The Research on the Coordinative and Competitive Relationship between MEA and DEA Absorbing CO₂ into Aqueous Blended Amine Solution

In this work, ¹³C NMR spectroscopy was used to study the reaction process of the 2.0 M blended amine of MEA-DEA (1:1) with CO₂. The concentrations of free amines, the carbamates of amines, protonated amines, HCO₃^- and CO₃^2- in the solutions were generated over the CO₂ loading range from 0 to 0.7 mol CO₂/mol amine at the temperature of 301K in order to understand the specific process of the reaction between the blended amine and CO₂. The results show that only the carbamate of MEA was generated under lower CO₂ loading, which means that MEA is more competitive than DEA, while when the CO₂ loading, the carbamate of DEA (namely, DEACOO^-) was also generated, which means that when the CO₂ loading reached 0.231 mol CO₂/mol amine and the concentration of MEA was decreased a certain extent, the abilities of MEA and DEA to react with CO₂ were well-matched.