Energy-Efficient CO2 Capture from Flue Gas by Absorption with Amino Acids and Crystallization with a Bis-Iminoguanidine

We report a hybrid solvent/solid-state approach to CO2 separation from flue gas, consisting of absorption with aqueous glycine or sarcosine amino acids, followed by crystallization of the bicarbonate salt of glyoxal-bis(iminoguanidine) (GBIG), and subsequent solid-state CO2 release from the bicarbonate crystals. In this process, the GBIG bicarbonate crystallization regenerates the amino acid sorbent at ambient temperature, and the CO2 is subsequently released by mild heating (120 degrees C) of the GBIG bicarbonate crystals, which results in quantitative regeneration of GBIG. The cyclic capacities measured from multiple absorption-regeneration cycles are in the range of 0.2-0.3 mol CO2/mol amino acid. The regeneration energy of this hybrid solvent/solid-state approach is 24% and 40% lower than the regeneration energy of benchmark industrial sorbents monoethanolamine and sodium glycinate, respectively. Finally, as the amino acid sorbent is never heated in the hybrid process, its loss through evaporation or degradation is minimized.