Assessing the Potential of Biochars Prepared by Steam-Assisted Slow Pyrolysis for CO(2) Adsorption and Separation

The potentialities in the use of biochars prepared by steam-assisted slow pyrolysis as adsorbents of gases of strategic interest (N(2), CO(2), and CH(4)) and their mixtures were explored. The biochars prepared from Populus nigra wood and cellulose fibers exhibited a narrow microporosity, with average pore sizes ranging between 0.55 and 0.6 nm. The micropore volume increased with the pyrolysis temperature, allowing CO(2) and CH(4) uptakes at room temperature between 1.5 and 2.5 mmol/g and between 0.1 and 0.5 mmol/g, respectively. These values are in line with those from the literature on biomass-derived carbon-based materials, exhibiting much higher porous features than those reported herein. As for the separation of CO(2)/N(2) and CO(2)/CH(4) gas mixtures, data showed that the prepared biochars exhibited good selectivities for CO(2) over both N(2) and CH(4): between ca. 34 and 119 for a CO(2)/N(2) mixture in typical post-combustion conditions (15:85, v/v) and between 14 and 34 for a CO(2)/CH(4) mixture typical of natural gas upgrading (30:70, v/v).