No abstract

Catalytic properties of Ni-and Co-based intermetallic compound (IMC) were assessed for the CO2 reforming of methane. Single-phase IMCs were prepared by arc-melting mixtures of stoichiometric amounts of nickel or cobalt and a second element. IMCs were crushed into particles and used as a catalyst for the CO2 reforming of methane at 1073 K. Ni-and Co-IMCs containing Ta, Hf and Sc showed higher initial activity than Ni and Co powders. Stability of these IMCs was examined for the reaction at 923 K because lower temperatures favor coke formation. Among Ni-IMCs, Ni7Hf2, NiHf and NiHf2 showed high stability for CO2 conversion. However, temperature programmed oxidation revealed that a relatively large amount of coke was formed on these catalysts. Filamentous carbon was observed by TEM on NiHf. High activity for the hydrogenation of ethene suggested that the surface of Ni _ Hf IMCs is separated into Ni particles and Hf species. Among Co-IMCs, Co2Sc and CoHf2 showed stable CO2 conversion at 923 K. Low ethene hydrogenation activity suggested that the surface of these Co-IMCs consists of each IMC phase. CoHf2 formed less coke than Co2Sc. Only a slight decrease in CO2 conversion was observed on CoHf2 after 100 h of the reforming reaction at 923 K. CoHf2 is a good catalyst for the CO2 reforming of methane with high stability for reforming activity and low activity for coke formation.