Potential of amine-based DES for separation of CO2 and H2S from NG: Study of temperature effect

Designing effective Deep eutectic solvents (DESs) for NG sweetening processes requires an understanding of how acid gases are absorbed by DESs. In this regard, the current work provides a summary of the complementary results from the structural, dynamical, and mechanistic absorption evaluation of DESs based on N-methyldiethanolamine (MDEA) using molecular dynamics simulation. The absorption capability of the MDEA-based DES for the extraction of acid gases from NG as a function of temperature demonstrated that the MDEA-based DES extracted 78% and 27% of H2S and CO2, respectively, at 320 K and 0.1 MPa. Additionally, structural analyses including density profiles, radial and spatial distribution functions, hydrogen bond numbers, and molecular interaction energies were explored to gain a more in-depth understanding of the mechanism of acid gas absorption. Moreover, to assess the efficacy of potential DES in NG sweetening procedures, the solubility of acid gases, solubility selectivity, and diffusivity selectivity parameters were determined as functions of temperature. Furthermore, at temperatures between 320 and 400 K, the diffusion coefficients of acid gases and CH4 are in the following order: CH4 > CO2 > H2S. Finally, we believe that new insights into the mechanism of the absorption of H2S and CO2 from NG will be beneficial to the design and applications of DESs for sweetening NG in the future.