Urea, as an ammonia source, has been known to be a highly selective and efficient reducing agent to remove NOx from the automobile exhaust gases. Transition metals, such as Pt, Pd, Ag and Cu, on alumina are active and stable for the reduction of NOx by urea. In this study, urea decomposition was investigated over a 1% Cu and 2% Pt on alumina catalysts prepared by a single step sol-gel technique. Urea decomposition over these catalysts was studied in helium atmosphere in the range of 100-400°C by using FTIR. The analysis of FTIR spectra gave information about NH3, NH4+, CO2 and isocyanate (CNO-) formation on 1% Cu/Al2O3 and 2% Pt/Al2O3 catalysts. OH and CH stretching vibration bands were also observed over these catalysts. Isocyanate peak was observed at 150°C on 2% Pt/Al2O3 catalyst. The corresponding peak was observed at 250°C on 1% Cu/Al2O3 catalyst. The peak corresponding to melamine was observed on 2% Pt/Al2O3 at all the temperatures except for 150°C. However, melamine peak was only detected on 1%Cu/Al2O3 at 150°C for two and four minutes. Reducing agents for NOx reduction were obtained over 1% Cu/Al2O3 catalyst at high temperatures and over 2% Pt/Al2O3 catalyst at low temperatures. It is concluded that the catalysts prepared using the sol-gel process are effective in the decomposition of urea as ammonia and isocyanate sources.
The Role of Nitrate on the Sol-Gel Spread Self-Combustion Process and Its Effect on the NH3-SCR Activity of Magnetic Iron-Based Catalyst