Effect of amine properties on developing CO2 phase change absorbents by means of cosolvent effect

As China pledges that its carbon emissions will peak before 2030 and that it will be carbon neutral by 2060, the CO2 capture technology with high efficiency and low energy-consumption was expected in industry. CO2 phase change absorbents, CPCAs, had shown a potential to reduce energy consumption for CO2 capture. Although a lot of CPCAs were reported in the last decade, it still suffered from the lack of theoretical guidance for development. The effect of amine structure, which mainly affects cosolvent effect of amine and salting-out effect of formed salts, on developing CPCAs by means of cosolvent effect was clarified. For cosolvent effect of amine, 12 amines with various carbon chain lengths, isomers and substituents were determined by thermodynamical method and the log P of amine were proposed to characterize the cosolvent effect. The amine with long carbon chain and steric effect showed a high ability to act as a cosolvent to enhance the solubility of 1-butanol in H2O. The salting out effect of formed salts by reacting amine and CO2 was related to pKa of amine. The absorbent comprising amine with low log P and high pKa was prefer to exhibit phase separation behavior, and benefit to develop CPCAs. Based on this guideline, all amines in this study could be developed as CPCAs by adjusting kinds of amine and diluent. Moreover, to explore the absorption-desorption performance of developed CPCAs, DEA/1-butanol/ H2O was used as example, the volume ratio, species distributions and CO2 cyclic capacity were measured. When the absorption temperature was 303 K and desorption temperature was 373 K, The maximum CO2 cyclic capacity of CPCA was 2.03 mol CO2.kg(-1), which was 34.4% higher than that of 30 wt% DEA/H2O.