Improvement of CO2 capture processes by tailoring the reaction enthalpy of Aprotic N‑Heterocyclic anion-based ionic liquids

Abstract

A wide variety of Aprotic N‑Heterocyclic Anion-based Ionic Liquids (AHA-ILs) were designed using DFT/COSMO-RS quantum chemical calculations to optimize their performance as chemical absorbents on industrial-scale CO2 capture processes by tailoring the enthalpy of reaction. Five different substituents located at multiple positions on eight different heterocyclic rings were considered to cover a wide range of CO2-IL reaction enthalpies. Twelve representative AHA-ILs based on [P66614] cation with an enthalpy of reaction from -30 to -64 kJ/mol were evaluated on post-combustion, biogas and pre-combustion CO2 chemical capture processes through Aspen Plus Rate-based simulations. AHA-ILs presenting a CO2 reaction enthalpy between -43 and -54 kJ/mol were found to minimize both solvent and energy consumptions and thus equipment and operating costs in all studied CO2 capture systems, since cyclic capacity is successfully optimized by a correct selection of the reaction enthalpy. Some non-synthesized AHA-ILs, as [P66614][4-BrPyra] (-49.3 kJ/mol), are proposed as promising CO2 chemical absorbents based on their enhanced performance in post-combustion, biogas and pre-combustion capture processes from current techno-economic analysis.

Keywords

• CO2 capture
• Ionic liquids
• Cost estimation
• Process simulation
• COSMO-based/Aspen