Ethanol steam reforming and water gas shift reaction over Co–Mn/ZnO catalysts

The promotion effect of Mn over Co/ZnO catalysts in the steam reforming of ethanol (ESR) and water gas shift (WGS) has been studied in samples prepared by impregnation or co-precipitation with Mnat/Coat = 0.05–0.35. Alloy particles in Co–Mn/ZnO catalysts prepared by impregnation are smaller as deduced from high resolution transmission electron microscopy (HRTEM) and exhibit a rapid and higher degree of redox exchange between reduced and oxidized Co as deduced from temperature programmed reduction (TPR) and oxidation pulse experiments with respect to Co–Mn catalysts prepared by co-precipitation, which show a stronger Mn segregation on the surface, as deduced from X-ray photoelectron spectroscopy (XPS). Honeycomb catalysts have been prepared with the best catalytic formulation, a sample prepared by impregnation with Mnat/Coat ∼ 0.1 and 10 wt.% Co, and tested in ESR and WGS as well. Honeycombs show good adherence of catalyst coatings and are significantly more active and selective than Co/ZnO honeycomb samples in both reactions.