The objective of this paper was to study a preferential oxidation (PROX) of carbon monoxide over monometallic catalysts including Pt, An and Pt-Au bimetallic catalyst supported on ceria in hydrogen-rich reformate. Single step sol-gel method (SSG) and impregnation on sol-gel method (ISG) were chosen for the preparation of the catalysts. The characteristics of these catalysts were investigated by X-ray diffractometer (XRD), Brunauer-Emmet-Teller (BET) method, transmission electron microscope (TEM), scanning electron microscope (SEM) and temperature-programmed reduction (TPR). The XRD patterns of the catalysts showed only the peaks of ceria crystallite and no metal peak appeared. From TEM images, the active components were seen to be dispersed throughout the ceria support. The TPR patterns of PtAu/CeO2 catalyst prepared by SSG showed the reduction peaks were within a low temperature range and therefore, the catalysts prepared by SSG exhibited excellent catalytic activity for preferential oxidation of CO. Bimetallic Pt-Au catalyst improved the activity (90% conversion and 50% selectivity at 90 degrees C) because of the formation of a new phase. When the metal content of (1:1) PtAu/CeO2 catalyst prepared by SSG was increased, the CO conversion did not change much while the selectivity decreased in the low temperature range (50-90 degrees C). The CO conversion increased with increasing W/F ratio. The presence Of CO2 and H2O had a negative effect on CO conversion and selectivity due to blocking of carbonate and water on active sites. (C) 2007 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.