Oxidation of nitric oxide to nitrogen dioxide over Ru catalysts

A series of TiO2 supported catalysts were prepared by impregnation method in a rotary evaporator and evaluated for the oxidation of NO to NO2. Among all catalysts studied, Ru/TiO2 catalyst exhibited the best activity and a maximal NO conversion of c.a. 94% could be achieved at c.a. 275 degrees C at a high GHSV of 180,000 h(-1). For ruthenium catalysts, the effects of supports, ruthenium loadings, pretreatment conditions and experiment conditions (feed gas composition, GHSV) on NO oxidation to NO2 were investigated in detail. The ruthenium catalysts were characterized by means of X-ray diffraction (XRD), CO pulse chemisorption, transmission electron microscopy (TEM) and temperature-programmed reduction (TPR) techniques. The active ruthenium species for NO oxidation were discussed based on the catalytic and characterization results. Moreover, the reaction mechanism for NO oxidation over Ru/TiO2 catalyst was studied by means of in situ diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS). (C) 2008 Elsevier B.V. All rights reserved.