Single-component and binary CO2 and H2O adsorption of amine-functionalized cellulose

Area of Science:

• Materials Science
• Chemical Engineering
• Environmental Science

Background:

• Direct air capture of carbon dioxide (CO2) is crucial for mitigating climate change.
• Nanofibrillated cellulose (NFC) offers a sustainable platform for developing novel adsorbents.
• Amine functionalization enhances the CO2 adsorption capacity of cellulosic materials.

Purpose of the Study:

• To investigate the adsorption behavior of CO2 and water vapor (H2O) on amine-functionalized NFC.
• To evaluate the performance of the adsorbent under conditions relevant to direct air capture.
• To determine the impact of H2O on CO2 adsorption and the energy requirements for regeneration.

Main Methods:

• Experimental adsorption isotherms for single-component CO2 and H2O.
• Fitting data to Toth and Guggenheim-Anderson-de Boer models.
• Calculation of adsorption enthalpies using the van't Hoff equation.
• Binary CO2/H2O adsorption experiments under simulated humid air conditions.

Main Results:

• Adsorption heats of -50 kJ/mol for CO2 and -48.8 kJ/mol for H2O were determined.
• H2O presence (2.55 kPa) enhanced CO2 adsorption, while CO2 presence (0.045 kPa) did not affect H2O adsorption.
• Increased H2O adsorption significantly raised the energy demand for CO2 desorption in a temperature-vacuum-swing process.

Conclusions:

• Amine-functionalized NFC is a viable adsorbent for CO2 capture.
• The adsorbent's hygroscopicity is a critical factor affecting the energy efficiency of direct air capture.
• Further material design is needed to minimize water co-adsorption and improve process economics.