The role of urea in Cu-Zn-Al catalysts for methanol steam reforming

Impregnated Cu-Zn over Al2O3 exhibits high activity with the use of a lower amount of active metal relative to conventional co-precipitation catalysts. The activity of the catalyst could be enhanced by addition of urea to the metal salt solution during impregnation. The H-2 yield from Cu-Zn catalysts with urea is 42%, while the H-2 yield from catalyst without urea is only 28% in a continuous system at 250 degrees C and 1.2 atm. The H-2 yield of the catalyst with urea in this study could compete with that of commercial catalysts. The role of urea in the Cu-Zn catalysts was investigated. X-ray diffraction (XRD) analysis of the catalysts shows that the crystal size of CuO could be reduced by the addition of urea. The XRD diffractogram of the catalyst prior to calcination also shows the formation of NH4NO3, which could aid in dissociation of metal clusters. Scanning electron microscopy (SEM) images of catalysts show the size of Cu-Zn compound clusters and also their dispersion over the Al2O3 surface on the impregnated catalysts. The addition of urea could also yield smaller Cu-Zn compound clusters and better dispersion compared with the impregnated catalyst without urea. Such impregnated Cu-Zn catalysts with urea could be alternative novel catalysts for methanol steam reforming.