The synergistic effects of CeO 2 -supported bimetallic NiCu, CoCu, and NiFe catalysts on the reduction properties, crystal structure, and catalytic performance during steam reforming of ethanol were investigated. Both metals in the bimetallic catalysts were reduced at lower temperatures than were the metals in the associated monometallic catalysts, and they formed alloy crystallites. It was confirmed from activity tests of the monometallic catalysts that Ni and Co were relatively active components and that Cu and Fe were less active. The combination of Ni and Co with Cu (NiCu/CeO 2 and CoCu/CeO 2 ) resulted in increases in H 2 and CO 2 yields and inhibition of carbon deposition during reactions at 673 K. On the other hand, the incorporation of Ni with Fe (NiFe/CeO 2 ) showed a lower activity than did Ni/CeO 2 at 673 K but exhibited a higher H 2 yield and higher resistance to carbon deposition at 873 K, in which case NiFe alloys were formed. These results indicate the advantages of alloying a catalytically active metal with a less active metal during steam reforming of ethanol.

Dependence of hydrogen production via the catalytic steam reforming of ethanol on the metal oxide support and first row transition metal catalyst was investigated. Ni supported on CeO2 was more easily reduced and began to produce hydrogen at a lower temperature than Ni supported on ZrO2, SiO2, Al2O3, and MgO. Ni/CeO2 also maintained a high activity at a constant reaction temperature of 673 K and inhibited carbon deposition. Therefore, CeO2 was adopted as the catalytic support. Compared with Ni/CeO2, Fe/CeO2 and Mn/CeO2 were less active. Contrarily, Co/CeO2 was slightly less active at 673 K, but exhibited a comparable hydrogen yield at 873 K. The Cu/CeO2 system was reduced more readily and produced hydrogen at a lower temperature, but its activity gradually deteriorated by carbon deposition. Thus we concluded that Ni/CeO2 exhibited the best combination of properties with the highest hydrogen yield at 673 K and a long stability.

We investigated the effects of the Ni : Cu ratio and metal loading of a CeO2-supported bimetallic Ni _ Cu catalyst on its reduction behavior and catalytic performance during steam reforming of ethanol for H2 production. Compared with monometallic Ni and Cu catalysts, both the NiO and CuO phases in the bimetallic catalysts were reduced at lower temperatures to form fine NiCu alloy crystallites. At a reaction temperature of 673 K, Ni/CeO2 exhibited a higher H2 yield than Cu/CeO2 but also produced a large quantity of CH4 and carbon deposits. The undesired byproducts were substantially inhibited by replacing a portion of the Ni with Cu. The highest H2 yield and an excellent carbon inhibition were achieved when the content of each metal was 5 wt%. Notably, a physical mixture of Ni/CeO2 and Cu/CeO2, each with the same metal contents, exhibited a lower H2 yield and heavy carbon deposition. This indicates that the higher reducibility and alloying in the bimetallic catalyst are key factors for synergistic improvements of the catalytic properties.

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