The Study Of Kinetics,Equilibrium Solubility Of CO₂ Absorption Into N¹,N²-dimethylethane-1,2-diamine Solution

Recently,the extreme weather caused by greenhouse effect are drawi ng more and more researchers'attention.The main cause of the greenhouse effect is excess emissions of greenhouse gases?CO₂?.Industrial and coal-fired power plants emissions are the main sources of CO₂ increased in atmosphere.The reduction of CO₂emissions by CO₂ capture,utilization and storage?CCUS?technologies from Industrial and coal-fired power plants is considered as a promising method to mitigate global warming.Among all the CCUS technologies,chemical absorption using aqueous amine solutions exhibit to be more mature,cost effective,and high treatment capacity.Over the last few decades,plenty of conventional alkanolamines,including primary amines,secondary amines and tertiary amines have been investigated extensively for the post-combustion CO₂ capture process.As is generally known,each monoamine has advantages and limitations.The tertiary amine has a smaller reaction rate and lower regeneration energy requirement.Primary?or secondary?amines show a fast reaction rate but high regeneration energy requirement.To seek for better solvents for CO₂ absorption process,Chakravarty et al.turned to study blended amine systems firstly.A small amount of primary or secondary amine is added into the tertiary amine solution,so that it can combine the high rate of reaction of the primary or secondary amine with CO₂ and the low regeneration energy requirement of the tertiary amine.Some other researchers were attracted by diamnies,such as piperazine?PZ?,2-?2-aminoethylamino?ethanol?AEEA?and ethylenediamine?EDA?.The biggest advantage of diamine is the fast reaction rate.The reaction rate of PZ,AEEA and EDA is several times more than that of primary amine?such as monoethanolamine?MEA??.Therefore,it is conjecturable that diamines are be tter alternatives as a blended amine reaction rate accelerator compared to primary.N¹,N²-dimethylethane-1,2-diamine?DMEDA?is a new diamine that adds one methyl to each of the two nitrogen atoms of EDA.It was found that branching can increase the reaction rate of amine,so DMEDA theoretically has a faster reaction rate than EDA.However,DMEDA is barely mentioned in CO₂ absorption area.In an effort to screen better absorbents for CO₂ capture process,we here report the equilibrium solubility and kinetics of a new diamine N1,N2-dimethylethane-1,2-diamine?DMEDA?via equilibrium solubility measurement device and stopped-flow apparatus.The equilibrium solubility were measured at298.15-333.15 K,CO₂ partial pressures of 5-100 kPa,respectively,in 2M DMEDA solution.The results show that the CO₂ equilibrium solubility of DMEDA increased as the CO₂ partial pressure increased but decreased as the temperature increased.In addition,the NMR analysis further confirmed that the above mechanisms can be applied to the CO₂-DMEDA-H₂O system and the formation of dicarbamate.The heat of CO₂ absorption in 2 M DMEDA solution was estimated by using the Gibbs-Helmholtz equation,and the value?-56.47 kJ/mol?.The pseudo-first-order rate constant?k0?of CO₂ absorption into aqueous DMEDA solution was investigated at different amine concentration?0.025-0.075 mol/L?and temperature?293.15-313.15 K?.The results show that the k0 value in the DMEDA solution rise with the rising temperature and amine concentration.The results also show that the predicted CO₂ absorption rate exhibits good agreement with the experimental data with an absolute average deviation?AAD?of 3.77%and 4.51%with respect to the zwitterion and termolecular models,respectively.