Equilibrium and kinetics of nitrous oxide, oxygen and nitrogen adsorption on activated carbon and carbon molecular sieve

Abstract

To evaluate candidate adsorbents for the recovery of nitrous oxide (N2O) from adipic acid off-gases, the equilibrium and kinetics of N2O and O2 adsorption on activated carbon (AC) and of N2O, O2, and N2 adsorption on a carbon molecular sieve (CMS) were evaluated at 293, 308, and 323 K under pressures up to 1000 kPa using a high-pressure volumetric system. Adsorption amount of N2O on AC and CMS exceeded those of N2 and O2, and the adsorption isotherms for O2 and N2 were similar. The experimental N2O and O2 uptakes on AC and CMS were fitted to a non-isothermal adsorption model, whereas the model was ineffective for predicting N2 uptake on CMS. The isothermal dual-resistance model, considering surface barrier resistance and pore diffusion, adequately predicted N2 uptake on CMS. The rate of adsorption of N2O on AC was much lower than that of O2 and N2 whereas the rate of adsorption on CMS flowed the order: O2 > N2O ≫ N2, even though N2O has higher adsorption affinity and smaller kinetic diameter than O2. The Lewis structure of N2O was also found to influence the adsorption kinetics.