AVS 47th International Symposium
    Material Characterization Tuesday Sessions
       Session MC-TuP

Paper MC-TuP18
XPS and XRD Characterization of CuO-TiO2-CeO2 Catalyst System

Tuesday, October 3, 2000, 5:30 pm, Room Exhibit Hall C & D

Session: Poster Session
Presenter: P.A.P. Nascente, Universidade Federal de Sao Carlos, Brazil
Authors: M.S.P. Francisco, Universidade de Sao Paulo, Brazil
P.A.P. Nascente, Universidade Federal de Sao Carlos, Brazil
V.R. Mastelaro, Universidade de Sao Paulo, Brazil
A.O. Florentino, Universidade Estadual Paulista, Brazil
Correspondent: Click to Email
The CuO-TiO@sub 2@ system has been widely studied due to its catalytic properties on methanol oxidation. However, disadvantages are related to TiO@sub 2@ as support: thermal instability, its sintering and the sintering of the active phase. The cerium addition to this system is known to stabilize the active phase in a fine dispersed state and to improve both the resistance to thermal loss of surface area and the catalytic activity of supported catalysts. The influence of loading cerium and cooper to TiO@sub 2@ on its superficial composition and on its structure have been studied by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS). The analyses revealed that with increasing amount of cerium on titania, cerium occurs mainly in a dispersed superficial specie and just a little as CeO@sub 2@ phase (cerianite). At higher loading of cerium, the CeO@sub 2@ phase increases and the Ce/Ti atomic rate is smaller than the bulk rate, as a consequence of cerium agglomeration. We have concluded that a limited amount of cerium can be spread on the titania surface. The Cu/(Ce+Ti) atomic rate showed no influence from cerium on the dispersion of cooper. For CuO-TiO@sub 2@ samples with low concentration of cerium, we could observe that cerium is found as Ce@super 3+@, at least partly. Also the XPS spectra confirmed the presence of a second titanium specie with a spin-orbit component at higher binding energy than the one presented by Ti@super 4+@ in CuO-TiO@sub 2@ samples rich in cerium. The structural results obtained by XAS were in good agreement with those obtained by XRD and XPS.