Experimental measurement and thermodynamic modeling of propylene and propane solubility in N-methyl pyrrolidone (NMP)

• Absorption kinetics and equilibrium data were gathered at different pressures and temperatures.
• Propylene is absorbed more than propane in NMP.
• The optimum binary interaction parameters of PR-EOS were calculated.
• Large values of kij regressed from the experimental data reduce the prediction error drastically.

In this study, the absorption performance of N-methyl pyrrolidone (NMP) was evaluated in propylene/propane separation. The kinetic and equilibrium data were obtained for pure gas absorption at different temperatures (276.1, 293.1, and 328.1 K) and various pressures (up to their dew points). It was shown that the selectivity for propylene/propane absorption at different conditions was less than 2.0, and it was nearly independent of pressure and temperature. The solubility was also calculated using 1-parameter and 2-parameter Peng–Robinson EOS by adjusting the binary interaction parameters kij and lij. The results demonstrated that relatively large values of kij (between 0.1 and 0.15 in 1-parameter model) regressed from the experimental data. It is predictable according to the dissimilar chemical structures of the solvent/solutes. It was also concluded that if the accurate values of kij have not been implemented in process simulators, the prediction of solubility data by using EOS could produce large errors of about 600% and 250% for propane/NMP and propylene/NMP, respectively. Furthermore, the presence of lij has a minor effect on the prediction of solubility data.