A carbon nanotube (CNT) was used as catalyst support impregnated with transition metal cobalt for CO oxidation at low temperature. Catalyst properties were analyzed by X-ray powder diffractometer (XRD), X-ray photoelectron spectrometer (XPS), and transmission electron microscope (TEM). Analytical results for TEM and XRD demonstrated that cobalt particles were highly dispersed on the carbon nanotube (20-30 nm) with nanosized cobalt particles (10-15 nm). These investigations indicated that CO/CNT generates about 99% of the high activity for CO conversion at 250 degrees C and thermally stability that is superior to Co/activated carbon (AC). The optimum reaction conditions for CO conversion were O-2 concentration 3%, operation temperature 250 degrees C, CO concentration 5000 ppm, and space velocity 156,000 h(-1). At 250 degrees C, CO may act as a reductant for NO reduction over Co/CNT in the presence of oxygen, whereas CO/NO = 2.5 showed that maximum NO reduction was 30%. Under H-2 rich conditions, the optimum reaction temperature for CO conversion was under 300 degrees C, and performance Of CO2 selectivity was better at 200 degrees C than 250 degrees C as the oxygen concentration increased. (c) 2006 Elsevier Ltd. All rights reserved.