Hybrid solvents based on ionic liquids/deep eutectic solvents for CO2 separation

Abstract

CO2 separation plays a vital role in reducing CO2 emissions to combat climate change, while the available technologies still face challenges, including high costs and intensive energy usage. It is still critical to develop an energy-efficient and cost-effective technology for CO2 separation. Ionic liquid/deep eutectic solvent (IL/DES) has drawn significant attention in CO2 separation because they are tunable and exhibit high thermal stability and high CO2 solubility. The technologies based on IL/DES show their potential to reduce cost and energy usage. However, their viscosity is relatively high. In our work, adding cosolvents was used to adjust the high viscosity of IL/DES. A universal framework of IL/DES-based hybrid solvents for CO2 separation, from properties determination, thermodynamic modeling, to process design and evaluation, has been built up. Several DESs/ILs interacted with CO2 chemically and/or physically were investigated, aiming for the gas streams with different CO2 concentrations (biogas, flue gas). A detailed comparison of the performance of IL/DES-based hybrid solvents in terms of energy usage and cost with respect to conventional solvents was provided to study their feasibility. Our research shows that IL/DES-based hybrid solvents are promising for CO2 separation for different gas streams to reach the aim of lowing energy usage and cost, while further improvement is still needed to reach a technological breakthrough.