Ethanol steam reforming for production of hydrogen on magnesium aluminate-supported cobalt catalysts promoted by noble metals

The performance of noble metal (Pt, Ru, Ir)-promoted Co/MgAl2O4 catalysts for the steam reforming of ethanol was investigated. The catalysts were characterized by energy-dispersive X-ray spectroscopy, X-ray diffraction, UV–vis diffuse reflectance spectroscopy, temperature-programmed reduction, temperature-programmed oxidation and X-ray absorption near edge structure (XANES). The results showed that the formation of inactive cobalt aluminate was suppressed by the presence of a MgAl2O4 spinel phase. The effects of the noble metals included a marked lowering of the reduction temperatures of the cobalt surface species interacting with the support. It was seen that the addition of noble metal stabilized the Co sites in the reduced state throughout the reaction. Catalytic performance was enhanced in the promoted catalysts, particularly CoRu/MgAl2O4, which showed the highest selectivity for H2 production.

The addition of the noble metals to the Co catalyst caused a marked modification in the Co K-edge XANES spectra from 250 °C (b), whereas the Co/MgAl2O4 catalyst (a) was reduced at higher temperatures. The decrease of the reduction temperature of the cobalt species, seen in the spectra of the promoted catalysts, may result from a hydrogen spillover phenomenon that occurs in noble metals. This enhancement of reducibility may be closely related to the improved catalytic performances of the promoted catalysts.Figure optionsDownload as PowerPoint slide