal the mechanism of effects of the relative volatility between the components under microwave irradiation, the non-equilibrium molecular dynamics is applied in this study and thermodynamics of microwave field state is also established. From the microscopic perspective, non-equilibrium molecular dynamics and statistical mechanics are combined to simulate the molecular motion to obtain the density distribution of the two-phase system, vapor-liquid interfacial tension, surface excess entropy parameters and so on. From the macroscopic perspective, we research the thermodynamics of the microwave field to describe the facts that multi-component chemical potential of microwave thermodynamic system is how to determine the direction and limits of components transfer. The long, medium and short carbon chain length of the fatty acid ethyl esters are selected as this study system. The experimental data of vapor-liquid phase equilibrium inspect transfer mechanism of heat and mass between vapor and liquid two-phase system. Microwave esterification reaction kinetics as well as microwave distillation separation process intensification of this system are studied and then the process intensification mathematical model is established. For the energy efficient of microwave reactive distillation process, the studies of the microwave field strengthening vapor-liquid phases mass transfer and thermodynamic have important theoretical and practical value.

微波精馏过程强化新技术的出现，推动人们探知微波场下汽-液相界面微观分子运动、相间传递与分离过程强化的本质。本项目重点研究微波场下脂肪酸乙酯体系汽-液界面分子热运动、传递与分离强化机理。运用非平衡分子动力学和建立微波场态热力学，阐明微波作用下体系的汽-液相界面传递规律，揭示微波对组分相对挥发度的影响机理。微观上运用非平衡分子动力学模拟分子运动，结合统计力学得到体系微波场态汽-液两相的密度分布、界面张力及表面过剩熵等参数；宏观上开展微波场态热力学研究,搞清楚多组分微波热力学体系化学势是怎样决定组分传递的方向和限度。本项目选定短、中、长不同碳链长度的脂肪酸乙酯化体系，其汽-液相平衡实验数据检验相间传热与传质传机理。开展此体系的微波酯化反应动力学以及微波强化精馏分离过程研究，继而建立过程强化数学模型。研究微波强化汽-液传质及热力学机理对于微波反应精馏过程节能高效有着重要的理论价值和实际应用价值。

本项目选定不同碳链长度的脂肪酸酯体系，测定其相平衡实验数据，为非平衡分子动力学模拟、相间传质机理及微波反应精馏研究提供相平衡基础。首先测定了短链物系异丙醇-乙酸异丙酯-DMSO、三元物系乙醇-丙酸乙酯-对二甲苯及三元物系异丙醇-乙酸异丙酯-[EMIM][BF4]的汽-液相平衡数据。其次测定了中链二元物系辛酸甲酯-癸酸甲酯及癸酸甲酯-月桂酸甲酯在低压下的汽液平衡数据。最后测定了长链二元物系十四酸甲酯-十六酸甲酯在低压下的汽液平衡数据。同时探索了微波场下的乙醇-苯汽液相行为。在分子模拟方面，采用吉布斯系综蒙特卡洛模拟方法，探索汽-液相界面传递规律，依次模拟了短、中、长链酯的纯组分物性。接着，模拟了短链物系乙酸甲酯-丙酸甲酯、中链物系辛酸甲酯-癸酸甲酯及癸酸甲酯-月桂酸甲酯、长链物系十四酸甲酯-十六酸甲酯的相平衡数据。通过计算电荷密度分布，考察了类导体屏蔽片段活度系数模型（COSMO-SAC模型）在相平衡预测中的应用。.探索了高真空间歇精馏的操作工艺参数对C18系列脂肪酸甲酯分离提纯效果的影响，并利用Aspen Plus软件模拟了脂肪酸甲酯体系的高真空间歇及连续分离过程。微波场中的酯化、酯交换反应动力学数据是开展微波反应精馏实验研究的基本前提，我们测定了微波及常规加热下固体酸催化制备乙酸乙酯，固体碱催化及酸性离子液体催化酯交换反应的动力学数据。研究表明微波可以显著加速酯化、酯交换反应速率，减少过程能耗，证实了微波对化学反应的强化作用。同时考察了微波对间歇精馏过程的影响。为了探索微波对反应精馏过程的影响，我们对连续及间歇酯化反应精馏进行了考察，对比研究了微波和常规两种加热方式下催化合成乙酸乙酯的反应精馏过程，并使用Aspen Plus软件对该间歇及连续反应精馏过程进行了模拟，证实了微波非热效应对间歇反应精馏过程具有强化传质、提高效率及节约能耗的作用。为了进一步提高反应精馏过程固体酸催化剂的催化效果，我们研究了高效离子液体的固定化过程并成功应用于脂肪酸甲酯化反应。