NOx reduction by urea under lean conditions over single step sol–gel Pt/alumina catalyst

We prepared 2% Pt on alumina catalyst using a single step sol–gel process (designated as 2% Pt-SG) and tested its activity for NOx reduction with aqueous urea solutions under oxidizing conditions. Our results show that ∼99% NOx conversion was obtained as low as 150 °C but above 350 °C, the conversion became negative because of the additional formation of NO and NO2 from the oxidation of nitrogen-containing compounds. We also found that NOx conversion activity of 2% Pt-SG is strongly dependent on water content rather than on urea amount and the presence of 7% oxygen in the feed lowers the maximum NOx conversion temperature from 250 to 150 °C.