High yield and high packing density porous carbon for unprecedented CO2 capture from the first attempt at activation of air-carbonized biomass

The first attempt at activation of air-carbonized carbon reveals unusual resistance to activation and unprecedentedly high yields (32–80 wt%) of high packing density (0.7–1.14 g cm−3) microporous carbon dominated by 5.5–7 Å pores, which are just right for CO2 uptake (up to 5.0 mmol g−1) at 1 bar and 25 °C. The high gravimetric uptake and packing density offer exceptional volumetric storage, and unprecedented performance for low pressure swing adsorption (PSA) with working capacity of 6–9 mmol g−1 for a pure CO2 stream (6 to 1 bar) and 3–4 mmol g−1 for flue gas (1.2 to 0.2 bar). The working capacity for vacuum swing adsorption (VSA) is attractive at 5.0–5.4 mmol g−1 under pure CO2 (1.5 to 0.05 bar), and 1.8–2.2 mmol g−1 for flue gas (0.3 to 0.01 bar). The pure CO2 volumetric working capacity breaks new ground at 246–309 g l−1 (PSA) and 179–233 g l−1 (VSA). For flue gas conditions, the working capacity is 120 to 160 g l−1 (PSA). The performance of the activated air-carbonized carbons is higher than the best carbons and benchmark zeolites or MOFs

A simple flash carbonization route for conversion of biomass to porous carbons with high CO2 storage capacity

This work offers a new, and simpler, method for the carbonisation of biomass that involves flash carbonisation of biomass at relatively low temperature (< 400 o C). We successfully converted the biomass precursor (eucalyptus sawdust) to carbonaceous matter via flash heating for a short period of time (5 –10 minutes) under a flow of air. On activation, the flash carbonized carbon offers high yields of activated carbons with higher microporosity compared to sawdust derived activated carbons prepared via hydrothermal carbonization or conventional pyrolysis. Depending on the level of activation, the flash carbonized sawdust-derived activated carbons retain some ‘woody’ morphology preserved from the sawdust. The porosity of the carbons can be tailored towards being predominantly microporous, which generates adsorbents that exhibit very attractive CO2 uptake (up to 5.0 mmol g-1) at 1 bar and 25 o C. Moreover, depending on the level of activation, it is possible to tailor the porosity of the carbons such that they simultaneously exhibit high post combustion (< 1 bar) and pre-combustion (20 bar) CO2 capture capability. The carbons exhibit exceptional performance for low pressure swing adsorption (PSA) with working capacity of up to 8.3 mmol g-1 for a pure CO2 stream (6 to 1 bar) and up to 5.6 mmol g-1 for flue gas (1.2 to 0.2 bar), while the working capacity for vacuum swing adsorption (VSA) reaches 5.3 mmol g-1 under pure CO2 (1.5 to 0.05 bar), and 2.1 mmol g-1 for flue gas (0.3 to 0.01 bar) conditions