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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.

Thermal or Lewis Acid-Promoted Electrocyclization and Hetero Diels-Alder Cycloaddition of α,β-Unsaturated (Conjugated) Carbodiimides: A Facile Synthesis of Nitrogen-Containing Heterocycles.-Aza-Wittig reaction of iminophosphoranes (I), (XI), and (XVII) with isocyanates affords the title α,β-unsaturated carbodiimides (III), (XII) and (XIX), respectively. While the carbodiimides (III) and (XII) undergo Diels-Alder reaction with several strong dienophiles like tetracyanoethylene (V), tosyl isocyanate (VIII) or dimethyl acetylenedicarboxylate (XV) to furnish pyrimidines, oxazines or pyridine derivatives, only compounds (III) possess the proper configuration for electrocyclization to isoquinolines (IV). In contrast, the β-styryl carbodiimide (XIX) is inert towards cycloaddition as well as electrocyclization. The observed differences in reactivity are shown to be due to the different values of heat of adduct formation and due to the probability of the existence of a reactive s-cis conformer in the carbodiimides. -(SAITO, T.; OHKUBO, T.; KUBOKI, H.; MAEDA, M.; TSUDA, K.; KARAKASA, T.; SATSUMABAYASHI, S.; J. Chem. Soc.