Experimental and theoretical study about sulfur deactivation of Ni/ CeO2 and Rh/CeO2 catalysts

BEATRIZ IRIGOYEN; MARCO OCSACHOQUE; DELIA GAZZOLI; JUAN E. RUSSMAN; M. GLORIA GONZALEZ

MATERIALS CHEMISTRY AND PHYSICS

ELSEVIER SCIENCE SA

Lugar: Amsterdam; Año: 2016 vol. 172 p. 69 - 76

0254-0584

Sulfur deactivation of Ni/CeO2 and Rh/CeO2 catalysts were examined through an experimental andtheoretical study. These catalysts were characterized by N2 adsorption, X-ray diffraction, temperatureprogrammed reaction, thermogravimetric analysis, Uvevisible spectroscopy and Raman spectroscopy,and tested under the methane dry reforming reaction in the presence of H2S. On the other hand, differentpossible interactions of sulfur with Rh, Ni or surface sites of the CeO2 support were evaluated by performingenergy calculations with the density functional theory (DFT). Overall, the results indicate thattolerance to sulfur of Rh/CeO2 catalyst is higher than that of Ni/CeO2 one. In this sense, TPR measurementsshow that reduction of CeO2 is promoted by the presence of Rh. This effect, probably caused byhydrogen spillover to CeO2 support during the reduction of RhOx species, could be linked to a highoxygen donation capacity of Rh/CeO2 catalysts. Accordingly, the O2 species existing on Rh/CeO2 catalysts,revealed by Raman spectra of these samples, could favor sulfur oxidation and prevent RheS interactions.Likewise, the theoretical calculations show that desorption of SeO species from Rh/CeO2system is more favorable than that from Ni/CeO2 one. Therefore, our experimental and theoretical studyabout sulfur deactivation of Ni and Rh supported on CeO2 allow us to postulate that Rh can help to desorbSOx species formed on the support, retarding sulfur poisoning of the Rh/CeO2 catalysts.