Inhibition of methane formation during the water gas shift reaction by Sn doping of Co-CeO2 catalysts

Co-Ce-Sn catalysts were developed for application in the water gas shift reaction (WGSR) at intermediate temperatures (350-400 °C). Ceria-based supports with tin loadings ranging from 2.5% to 30% mol (CeSn(X%)) were synthesized via co-precipitation. Using these supports, cobalt catalysts were developed using the incipient wetness impregnation method, yielding Co-Ce-Sn catalysts (15Co/CeSn(X%)). Physicochemical techniques were employed to characterize the supports and catalysts. XRD and Raman spectroscopy analyses confirmed the presence of solid solutions between CeO2-SnO2 oxides. Notably, a higher Sn loading increased specific surface area and decreased support basicity. H2-TPR and XPS analyses of the catalysts indicated a higher metal-support interaction in the presence of tin. Under all conditions evaluated, the 15Co/CeSn(5%) material was active and presented 100% selectivity towards H2. While the 15Co/CeO2 material presented methane formation. Both samples were stable over 15hours in the WGSR at 350°C. These findings suggest that the tin loading enhances hydrogen selectivity compared to samples without tin, due to the inhibition of methane formation. Raman spectroscopy analysis of used samples revealed the presence of carbon deposits in the 15Co/CeO2 sample but not in the 15Co/CeSn(5%) sample, suggesting that tin would also have disfavored the carbon formation during the WGSR.