CO₂ Capture By Amine Modified Type Ⅲ Porous Liquids:Absorption/Desorption Performance And Mechanism

"Carbon peaking"and"carbon neutrality"are solemn commitments made by China to address global climate change,reflecting Chinese responsibility as the world’s largest developing country.From the perspective of the source of global CO₂ emissions,the flue gas of coal-fired power plants is the most significant component of the complete source of carbon emissions,emitting about 32 billion tons per year.An important method to achieve CO₂ emission reduction in coal-fired power plants is CCS（carbon capture and storage）technology.However,limited by the energy consumption of absorbent regeneration,the overall capture cost of CCS is relatively high.The current research focuses on screening out a type of absorbent with good CO₂ absorption performance and low regeneration energy so that the CO₂ capture process of power plant flue gas using the absorbent with both energy saving and emission reduction.As a new CO₂ capture material,Porous liquids have significant advantages in capturing and separating CO₂.Herein,we report a new class of Type 3 porous liquids with good absorption performance and low regeneration energy consumption based on rational coupling of MEA-modified PSNs as porous hosts with a bulky 2-[2-（dimethyl amino）ethoxy]ethanol（DMEE）as the fluid media.The synthetic route of type III porous liquid absorbent and its absorption/regeneration performance under various parameters were studied.The results of the study are as follows:（1）PSNs can be successfully synthesized and modified by the sol-gel and impregnation methods.After removing the template,the hosts showed a regular shape and uniform particle size,with an average particle size of about 300 nm.Comparison of the average pore size fore and aft impregnated amine,the effect showed that the pore size was slightly reduced for the PSNs.And the impregnating functional groups and impregnating ratio were consistent with the sample used in the experiment.The adsorption performance of the MEA modified PSNs was further tested by TGA,which found its amine group utilization was only 0.063 mol CO₂/mol MEA.PSNs had a slight advantage as adsorbents directly.（2）External operating parameters and the composition of PLs are essential factors that affected the absorbent’s CO₂ performance.The optimal ratio of the absorbent in the experiment under simulated flue gas conditions was 50%MEA-PSNs（10%）/DMEE,the corresponding saturated absorption amount was 0.826 mmol/g,and the utilization rate of amine groups was 1.06 mol CO₂/mol MEA.After that,the influence of the operating parameters of the absorbent on the absorption performance was studied.It was found that the average absorption rate and the saturated absorption amount of the absorbent were proportional to the total flow rate of inlet gas and the fraction of CO₂,inversely proportional to the absorption reaction temperature.Finally,the changes of functional groups on the hosts before and after the reaction were compared using FTIR.It was found that DMEE not only played the role of dispersing the main unit when used as a site-blocking solvent but also participated in the deprotonation process of the loaded amine group when reacting with CO₂ as a reactant,which improved the overall absorption amount of the absorbent.（3）The operating parameters can significantly affect the desorption performance and regeneration energy of the loaded CO₂ absorbents.The regeneration characteristics of the absorbent under various purge gas flow and regeneration temperatures were investigated experimentally,and it was found that the desorption rate of the absorbent was proportional to the purge gas flow rate and the regeneration temperature.The regeneration energy is proportional to the desorption temperature while inversely proportional to the purge gas flow rate.From the perspective of the composition of absorbent regeneration energy,its sensible heat>solvent evaporation heat>reaction heat.When the rich CO₂ absorbent was regenerated at 80°C and 200 m L/min,the regeneration energy was 4.0 GJ/t CO₂,significantly smaller than the regeneration energy of commercial absorbent MEA（9.54 GJ/t CO₂）.Proving the absorbent is energy saving.