- By:
- Custelcean, Radu ; Williams, Neil J; Garrabrant, Kathleen A; Agullo, Pierrick ; Brethome, Flavien M; Martin, Halie J; Kidder, Michelle K
- Journal Name:
- Industrial & Engineering Chemistry Research
- Page Number:
- 23338-23346
- Volume:
- 58
- Issue Number:
- 51
- Publication Date:
- December 27, 2023
- View DOI Listing:
- https://doi.org/10.1021/acs.iecr.9b04800
Abstract
We report a bench-scale direct air capture (DAC) process comprising CO2 absorption with aqueous amino acid salts (i.e., potassium glycinate, potassium sarcosinate), followed by room-temperature regeneration of the amino acids by reaction with solid meta-benzene-bis(iminoguanidine) (m-BBIG), resulting in crystallization of the hydrated m-BBIG carbonate salt, (m-BBIGH2)(CO3)(H2O)n (n = 3–4). The CO2 is subsequently released by mild heating (60–120 °C) of the carbonate crystals, which regenerates the m-BBIG solid quantitatively. This low-temperature crystallization-based DAC process circumvents the need to heat the aqueous amino acid sorbents, thereby minimizing their loss through thermal and oxidative degradation. The CO2 cyclic capacity for the sarcosine/m-BBIG system, measured over three consecutive absorption/regeneration cycles, is in the range of 0.12–0.20 mol/mol. The regeneration energy of m-BBIG, comprising the enthalpy of CO2 and water release, and the sensible heat, is 360 kJ/mol (8.2 GJ/ton CO2). Alternatively, the aqueous amino acids can be regenerated by boiling under reflux, with measured cyclic capacities of up to 0.64 mol/mol.
