背包式气相反应器强化的甲醇与CO2直接合成碳酸二甲酯反应精馏过程研究

Reactive distillation is very potential for many chemical reactions but restricted to the innvolved non-condesnable gas reactant and the complex phase behavior. In this proposal, a side vapor phase fixed bed reactor intensified reactive distillation process for the reaction of synthesis dimethyl carbonate (DMC) from CO2 and methanol is proposed. The complex phase behavior of vapor-iquid-liquid equilibria is investigated with special focus on CO2. The models of the coupled side reactor and the distillation column are structred based on the simulation platform gPROMS, where the distillation is described by a non-equilibrium stage model and reactor by an one- and two-dimension fix-bed reactor model. The kinetics of the reaction is described by two expressions, namely LHHW and Power Law models, their parameters are determined based on the experimental data. In addition, the complex gas-vapor-liquid-liquid equilibrium of the system containing the non-condensable compound CO2 is also carefully evaluated and determined by the data from literature and software badabanks. The solubility of CO2 in the liquid under pressure, the liquid splitting and the azeotropes are focused. The solvers of dynamic and steady-state simulations from gPROMS is applied to investigate the process behaviors. The arc-length homotopy continuation algorithm is also built as a solver, which is applied to carry out the bifurcation analysis of the important parameters. With the simulation of the coupled side reactor-distillation system, the influence of the flow structure and the parameters can be figured out, the intensification mechanism of the vapor phase side-reactors can be explained, and the optimized configurations and operating parameters for synthesis of DMC from CO2 and methanol can be determined. The proposed study of the vapor phase side-reactor intensified reactive distillation could be very helpful to overcome the shortcomings of tranditional reactive distillation and extended to other reactions with non-condensable reactant.

针对传统反应精馏技术潜力巨大而又难以直接应用于含不凝性气体反应过程的关键问题，本项目以CO2和甲醇直接转化为碳酸二甲酯（DMC）为研究对象，发展基于气相反应器的背包式反应精馏强化方法，探索含不凝性气体反应物的新型反应精馏共性关键技术。通过确定含不凝性气体体系气-液-液相平衡和气相反应动力学的模型及参数，建立非平衡级精馏过程和气相反应器的过程机理模型，构建多级背包式气相反应器与精馏塔耦合系统的流程拓扑结构，并进行过程模拟模拟与优化，理解背包式气相反应器与精馏塔的协同作用，阐明背包式反应器对过程的强化机理和引入机制；同时结合耦合过程动态特性和非线性多态特性分析，考察多级反应器与精馏塔耦合拓扑结构以及关键工艺参数的影响，优化耦合反应精馏过程的工艺参数，同时结合过程实验，获得以气相反应器强化的CO2和甲醇直接合成DMC反应精馏基本工艺条件，为开发可大规模生产的CO2转化关键技术奠定基础。

以碳酸二甲酯（DMC）为代表的有机碳酸酯类化合物具有毒性低，附加值高等优点，可作为绿色环保的有机溶剂和良好的油品添加剂，同时也是锂电池中的电解质以及有机合成过程中重要的平台化合物，在化学工业中有着广泛的应用前景。由醇类与CO2直接合成的反应工艺原料来源广，价格低廉且原子经济性高，成为生产有机碳酸酯重要的研究方向。针对CO2不易活化，产物选择性和收率低，以及后续分离困难等一系列核心问题，我们制备适宜的催化剂或吸收剂提高对CO2的捕集能力和活化效果，并以过程强化概念为指导，通过耦合脱水反应，采用反应精馏技术，以及加入低极性有机溶剂的方法实现反应物与产物的原位分离，打破化学平衡，从而克服该体系在反应和分离上所受的制约。上述研究为高效率和低能耗捕集利用CO2以及实现有机碳酸酯工业化提供技术参考。.针对由甲醇和CO2直接合成DMC的气相反应提出一种背包式反应精馏工艺过程。系统地研究了反应精馏塔结构参数（如侧线采出与侧线回流位置）和操作条件（如进料比与回流比）等对过程强化效果的影响规律。采用此工艺，通过精馏作用原位分离反应物（甲醇与CO2）和产物（DMC和水），打破反应平衡的限制，使反应转化率能够从10%上升至99%以上。在此基础上，耦合环氧乙烷水合反应，消耗系统中产生的水，在将甲醇转化率提高至99.5%的同时大幅降低反应循环量与塔釜能耗。.考虑到气相过程中操作条件苛刻，原料难以分离回收的局限性，我们在液相常温常压条件下构建咪唑类离子液体和卤代烃协同的CO2与醇合成有机碳酸酯的两步法反应过程。利用咪唑类离子液体对CO2的化学吸收作用捕集和活化CO2，负载的CO2在体系中所占质量分数最高可达26.9%。再加入醇与卤代烃，得到有机碳酸酯的选择性和收率最高可达99.9%和40.1%。醇作为亲核试剂和烷氧基化试剂直接参与有机碳酸酯的生成。而卤代烃展现其良好的溶剂化效应并以烷基化效应调控反应路径，降低反应活化能，原位除去反应生成的水，打破化学平衡，极大地提高了产物选择性和收率。