Vapor–Liquid Equilibria and Density of CO2-Loaded Aqueous Methyldiethanolamine + Piperazine + Sulfolane Solutions

Abstract

CO₂-loaded and unloaded densities of N-methyldiethanolamine (MDEA) + piperazine (PZ) + tetramethylene sulfone (SFL) aqueous mixtures were measured concurrently with CO₂ solubility from 303.15 to 363.15 at 20 K steps and pressures of about 1200 kPa using a developed, sophisticated isochoric pressure drop method. Moreover, the CO₂ solubility was measured at 313.15, 328.15, and 343.15 K using a conventional isochoric saturation system to check the reliability and consistency of the solubility data from low pressure to 3000 kPa. Increasing the PZ concentration improved the MDEA absorption capacity in aqueous and mixed aqueous sulfolane solutions in the low-loading region. Furthermore, solution densities decreased by increasing the temperature at all loadings while increasing by increasing the CO₂ loading at each isotherm. CO₂-loaded and unloaded/fresh solution densities were correlated using a modified Setchenow equation. The average percent relative deviation (AARD %) of correlated densities from the experimental data was 0.21%, indicating the completely good correlative accuracy of the Setchenow model. Furthermore, a combination of the Deshmakh–Mather (DM) activity coefficient model and Peng–Robinson (PR) equation of state for electrolytic liquid and vapor phases, respectively, was used to correlate the vapor–liquid equilibrium data for the CO₂ + H₂O + MDEA + PZ + SFL system. The DM–PR model showed a good correlative accuracy with AARD % = 10.2 and was used to assess the accuracy and reliability of reported data for aqueous MDEA/PZ/SFL solutions.