Stability of Amine-Functionalized Cellulose during Temperature-Vacuum-Swing Cycling for CO2 Capture from Air

The stability of amine-functionalized nanofibrilated cellulose sorbent for direct air capture of CO2 is investigated during temperature-vacuum-swing (TVS) cycling. The presence of O2 at 90 °C degrades the sorbent, reducing its CO2 adsorption capacity by 30% after 15 h of treatment in moist air with a dew point of 22 °C. In contrast, exposure to moist CO2 at 90 °C with a dew point of 22 °C does not deteriorate its CO2 adsorption capacity after 15 h. Performing 100 TVS consecutive cycles, with CO2 adsorption from ambient air containing 400-530 ppm CO2 at 30 °C and 60% relative humidity and with CO2 desorption at 90 °C and 30 mbar, resulted in a reduction of the equilibrium CO2 adsorption capacity by maximum 5%. The average CO2 adsorption capacity during TVS cyclic operation is 0.90 mmol CO2/g.