Hydrogenations of nitrate and nitrite in water over Pt–promoted Ni catalysts

Hydrogenations of nitrate (NO3−) and nitrite (NO2−) in water were studied with 40–5000 ppm of the reactant at 333 K using a gas–liquid flow reactor over Pt–promoted Ni catalysts. Porous Ni was highly active for hydrogenation of NO3− to form NH3 exclusively, but rapid deactivation was observed during the reaction. It was found that the addition of a small amount of Pt to the porous Ni greatly enhanced the stationary activity. The loading amount of Pt was sensitive to the activity; 1 wt.% Pt–Ni exhibited the maximum activity. XPS measurements revealed that Pt suppressed the oxidation of the Ni0 atoms on the surface. The kinetic equation, vv = k[NO3−]0.8PH20.8, was obtained for the hydrogenation of NO3− over 1 wt.% Pt–Ni. Results showed that 1 wt.% Pt–Ni was highly active and stable even for 5000 ppm of nitrate without the dissolutions of Pt and Ni. The product was mainly NH3 over Pt–Ni, independent of the concentration of NO3− or NO2−, the pressure of hydrogen or the reaction temperature.