Synthesis and characterization of ammonium-based protic ionic liquids for carbon dioxide absorption

Area of Science:

• Materials Science
• Chemical Engineering
• Environmental Science

Background:

• Ammonium-based protic ionic liquids (APILs) are explored as alternatives for CO2 separation.
• Existing methods like monoethanolamine (MEA) have limitations in recyclability.
• Developing efficient and recyclable CO2 absorbents is crucial for climate change mitigation.

Purpose of the Study:

• To synthesize and characterize a series of APILs for their physicochemical properties.
• To evaluate the CO2 absorption capacity and recyclability of synthesized APILs.
• To compare the performance of APILs with traditional absorbents like MEA.

Main Methods:

• Synthesis of six APILs via proton transfer.
• Characterization of thermal stability, phase transitions, density, heat capacity (Cp), and refractive index (RI).
• CO2 absorption performance assessed using a pressure drop technique (1-20 bar, 298.15 K) and recyclability studies.

Main Results:

• Synthesized APILs include ethanolammonium and triethanolammonium pentanoate/heptanoate variants.
• Triethanolammonium APILs exhibited crystallization peaks between -31.67 to -1.00 °C.
• Tributylammonium heptanoate ([TBA][C7]) showed the highest CO2 absorption (0.74 mole fraction at 20 bar) with minimal capacity loss after recycling.

Conclusions:

• APILs possess favorable physicochemical properties, including low heat capacity compared to MEA.
• [TBA][C7] demonstrates excellent CO2 absorption capacity and recyclability.
• APILs represent a promising class of liquid absorbents for efficient CO2 removal in industrial applications.