Experimental and theoretical investigation of solubility of carbon dioxide in concentrated aqueous solution of 2-amino-2-methyl-1-propanol and piperazine

In this work, new experimental results for the (vapour + liquid) equilibrium (VLE) of CO2 in piperazine (PZ)-activated concentrated aqueous 2-amino-2-methyl-1-propanol (AMP) are presented for the temperature range of (303 to 328) K and PZ concentration range of (2 to 8) wt.%, keeping the total amine concentration in the solution at 40% and 50 wt.%. The partial pressures of CO2 are in the range of (0.2 to 1500) kPa. The electrolyte non-random two-liquid (ENRTL) theory has been used to develop the VLE model for the quaternary system (CO2 + AMP + PZ + H2O) to describe the equilibrium behaviour of the solution. The CO2 cyclic capacity of these solvents is determined between the rich and lean CO2 loadings. It is found that the CO2 cyclic capacity increases with the addition of PZ in aqueous AMP and also with the increase in AMP concentration in the aqueous solution. However, solid precipitation has been observed for 50 wt.% total amine concentration below T = 318 K for all relative compositions of AMP and PZ in the solvent at higher CO2 loading. The model results of equilibrium composition, pH of the loaded solution and amine volatility of the mixed solvent system, are also presented.

► New VLE data of CO2 in aqueous 40 wt.% and 50 wt.% (AMP + PZ), experimental and modelling.
► Solid precipitation observed in 50 wt.% (AMP + PZ) below 318 K and at high loading.
► CO2 cyclic capacity of concentrated (AMP + PZ) at low CO2 partial pressure range.
► Relation among CO2 cyclic capacity, total solution molality and partial pressure.
► Model predicted heat capacity, pH and amine volatility of (CO2 + AMP + PZ + H2O) system.