Enhancing CO2 capture performance of N-methylpyrrolidone with 2-methylimidazole aqueous solution

N-Methylpyrrolidone (NMP) is a traditional physical absorbent for CO2, but exhibits low CO2 solubility and selectivity under low pressure. To improve CO2 absorption and separation efficiency, a complex solution was developed by adding an aqueous 2-methylimidazole (2-mIm) solution to NMP. The CO2 solubility, desorption heat, separation performance, and recyclability were evaluated to determine the optimal composition and conditions. The results show that the addition of 2-mIm solution significantly increased CO2 solubility, particularly at low pressures. Although the desorption heat of the complex solution was higher than pure NMP, it remained much lower than MDEA solutions. The complex solution also demonstrated significantly higher CO2 selectivity, aiding in CO2 separation and purification. In CO2/CH4 separation, the complex solution showed over twice the separation factor and a higher CO2 capture ratio than pure NMP. Increasing the gas-to-liquid ratio decreased separation efficiency, while a higher equilibrium pressure improved separation performance. The complex solution maintained effective separation across a wide range of CO2 concentrations with fewer theoretical plates needed for high-purity separation. Additionally, the complex solution showed excellent recyclability, fully restoring CO2 absorption capacity after desorption at room temperature under vacuum conditions. These findings can support the development of an energy-efficient CO2 capture process.