Stability of TEPA-biochar for CO2 capture under dry and wet conditions

“The cycle stability determines the service life of the adsorbent. Figure 9 shows the cycle experiments (adsorption temperature: 60 °C, desorption temperature: 100 °C) of CBC-50-TEPA in the dry and 10% H₂O (g) SFG. The experimental results show that the adsorption capacity of adsorbents decreased from the initial 2.82 to 0.86 mmol g⁻¹ after ten cycles in dry SFG. It was not easy to regenerate the adsorption of the product just by changing the temperature. Under dry conditions, amine-group adsorption of CO₂ generated extremely stable adsorption products of urea functional groups [43,45]. Whenever H₂O (g) was present, the adsorption capacity of the adsorbent decreased by only 0.08 mmol g⁻¹ from the initial 3.31 after ten cycles, which was almost unchanged. H₂O (g) caused the reaction products between amino groups and CO₂ to be transformed into carbamates [44,46]. It could be effectively regenerated by increasing the temperature, thus keeping the capacity of the adsorbent stable.” https://doi.org/10.3390/atmos13040579

“Figure 9. Ten cycles of adsorption capacity of CBC-50-TEPA in different SFGs.”

“Figure 10 shows the FTIR spectra of the fresh adsorbent and the adsorbent circulating in the 10% H₂O (g) SFG and dry SFG. A new absorption peak appeared at 1658 cm⁻¹ after circulating in 10% H₂O (g) SFG, which was the carbonyl peak in urea. Meanwhile, the N–H and C–H vibration peaks were located at 1570 cm⁻¹ and 1460 cm⁻¹, whose intensity weakened compared with the fresh adsorbent [47,48,49]. However, the adsorbent recycled in dry SFG had a lower peak at 1570 cm⁻¹; the C–H vibration peak at 1460 cm⁻¹ almost disappeared. The carbonyl vibration peak at 1658 cm⁻¹ was further strengthened. FTIR spectra show that in dry SFG, CBC-50-TEPA formed many urea groups after ten cycles.”

“Figure 10. FTIR spectra of the CBC-50-TEPA after 10 cycles in different SFGs.”