The Study Of CO₂ Absorption In Mixed Aqueous Solution Of MDEA And Amino Acid Ionic Liquid

Excessive emissions of carbon dioxide has caused serious negative impact in many aspects of society. The removal of carbon dioxide is directly related to industrial production, climate, human health and utility of energy sources, thus the research about decarbonization technology is particularly important and urgent. At present, the main absorbents for removing carbon dioxide in industry are alkanolamines solutions which have many disadvantages, for instance, MEA absorbs CO2 rapidly, but the corrosion is strong and energy consumption of regeneration is high; MDEA has a higher load of CO2 absorption, but the slower absorption rate. Ionic liquids (ILs) have some special properties. It can be used as a good environmentally friendly decarburization absorbent and amino acid ionic liquids have a higher CO2 absorption rate. To improve the properties of alkanolamines absorbent and develop new decarbonization absorbent, tetramethylammonium glycinate ([N1111][Gly]) was synthesized and mixed with N-methyldiethanolamine (MDEA) aqueous solutions to bring complex absorbents at three different concentrations:5%[N1111][Gly]+ 15%MDEA,10%[N1111][Gly]+15%MDEA and 15%[N1111][Gly]+15MDEA.First, the CO2 absorption capabilities of the three complex absorbents were measured with the Constant Volume Method. The Analysis and comparison indicated that the absorption capacity per volume increased with a rise in CO2 pressure and concentration of [N1111][Gly], while the mole absorptivity at absorption equilibrium was unrelated with concentration of [N1111][Gly] under different CO2 pressures.This work designed and built a set of countercurrent falling film column to investigate falling film absorption of pure CO2 and CO2-N2 gas mixture (20%CO2+80%N2). The result showed that the concentration of [N1111][Gly], flow characteristics of gas and absorbents all influenced the mass transfer coefficient. Taking all factors, the effect of these influence factors on mass transfer coefficient could be described as: Pure CO2:Sh= 5.637×10-11ReL1.225ReG0.695ScL2.085 The correlation predicts the experimental data with a mean deviation of 8.46% CO2-N2 gas mixture:Sh= 0.0247ReL0.495ReG0.371ScL0.065 The correlation predicts the experimental data with a mean deviation of 10.03%By comparison with 30%MDEA in falling film absorption experiment, it was found that [N1111][Gly] could greatly enhance the absorption of MDEA aqueous solution, confirming that amino acid ionic liquid had potential to improve MDEA absorbent.This article has also designed and synthesized a new type of Dicationic Ionic Liquid (DIL), Di-tetraalkylammonium amino acid ionic liquids which were analyzed by 1HNMR. C2(N114)2Gly2 was mixed with water to bring aqueous solutions at different concentrations for CO2 absorption. The results indicated that the absorption rate was based on the concentration and the viscosity.In the present, the results lay a certain foundation for further exploration and research of CO2 absorption by aqueous solution of MDEA and amino acid ionic liquid for industrial applications in the future.