Challenges and opportunities for the utilisation of ionic liquids as solvents for CO₂capture

Abstract

Ionic liquids (ILs) have the potential to outperform traditional solvents for CO2 capture, with a great many ILs having been studied to date. In this contribution we present a new approach for their evaluation, and identify which physical properties most infl uence their technical and economic performance. This work highlights a range of potential challenges that ionic liquids will face before they can be applied at process scale, and identifi es some key research opportunities. Ionic liquids have been extensively investigated as promising materials for several gas separation processes, including CO 2 capture. They have the potential to outperform traditional solvents, in terms of their capacity, selectivity, regenerability and stability. In fact, hundreds of ionic liquids have been investigated as potential sorbents for CO 2 capture. However, most studies focus on enhancing equilibrium capacity, and neglect to consider other properties, such as transport properties, and hence ignore the effect that the overall set of properties have on process performance, and therefore on cost. In this study, we propose a new methodology for their evaluation using a range of monetised and non-monetised process performance indices.Our results demonstrate that whilst most research effort is focused on improving CO 2 solubility, viscosity, a transport property, and heat capacity, a thermochemical property, might preclude the use of ionic liquids, even those which are highly CO 2 -philic, and therefore increased effort on addressing the challenges associated with heat capacity and viscosity is an urgent necessity. This work highlights a range of potential challenges that ionic liquids will face before they can be applied at process scale, and identifies some key research opportunities.

The Nature of Carbon Dioxide in Bare Ionic Liquids

“…[1,2] The ideal process would certainly be a one-pot solution in which the device could capture, activate, and transform the CO 2 available from different sources (ideally from air and exhaust gases). [3] Ionic liquids (ILs, Figure 1), mainly those that are thermally, photo-, electro-, and chemically stable and display very low vapor pressures, [4] are among the most promising materials to perform this multitask transformation. [5,6] The first report showing that certain ILs can sorb up to 0.6 mole fraction of CO 2 at 8 MPa [7] has opened a new window of opportunity for CO 2 capture and transformation.…”

Xenon Dynamics in Ionic Liquids: A Combined NMR and MD Simulation Study

“…1 − 3 Due to their peculiar physicochemical characteristics, IL solutions are ideal solvents for many reaction, separation, and extraction processes. 4 − 7 Several studies have pointed out their utility in gas capture 8 − 10 and separation, highlighting that the absorption capability strongly depends on the local liquid structure 11 and mechanism of gas confinement. 12 − 14 …”

Natural gas and BECCS: A comparative analysis of alternative configurations for negative emissions power generation

“…The fact that CCS is included in the system incorporates further challenges besides biomass conversion at large scale. The solvent regeneration step has been extensively studied, which highly depends in the composition of CO 2 in the gas [49], solvent use [50,51,52], or even on the degree of heat integration [41]. Therefore, co-firing biomass with natural gas is an attractive alternative to counteract all possible disadvantages.…”