(223b) Dynamic Behavior of Pressure Swing Adsorption Process for Nitrous Oxide Recovery from the Off-Gas of Adipic Acid Production

Most of the adipic acid is used to manufacture synthetic polymers such as nylon 6/6 and polyurethanes. The off-gas of adipic acid production mostly consists of N₂O, O₂, N₂, CO₂, and H₂O. A significant amount of N₂O (at a typical world scale plant: 13-26 MtCO₂e per year) is emitted from the process. Since the global warming potential of N₂O is about 330 times that of CO₂, N₂O is one of the representative non-CO₂ greenhouse gases. Therefore, it should be recovered from the off-gases for the mitigation of global climate change. The recovered N₂O can be widely applied to many industrial areas such as medicine, automotive, and food and beverage. In particular, high purity N₂O is a high value-added chemical used in chemical vapor deposition process in semiconductor production. Proper adsorbent selection is required for the design of adsorption separation process. In this study, we evaluate the performance of adsorbents and examine the adsorbents are applicable to the adsorption equilibrium separation and kinetic separation process. Adsorption isotherms of N₂O, O₂, and N₂ were measured on various carbon-based (activated carbon and carbon molecular sieve) and silica-based (zeolite and silica) adsorbents by a volumetric method. Adsorption amount, adsorption affinity and working capacity are compared among the adsorbents for equilibrium separation. Also, adsorption kinetics for each adsorbent is also evaluated by applying either the non-isothermal model or isothermal dual resistance model to experimental uptake curves. The parameters in each model considers the physical properties and adsorption characteristics of adsorbent-adsorbate systems. The validity of the equilibrium and kinetic results are confirmed by comparing the experimental breakthrough curves with the dynamic simulation results using the obtained values. Based on the breakthrough results, the simulations of the pressure swing adsorption process are conducted.