Evaluation of the effect of water on CO absorption in AMP and DMSO systems

Non-aqueous precipitating amine systems for carbon capture allows for CO desorption at lower temperatures than conventional aqueous amine systems and can potentially reduce the energy requirement for regeneration. In this work, the influence of water accumulation that may arise from humid gases entering the absorption column was investigated for absorption systems containing 2-amino-2-methyl-1-propanol (AMP) and dimethyl sulfoxide (DMSO). The physical solubility of CO decreased with increasing water concentration, as expected from the lower solubility of CO in water than in DMSO. The CO loading capacity was increased with the addition of water, resulting from formation of bicarbonate with water present in the system. Low lean loadings of 0.1 mol CO/mol AMP and precipitation was observed in 23 wt% AMP/DMSO with 9 wt% added water, suggesting that some water accumulation might be tolerable while still maintaining the desired properties of the absorption system. NMR was used to study the CO reaction products at 30–88 °C. The results suggested that 88 °C can be used for regeneration of the system even with water accumulated in the system. At 80 °C formation of the tentatively assigned species 4,4-dimethyl-1,3-oxazolidin-2-one was observed, indicating that thermal degradation of AMP may occur above this temperature.