Tuning and optimization of two-phase absorbents (DEEA/AEEA/H2O) with hybrid phase splitter (n-butanol/DEEA) for several properties: Carbon capture, phase separation, physical properties

Abstract

In this study, we examined the impacts of complete and partial substitution of DEEA with physical solvents (n-butanol) on the performance of AEEA/H2O absorption, regeneration, and phase separation. The higher hydrophobicity (log P) of n-butanol, as a phase splitter, expedites the separation process from the AEEA-CO2 product. Through additional refinement of the mass ratio between n-butanol and DEEA, it was observed that substituting a small portion of DEEA with n-butanol had negligible impact on the absorption capacity and enrichment of the enriched phase. However, it significantly reduced the phase separation time between the two solvent phases. Furthermore, an increase in n-butanol concentration can enhance cyclic loading. On the other hand, it reduces the production of AEEACOO−/DEEAH+, which is more stable compared with AEEACOO−/AEEAH+. Molecular dynamics simulations revealed that n-butanol can modulate the reduction of water molecules surrounding AEEA, creating a lower water molecule environment, which improves the absorption rate of the absorbent in the pre-absorption phase. The addition of a low concentration of n-butanol improves the initial absorption rate, phase separation performance, circulation capacity, and further reduces the regeneration energy of the absorption solution without compromising the CO2 loading and regeneration energy.