TEPA调控AMP-DGDE水溶液相变吸收CO2性能及机理

相变吸收剂在降低CO₂捕集能耗方面具有较大优势，但现有吸收剂普遍存在再生性能差的问题。基于2-氨基-2-甲基-1-丙醇 (AMP) 的吸收剂再生性能优异，但通常难以发生相变。利用四乙烯五胺 (TEPA) 作为相变调控剂引入AMP-二乙二醇二甲醚 (DGDE) 水溶液，构建了具有良好再生性能的新型相变吸收剂AMP-DGDE-TEPA。在最佳配比下，AMP-DGDE-TEPA的吸收负荷可达0.88 mol∙mol⁻¹，其中97.6%的CO₂富集于溶液下层，下层体积仅占总体积51%。经7次吸收-解吸循环，吸收剂的吸收负荷仍能保持0.63 mol∙mol⁻¹，再生效率为71.6%。¹³C核磁共振结果表明，AMP与CO₂反应生成易于分解的碳酸氢盐，因而吸收剂具有良好的再生性能；而TEPA的引入可使系统中生成稳定的质子化TEPA和氨基甲酸盐。质子化TEPA和氨基甲酸盐具有高极性，可打破吸收剂原有的均相状态，促使吸收剂发生液-液相变。相比于DGDE，H₂O和极性反应产物之间具有更强的相互作用力，这些物质聚集形成CO₂富相，而DGDE则单独形成CO₂贫相。此外，AMP-DGDE-TEPA的再生显热和潜热仅为0.33和0.43 GJ∙t⁻¹ CO₂，具有良好的节能潜力。该研究结果可为高效低能耗碳捕集材料的制备提供参考。

Performance of phase change CO2 absorption in TEPA-regulated AMP-DGDE aqueous solution and its mechanism

Phase change absorbents have great advantages in reducing the energy consumption of CO2 capture, but the existing absorbers generally suffer disadvantages in regenerability. 2-Amino-2-methyl-1-propanol (AMP)-based absorbents have excellent regeneration performance but are generally difficult to undergo phase change. In this study, tetraethylenepentamine (TEPA) was introduced as a phase change regulator into AMP-diethylene glycol dimethyl ether (DGDE) aqueous solution, aiming to develop a new AMP-based phase change absorbent with good regeneration performance, namely, AMP-DGDE-TEPA. Under the optimal ratio, the absorption loading of AMP-DGDE-TEPA reached 0.88 mol∙mol-1, of which 97.6% of the absorbed CO2 was enriched in the lower phase with only 51% of the total volume. After 7 cycles of absorption-desorption, the absorption loading of AMP-DGDE-TEPA remained at 0.63 mol∙mol-1, and the corresponding regeneration efficiency was 71.6%. The species in the CO2-loaded A-D-T solution were identified by 13C nuclear magnetic resonance technique. AMP reacted with CO2 to produce bicarbonate species that was easy to decompose, ensuring the good regenerability of AMP-DGDE-TEPA. Meanwhile, with the introduction of TEPA, stable protonated TEPA and TEPA-carbamate formed in the AMP-DGDE-TEPA system. The results of quantum chemical calculations indicated that protonated TEPA and TEPA-carbamate were highly polar, which broke the original assimilation state of AMP-DGDE-TEPA and drove it to undergo phase change. Since H2O had strong affinity to polar reaction products, they gathered together to form the CO2-rich phase, while DGDE showed a relatively weak affinity to polar reaction products and was solely separated from the solution to form the CO2-lean phase. During desorption, the sensible and latent heat of AMP-DGDE-TEPA was calculated to be 0.33 and 0.43 GJ∙t-1 CO2, which indicated the good energy-saving potential of AMP-DGDE-TEPA.