Molecular Modeling of the Physical Properties for Aqueous Amine Solution Containing a CO₂ Hydration Catalyst

The effects of an amphiphilic CO₂ hydration catalyst (C3P) on the physical properties of aqueous monoethanolamine (MEA) solutions were studied using molecular simulations and verified experimentally. Adding 2.7-27.7 g/L of C3P in 30 wt % MEA aqueous solution did not significantly affect the solution viscosity, surface tension, or CO₂ diffusivity. These results confirm that the previously reported increase in CO₂ mass transfer by C3P is due to CO₂ hydration catalysis and not due to changes in the physical properties of the MEA solution. Additional simulations indicate that the catalyst molecules tend to aggregate in MEA solution and are preferentially adsorbed at the gas-liquid interface region. For the catalyst molecules remaining in the bulk solution, the local concentrations of CO₂ and MEA in the area immediately around the catalyst are increased while the local water concentration is decreased, relative to their concentrations in the rest of the bulk MEA solution.