Reaction Mechanism And Kinetics Study Of CO₂ Absorption Into [C₂OHmim][Lys]

The greenhouse effect is one of the most serious environmental problems currently.As the most significant anthropogenic greenhouse gas,CO₂ control and emission reduction has been urgent.In China,CO₂ emissions from power plant is more than 35%of total emissions.To develop an efficient absorbent for the capture of CO₂ from power plant is an important task for the control and reduction of CO₂ emissions.In recent years,ionic liquids are very attractive for capturing CO₂ in practice because of their negligible vapor pressure,high thermal stability,and easy assembly.In this work,a novel hydrophilic amino acid functionalized ionic liquid 1-hydroxyethel-3-methylimidazolium lysine?[C₂OHmim][Lys]?with high absorption capacity and high absorption rate was synthesized.The absorption performance,reaction mechanism and kinetics study of CO₂ absorption into neat[C₂OHmim][Lys]and the aqueous solution of[C₂OHmim][Lys]were investigated.The main conclusions of this dissertation are:?1?The absorption capacity of neat[C₂OHmim][Lys]and the aqueous solution of[C₂OHmim][Lys](1 mol·L^-1)is 1.684 mol CO₂/mol IL and 1.260 mol CO₂/mol IL.The regeneration performance of neat[C₂OHmim][Lys]is 66.27%.The regeneration performance of the aqueous solution of[C₂OHmim][Lys]was quite excellent.The first regeneration efficiency is 90.47%,and the regeneration efficiency was stable at more than 85%in the five absorption-desorption cycles.?2?The recation mechanism of CO₂ absorption into neat[C₂OHmim][Lys]was investigated by 13C NMR and FTIR.The reaction product was[CaOHmim+COO-----C₂OHmim+][1.5CO₂-Lys----Lys^-1.5CO₂],and the theoretical CO₂ absorption capacity of neat[C₂OHmim][Lys]was 2 mol CO₂/mol IL.The absorption rate was slowly because of formation of hydrogen bond.Besides,part of products were non-renewable,resulting in poor regeneration performance.?3?The reaction mechanism of CO₂ absorption into the aqueous solutions of[C₂OHmim][Lys]was investigated by 13C NMR.The aqueous solution of[C₂OHmim][Lys]reacted with CO₂ to form carbamate at low CO₂ loading,and the carbamate linked to the-COO-in lysine anion participated in the hydration reaction.Meanwhile,we also calculated the Mulliken atomic charge of N atom in the lysine anion using the DFT.The result showed the interaction between the N atom linked to the-COO-in lysine anion and CO₂ was weaker.The theoretical CO₂ absorption capacity of the aqueous solutions of[C₂OHmim][Lys]was 1.5 mol CO₂/mol IL.?4?The kinetics study of CO₂ absorption into the aqueous solutions of[C₂OHmim][Lys]was investigated by wetted wall column.The kinetics region the absorption was considered to be a fast pseudo^-1 order reaction.The liquid-film mass transfer coefficient decreased with a increase in CO₂ loading at each temperature.At low C02 loading,the liquid-film mass transfer coefficient increased with the tempera-ture increasing.At high CO₂ loading,the influence of temperature on the liquid-film mass transfer coefficient was not significant.The rate constants of[C₂OHmim][Lys]ere fitted as a function of temperature by the Arrhenius equation as:k2 = 1.177×108×exp?-3416.3/T?.The activation energy was 28.40 kJ·mol^-1.At low CO₂ loading,the can be predicted by a formula of temperature and CO₂ loading as follows:kov=1.491×10¹¹×exp?-3927.39/T?×exp?-5.554×?1-?/4??×?1-??^1.862...