Potential use of deep eutectic solvents based on sugar as green separation media for the acidic gases capture process from the gas mixtures: molecular dynamics simulation and COSMO-RS insights

Abstract

Context

The global greenhouse gas (GHG) emissions originate from five main economic sectors: energy, industry, construction, transportation, and AFOLU (agriculture, forestry, and other land uses). The emissions of these gases from fossil fuels and land use have reached their highest levels since the nineteenth century. Consequently, urgent actions are required to address this issue worldwide to deal with specific challenges affecting air quality and weather conditions. For this purpose, the reduction of environmental pollutants requires finding methods, including extraction techniques using green solvents (DESs). Understanding the interactions between acid gases (H₂S/CO₂) and the eutectic solvent components (HBA/HBD) determines how much pollutant is absorbed by deep eutectic solvents (DESs). In this regard, to better comprehend the mechanism of H₂S gas absorption, we calculated the combined distribution functions (CDFs) involving the radial distribution functions (RDFs) and the angular distribution functions (ADFs). Additionally, we examined the hydrogen-bonding network, density profiles, spatial distribution functions (SDFs), and the nonbonded energies between H₂S and DES (choline chloride (ChCl)-glucose (Glu)/fructose (Fru) with a molar ratio of 2:1) components were calculated at 333 K. Furthermore, at the pressure between 1 and 15 atm, we obtained the solubility of H₂S/CO₂ gases, solubility selectivity, and diffusivity selectivity parameters as pressure functions to assess the efficacy of sugar-based DES in natural gas sweetening procedures. By analyzing how the interaction of H₂S molecules with the DES components, we concluded that the eutectic solvents based on glucose (Glu)/fructose (Fru) and choline chloride (ChCl) can absorb H₂S molecules.

Methods

The molecular graphics program VMD and the PACKMOL package have been used to prepare DES components and simulation boxes. First, initial configurations were minimized under the periodic boundary condition, and then the systems were heated to T = 333 K. Then, a 50 ns NPT simulation was performed at 333 K, while gradually decreasing the distance between the two boxes until reaching equilibrium. The conductor-like screening model (COSMO), as a novel method, has been utilized to predict some properties. The TURBOMOLE program package has been employed to determine the geometries of the electronic density of each HBA and HBD in targeted deep eutectic solvents (optimizing the geometry of DESs components with Becke–Perdew-86 (BP86) functional along with a triple zeta valence potential (TZVP) basis set).