Designing cellulose based biochars for CO2 separation using molecular simulations

This study investigates the pyrolysis mechanism of cellulose using reactive molecular dynamics simulations to prepare biochars for CO₂ separation applications. Six biochars with densities ranging from 0.160 to 0.987 g/cm³ were prepared, and their performance in adsorbing CO₂, CH₄, and N₂ gases, as well as CO₂/CH₄ and CO₂/N₂ gas mixtures, was evaluated using Grand Canonical Monte Carlo (GCMC) simulations. The adsorption isotherms were fitted to the Dual-Site Langmuir (DSL) equation, and subsequently, the isosteric heat of adsorption, Gibbs free energy, and entropy changes were calculated. It was found that the results indicated that the density of biochar had a strong impact on gabs adsorption. CO₂ had much better interactions with biochars than CH₄ and N₂. The 0.351 g/cm³-density biochar presented the highest selectivity for CO₂. The effect of water vapor was also covered which remarkably decreased the adsorption of CO₂ by the competition of active sites for adsorption. These results indicate that optimized cellulose-derived biochars could be a promising material for CO₂ separation in sustainable gas purification technologies.