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Manuscript number SEPPUR_2019_686_R1Title Equilibrium and kinetics of nitrous oxide, oxygen and nitrogen adsorption on activated carbon and carbon molecular sieve Article type Full Length Article AbstractTo 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 nonisothermal 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.

The adsorption uptake curves of CO 2 , CO, N 2 and CH 4 on zeolite LiX and activated carbon were measured using a volumetric method at 293, 308 and 323 K and pressure up to 100 kPa. The experimental uptake curves were correlated with a non-isothermal kinetic model because the adsorption kinetics was controlled by heat generation and transfer, and an isothermal model showed large deviation from experimental uptake. The adsorption rates of the gases on zeolite LiX and activated carbon were affected by the isosteric heat of adsorption, heat transfer rate and adsorption affinity. At the same pressure and temperature, the sequence of effective diffusion time constants was CO 2 ( CO \ N 2 \ CH 4 for zeolite LiX and CO 2 ( CH 4 B N 2 \ CO for activated carbon. The adsorption rate of CO showed the largest difference between the two adsorbents. Effective diffusion time constants (D/R 2 ) for all cases were provided, which depended on pressure and temperature.Keywords Activated carbon Á Zeolite LiX Á Adsorption kinetics Á Heat of adsorption Á Non-isothermal model List of symbols a External surface area divided by the volume of the adsorbent (m -1 ) c p Concentration in the particle (mol kg -1 ) C s Heat capacity of the sample (J g -1 K -1 ) D/R 2 Effective diffusion time constant (s -1 ) D Diffusivity (m 2 s -1 ) D c /r c Micropore diffusion time constant (s -1 ) D p /R p Effective macropore diffusion time constant (s -1 ) hOverall heat transfer coefficient (J m -1 s -1 K -1 ) K Henry constant (-) P Pressure (kPa) Q Adsorbed amount (mol kg -1 ) Q st Isosteric heat of adsorption (kJ mol -1 ) R Ideal gas constant (J mol -1 K -1 ) R 2 Coefficient of determination (R 2 ) (-) T Time (s) T Temperature (K) V g Volume occupied by the gas (m 3 ) V s Volume occupied by the adsorbent (m 3 ) a Dimensionless parameter defined by nonisothermal model (-) bDimensionless parameter defined by nonisothermal model (-) q s Density of the adsorbent (g m -3 )

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