Adsorption of H2O and CO2 on supported amine sorbents

• Lewatit VP OC 1065 can adsorb 4 times more H2O than CO2.
• Co-adsorption of H2O could significantly affect the energy demand of the process.
• The sorbent will adsorb all H2O present in flue gas from a coal-fired power plant.
• The presence of amine groups causes the affinity towards the adsorption of H2O.
• Pre-conditioning of the flue gas is the best way to prevent co-adsorption of H2O.

In this work the adsorption of H2O and CO2 on Lewatit VP OC 1065 was studied in view of the potential application of this sorbent in post combustion CO2 capture. Both CO2 and H2O were found to adsorb on the amine active sites present on the pore surface of the sorbent material. However, where the interaction between CO2 and the amine groups is chemical, the adsorption behaviour of H2O on Lewatit VP OC 1065 shows the characteristics of physical multilayer adsorption. The difference in interaction is also clearly reflected in the differences in the adsorption heat (ΔHH2O=43 kJ mol−1, ΔHCO2 = 70–80 kJ mol−1) and the capacity. The highest H2O capacity observed was 12.5 mol kg−1 (at 95% RH). The highest CO2 capacity observed was 2.8 mol kg−1 (303 K, PCO2PCO2 = 81 kPa).Due to these high H2O capacities the sorbent material can adsorb practically all water that enters the adsorber column which increases the total energy demand of the sorbent based post-combustion capture process with 40%. To prevent the co-adsorption of large quantities of water several options were analyzed using the adsorption isotherms obtained for CO2 and H2O. Lowering the dew point of the flue gas upstream of the adsorber was identified as the most viable option.