Chapter 3 - Choline-Based Deep Eutectic Solvents for Mitigating Carbon Dioxide Emissions

Abstract

Global warming is a critical issue facing human beings due to greenhouse gas emissions, especially CO2 emissions. Mitigating CO2 emissions by Carbon capture and storage (CCS) has become a hot topic today. CO2 separation is a crucial step in CCS and is an energy-intensive process. Ionic liquids (ILs) as green solvents have gained tremendous attention for use as liquid absorbents for CO2 separation. However, the high price, toxicity, and poor biodegradability limit the application of ILs. Recently, deep eutectic solvents (DESs) based on choline chloride (ChCl) (i.e., choline-based DESs) were proposed as a new type of ILs but with additional advantages in cost, environmental impact, and synthesis. To promote the application of choline-based DESs in CO2 separation, the research work on the microstructure and physicochemical properties of choline-based DESs as well as the water effect were surveyed and compared with traditional ILs. The potential applications of choline-based DESs in CO2 separation and the challenges were further analyzed. It is shown that choline-based DESs are promising for use as liquid absorbents for CO2 separation, and the performance of ChCl/urea (1:2) is better than that for other choline-based DESs. However, uncertainties and bottlenecks still exist, and further study on the microstructure and properties needs to be carried out from experimental measurements to model developments.