Novel Nonaqueous Liquid-Liquid Biphasic Solvent For Carbon Dioxide Capture With Low Corrosivity

Nowadays,global warming has become a major environmental problem in today’s society.And it was mainly caused by the excessive emission of carbon dioxide（CO₂）.Among them,carbon dioxide（CO₂）emissions by human,especially from the power plant,are the main sources of excessive emissions of CO₂.Therefore,in order to control the excessive emissions of CO₂,we should wake our focus on controlling the CO₂ emission from the power plant.Chemical absorption based on organic amine solution is currently the most advanced method for capturing CO ₂.However,the conventional aqueous amine-based process is limited in industrial applications because of its downside of a high energy penalty for solvent regeneration.The energy consumption of phase change absorption system is reduced due to the reduced volume of solution used for regenera tion.For the conventional aqueous amine-based process,the high regeneration energy consumption is due to the high sensible heat and vaporization heat of solvent water.Compared with water,organic solvents have lower specific heat capacity and enthalpy o f evaporation.Thus,nonaqueous solvents can greatly save energy consumption.Moreover,in the absence of water,amines could absorb CO₂ to generate noncorrosive products via specific reaction pathways.Therefore,this paper intends to construct novel nona queous liquid-liquid biphasic absorption system,which is expected to minimize the renewable energy consumption of the absorption system and noncorrosive CO₂capture.Three novel nonaqueous biphasic solvent s were proposed for CO₂ capture in this study.Including monoethanolamine（MEA）/2-amino-2-methyl-1–propanol（AMP）/dimethyl sulfoxide（DMSO）/pentamethyldiethylenetriamineamine（PMDETA）（M/A/D/P）,2-（（2-aminoethyl）-amino）ethanol（AEEA）/DMSO/PMDETA（A/D/P）,and 2-methyl-ethynolamine（MAE）/DMSO/PMDETA（M/D/P）.The CO₂ absorption performance,reaction mechanism,phase-changing mechanism,thermodynamics,and corrosivity were studied.The main contents and results of this paper are as follows:（1）The CO₂ loading of M/A/D/P,A/D/P,M/D/P were all much higher than benchmark MEA（0.55 mol/mol）,and they could respectively achieve high CO₂loading of 0.88mol/mol,1.75 mol/mol,and 0.84 mol/mol.For all,more than 90%of the absorbed CO₂ was enriched in the lower phase with only around 50%of the total volume.（2）¹³C NMR analysis and quantum chemical calculations showed:The three novel biphasic solvents（M/A/D/P,A/D/P,M/D/P）all could absorb CO₂ to form protonated amines,carbamates and carbamic acid species.Among them,the products with high polarity were dissolved in DMSO according to the similarity intermiscibility theory.What’s more,the products with less polarity(carbamic acid species and AMPH⁺formed by M/A/D/P after absorb CO_2,and carbamic acid species formed by A/D/P after absorb CO₂)also dissolved in DMSO due to the interaction of hydrogen bonds.（3）Thermodynamics analysis showed that this three biphasic solvent（M/A/D/P,A/D/P and M/D/P）could sharply cut down the heat duty during CO ₂desorption.Compared with the benchmark MEA(3.59 GJ·ton^-1 CO₂),could reduced the heat duty of this three biphasic solvent by 90%,60%and 46.3%,respectively.Moreover,nonaqueous biphasic solvents presented a noncorrosive behavior to steel after CO₂ saturation.In addition,in nonaqueous biphasic solvents,the hydrolysis of carbamate and the hydration reaction of CO₂were unable to occur in the absence.Therefore,the nonaqueous biphasic solvents were virtually noncorrosive to carbon steel.