The CO₂ Absorption in Flue Gas Using Mixed Ionic Liquids

Area of Science:

• Materials Science
• Chemical Engineering
• Environmental Science

Background:

• Ionic liquids (ILs) possess appealing properties for CO2 absorption in flue gas applications.
• Previous studies utilized specific ILs like [NH2emim][BF4], [C4mim][OAc], and [NH2emim[OAc] for CO2 capture.
• The presence of sulfur dioxide (SO2) in flue gas negatively impacts ILs' CO2 absorption efficiency.

Purpose of the Study:

• To investigate the CO2 absorption performance of various ionic liquids in simulated flue gas.
• To explore the structural changes of ILs after CO2 absorption using advanced analytical techniques.
• To develop an improved IL-based system for enhanced CO2 capture in the presence of SO2.

Main Methods:

• Experimental CO2 capture using [NH2emim][BF4], [C4mim][OAc], and [NH2emim[OAc] with simulated flue gas.
• Quantum chemical calculations, Fourier-transform infrared (FTIR) spectroscopy, and Nuclear Magnetic Resonance (NMR) for structural analysis.
• Evaluation of a mixed ionic liquid system ([C4mim][OAc]/[NH2emim][BF4]) for CO2 absorption.

Main Results:

• SO2 significantly hinders CO2 absorption by individual ILs, as it reacts preferentially with active sites.
• The IL mixture [C4mim][OAc]/[NH2emim][BF4] demonstrated a 25% increase in CO2 absorption capacity, even with SO2 present.
• Theoretical calculations suggest SO2 is captured by [NH2emim][BF4], allowing [C4mim][OAc] to absorb CO2 without interference.

Conclusions:

• The developed IL mixture effectively overcomes the negative impact of SO2 on CO2 capture.
• Selective SO2 capture by one component of the IL mixture is key to enhancing overall CO2 absorption.
• This strategy offers a promising approach for efficient CO2 capture from industrial flue gases.