Effect Of Interaction On CO₂ Absorption Kinetics Of Blended Amine Solution

The chemical absorption of CO₂ by amines is the most mature,industrialized and widely used,and it is also one of the most promising technologies in the field of CO₂ capture.However,this technology also has the disadvantage that a single amine solvent does not have all optimal properties.Therefore,researching and developing the ideal mixed amine solvent,studying the intrinsic reaction mechanism of the mixed amine,establishing the physicochemical property model of the mixed amine system are the research focus of the amine-base CCS technology.Although the interactions in blended amines have been noticed,their research is still quite limited.However,the existence of interaction does affect the performance of blended amines.The kinetics of CO₂ absorption into aqueous solutions of N,N-diethylethanolamine?DEEA?,and N,N-dimethylethanolamine?DMEA?,and their blends with monoethanolamine?MEA?have been studied in a stopped-flow apparatus,respectively.The kinetics experiments were carried out at the concentrations of DEEA and DMEA varying from 0.075 to 0.175kmol/m³ respectively,that of MEA ranging between 0.0075 and 0.0175 kmol/m³,and over the temperature range of 293K to 313K.Two kinetics models were proposed to interpret the reaction in the blended amine systems.And,the results showed that the model which incorporates the base-catalyzed hydration mechanism and termolecular mechanism presented a better prediction.The average relative deviations of the fitted DEAE/MEA and DMEA/MEA blended amine systems by using this Model were 6.45%and 9.19%,respectively.In order to further investigate the interaction between tertiary amines and primary amines in blended amines,the kinetics of CO₂ absorption into MEA monoamines,DEEA/MEA mixed amines,and DMEA/MEA blended amines under non-aqueous systems was studied using the stopped-flow apparatus.The concentration of MEA and tertiary amine is 0.2-0.4kmol/m³,and the temperature range is 293-313K.The experimental data is processed using a simplified trimolecular mechanism.In addition,by comparing the reaction kinetic constants of the two tertiary amines in the single amine system,the influence of the molecular structure of tertiary amines on the kinetics was studied and it was found that the longer the linked alkyl branches on the tertiary amine nitrogen atoms,the faster the reaction rate of tertiary amine with CO₂.By comparing the kinetic results of the two blended amine systems in aqueous and non-aqueous systems,it was found that tertiary amines can participate in the trimolecular reaction of primary amines,and that the protonated MEA can be reconverted to free MEA by tertiary amine,and make it easier for MEA to participate in its own trimolecular reactions,so that the overall reaction rate of the blended amine system is accelerated.We can conclude that there are interactions between tertiary amines and primary amines in the blended amine system and positively promote the kinetics.This article mainly studied the kinetics properties of the blended amine system and explored the influence of the interaction between primary and tertiary amines in blended amines on the kinetics.We have found the rules for the absorption of CO₂ by blended amines and we can more quickly and easily screen out the better mixed amine solvents by using the rules as a guide,in the future.