Phase equilibria for the binary mixture of n-vinyl pyrrolidone and N,N-dimethylacrylamide in supercritical carbon dioxide

High pressure phase equilibria for the (carbon dioxide + n-vinyl pyrrolidone) and (carbon dioxide + N,N-dimethylacrylamide) systems are measured in a static apparatus at five temperatures of 313.2, 333.2, 353.2, 373.2 and 393.2 K and pressures up to 24.66 MPa. These two systems exhibit maximums in pressure at temperatures between the critical temperatures of carbon dioxide and n-vinyl pyrrolidone or N,N-dimethylacrylamide. The solubility of n-vinyl pyrrolidone and N,N-dimethylacrylamide for the carbon dioxide + n-vinyl pyrrolidone and carbon dioxide + N,N-dimethylacrylamide systems increases as the temperature increases at a fixed pressure. The carbon dioxide + n-vinyl pyrrolidone and carbon dioxide + N,N-dimethylacrylamide systems exhibit type-I phase behavior. The experimental results for the carbon dioxide + n-vinyl pyrrolidone and carbon dioxide + N,N-dimethylacrylamide systems are correlated with the Peng–Robinson equation of state using a mixing rule including binary interaction parameters ( k ij and η ij ).