Efficient desorption and energy-saving carbon capture using a nonaqueous primary alkanolamine-based biphasic absorbent

Abstract

The nonaqueous biphasic absorbent was a great choice to overcome the difficulties of high energy consumption and lower desorption efficiency in carbon dioxide (CO₂) regeneration processes of traditional chemical absorbents. In this work, a poly-ether solvent poly(oxymethylene) dimethyl ethers (PODE_3-5) was introduced as phase separation agent in the anhydrous solution of primary amine 2-(2-aminoethoxy) ethanol (DGA) and dimethyl sulfoxide (DMSO). The optimal DGA/PODE_3-5/DMSO biphasic absorbent could have a CO₂ capacity of 0.60 mol/mol, with 94.2 % of the charged CO₂ concentrated in the lower phase that representing only 48.1 % of the total liquid volume. And the DGA/PODE_3-5/DMSO biphasic absorbent had a high CO₂ desorption efficiency of up to 90 % in 30 min and a stable cycling capacity of 0.54 mol/mol. Further, the products and reaction mechanism of CO₂ absorption process were analyzed based on the results of ¹³C NMR. The phase separation was triggered by the polarity enhancement of products and the affinity difference to products between PODE_3-5 and DMSO. Particularly, the regeneration energy requirement of the DGA/PODE_3-5/DMSO biphasic absorbent was 1.90 GJ ton^-1 CO₂, which is 51.1 % less than 30 wt% MEA-H₂O solution.