Study On The Performance And Mechanism Of CO₂ Capture By Nonaqueous Blended Amine-Based Solid-Liquid Phase-Change Absorbents

To combat global warming,it is imperative to reduce anthropogenic CO₂emissions,especially from fossil energy use.organic amine absorption is currently the most mature and commonly used CO₂ capture technology,but the regeneration of traditional organic amine absorbents is highly energy intensive.Solid-liquid phase change absorbents have become a hot research topic in recent years due to their significant energy saving potential.However,the existing solid-liquid phase change absorbents have high viscosity of solid phase products and difficult to control the phase change nodes,which easily lead to equipment blockage during the capture process.In order to break through the above dilemma,this study intends to construct a new anhydrous composite amine solid-liquid phase change absorbent with low solid phase product viscosity and controllable phase change nodes for CO₂ capture based on the modulator control strategy,and to investigate its CO₂ capture performance,phase change mechanism and control mechanism.The main research results are as follows:（1）In order to solve the problem of high viscosity of solid phase products,triethylenetetramine（TETA）/N-methylpyrrolidone（NMP）absorbent was introduced into 2-amino-2-methyl-1-propanol（AMP）as product viscosity control agent,and TETA/AMP/NMP absorption system was constructed.The results show that the viscosity of saturated absorption solution decreases from 141.2 m Pa·s to 11.8 m Pa·s after the introduction of AMP.The CO₂ load of TETA/AMP/NMP（TETA:AMP=2:8）is up to 0.94 mol·mol^-1,and the regeneration efficiency is 84.14%.After 5 cycles,the CO₂ load can still reach 0.60 mol·mol^-1.（2）Nuclear magnetic resonance carbon spectroscopy(¹³C NMR)results showed that the products of CO₂ absorption by TETA/AMP/NMP are carbamates and protonated amines,both of which are highly polar and can be precipitated and precipitated from the less polar solvent NMP.The AMP-regulated viscosity mechanism was investigated by quantum chemical simulation（QCS）.Before the addition of AMP,the TETA-derived carbamate and protonated amine products could form multiple hydrogen bonds and aggregate,and the solid-phase products were highly viscous.After the introduction of AMP,its derivatives bind to TETA products through strong electrostatic attraction and van der Waals forces,which inhibit the aggregation of TETA products and avoid gel formation,and then promote the generation of crystal powder products.（3）To address the problem that the phase change node is difficult to control,the AEEA/AMP/NMP absorption system was constructed by using hydroxyethyl ethylenediamine（AEEA）as an activator.the introduction of AEEA can effectively regulate the phase change node so that the solid phase product is generated near the absorption saturation.The results of performance investigation showed that the CO₂absorption load of AEEA/AMP/NMP could reach 0.64 mol·mol^-1 and the regeneration efficiency was 90.1%.After five absorption-desorption cycles,the absorption load of AEEA/AMP/NMP could still be maintained at 0.43 mol·mol^-1.Thermodynamic analysis showed that the total regeneration energy consumption of AEEA/AMP/NMP was 1.94 GJ·ton^-1,which was 48.9%lower compared with the aqueous MEA solution.（4）The mechanism of AEEA regulation of phase transition nodes was investigated by ¹³C NMR and QCS.The results showed that in the absence of AEEA,the reaction products were AMP carbamate（AMPCOO^-）and protonated AMP（AMPH⁺）,both of which were rapidly aggregated and precipitated by strong hydrogen bonding.After the addition of AEEA,the AEEA-derived product AEEAH⁺COO^-binds to AMPCOO^-and AMPH⁺by strong electrostatic attraction and van der Waals forces,which inhibits the formation of hydrogen bonds between AMPCOO^-and AMPH⁺under low CO₂loading and avoids the premature formation of the solid phase.When the absorbent is close to saturation,the overall hydrogen bonding number of the product increase,and the precipitation can only precipitate out.