Measurement and thermodynamic modeling of partition coefficients in N,N-dimethylacetamide–water–carbon dioxide system

Abstract

The partition coefficients of N,N-dimethylacetamide (N,N-DMA) between the water and the super-critical and near-critical carbon dioxide (CO2) phases were measured in the temperature range of 298.15-328.15 K and the pressure range of 8.3-24.1 MPa. The measurements were carried out in a 56 ml vessel by contacting the carbon dioxide and the aqueous phases. The partition coefficients of N,N-DMA increased from 0.05 to 0.150 with increasing pressure at a constant temperature and increased with temperature at a constant density. The bubble point pressures of N,N-DMA-CO2 mixtures were measured at 298.15K. 308.15K and 318.15K and were found to increase with increasing mole fraction of CO2. The partition coefficients were modeled using the Peng-Robinson Equation of State (PREOS) combined with modified van der Waals mixing rule. The binary interaction parameters for the CO2-H2O pair were taken from the literature and were regressed for CO2-N,N-DMA and H2O-N,N-DMA pairs by fitting partition coefficients data. The binary interaction parameter for CO2-N,N-DMA pair was found to depend linearly on temperature. The bubble point pressures of N,N-DMA and CO2 were also measured and could be predicted fairly well using the regressed binary interaction parameters.