CO2 Capture by Liquid Solvents and their Regeneration by Thermal Decomposition of the Solid Carbonated Derivatives

The chemical capture of CO2 by either aqueous Na2CO3 and K2CO3 or nonaqueous solutions of the amines 2-amino-2-methyl-1-propanol (AMP) or piperazine (PZ) is described. The captured CO2 is stored as solid NaHCO3, KHCO3, and AMP or PZ carbamates. Solid NaHCO3 and KHCO3 are decomposed at 200 degrees C and 250 degrees C, respectively, to regenerate the carbonates for their reuse. In the experiments with AMP or PZ, the solid carbamates are decomposed at 80 degrees C-110 degrees C to regenerate the free amines. The absence of water in the desorption-regeneration step is intriguing and could have the potential of reducing one of the major disadvantages of aqueous absorbents, namely the energy cost of the regeneration step and amine degradation, yet preserving the efficiency of the absorption in the liquid phase.