Theoretical and experimental analysis of CO₂ capture into 1,5-diamino-2--methyl-pentane/n-propanol non-aqueous absorbent regulated by ethylene glycol

The non-aqueous amine solvents for CO2 capture gaine an advantage in energy-saving potential, but with a sharp increase viscosity after saturated absorption would easily cause problems such as equipment scaling and pipe blockage. In the present work, the ethylene glycol (EG) was used as co-solvent and activator to regulate the nonaqueous absorbent of 1,5-diamino-2-methyl-pentane (DA2MP) and n-propanol (PrOH) for CO2 capture. The absorption loading of the mixture solution was 1.13 mol.mol(-1) when the mass concentration of DA2MP was 25 wt% and the volume ratio of PrOH to EG was 8:2. By activated by EG, the viscosity of the saturated solution was only 9.05 mPa.s, which changed from viscous precipitation to clarify liquid compared with that of DA2MP/PrOH. The absorbent maintained 90.30% of its initial CO2 absorption loading after 10th cycle regeneration under 393.15 K for 60 min. According to the quantum chemical calculations and experimental results, the reaction and regulation mechanism of CO2 capture into DA2MP/PrOH/EG was clarified. In DA2MP-PrOH solution, CO2 firstly reacted with DA2MP to form carbamate, and them the product further reacted with PrOH to form alkyl carbonates, which was viscous and insoluble due to the high intermolecular force between the CO2 products. After adding appropriate amount of EG, the solubility of insoluble products in solvent was increased through weakening the intermolecular interaction of products and enhancing the intermolecular interaction between products and solvents, which further converted them into soluble alkyl carbonate and realized viscosity reduction. The regeneration heat duty of DA2MP/PrOH/EG solution was estimated as 1.58 GJ.ton(-1) CO2, which was 29.5% and 58.42% less than that of DA2MP/PrOH and bench mark MEA solution, respectively, indicating a alternative candidate for CO2 capture.