Abstract:

The chemical conversion of CO₂ to obtain energy or chemicals with economic value can realize the resource recycling of CO₂, which is one of the ideal ways to solve the problem of carbon neutralization in China. The production of dimethyl carbonate (DMC) and by-product ethylene glycol by two-step transesterification is an effective way to realize the chemical conversion and high-value utilization of CO₂. In view of the technical problems of difficult CO₂ activation and high production cost faced by the process, the process enhancement methods such as one-step absorption of ethylene oxide by ethylene carbonate, ionic liquid catalyst, reactive distillation to realize transesterification and extractive distillation to separate dimethyl carbonate and methanol were used. The whole process simulation was completed by Aspen plus followed by the transesterification parameter optimization using BP neural network and multi-objective genetic algorithm (NSGA-Ⅱ). And energy integration by pinch technology of transesterification process and carbon flow analysis of whole process were performed. The optimization results show that the consumption of thermal utilities in the transesterification process is reduced by 40.34%. The carbon flow analysis results show that the total carbon atom utilization rate in the system reaches 99.81%. Considering the indirect carbon emissions from energy consumption, the carbon atom utilization efficiency is 86.90%, and the net CO₂ emission is 0.314kg CO₂/kg DMC. Compared with the processes reported in the literature, the DMC product obtained in this process has a higher purity (99.9995%) and lower energy consumption (1.10kW·h/kg DMC), which can provide technical guidance for the chemical conversion of dimethyl carbonate and ethylene glycol from CO₂.

Key words: chemical transformation of CO₂, transesterification, reactive distillation, genetic algorithm, pinch technology, carbon flow analysis

摘要：

CO₂化学转化可获得高值化学品，实现CO₂资源化利用，是解决“碳中和”问题的理想方法之一。两步酯交换法生产碳酸二甲酯（DMC）、副产乙二醇，是实现CO₂高值化利用的有效途径。针对该过程面临的CO₂活化难、生产成本高的技术难题，本文采用碳酸乙烯酯一步吸收环氧乙烷、离子液体催化剂、反应精馏实现酯交换以及变压精馏分离碳酸二甲酯和甲醇共沸物等过程强化方法实现CO₂两步转化。本文首先利用Aspen Plus完成全流程模拟，再采用BP神经网络和第二代非支配排序多目标遗传算法（NSGA-Ⅱ）优化酯交换过程参数，基于夹点技术对酯交换过程进行能量集成并对全过程进行严格的碳流分析。能量集成结果表明，酯交换过程热公用工程用量降低40.34%；碳流分析结果表明，全过程总碳原子利用率达到99.81%，考虑能源消耗的间接碳排放，碳原子利用效率为86.90%，净CO₂排放量0.314kg CO₂/kg DMC。与文献报道的工艺相比，本文工艺流程所得DMC产品纯度较高（99.9995%）、能耗更小（1.10kW·h/kg DMC），可为CO₂化学转化碳酸二甲酯和乙二醇提供技术指导。

关键词: CO₂化学转化, 酯交换, 反应精馏, 遗传算法, 夹点技术, 碳流分析