CO2/N2 Separation on Highly Selective Carbon Nanofibers Investigated by Dynamic Gas Adsorption

doi: 10.1002/cssc.202200761

The vast emission of CO₂ as a greenhouse gas is the main cause for the anthropogenic climate change. However, efficient separation technologies appear capable to reduce CO₂ emissions by carbon capture and storage (CCS) or utilization (CCU). Currently, adsorption-based processes like pressure swing adsorption (PSA) are considered as promising and energy efficient approaches. A key component in these processes is the adsorbent material since its properties such as CO₂ selectivity, ad- and desorption kinetics, long-term stability and regeneration conditions influence the performance of the separation process significantly. To evaluate the separation capability of a material on a laboratory scale, dynamic gas adsorption is a powerful tool as it offers the possibility to measure mixed gas adsorption under relevant conditions and allows to deduct important parameters such as the aforementioned CO₂ selectivity from the resulting breakthrough curves.

In this work, Polyacrylonitrile (PAN) based carbon nanofibers (CNFs) are investigated for their CO₂ separation capabilities using dynamic gas adsorption. The CNFs are prepared by electrospinning and subsequent carbonization at various temperatures ranging from 600 °C to 1000 °C. A thorough investigation of the CO₂/N₂ selectivity resulted in measured values of 53 to 106 at 1 bar and 25 °C on CNFs carbonized at 600 °C, 700 °C or 800 °C. Moreover, the selectivity increased with lower measurement temperatures and lower CO₂ partial pressures reaching values up to 194. Further analysis revealed high long-term stability with no degradation over 300 cycles and fast adsorption kinetics for CNFs carbonized at 600 °C or 700 °C. These excellent properties make PAN-based CNFs carbonized at 600 °C or 700 °C promising candidates for the capture of CO₂.