Corrosion Behavior Of Carbon Steel And Corrosion Inhibition Of Inhibitor To Carbon Steel In Amino-Functionalized Ionic Liquids For CO₂ Capture

Carbon dioxide?CO₂?is regarded as the most important greenhouse gas,and its excessive emission from the combustion of fossil fuel is believed to be the main reason leading to the global warming.Carbon capture and storage?CCS?technology is regarded as an effective and promising method to minimize the release of CO₂ into the environment.Nowadays,the aqueous alkanolamine solutions has been widely applied in industry for CO₂ capture.However,there are some severe operational hitches of the application of organic amines.For example,amine degradation and evaporation,high energy consumption for regeneration,easy foaming and equipment corrosion,this will affect the long-term stable operation of the process.The equipment corrosion is one of the severe challenges in this regard.Corrosion has become an unavoidable problem in industrial applications,and it has become one of the key topics of scholars around the world.Amino-functionalized ionic liquids?AFILs?are one of the most promising methods for capturing CO₂ due to their negligible vapor pressure,high thermal stability and high absorption capacity.Nevertheless,there are few works concerning the equipment corrosion of AFILs solution for CO₂ capture.The exploration of this aspect is crucial for the promotion and application of AFILs absorbents.Therefor,in the present work,the corrosion behavior,corrosion mechanism and corrosion protection of five AFILs solutions(tetramethylammonium glycinate([N₁₁₁₁][Gly]),1-aminoethyl-3-methylimidazolium glycinate?[AEMIm][Gly]?,1-aminoethyl-3-methylimidazoliumlysinate?[AEMIm][Lys]?,diethylenetriaminelysinate?[DETAH][Lys]?,and triethylenetetramine lysinate?[TETAH][Lys]?)for CO₂ capture were studied.The corrosion behavior of 20#carbon steel in fresh AFILs and saturated AFILs-CO₂solution was studied by weight loss method and electrochemical method;The effects of different factors on corrosion behavior were investigated;The corrosion mechanism of 20#carbon steel in AFILs was discussed.In addition,based on the above experimental results,combined with quantum chemical calculations to theoretically guide and screen high-efficiency corrosion inhibitors to suppress corrosion reactions;The preferred corrosion inhibitors were conducted to corrosion inhibition experiments,which verified the theoretical results;Carbon steel corrosion inhibition behavior and microscopic mechanism was discussed,it provided effective corrosion protection methods for AFILs to capture CO₂ technology.The main results are as follows:?1?Weight loss method and electrochemical measurement showed that all fresh AFILs solution could be considered as non-corrosive;In saturated AFILs-CO₂solution,the corrosion rate of 20#carbon steel increased with the number of amino functional groups of AFILs;its corrosion behavior was controlled by charge transfer,and the reaction process was controlled by anode reaction;The effect of AFILs cationic structure for corrosion rate on carbon steel was more significant than that on anion structure.The effect of different factors on corrosion behavior indicated that with the increase of CO₂ loading,the corrosion rate of carbon steel increased,and the reaction process was controlled by anode reaction.Similarly,with the increase of reaction temperature,the corrosion rate increased sharply.?2?On the basis of experimental data and characterization(SEM/EDS,XRD,¹³C NMR)results,the corrosion mechanism of carbon steel in AFILs system was proposed.In the fresh AFILs solutions,there were no cathodic substances?HCO₃^-,H⁺?to promote the dissolution of iron.In the CO₂-saturated AFILs solutions,CO₂ was absorbedtoformHCO₃^-/CO₃^2-,carbamates.Themoreamountof amino-functionalized groups,the greater the absorption loading,resulting in the increase of HCO₃^-/CO₃^2-and carbamates,in which inducing the rapid dissolution of iron on carbon steel surface to promote corrosion.?3?On the results of the quantum chemical parameters??E,?,?,?,?N?and experiment comparing and excluding,MBI and Na₂MoO₄ were selected as efficient corrosion inhibitors,which corrosion inhibition performance on 20#carbon steel in0.5 M CO₂-saturated[TETAH][Lys]solution were investigated.Electrochemical measurements showed that MBI was a mixed corrosion inhibitor with a corrosion inhibition efficiency of 97.30%at a concentration of 0.15 g/L.Na₂MoO₄ was an anode-type corrosion inhibitor with a corrosion inhibition efficiency of 95.46%at a concentration of 0.5 g/L.The addition of MBI and Na₂MoO₄ corrosion inhibitors into0.5 M[TETAH][Lys]solution had little effect on the absorption and desorption performance of the absorbed system.?4?In the corrosion inhibition kinetics study,the absorption behavior of MBI and Na₂MoO₄ corrosion inhibitors on the surface of carbon steel in the system followed the Langmuir adsorption model,the adsorption mechanisms were between physical adsorption and chemisorption.By comparing the thermodynamic parameters and the apparent activation energy,in turn,compared the inhibition mechanism of MBI and Na₂MoO₄ in the system.Quantum chemical parameters of frontier molecular orbital electron density distribution and Mulliken atomic charges showed that the greatest contribution to the adsorption of MBI and Na₂MoO₄ was S15,Mo1,respectively.