CO₂ Reforming of Methane on Ni- and Co-based Intermetallic Compound Catalysts

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.

Steering the Catalytic Properties of Intermetallic Compounds and Alloys in Reforming Reactions by Controlled in Situ Decomposition and Self-Activation

“…39 In a similar fashion, the stability of different Hf-based intermetallic compounds (e.g., NiHf or CoHf 2 ) during dry reforming has been assessed. 40 The same concept of creating supported-metal catalysts via decomposition of precursor structures was previously discussed for amorphous metal alloys (i.e., "metal glasses"). Several examples in the literature exist, which have demonstrated the potential to use such materials as promising catalyst precursors.…”

“…A recent study on Ni–Y alloys also revealed in situ decomposition into Ni/Y 2 O 3 composites with superior dry reforming activity . In a similar fashion, the stability of different Hf-based intermetallic compounds (e.g., NiHf or CoHf 2 ) during dry reforming has been assessed …”

“… 39 In a similar fashion, the stability of different Hf-based intermetallic compounds (e.g., NiHf or CoHf 2 ) during dry reforming has been assessed. 40 …”

Intermetallic Compounds: Promising Inorganic Materials for Well-Structured and Electronically Modified Reaction Environments for Efficient Catalysis

“…As a reaction related to CO x reduction, they also tested the application of Ni- and Co-based intermetallic compounds to CO 2 reforming of methane. Among the various unsupported intermetallic compounds, CoHf 2 exhibited 8- and 2.5-fold higher CO 2 conversions than monometallic Co and Ni, respectively at 750 °C . CoHf 2 also showed long-term stability of CO 2 conversion over 100 h, whereas that of monometallic Ni declined to half over the same time.…”

Catalytic Properties of Single-Phase Intermetallic Compounds

“…The CO 2 reforming of methane was studied on Ni-and Cobased unsupported IMC catalysts with the continuous flow reactor under atmospheric pressure [33]. Among various IMCs, those with Ta, Hf and Sc were more active than pure Ni and Co. Because the CO 2 reforming is always accompanied by the severe coke formation to shorten the catalyst life, the reaction was carried out for 24 h on these active IMCs to obtain the rate of deactivation and the amount of coke.…”