Our recent research works on the selective catalytic reduction (SCR) of diesel engine NO, by hydrocarbons over alumina-supported silver(Ag/Al2O3) were reviewed. The reaction mechanism of the SCR of NO, by C2H5OH over Ag/Al2O3 was studied using in situ DRIFTS and DFT calculations. A novel enolic species originating from the partial oxidation Of C2H5OH and C3H6, was found on the surface of Ag/Al2O3. during the SCR of NO, by in situ DRIFFS, which was also supported by DFT calculations. Based on this, a mechanism of the NO, reductior was proposed, which can successfully explain the high efficiency of the NO, reduction by C2H5OH over Ag/Al2O3. A palladium promoted. Ag/Al2O3 catalyst (denoted Ag-Pd/Al2O3) was developed for the SCR of NOx by C3H6. The Ag-Pd/Al2O3 showed a higher NOx conversion than Ag/Al2O3, especially at temperatures ranging from 300 to 450 degrees C. The engine bench tests showed that the average NOx conversion was, greater than 80% in the diesel engine exhaust temperature range of 300-400 degrees C using our catalytic converter with C2H5OH as reductant, which represents a leap from the Euro II standard to the Euro III standard for NOx emission control in diesel engines. (c) 2004 Elsevier B.V. All rights reserved.