pilot plant

carbon capture

techno-economic analysis

direct air capture

regeneration energy

Industrial & engineering chemistry research

We report a bench-scale direct air capture (DAC) process comprising CO&lt;sub&gt;2&lt;/sub&gt; 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-BBIGH&lt;sub&gt;2&lt;/sub&gt;)(CO&lt;sub&gt;3&lt;/sub&gt;)(H&lt;sub&gt;2&lt;/sub&gt;O)&lt;sub&gt;n&lt;/sub&gt; (n = 3–4). The CO&lt;sub&gt;2&lt;/sub&gt; 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 CO&lt;sub&gt;2&lt;/sub&gt; 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 CO&lt;sub&gt;2&lt;/sub&gt; and water release, and the sensible heat, is 360 kJ/mol (8.2 GJ/ton CO&lt;sub&gt;2&lt;/sub&gt;). Alternatively, the aqueous amino acids can be regenerated by boiling under reflux, with measured cyclic capacities of up to 0.64 mol/mol.

Direct Air Capture of CO2 with Aqueous Amino Acids and Solid Bis-iminoguanidines (BIGs)