Introduction Worldwide efforts to control and limit the emission of CO2 are directly linked to the necessity of controlling the pollution of coal-fired power plants.1 The residual gaseous H2O in the flue gas will strongly influence the heat and mass transfer of the sorbents. Additionally, changes in the adsorption kinetics are expected by formation of a H2O film that partially or fully covers the surface of the adsorbents. Experimental In our work, we studied the impact of amine loadings on the CO2 adsorption mechanism and uptake capacity of the sorbents. The adsorption mechanism and diffusion in non‑hydrated sorbents was investigated by adsorption of CO2 monitored by IR spectroscopy. 13C MAS NMR was applied to differentiate between the adsorption mechanism of non- and fully‑hydrated adsorbents. The influence of H2O on the adsorption kinetics and thermodynamics was explored by performing breakthrough experiments with varying gaseous water contents of the flue gas. Results and Discussion The impact of H2O on the adsorption mechanism of CO2 with amine-impregnated SBA‑15 as well as the kinetics and thermodynamics have been systematically investigated. The water free adsorption mechanism proceeds predominantly via the carbamate mechanism, whereas additionally the formation of bicarbonates takes place for hydrated sorbents. Film diffusion limitations were not observed for the adsorption of CO2 even at higher amine loadings. The presence of gaseous water decreased the adsorption rate but enhanced the maximum uptake of the adsorbent bed. A water film is formed on the silica particles for gaseous water contents of more than 5 vol.% that limits the interaction of CO2 with the active amine sites and therefore the uptake kinetics are retarded. The higher uptake of CO2 is a result of a change in the adsorption mechanism that directly increases the amine efficiency, thus leading to a higher adsorption capacity. Conclusions Not only changes in mechanism have to be considered, also kinetic parameters have to be taken into account when the influence of water on CO2 capture via amine-functionalized solid adsorbents is discussed. Acknowledgement The work is financially supported by the BMBF iC4 project (01RC1106A), DFG (LE 1187/10) and Clariant. References (1) MacDowell, N.; Florin, N.; Buchard, A.; Hallett, J.; Galindo, A.; Jackson, G.; Adjiman, C. S.; Williams, C. K.; Shah, N.; Fennell, P. Energ Environ Sci 2010, 3, 1645.

Role of residual H2O on the adsorption mechanism and kinetics of solid amine-functionalized sorbents for CO2 capture

249th National Meeting (2015)

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