In this study, a rate-based model of post-combustion CO2 capture was developed for an absorption column packed with Sulzer DX. A new amine solution, 4-diethylamino-2-butanol (DEAB), was applied to the absorber as an active CO2 capture solvent, and a sensitivity analysis on mass-transfer coefficients in liquid and gas phases ( and ), effective interfacial area (), and enhancement factor ( correlations was conducted to enhance the performance of the absorber. In the modeling, the absorber was divided into two sections—low capacity (less than 0.5 mol CO2/mol DEAB) and high capacity (more than 0.5 mol CO2/mol DEAB)—to improve model prediction accuracy, especially at high CO2 loading (). At of less than 0.5, the CO2 equilibrium molar concentration () was neglected, while at higher , the Deshmukh–Mather activity coefficient model was used to calculate . The solution procedure was validated against the axial experimental data of the CO2 mole fraction in the gas phase () and the liquid-phase temperature (). Then, a sensitivity analysis was performed for the profiles of , , H2O mole fraction in the gas phase (), , and gas-phase temperature () through various mass-transfer correlations for the Sulzer DX packing. The rate-based model with , and found that the correlation coefficient () and average absolute relative deviation () of data were 0.9889 and 3.12, and those of data were 0.9685 and 2.09. The sensitivity analysis of various correlations also revealed no significant difference between the calculated values using the different relationships. Finally, the effects of , , and liquid flow rate () as the most important parameters of the absorber on the value were investigated. The results indicated that has a significant impact on the values and consequently on the reaction rate.