No abstract

The new experimental vapor−liquid equilibrium data for CO 2 solubility into two different combinations of alkanolamine + amino acid, alkanolamine + chemical additive, and one aqueous alkanolamine were attained at 328.15, 343.15, and 363.15 K and in the CO 2 partial pressure range from 40 to 3800 kPa. The measurements are performed for the mixture of diisopropylamine (DIPA) + L-lysine with the compositions of (37.5−2.19) wt %, (35.0−4.38) wt %, and (30−8.77) wt %, and a blend of DIPA + piperazine (PZ) + L-lysine with the compositions (30.0−7.5−2.19) wt % and (30.0−5−4.38) wt %. Besides, the CO 2 partial pressure against its loading was acquired for the aqueous systems of DIPA + PZ (30.0−10.0) wt % and DIPA (40.0) wt %. The results illustrate that the CO 2 loading in the solvents was enlarged with declining temperature and increasing pressure. For the system of DIPA (40.0) wt %, it was deduced that CO 2 solubility improves by substituting the 10 wt % of DIPA with PZ. In other comparisons, we found that, at a constant weight percentage of L-lysine and water and total alkanolamines, the degree of selectivity toward CO 2 solubility is as follows: DIPA + PZ + L-lysine + H 2 O > DIPA + L-lysine + H 2 O. Accordingly, the ability of PZ to remove CO 2 is more than DIPA. Besides, a quadratic equation is employed to correlate the CO 2 partial pressure versus its loading so that the calculated values reveal a great agreement with the experimental data. Lastly, the Clausius−Clapeyron equation is applied to compute and compare the enthalpy of CO 2 absorption for the current systems. We found that, among the utilized solvents, the aqueous systems of DIPA + L-lysine + water (30−10−60) wt % and DIPA+ water (40.0-60.0) wt % have the maximum and minimum heats of absorption, respectively.

The sets of vapor–liquid equilibrium (VLE) data for CO2 solubility in a combination of (N-methyldiethanolamine (MDEA) + 2-(2-aminoethylamino) ethanol (AEEA)) and (diethanolamine (DEA) + AEEA) as a chemical solvent blended with sulfolane as a physical solvent are acquired at 313.15–343.15 K within the CO2 partial pressure range up to 5600 kPa. The measurements are fulfilled for two different hybrid solvents of MDEA + AEEA + sulfolane with the weight compositions of (20–10–10) wt % and (20–10–20) wt % and a mixed solvent of DEA + AEEA + sulfolane with (20–10–10) wt %. It is deduced that CO2 loading was enhanced by substituting the MDEA with DEA, diminishing the temperature, and raising the pressure. Besides, increasing the sulfolane concentration in the aqueous system of MDEA + AEEA + sulfolane leads to enrichment in the effectiveness of the solution in CO2 absorption in the high loading region. In contrast, at low pressures, it adversely affects the acid gas loading. Moreover, it was displayed that at the same total mole of alkanolamines and sulfolane, the CO2 solubilities of AEEA + sulfolane and AEEA + MDEA + sulfolane are higher than those of AEEA + MDEA + sulfolane and MDEA + sulfolane, respectively. Therefore, it could be claimed that AEEA presents a better performance in CO2 capturing than MDEA. Besides, it was demonstrated that AEEA + sulfolane represents a higher capability in CO2 elimination than DEA + AEEA + sulfolane. Thus, the ability of DEA to remove CO2 is lesser than AEEA. Altogether, the degree of alkanolamines’ selectivity toward CO2 is found as AEEA > MDEA > DEA.