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

Photocatalytic oxidation (PCO) of nitric oxide (NO) over TiO2 catalyst was studied at source levels (5–60 ppm). The PCO process involves a series of oxidation steps by the OH radical: NO→HNO2→NO2→HNO3. The product NO2 can be collected in an adsorbent bed and either recycled back to the combustion chamber or recovered as nitric acid. The ratio of NO2− to NO3− 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 R2=0.9208.