A comprehensive study on carbon capture potential of lactic acid based deep eutectic solvents at wide process conditions

Abstract

This study explores the solubility and absorption kinetics of CO2 in novel Natural Deep Eutectic Solvents (NADES) with a focus on three systems: carvone-lactic acid (1:1), cineole-lactic acid (3:1), and cineole-lactic acid (1:1). The CO2 absorption experiments were carried out in the pressure range of 4.5 to 37 bar at 25 °C and 35 °C isotherms. The absorbed CO2 was quantified as a mole fraction in the NADES and demonstrated that the absorption was positively influenced by pressure and inversely by temperature. Among the systems, cineole-lactic acid (3:1) showed the highest CO2 absorption capacity at both isotherms. The experimental data were compared with the COSMO-RS predictions, revealing a systematic deviation, with all experimental results being higher than the predictions. The deviation increased with the decrease of temperature and the increase of pressure. Absorption kinetics was also studied, revealing that pressure increase accelerates the absorption process. Furthermore, cineole-lactic acid (1:1) absorption was notably faster at 35 °C than at 25 °C, possibly due to a reduction in viscosity. The study also calculated the heat of absorption for each system using the Clausius-Clapeyron equation. The heat of absorption values fell within the physi-sorbents heat of absorption range and were lower than traditional monoethanolamine (MEA), indicating less energy-intensive regeneration for these NADES. Overall, these findings point to the potential of these NADES for CO2 capture with efficient energy utilization and reduced environmental impact.