Kinetics Of Mass Transfer With Chemical Reaction Of CO₂ Capture Into Novel AEP/1-propanol/H₂O Biphasic Solvent

Global warming caused by CO₂ is one of the most emerging environmental issues.CO₂ capture technology is therefore proposed.In industry,chemical absorption is the most utilized CO₂ capture technology,and amine aqueous solution such as ethanolamine（MEA）is the main absorbent.Amine aqueous solution contains much water,therefore high energy is needed for solution heating during regeneration.The high regeneration energy largely limits the application of the technology.To reduce the regeneration energy,biphasic solvent for CO₂ capture has been gaining increasing attention these days.Biphasic solvent is homogeneous at first.After absorption,it can separate into two different phases,the rich phase and the lean phase.The rich phase contains over 95%of the CO₂ absorption products.Only the rich phase needs to be regenerated,therefore the amount of the heating solution is reduced and the regeneration energy is reduced.However,the biphasic solvents published still have the problem of limited desorption performance.The work proposes a novel biphasic solvent,1-（2,3 aminoethyl）piperazine（AEP）/1-propanol/H₂O solution,and investigates the absorption-desorption performance,regeneration energy,mechanism and kinetics.First of all,the absorption-desorption performance and regeneration energy of AEP/1-propanol/H₂O solution capturing CO₂ is investigated.Through absorption-desorption experiments,the absorption capacity is 1.26 mol CO₂·mol-1 amine,which is 2.3 times that of 30 wt%MEA/H₂O solution;the regeneration efficiency is 74%,and the cyclic capacity is 0.90 mol CO₂·mol-1 amine,which is 2.7 times that of 30 wt%MEA/H₂O solution.The results show that AEP/1-propanol/H₂O solution has great absorption-desorption performance.Through regeneration energy evaluation,the regeneration energy is 2.74 GJ·t-1-CO₂ and is 27.9%lower than that of 30 wt%MEA/H₂O solution,which indicates that AEP/1-propanol/H₂O solution can reduce the CO₂ capture cost.Then,the reaction mechanism of AEP/1-propanol/H₂O solution capturing CO₂ is investigated.The absorption products and desorption products are characterized via 13C NMR.During absorption,AEP acts as the main absorbent.The primary amino group and secondary amino group of AEP can react with CO₂ to produce carbamate,while the tertiary amino group reacts with CO₂ to produce carbonate.The CO₂ absorption products mainly concentrate in the rich phase,while the lean phase is 1-propanol aqueous solution.Desorption is a converse process of absorption.During desorption,most CO₂ absorption products are decomposed and only a little carbamate remains in the solution.Finally,the kinetics of AEP/1-propanol/H₂O solution capturing CO₂ is investigated.Based on two-film theory,the kinetics model is built and the kinetics parameters are obtained.The reaction rate constant can be fitted with Arrhenius equation:kmix=1.20×108exp（-3531/T）,R2=0.99,which can be used to predict the reaction rate constant.The enhancement factor is 4.6-73.8 during the absorption process,which indicates the reaction between CO₂ and AEP/1-propanol/H₂O solution is a fast pseudo first-order reaction.AEP/1-propanol/H₂O solution has great absorption-desorption performance and low regeneration energy,therefore being a potential energy-saving candidate for CO₂ capture.The mechanism and kinetics study provides theory basis for its further industrial application.