High-purity nitrogen production from air by pressure swing adsorption combined with SrFeO₃ redox chemical looping

The combination of pressure swing adsorption (PSA) with a downstream redox chemical looping cycle to remove trace oxygen is proposed for the production of high-purity nitrogen from atmospheric air. The non-stoichiometric perovskite SrFeO_3−δ is selected for the redox chemical looping cycle because of its favourable thermodynamics, rapid oxidation kinetics and intermediate reduction temperatures. Long term stability of the material was demonstrated over 250 redox cycles via thermogravimetry. Oxidation kinetics were measured and incorporated in a 1D convection–diffusion model of a packed bed reactor configuration. The model indicates that, for a targeted oxygen impurity level of x_O2<3×10⁻⁶, a chemical looping unit added to a PSA system could approximately triple the capacity and reduce the energy demand to 14kJmol⁻¹ of N₂.