以异丁酸异丁酯为例的长链酯合成反应萃取强化过程离子液体溶剂设计

Long-chain esters are widely used as solvent, additive and raw materials in many fields, and they are more and more applied in new material development. However, the traditional technologies for producing the long-chain esters rely on entrainer to remove water by forming azeotrope and suffering from serious problems using strong acid as catalyst, which leases mixture of produced ester, unconverted acid and alcohol, together with catalyst, from the bottom of the reactor. In this proposal, a novel intensified technology of reactive extraction is proposed, which employs ionic liquid as catalyst and solvent simultaneously. The innovative process makes use of the advantages of thermodynamic features of the ester system of forming two liquid phases, each hosts water and ester respectively and helps to overcome the limitation of chemical equilibrium by removing them simultaneously. The liquid-liquid equilibrium of such system with ionic liquid as solvent is developed by UNIFAC-IL model to predict activity coefficient covering groups of potentials ionic liquids. The parameters of the UNIFAC-IL model are fitted based on reported experimental data, and therefore the liquid-liquid equilibrium predictions are more reliable and can be used for designing ionic liquid in reactive extraction process. The ionic liquid is designed by solving a Mixed-Integer Nonlinear Programming problem (MINLP), where the objective function of the reactive extraction process performance and constrained conditions of molecular structure feasibility and physical properties to guarentee the designed ionic liquid can be formulated and can be used in the process. As an example, the formation of isobutyl isobutyrate from isobutyric acid and isobutanol is investigated. By solving the MINLP problem, top 5 ionic liquid candidates are designed. With the activity coefficients, the reactive extraction process of isobutyl isobutyrate formation with the top 5 ionic liquid candidates is simulated by Aspen Plus, and the parameters will be optimized by investigating the effect of the important parameters. Finally, the reactive extraction experiment under the guide of the process simulation will be completed. The project will contribute a comprehensive approach for solvent design and innovative technology for long-chain ester formation.

针对长链酯合成传统工艺普遍以强酸为催化剂并采用共沸精馏脱水而无法利用反应体系分相的热力学优势等关键问题，本项目提出以离子液体为催化溶剂的长链酯合成反应萃取过程强化技术，并以代表性长链酯异丁酸异丁酯合成为例，重点发展反应萃取过程离子液体溶剂的系统性设计方法和共性关键技术。通过拟合大量实验数据，拓展专门针对含离子液体酯化反应体系的UNIFAC-IL模型；通过分析反应体系液液相平衡，阐明离子液体阴阳离子种类和链长对于促进体系分相和强化酯与水分离的作用机理，理解长链酯合成反应过程的溶剂效应，确定离子液体阴阳离子的引入机制；构建和求解包含酯化反应萃取过程目标函数和多约束条件的MINLP问题，并结合Aspen Plus流程模拟和实验，优化长链酯合成反应萃取优化的离子液体结构和基本工艺条件，并形成长链酯合成具有指导性的离子液体设计原则，为开发高效绿色的长链酯合成反应萃取共性关键技术奠定理论基础。

针对以离子液体类溶剂强化的长链酯合成反应萃取过程，研究了溶剂筛选方法，过程强化机理，典型反应过程动力学和热力学模型，以及过程设计。基于深度神经网络的推荐系统开发了离子液体高精度活度系数预测模型，作为直接筛选依据，并扩展了UNIFAC-IL模型；设计了两种酯化反应萃取过程双功能离子液体的系统性筛选方法，分别具有通用快速和高精度的特征。合成了新一代离子液体替代物，即酸碱可调的低共熔溶剂[Im:2PTSA]，并探索其性质和形成机理。以代表性长链酯异丁酸异丁酯的反应萃取合成过程为研究对象，使用筛选获得的离子液体[BMIm][HSO4]和合成的低共熔溶剂[Im:2PTSA]强化异丁酸异丁酯合成反应萃取过程，从反应动力学、热力学和流程模拟方面对反应萃取过程进行了系统地研究，阐明了长链酯合成反应萃取过程的溶剂效应，获得了双功能溶剂的强化机制，并优化了异丁酸异丁酯合成反应萃取过程的工艺条件。项目执行期间，将离子液体和低共熔溶剂强化的长链酯合成反应萃取过程拓展到了其他酯化反应体系，包括丙烯酸异辛酯、己酸丁酯和辛酸单甘油酯合成体系等，均得到了优于常规合成方法的效果，形成对不同长链酯合成的反应萃取过程具有指导性的溶剂设计原则，为开发更为环境友好的长链酯合成反应萃取共性工艺技术奠定理论基础。