Experiments On The Surface Tensions, Kinetics And Activation Mechanism Of CO₂Loaded MEA-MDEA Aqueous Solution

The surface tensions of CO2unloaded and CO2loaded monoethanolamine(MEA)-N-methyldiethanolamine (MDEA) aqueous solutions were measured byusing the BZY-1surface tension meter, which employs the Wilhemy plate principle.For CO2unloaded solutions, the temperatures ranged from293.15to333.15K, andthe mass fractions of MEA (wMEA) and MDEA (wMDEA) respectively ranged from0.05to0.20, and0.05to0.45. For CO2loaded solutions, the temperatures ranged from293.15to323.15K, and wMEA and wMDEA respectively ranged from0.05to0.10and0.30to0.45. The uncertainty of the surface tensions is±0.1mN m1. A modelwas proposed to correlate the surface tensions of both CO2loaded and CO2unloadedsolutions. For CO2unloaded MEA–MDEA solutions, with3adjustable parameters asinput, the average relative deviation (ARD) between experiments and calculations is1.63%. For CO2loaded MEA–MDEA solutions, with5adjustable parameters as input,ARD is1.76%. The temperature, mass fractions of amines and CO2loadingdependence of the surface tensions were demonstrated on the basis of experimentsand calculations. Our results showed that:(1) For both the unloaded and loaded MEA–MDEA aqueous solutions, theincrease of amine concentration and temperature tends to decrease the surfacetensions.(2) For unloaded MEA–MDEA aqueous solutions, at a given temperature,the decreasing surface tension is mainly due to increasing MDEA concentration, sinceMDEA has a lower surface tension than MEA at any given temperature.(3) For theCO2loaded MEA–MDEA aqueous solutions, the increase of CO2loading tends toincrease the surface tensions at given amine concentration.The solubility and absorption rate of CO2in MEA promoted MDEA aqueoussolution were measured at normal pressure with temperatures ranging from303.15-323.15K. The temperature and the mass fraction dependences of the solubilityof CO2and CO2loading were determined. The influence of the mass fraction of MEAon the absorption rate of CO2was illustrated.Our results showed that:(1) When the mass fraction is of very small value,MEA promotes the absorptionrate of CO2very significantly. Moreover,the absorption rate of CO2increases with theincrease of temperature;(2)The temperature and the mass fraction dependences of thesolubility of CO2can be approximately expressed by linear relationships. The solubility of CO2respectively increases and decreases with increasing mass fractionof MEA and temperature;（3）The temperature and the mass fraction dependences ofCO2loading can also be approximately expressed by linear relationships. However,CO2loading decreases with the increase of both mass fration of MEA andtemperature.