The preparation of synthesis gas from carbon dioxide reforming of methane (CDR) has attracted increasing attention. The present review mainly focuses on CDR to produce synthesis gas over Ni/MOx/Al2O3 (X = La, Mg, Ca) catalysts. From the examination of various supported nickel catalysts, the promotional effects of La2O3, MgO, and CaO have been found. The addition of promoters to Al2O 3-supported nickel catalysts enhances the catalytic activity as well as stability. The catalytic performance is strongly dependent on the loading amount of promoters. For example, the highest CH4 and CO2 conversion were obtained when the ratios of metal M to Al were in the range of 0.04-0.06. In the case of Ni/La2O3/Al2O 3 catalyst, the highest CH4 conversion (96%) and CO 2 conversion (97%) was achieved with the catalyst (La/Al = 0.05 (atom/atom)). For Ni/CaO/Al2O3 catalyst, the catalyst with Ca/Al = 0.04 (atom/atom) exhibited the highest CH4 conversion (91%) and CO2 conversion (92%) among the catalysts with various CaO content. Also, Ni/MgO/Al2O3 catalyst with Mg/Al = 0.06 (atom/atom) showed the highest CH4 conversion (89%) and CO 2 conversion (90%) among the catalysts with various Mg/Al ratios. Thus it is most likely that the optimal ratios of M to Al for the highest activities of the catalysts are related to the highly dispersed metal species. In addition, the improved catalytic performance of Al2O 3-supported nickel catalysts promoted with metal oxides is due to the strong interaction between Ni and metal oxide, the stabilization of metal oxide on Al2O3 and the basic property of metal oxide to prevent carbon formation.
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Acknowledgements This work was conducted as a subject (KK-0803-D0) of KRICT research program ‘‘Sustainable Chemical Technology’’ and also supported in part by Yonsei University Research Fund of 2008.
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