CO₂ solubility in small carboxylic acids

Abstract

Carbon dioxide (CO₂) can electrochemically be converted to a range of products including formic acid (HCOOH) and acetic acid (CH₃COOH). The yield of the products in an electrolysis cell depends on the solubility of CO₂ in the (aqueous) mixture. In absence of experimental data, Monte Carlo simulations in the Gibbs ensemble are used to compute the VLE of the binary systems, CO₂-H₂O, CO₂-HCOOH and CO₂-CH₃COOH, and the ternary systems, CO₂-HCOOH-H₂O and CO₂-CH₃COOH-H₂O. In addition, the PC-SAFT equation of state (EoS) is used to model the VLE of these strongly associating mixtures. Both methods correctly predicts the liquid-phase compositions, but the gas-phase compositions are less accurately described. The challenges to model these systems are related to the simultaneous formation of dimers, rings, and chains, which requires accurate force fields and advanced biasing schemes in MC simulations, and association theories that can account for this effect.