Effect of titania structure on the properties of its supported copper oxide catalysts

Anatase and rutile have the same chemical composition as TiO(2) but different crystalline structures (space group of D(4h)(19)-I4(1) for anatase and D(4h)(14)-P4(2) for rutile, respectively), which result in different surface structures and can be used ideally to investigate the effects of support and surface structure on the properties of their supported catalysts. In this work, anatase- or rutile-supported copper oxide catalysts (signed as Cu-A and Cu-R, thereafter) prepared by the impregnation method were characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area, X-ray photoelectron spectroscopy (XPS), and H(2) temperature-programmed reduction (H(2)-TPR) to study the support effect of titania on the physicochemical properties and catalytic properties for the NO reduction by CO of these supported copper oxide catalysts. The results indicated that (1) copper oxide presented different dispersion capacities on anatase or rutile; (2) dispersed copper oxide species on anatase and rutile also showed different reduction behaviors; i.e., one-step reduction for dispersed copper oxide species in Cu-A and stepwise reduction for that in Cu-R; (3) the NO+CO activity test suggested dispersed copper oxide and small CuO particles on rutile are the main active species under the current reaction conditions and copper oxide supported on rutile is more active than that on anatase, which might result from Cu(+) species in Cu-R sample formed during the reaction due to its stepwise reduction behavior.