新型相变吸收剂捕集二氧化碳的分相调控及传质-反应机理

Biphasic solvent is regarded as an advanced solvent with a low heat duty because of the small amount of the rich phase for regeneration. However, in order to form biphase, the conventional biphasic solvent can only load portion of CO2 as the biphase will disappear after the solvent is fully loaded. To that end, this project aims at developing a novel biphasic solvent featuring the high CO2 absorption rate, capacity, and the tunable phase change ability by the addition of an inert organic component. This novel biphasic solvent consists of three components: an absorption promoter (A), a CO2 capacity provider (B), and a phase separation controller (C). The novel biphasic solvent was screened and optimized based on the absorption rate, capacity, phase separation ratio, and stripping pressure. The optimized novel biphasic solvent will be used to validate the zwitterion mechanism based on the analysis of the intermediate product and end-product after CO2 absorption. The mechanism of the phase separation in the novel biphasic solvent is also investigated according to the species migration and distribution between the two separated phases. In addition, the kinetic and thermodynamic data will be obtained in a wetted wall reactor and a vapor-liquid equilibrium reactor based on the classic mass transfer theory and van’t Hoff equation to investigate the interaction between the amines and evaluate the heat duty of the tested solvent. This project will provide significant insight into the development of the advanced solvent for the CO2 capture and offer the kinetic and thermodynamic data for its industrial application in the future.

CO2负荷控制型相变溶剂是一类新兴的CO2吸收剂，因再生质量小（仅CO2富相）而具有较大节能潜力，但需要牺牲部分吸收负荷来达到分相目的。本项目在现有相变吸收剂中创新性得引入一种惰性有机物作为相变调控剂，形成有机胺A（吸收快）+有机胺B（容量大）+相变调控剂C的复合吸收剂，既能保证高吸收速率和吸收负荷，又能有效调控分相。通过研究该复合吸收剂的吸收-解吸特性，依据吸收速率、吸收容量、分相比例及解吸压力等参数，优化吸收剂组分及配比。基于中间产物及终产物分析，探明新体系下CO2反应机理，论证“两性离子”反应机理的适用性。探索吸收剂各组分及其产物在两相中的迁移转化规律，阐明相变调控剂的分相调控机制。基于经典双膜理论及van’t Hoff方程，获取动力学和热力学参数，探讨新体系下有机胺的交互作用机理，评价吸收剂再生能耗。本课题研究可为CO2吸收剂选择提供新的参考，并为其工业化应用奠定理论基础。

相变吸收剂是一种新型的CO2吸收剂，因仅需再生富相减少能耗而受到广泛关注，但是往往需要牺牲部分吸收容量来达到分相目的，同时现有相变吸收剂开发缺少理论依据，其CO2反应机理也尚未探明。本项目通过研究有机胺物性（碱度pKa和疏水性log P）与吸收剂性能之间的关系构建起了一套有机胺物性筛选指标体系，实验结果表明当叔胺pKa为9.8左右时，吸收剂CO2吸收负载达到最大，而低log P值的伯胺和高log P值的叔胺更有利于相变胺基吸收剂的相分离表现；通过引入一种惰性溶剂作为相变调控剂，间接改变水含量来调控相变吸收剂的分相表现，发现当吸收剂的水含量越低时，富相所占体积就越小，分相表现就越优异，但吸收性能反而会下降；分析实验过程中分相及吸收速率的变化，结合13C NMR与量子化学计算，提出并阐明了相变吸收剂吸收CO2的双阶段协同反应机理，在一阶段时质子传递是由两性离子经过伯、仲胺再传递给叔胺，反应主要受反应动力学控制，活化自由能较低，表观吸收速率较快，而在二阶段时两性离子的质子直接传递给叔胺，此时吸收反应主要受热力学控制，表观吸收速率变慢，产物更稳定；通过实验获取基础动力学及热力学数据，动力学分析表明富液的总传质阻力随叔胺log P值的增大而减小，而热力学分析表明随着三级胺log P值的增加，再生过程中的显热就会减小，而潜热反而增大。此外本项目还利用自构建的筛选指标体系得到了一种低耗高效的相变吸收剂1M TETA-3M DMCA，其吸收容量是MEA的1.6倍（0.83 mol mol-1），富相粘度仅为16-40 mPa s，再生能耗相比MEA降低了40%（2.07 GJ t-1 CO2）。