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

To evaluate candidate adsorbents for the recovery of nitrous oxide (N2O) from adipic acid off-gases, the equilibrium and kinetics of N2O and O-2 adsorption on activated carbon (AC) and of N2O, O-2, and N-2 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 N-2 and O-2, and the adsorption isotherms for O-2 and N-2 were similar. The experimental N2O and O-2 uptakes on AC and CMS were fitted to a non-isothermal adsorption model, whereas the model was ineffective for predicting N-2 uptake on CMS. The isothermal dual-resistance model, considering surface barrier resistance and pore diffusion, adequately predicted N-2 uptake on CMS. The rate of adsorption of N2O on AC was much lower than that of O-2 and N-2 whereas the rate of adsorption on CMS flowed the order: O-2 > N2O >> N-2, even though N2O has higher adsorption affinity and smaller kinetic diameter than O-2. The Lewis structure of N2O was also found to influence the adsorption kinetics.