A facile synthesized robust catalyst for efficient regeneration of biphasic solvent in CO2 capture: characterization, performance, and mechanism

Amine-based technology is promising for CO2 capture from the flue gas. However, it encounters high energy penalty and thus hampers its industrial application. Currently, the catalytic solvent regeneration is developing to lower down regeneration temperature, accelerate regeneration rate, and cut down energy consumption for monoethanolamine (MEA)-based process. However, the information on catalytic regeneration of biphasic solvent is seldom available. This work develops a facile synthesized robust catalyst, α-Fe2O3, to promote the biphasic solvent regeneration such as triethylenetetramine (TETA) and 2-(diethylamino) ethanol (DEEA) blend. Experimental results revealed that, with the aid of α-Fe2O3, the efficient regeneration of TETA-DEEA occurred at 94 °C, which is far below the conventional MEA-based process (110–120 °C). The corresponding CO2 stripping rate increased by 2.4 times compared with uncatalytic scenario. Furthermore, the relative energy consumption was furtherly decreased by 41.6%. Different from MEA regeneration, the biphasic solvent regeneration with α-Fe2O3 depended on the enhancement of water molecules proton donation rather than the abundant Brønsted acid and Lewis acid of the catalyst. Based on DFT calculation and 13C NMR spectra analysis, the water molecules on α-Fe2O3 surface and the protonated DEEA were parallel served as proton donors for carbamate decomposition. Consequently, a novel proton transfer mechanism was proposed for the biphasic solvent TETA-DEEA regeneration. The water molecules adsorbed on α-Fe2O3 surface generated oxyhydrogen groups and thus donate protons for the carbamate decomposition. This work proposes a novel proton transfer mechanism for solvent regeneration and advances its industrial application with a low energy penalty.