Solubility of CO2 and H2S in carbonates solvent: Experiment and quantum chemistry calculation

Abstract

The presences of CO2 and H2S are major contamination in synthesis gas, natural gas or other industrial gases, which can lead to economic, environmental losses, corrosion of the equipments and other problems. Therefore, it will be important to remove these acid gases from the industrial gases stream. In this work, the constant-volume method was used to determine the solubility of CO2 and H2S in propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and diethyl succinate (DES) at 298.15–328.15K and the pressures up to about 1MPa. The quantum chemical calculations at DFT/B3LYP level of theory using 6−311+G(d,p) basis sets are taken to investigate the interaction mechanism between CO2/H2S and the carbonates from a molecular point of view. The results show that the CO2 or H2S absorption in these solvents is physical process and the solubility is in the same order: PC<DMC<DEC<DES while the ideal selectivity of H2S/CO2 for these carbanates generally is in the order: DEC<DMC<DES<PC. The quantum chemistry calculation result shows the higher the interaction energy between the solvent molecules and the acid gases molecules, the more CO2 or H2S dissolve in carbonates and the interaction energy is in the order: PC<DMC<DEC<DES which coordinated with the experimental results. As a result, the high solubility of CO2 and H2S in carbonates and the ideal selectivity of H2S/CO2 make this kind of solvents possible to be used in large-scale industrial applications in the future.