Highly active copper/ceria catalysts for steam reforming of methanol

Abstract

The Ce 1− x Cu x O 2− 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 Cu 2+-ions were dissolved into the CeO 2 lattices to form a solid solution by calcination at 723 K when x<0.2 in the Ce 1− x Cu x O 2− x mixed oxides. The Ce 1− x Cu x O 2− x mixed oxides were reduced to form the Cu/CeO 2 (cop) catalysts for the steam reforming of methanol. The activity and selectivity of Cu/CeO 2 (cop) were compared with those of Cu/ZnO, Cu/Zn(Al)O and Cu/Al 2O 3. All the Cu-containing catalysts tested in this study showed high selectivities to CO 2 (over 97%) and H 2. A 3.9 wt.% Cu/CeO 2 (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/Al 2O 3 (11.2%) with the same Cu loading under the same reaction conditions. The high activity of the 3.9 wt.% Cu/CeO 2 (cop) catalyst may be due to the highly dispersed Cu metal particles and the Cu + species stabilized by the CeO 2 support. Slow deactivation was observed over the 3.9 wt.% Cu/CeO 2 (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 H 2 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/CeO 2 (cop) catalyst were 0.8 wt.% at 493 K and 1.7 wt.% at 513 K after 24 h on stream.