聚离子液功能化支撑液膜直接吸收-转化CO2合成碳酸酯研究

The high-value utilization of CO2 is of great significance to the mitigation of global warming. The routing using ethylene oxide (EO) to activate CO2 to produce high-value carbonates has mild reaction conditions and good economic benefit. However, the existing technology for ethylene carbonate (EC) production is still using pure EO and CO2 as the raw materials, which is energy-consumption to separate and purify CO2 and EO for the gas mixtures. This project intends to combine the reactor and membrane contactor to synthesize EC by directly absorbing-catalyzing low concentration CO2 (1-15%) and EO (1-3%) in the mixture gas obtained from the ethylene oxidation. The polymerizable ionic liquids containing amidogen was used to prepare CO2-affiliative porous catalytic membrane, which will be used to prepare supported liquid membrane (SLMs). The catalytic activity of ionic liquids and the separation characteristic of liquid membrane will be used in the synthesization of EC. The experiments and theoretical calculation will carry out in the preparation of poly(ionic liquids) based catalytic porous membranes, the kinetics and thermodynamics of gas absorption in EC liquid membrane, synthesis of EC using SLMs to absorb-catalyze low-concentration CO2 and EO. The effects of the functional group in ionic liquids (ILs), the micro-structure of liquid membrane on the catalytic activity and gas absorptivity will be investigated. The solution-diffusion law of gas in EC liquid membranes will be studied to reveal the mechanism of the reaction and absorption of low-concentration CO2 and EO. Through the studies in the project, the laws of reaction and absorption of low-concentration CO2 and EO in SLMs will be revealed, which will lay the foundation for the high-efficient conversion of CO2 using SLMs.

CO2资源化利用对缓解全球变暖具有重要意义，利用环氧乙烷(EO)活化CO2合成碳酸酯类高值化学品的路线，条件温和、经济性好。目前，合成碳酸乙烯酯(EC)仍以纯CO2和EO为原料，其分离和纯化过程需耗费大量能源。本项目拟将反应与膜吸收过程偶合，采用含氨基可聚合离子液体构建亲CO2的多孔催化膜，并制成支撑液膜，利用离子液体的催化活性和吸收剂液膜的分离特性，直接吸收-转化乙烯氧化所得混合气中的低浓度CO2 (1-15%)及EO (1-3%)合成EC。围绕聚离子液体多孔催化膜制备、气体在支撑液膜中的吸收动力学及热力学、支撑液膜吸收-转化低浓度CO2、EO合成EC，开展实验和理论计算。研究离子液体功能基团、液膜性质及微观结构等对支撑液膜催化活性、气体吸收性能的影响，阐明气体在液膜中的溶解-扩散规律，揭示催化支撑液膜对低浓度CO2、EO的选择性吸收和反应机理，为支撑液膜高效转化CO2提供基础。

CO2高值化利用对于实现“双碳”目标具有重要意义。利用环氧活化CO2合成碳酸酯类高值化学品的路线，条件温和、经济性好。本项目采用聚离子液体膜(PILMs)，实现了气相CO2和环氧的直接吸收转化，对于简化碳酸酯合成工艺具有参考意义。首先以EC为吸收剂，探究了CO2、CH4、C2H4和EO气体在EC中的溶解度性质，并采用NRTL模型关联相关实验数据，获得二元交互参数，平均偏差小于5.4%，为预测支撑液膜中，EO和CO2浓度提供理论模型。基于DMAEMA和乙烯基咪唑两类离子液体单体，采用不同的共聚单体和交联剂制备了两类聚离子液体膜，研究了膜结构对气相/液相催化性能的影响。结果表明离子液体单体中的卤素阴离子和羧基/羟基官能团对于提高催化活性具有重要作用。其中，最佳的DMAEMA类PILMs，MEM01(基于[DMAEMA-EtOH]Br)在110℃、3h、3MPa条件下，液相催化PO、EO转化率可达98.0%和99.2%；最佳的咪唑类PILMs，PILM-VCPImBr在130℃、3 h、2 MPa条件下PO转化率可达96.7%。PILMs聚合结构对于气相环氧和CO2的转化也具有重要影响。采用块状纯聚离子液体催化气相PO转化率仅为3.1%，而通过MMA、EA、PEGDMA等共聚单体调控PILMs结构，可提高PILMs强度、韧性和溶胀性能，分散离子液体活性位点，使得PILMs吸收EC后形成大量孔道从而大幅提高了气相催化活性，在相同条件下MEM01催化气相PO、EO转化率可达87.3%和99.2%。优异的溶胀性能提高PILMs活性的同时，也导致溶胀后的PILMs机械强度大幅下降，不能用于分离操作。项目取得的成果对聚离子液体基支撑液膜反应-分离一体化的工艺过程提供了重要的方法和参考，并为后续离子液体支撑液膜强化环加成反应-分离的工业化应用奠定了基础，相关研究成果发表论文4篇，申请专利3项。