Co/KxTi2O5 catalysts prepared by ion exchange method were tested for NO oxidation to NO2. Their catalytic activities are similar to Pt-based catalysts and much higher than Co impregnated on TiO2 with or without doped K. The conversion pattern shows a typical kinetic control at low temperatures and thermodynamic control at higher temperatures, exhibiting a peak temperature at which the conversion becomes a maximum. Conversion decreases sharply as oxygen concentration decreases below 1.0%. NO concentration shows a positive effect on the conversion. The presence Of Co3O4 and K ion remaining in KxTi2O5 after the ion exchange is responsible for the observed catalytic activity. Thus, Co/KxTi2O5 having a complete ion exchange with little K is not active for the reaction. Unlike Pt-based catalyst, the presence of NO2 does not inhibit catalytic activity. Co/KxTi2O5 was resistant to the presence of SO2 less than 10 ppm. High-NO oxidation activity and high resistance to SO2 and NO2 make Co/KxTi2O5 a promising catalyst for NO oxidation. (c) 2007 Elsevier B.V. All rights reserved.