Study on CO2 capture in humid flue gas using amine-modified ZIF-8

The CO2 adsorption performance of most adsorbents were inhibited by water vapor which is a ubiquitous component of flue gas. It is critical to find an adsorbent with long-term stability in the presence of water vapor. In this study, both theoretical and experimental study were carried out to investigate the CO2 capture capacity in humid flue gas of PEI impregnated ZIF-8. Grand canonical Monte Carlo (GCMC) simulation was performed to calculate the co-adsorption of CO2 and H2O on ZIF-8-PEI. The simulation result indicates that water vapor has no negative impact on CO2 adsorption of ZIF-8-PEI. Then, ZIF-8 with different PEI weight was synthesized and characterized. It is found that ZIF-8 with 30 wt.% PEI not only shows the highest CO2 uptake of 1.4 mmol/g in dry condition but also exhibits excellent CO2/N-2 separation performance. More important is that the adsorption capacity of ZIF-8-PEI30% was improved to 1.7 mmol/g when the adsorbents were imposed to humid flue gas with 50% relative humidity (RH). Moreover, it only shows a slight decrease after 50 adsorption/desorption cycles. Hence, water plays an excellent promoter role in CO2 capture of ZIF-8-PEI30%, and it is a promising adsorbent to be used in humid flue gas.