Selective catalytic reduction of nitric oxide with hydrogen over Pd-based catalysts

Catalytic reduction of NO with hydrogen in the presence of excess oxygen was studied using Pd-based catalysts. High steady-state conversion of NO (>80%>80%) is achieved, using 1%Pd/TiO2/Al2O3 as the catalyst and at temperatures ranging from 140 to 180 °C. The addition of V2O5 to this catalyst not only increases NO conversion, but also widens the reaction temperature window to 250 °C. The effects of CO, O2, and H2 concentrations on the NO conversion were also investigated. It was found that the reaction order is nearly first order with respect to NO, 0.6 with respect to H2 and −0.18 with respect to CO. Increasing the O2 concentration from 2 to 10% produced only a slight decrease in NO conversion. FTIR studies showed that a significant amount of NH4+ was formed over the V2O5-containing catalyst, during the reaction, at temperatures >200 °C>200 °C, compared with almost no NH4+ formation over the V2O5-free sample. The higher activity of 1%Pd–5%V2O5/TiO2–Al2O3 is partly attributed to the in situ formation of NH4+.