Studies of the dispersion state of CuO on TiO2 and CeO2-TiO2 and activity for NO plus CO reaction

The activities of CuO supported on TiO2 and ceria-modified TiO2 in catalyzing the NO reduction by CO have been examined with a microreactor-GC NO+CO reaction system, and the catalysts characterized by physical adsorption, TPR, XRD and NO-TPD. The CuO/TiO2 and CuO/CeO2-TiO2 catalysts increase the NO reduction by CO, probably due to the surface dispersed CuO and fine CuO crystallites. Pore structure data show that the pore size distribution of TiO2 is mainly as micro-pores and meso-pores, and the adsorption-desorption isotherm is the type IV of BDDT classification. TPR profiles indicate that Cu-Ti has four TPR peaks, alpha peak from highly dispersed CuO species, beta peak from oxide clusters with a structure similar to CuO, gamma peak from CuO crystallites and delta peak from the interaction of CuO and TiO2. TiO2 surface oxygen reduction. In addition, the phase change of TiO2, doesn't show negative influence in catalytic activities. Among the tested catalysts, the catalyst with 12% CuO loading has the highest activity for NO+CO reaction, but at CuO loading of greater than or equal to 3%, a crystallite of CuO has already been formed, which means that besides highly dispersed CuO. the CuO crystallite also plays an important role in NO+CO reaction, and the catalytic activities have a close relation with the CuO crystallite size and its micro structure data. NO-TPD profile also shows that the catalytic activities are closely related to NO dissociation - a rate-determining step for the NO+CO reaction, but are not affected by the amount of adsorbed NO2.