Hydroxylation and N-doping synergistically enhance the CO2 adsorption and regeneration of amine-loaded mesoporous carbon in flue gas

Amine-loaded mesoporous carbon is a promising adsorbent for capturing low-concentration CO2 from flue gas. Currently, many amine-loaded mesoporous carbons have been used for CO2 adsorption in flue gas. However, due to the lack of systematic study on the factors affecting the regeneration performance of amine-loaded mesoporous carbon, the cycle performance is poor. In this study, a series of different amine-loaded mesoporous carbons were prepared by the wet impregnation method. Among them, the hydroxylated and N-doped mesoporous carbon loaded with 50 % TEPA had a high adsorption capacity of 2.73 mmol/g at 85 degrees C and 15 % CO2, which is 17 times higher than the pure mesoporous carbon under the same conditions and higher than most of the studies published so far. This material also showed excellent cyclic performance, with only a 4.9 % loss in adsorption capacity after 50 cycles. Mechanistic studies have found that the performance improvement is partly due to the defects and hydroxyl groups generated by pre-oxidation acting as proton acceptors for the adsorption between CO2 and amine, enhancing the adsorption performance. On the other hand, the synergistic effect of hydroxyl groups and N-doping significantly enhances the binding stability between mesoporous carbon and amine. Moreover, the optimal adsorption temperature was found to be 85 degrees C, which falls within the temperature range of coal-fired flue gas. The material also exhibited extremely high CO2/N2 selectivity, and its adsorption capacity further increased in the presence of water. This indicates that the material is perfectly suitable for capturing CO2 from flue gas.