Catalytic Ozonation of NO with Low Concentration Ozone over Recycled SAPO-34 Supported Iron Oxide

A series of SAPO-34 supported iron oxide (FeOₓ/SAPO-34) catalysts were prepared by a two-step liquid ion-exchange method. The effects of the exchange time and iron nitrate concentration on the structure and properties of the catalysts were investigated. The results showed that the FeOₓ/SAPO-34 catalysts significantly enhanced the ozonation of NO. The 0.05-FeOₓ/SAPO-34-15 catalyst prepared by mixing NH₄⁺/SAPO-34 with 0.05 M iron nitrate solution for 15 h showed the most effective NO oxidation. Oxygen vacancies acted as the active sites for the catalytic oxidation of NO. The electron paramagnetic resonance results showed that the hydroxyl and superoxide radicals generated from ozone and the oxygen vacancies on the surface of the catalysts promoted the oxidation of NO. The 0.05-FeOₓ/SAPO-34-15 catalyst has a certain stability when the volume fraction of water vapor is in the range 0–8%.