Solubility of CO2 in Aqueous Formic Acid Solutions and the Effect of NaCl Addition: A Molecular Simulation Study

Dominika O Wasik; H Mert Polat; Mahinder Ramdin; Othonas A Moultos; Sofia Calero; Thijs J H Vlugt

doi:10.1021/acs.jpcc.2c05476

Solubility of CO₂ in Aqueous Formic Acid Solutions and the Effect of NaCl Addition: A Molecular Simulation Study

J Phys Chem C Nanomater Interfaces. 2022 Nov 17;126(45):19424-19434. doi: 10.1021/acs.jpcc.2c05476. Epub 2022 Nov 4.

Authors

Dominika O Wasik^{1

2}, H Mert Polat^{3

4

5}, Mahinder Ramdin³, Othonas A Moultos³, Sofia Calero^{1

2}, Thijs J H Vlugt³

Affiliations

¹ Materials Simulation and Modelling, Department of Applied Physics, Eindhoven University of Technology, Eindhoven5600MB, The Netherlands.
² Eindhoven Institute for Renewable Energy Systems, Eindhoven University of Technology, P.O. Box 513, Eindhoven5600 MB, The Netherlands.
³ Engineering Thermodynamics, Process & Energy Department, Faculty of Mechanical, Maritime and Materials Engineering, Delft University of Technology, Leeghwaterstraat 39, Delft2628CB, The Netherlands.
⁴ CCUS and Acid Gas Entity, Liquefied Natural Gas Department, Exploration Production, TotalEnergies S.E., Paris92078, France.
⁵ CTP-Centre of Thermodynamics of Processes, Mines ParisTech, PSL University, 35 rue Saint Honoré, Fontainebleau77305, France.

Abstract

There is a growing interest in the development of routes to produce formic acid from CO₂, such as the electrochemical reduction of CO₂ to formic acid. The solubility of CO₂ in the electrolyte influences the production rate of formic acid. Here, the dependence of the CO₂ solubility in aqueous HCOOH solutions with electrolytes on the composition and the NaCl concentration was studied by Continuous Fractional Component Monte Carlo simulations at 298.15 K and 1 bar. The chemical potentials of CO₂, H₂O, and HCOOH were obtained directly from single simulations, enabling the calculation of Henry coefficients and subsequently considering salting in or salting out effects. As the force fields for HCOOH and H₂O may not be compatible due to the presence of strong hydrogen bonds, the Gibbs-Duhem integration test was used to test this compatibility. The combination of the OPLS/AA force field with a new set of parameters, in combination with the SPC/E force field for water, was selected. It was found that the solubility of CO₂ decreases with increasing NaCl concentration in the solution and increases with the increase of HCOOH concentration. This continues up to a certain concentration of HCOOH in the solution, after which the CO₂ solubility is high and the NaCl concentration has no significant effect.