Abstract
Up to now, many kinds of deep eutectic solvents (DESs) were investigated for the capture of acidic gases from flue gases. In this review, non-functionalized and functionalized DESs, including binary and ternary DESs, for SO2, CO2 and NO capture, are summarized based on the mechanism of absorption, physical interaction or chemical reaction. New strategies for improving the absorption capacity are introduced in this review. For example, a third component can be introduced to form a ternary DES to suppress the increase in viscosity and improve the CO2 absorption capacity. DESs, synthesized with halogen salt hydrogen bond acceptors (HBAs) and functionalized hydrogen bond donors (HBDs), can be used for the absorption of SO2 and NO with high absorption capacities and low viscosities after absorption, due to physicochemical interaction between gases and DESs. Emphasis is given to introducing the absorption capacities of acidic gases in these DESs, the mechanism of the absorption, and the ways to enhance the absorption capacity.
Highlights
Flue Gas by Deep Eutectic Solvents.Acidic gases, such as sulfur dioxide (SO2 ), nitric oxide (NO) and carbon dioxide (CO2 ), are the main pollutants of fuel gases, which are mainly released from the combustion of fossil fuels, posing a significant threat to the environment by forming acid rain, ozone destruction, global warming and so on
deep eutectic solvents (DESs) can effectively absorb SO2, CO2 and NO of low concentrations in flue gas, and generally have lower viscosity before absorption compared to ionic liquids (ILs)
The absorption capacity and viscosity can be adjusted by changing the molar ratio of hydrogen bond donors (HBDs) to hydrogen bond acceptors (HBAs), which makes a great room for cost adjustment
Summary
Chen et al [28] gave a comprehensive summary of toxic gases capture by DESs, and reviewed the effects of HBD and HBA, temperature, their molar ratio, water content and gas flow rate on the absorption capacity. The factors that affect the gases capture capability of DESs can be divided into two categories: internal factors (e.g., structure of HBA and HBD, and molar ratio) and external factors (e.g., temperature, pressure, time, gas flow rate, and water content). The functionalized and non-functionalized DESs were reviewed, according to whether chemical reactions occurred to form new substances or not, for SO2 , CO2 and NO capture, respectively. This perspective includes the following sections: (1).
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