Highly active copper/ceria catalysts for steam reforming of methanol

The Ce1-xCuxO2-x mixed oxides were synthesized using the coprecipitation method. The X-ray diffraction (XRD) patterns and the temperature-programmed reduction (TPR) profiles indicated that the Cu2+-ions were dissolved into the CeO2 lattices to form a solid solution by calcination at 723 K when x < 0.2 in the Ce1-xCuxO2-x mixed oxides. The Ce1-xCuxO2-x mixed oxides were reduced to form the Cu/CeO2 (cop) catalysts for the steam reforming of methanol. The activity and Selectivity of Cu/CeO2 (cop) were compared with those of Cu/ZnO, Cu/Zn(Al)O and Cu/Al2O3. All the Cu-containing catalysts tested in this study showed high selectivities to CO2 (over 97%) and H-2. A 3.9 wt.% Cu/CeO2 (cop) catalyst showed a conversion of 53.9% for the steam reforming of methanol at 513 K, which was higher than the conversions over Cu/ZnO (37.9%), Cu/Zn(Al)O (32.3%) and Cu/Al2O3 (11.2%) with the same Cu loading under the same reaction conditions. The high activity of the 3.9 wt.% Cu/CeO2 (cop) catalyst may be due to the highly dispersed Cu metal particles and the Cu+ species stabilized by the CeO2 support. Slow deactivation was observed over the 3.9 wt.% Cu/CeO2 (cop) catalyst at 493 and 513 K The activity of the deactivated catalysts can be regenerated by calcination in air at 723 K, followed by reduction in H2 at 673 K. Such success indicated that the carbonaceous deposit on the catalysts surface caused the catalysts' deactivation. The temperature-programmed oxidation (TPO) method indicated that the amounts of coke on the 3.9 wt.% Cu/CeO2 (cop) catalyst were 0.8 wt.% at 493 K and 1.7 wt.% at 513 K after 24 h on stream. (C) 2002 Elsevier Science B.V. All rights reserved.