Adjusting the phase transition time node of a solid–liquid biphasic solvent based on 2-amino-2-methyl-1-propanol for efficient CO2 capture: Insight into the regulatory effect of aminoethylethanolamine

Solid-liquid biphasic solvents (SLBSs) hold promise as energy-efficient candidates for CO 2 capture. Nevertheless, the premature phase transition of current SLBSs leads to inopportune solid precipitation, posing operational challenges for the CO 2 capture system. This study proposed a promising strategy that using aminoethylethanolamine (AEEA) as a regulator to fine-tune the phase transition time node of the 2-amino-2-methyl-1-propanol (AMP)/N-methylpyrrolidone (NMP) SLBS, enabling the phase transition to occur precisely as desired. Experimental results showed that the AEEA/AMP/NMP (A/A/N) SLBS exhibited tunable phase transition time nodes, modulated by the concentration of AEEA. Specifically, with the addition of 0.2 mol·L −1 AEEA, the CO 2 loading associated with the phase transition increased significantly, from 0.19 to 0.54 mol·mol −1 , approaching the saturation loading of 0.57 mol·mol −1 . The delayed phase transition would facilitate the CO 2 absorption operation. The regulatory mechanism of AEEA on the phase transition were thoroughly studied via 13 C NMR and quantum calculations. AMP reacted with CO 2 to produce AMPCOO − and AMPH + , which had a significantly stronger affinity for each other than for the solvent NMP, mediated by strong hydrogen bond interactions. Consequently, the continuous and fast aggregation of AMPCOO − and AMPH + caused their swift precipitation from NMP. With the introduction of AEEA, the derived product AEEAH + (S) COO – (P) acted as a bridge-builder, connecting AMPCOO − or AMPH + and NMP via hydrogen bonds, increasing the solubility of the AMP-derived products in NMP, thus effectively delaying the phase transition. Thermodynamic analysis revealed that the A/A/N SLBS exhibited a total regeneration energy consumption of 1.94 GJ·ton −1 CO 2 , representing a significant reduction of 48.9 % compared to that of 30 wt% MEA. This study provided a novel idea for designing SLBSs with controllable phase transition behavior, and offered a promising A/A/N SLBS for energy-efficient CO 2 capture.