Nano-sized gold particles supported on titania catalysts (Au/TiO2) were prepared by metal sol method. The catalytic activity of the nano-sized Au/TiO2 catalysts for selective catalytic reduction (SCR) of NOx by propene in the presence of excess oxygen was investigated. The maximum NOx conversion to N-2 over Au (1 wt.%)/TiO2 Was obtained at 325 degrees C which is relatively lower than was the case for Au/Al2O3. Anatase crystalline type is preferable for Au/TiO2 Catalyst because of the higher NOx reduction and C3H6 oxidation performance at low temperatures compared with the rutile form. When the Au loading was lowered to 0.1 wt.%, the peak temperature shifted to 375 degrees C but the maximum NOx conversion remained the same as that of 1 wt.% Au loading sample. The full width at half maximum of conversion (FWHM) increased significantly as the loading of Au decreased. FWHM of 0.1 wt.% Au loading was almost two times wider than that of the 1 wt.% Au loading sample. The effect of feed composition, including moisture, was also investigated. (c) 2008 Elsevier B.V. All rights reserved.