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Structure/Activity Correlation for un-promoted and CeO2-promoted MnO2/SiO2 Catalysts

Domenii publicaţii > Stiinte ingineresti + Tipuri publicaţii > Articol în revistã ştiinţificã

Autori: Radu Craciun

Editorial: Catalysis Letters, 55, p.25-31, 1998.

Rezumat:

The goal of this study was to understand the structure-activity relationship for unpromoted and ceria-promoted MnOx/SiO2 catalysts used in CO oxidation. SiO2 and CeO2-promoted SiO2 (20% CeO2) were used as supports to prepare MnOx/SiO2 catalysts with various manganese (Mn) loadings. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) data indicated a higher Mn dispersion on ceria-promoted than on unpromoted MnOx/SiO2 catalysts. Analysis of the XRD patterns and Mn2p XPS spectra indicated that Mn was present as MnO2 on MnOx/SiO2 with low Mn loadings and ceria-promoted MnOx/SiO2 catalysts and as mixed MnO2/Mn2O3 on MnOx/SiO2 catalysts with high Mn loadings. Kinetic data obtained for CO oxidation on unpromoted and ceria-promoted MnOx/SiO2 catalysts are presented and interpreted in correlation with the catalyst surface and bulk structure. A synergistic catalytic effect was observed in the case of the ceria-promoted MnOx/SiO2 catalysts. Post-reaction XRD and XPS analysis of catalysts indicated that the presence of ceria precludes formation of the less catalytically active Mn3O4 species from MnO2 deposited initially on the SiO2 support.

Cuvinte cheie: Ceria promoter, manganese oxides, silica, CO oxidation, synergism