Screening of Ionic Liquids and Deep Eutectic Solvents for Physical CO2 Absorption by Soft-SAFT Using Key Performance Indicators

Ismail I I Alkhatib,Lourdes F Vega,Fèlix Llovell,Mohammad R.M Abu-Zahra,João M M Araújo,Margarida L Ferreira,Daniel Bahamon,Carlos G Alba,Ana B Pereiro

doi:10.1021/acs.jced.0c00750

Abstract

The efficient screening of solvents for CO2 capture requires a reliable and robust equation of state to characterize and compare their thermophysical behavior for the desired application. In this work, the potentiality of 14 ionic liquids (ILs) and 7 deep eutectic solvents (DESs) for CO2 capture was examined using soft-SAFT as a modeling tool for the screening of these solvents based on key process indicators, namely, cyclic working capacity, enthalpy of desorption, and CO2 diffusion coefficient. Once the models were assessed versus experimental data, soft-SAFT was used as a predictive tool to calculate the thermophysical properties needed for evaluating their performance. Results demonstrate that under the same operating conditions, ILs have a far superior performance than DESs primarily in terms of amount of CO2 captured, being at least two-folds more than that captured using DESs. The screening tool revealed that among all the examined solvents and conditions, [C4 py][NTf2] is the most promising solvent for physical CO2 capture. The collection of the acquired results confirms the reliability of the soft-SAFT EoS as an attractive and valuable screening tool for CO2 capture and process modeling.

Highlights

The global energy market is substantially dependent on fossil fuels as primary energy resources, with a dominating share of 84.3% through 2019.1 The price paid for this behemoth dependency is the emergence of dire environmental issues manifested in global warming phenomenon and climate change, posing a threat to the sustenance of humanity on the planet in the long term
We demonstrate the feasibility of employing a molecular-based equations of state (EoSs), the soft-Statistical Associating Fluid Theory (SAFT) EoS,[65,66] for the screening of physical solvents for CO2 capture at industrially relevant conditions
The description of the liquid density at atmospheric pressure for the pure solvents as obtained from soft-SAFT with the transferred molecular parameters, compared to experimental data for ILs72,99,103−107 and DESs108−111 is shown in Figure S1 in the Supporting Information, highlighting the quantitative accuracy of the models used in this work for ionic liquids (ILs) and deep eutectic solvents (DESs)

Summary

■ INTRODUCTION

The global energy market is substantially dependent on fossil fuels (i.e., coal, oil, and natural gas) as primary energy resources, with a dominating share of 84.3% through 2019.1 The price paid for this behemoth dependency is the emergence of dire environmental issues manifested in global warming phenomenon and climate change, posing a threat to the sustenance of humanity on the planet in the long term. Equations of state, those based on the Statistical Associating Fluid Theory (SAFT),[56−59] provide a viable alternative for the development of solvent screening tools owing to their outstanding ability in capturing the physical nature of complex fluids in a representative manner These models are capable of predicting a full range of information needed for accurate process design and modeling, along with offering additional fundamental insight and understanding on the thermodynamic behavior of these solvents, encompassed in a single model. The development of coarse-grain molecular models for ILs and DESs is relatively similar due to their parallel molecular nature, being mixtures of individual components/species bounded by some form of physical strong and highly directional interactions, well captured by the association term in SAFT-type equations.

■ RESULTS AND DISCUSSIONS

■ CONCLUSIONS

■ ACKNOWLEDGMENTS

■ REFERENCES