Sustainable biomass-based carbon adsorbents for post-combustion CO2 capture

• Sustainable carbon adsorbents optimised to develop narrow micropores for CO2 capture at post-combustion conditions.
• CO2 adsorption capacities at low pressures among the highest reported for carbon materials.
• Multicomponent experiments demonstrated the adsorbents capability of separating CO2 (14%) and N2 (balance).

Sustainable carbon adsorbents have been produced from biomass residues by single-step activation with CO2. The activation conditions were optimised to develop narrow micropores in order to maximise the CO2 adsorption capacity of the carbons under post-combustion conditions. The equilibrium of adsorption of pure CO2 and N2 was measured between 0 °C and 50 °C up to 120 kPa for the outstanding carbons. The CO2 adsorption capacity measured at low pressures is among the highest ever reported for carbon materials (0.6–1.1 mmol g−1 at 15 kPa and 25–50 °C), and the average isosteric heat of adsorption is typical of a physisorption process: 27 kJ mol−1. Dynamic experiments carried out in a fixed-bed adsorption unit showed fast adsorption and desorption kinetics and a high CO2-over-N2 selectivity. These adsorbents are able to separate a mixture with 14% CO2 (balance N2) at 50 °C, conditions that can be considered as representative of post-combustion conditions, and they can be easily regenerated.