Regulatory mechanism of a novel non-aqueous absorbent for CO2 capture using 2-amino-2-methyl-1-propanol: Low viscosity and energy efficient

The large-scale deployment of non-aqueous amine solution for carbon dioxide (CO2) capture is mainly limited by its high viscosity, even insoluble substances in saturated solution, which may result in equipment fouling and pipeline blockage. To avoid this problem, the polyamine 1,5-diamino-2-methyl-pentane (DA2MP) was screened as the main absorbent to ensure the high absorption load. While 2-amino-2-methyl-1-propanol (AMP) was used as the regulator to reduce the viscosity and eliminate insoluble substances, which dissolved in n-propanol (PrOH) to from the novel non-aqueous absorbent for CO2 capture. The CO2 absorption load of the novel absorbent was 0.95 mol·mol−1, and the viscosity of saturated solution was only 15.00 mPa·s, remarkably lower than that of the solution without AMP regulation. The solution maintained 97% of its initial CO2 absorption capacity after fourth regeneration cycle. The regulation mechanism was investigated using 13C nuclear magnetic resonance (NMR) and quantum chemical calculations. It was proved that a strong and dense hydrogen bond network between DA2MP-carbamates was formed due to the self-deprotonation process, leading to insoluble products in the saturated DA2MP/PrOH solution. Through AMP regulation, there was another type of DA2MP-carbamates deprotonated by AMP formed in the solution with less hydrogen bond network, which could further react with PrOH to produce alkyl carbonates, achieving the elimination of insoluble products and reducing viscosity. Overall, the total regeneration energy consumption was 1.86 GJ·ton−1 CO2, only 50.27% of that of the benchmark monoethanolamine (MEA)-based solution, which would be a promising candidate for CO2 capture.