TiO2 photocatalytic oxidation of nitric oxide: transient behavior and reaction kinetics

Abstract Photocatalytic oxidation (PCO) of nitric oxide (NO) over TiO 2 catalyst was studied at source levels (5–60 ppm). The PCO process involves a series of oxidation steps by the OH radical: NO→HNO 2 →NO 2 →HNO 3 . The product NO 2 can be collected in an adsorbent bed and either recycled back to the combustion chamber or recovered as nitric acid. The ratio of NO 2 − to NO 3 − from spent catalyst liquor drops with irradiation time until a steady state is reached. The reactions are limited by thermodynamic equilibrium after ∼12 s space time. The steady-state experimental data from space time and inlet concentration effects can be described with the Langmuir–Hinshelwood (L–H) kinetic model with R 2 =0.9208.