The greenhouse effect is one of the most destructive global climate change phenomena. The CO2 released into the atmosphere via the combustion of fossil fuels presents the largest portion of the total greenhouse gas emission. Therefore, in spite of technical challenges associated with it, “Direct Air Capture” (DAC), i.e. CO2 capture from ambient air, has been considered an option to mitigate CO2 emissions from the transportation sector. In addition, by turning the air-captured CO2 into liquid fuel via a solar thermochemical redox cycle 1, the carbon footprint of the conventional transportation fuels can be considerably lowered. To achieve these goals, we consider a DAC technology based on amine functionalized nanofibrillated cellulose (NFC) sorbent subjected to cyclic temperature-vacuum swing (TVS) adsorption/desorption. The simultaneous amine-based CO2 and H2O chemisorption from air offers two advantages for the coupling of DAC technology with solar thermochemical fuel production: (i) simultaneous adsorption of H2O from air, which is another feedstock for the solar thermochemical fuel production process, and (ii) the enhancement of CO2 adsorption with the presence of humidity. Substantial work on the characterization the adsorbent material and the TVS process have been performed2-6. However, the adsorption kinetics, which is the key to the design and modeling of the reactor and the process, has not been resolved yet. This work focuses on development of an experimental setup for determination of the co-adsorption kinetics of CO2 and H2O on the amine-functionalized NFC. The approach combines the concepts of a differential packed bed and a volumetric adsorption system. The use of a differential packed bed allows a simpler mathematical treatment of the experimental data and isothermal adsorption condition. The difficulty of quantifying the small sorbate concentration difference between the upstream and the downstream of the differential packed bed is compensated by placing it in a closed system, where a fixed volume of gas is constantly circulated through the packed bed. Subsequently, the adsorption kinetics is extracted from the transient sorbate concentration profile in the system. The characterization of the experimental setup will be presented along with the preliminary adsorption kinetics of the CO2-H2O co-adsorption on amine functionalized NFC.
1. Chueh WC, Falter C, Abbott M, et al. High-Flux Solar-Driven Thermochemical Dissociation of CO2 and H2O Using Nonstoichiometric Ceria. Science. December 24, 2010 2010;330(6012):1797-1801.
2. Gebald C, Wurzbacher JA, Borgschulte A, Zimmermann T, Steinfeld A. Single-Component and Binary CO2 and H2O Adsorption of Amine-Functionalized Cellulose. Environmental Science & Technology. 2014.
3. Gebald C, Wurzbacher JA, Tingaut P, Steinfeld A. Stability of Amine-Functionalized Cellulose during Temperature-Vacuum-Swing Cycling for CO2 Capture from Air. Environmental science & technology. 2013;47(17):10063-10070.
4. Gebald C, Wurzbacher JA, Tingaut P, Zimmermann T, Steinfeld A. Amine-based nanofibrillated cellulose as adsorbent for CO2 capture from air. Environmental science & technology. 2011;45(20):9101-9108.
5. Wurzbacher JA, Gebald C, Piatkowski N, Steinfeld A. Concurrent Separation of CO2 and H2O from Air by a Temperature-Vacuum Swing Adsorption/Desorption Cycle. Environmental science & technology. 2012;46(16):9191-9198.
6. Wurzbacher JA, Gebald C, Steinfeld A. Separation of CO2 from air by temperature-vacuum swing adsorption using diamine-functionalized silica gel. Energy & Environmental Science. 2011;4(9):3584-3592.