AMORPHOUS FE-VALVE METAL-PT GROUP METAL ALLOY CATALYSTS FOR METHANATION OF CO2

Amorphous Fe-valve metal alloys containing a small amount of Pt group elements were activated by immersion in HF acid for surface roughening and for surface enrichment of Pt group elements, and were used for me thanation of CO2. The Fe-Zr-Ru alloy showed an activity about one orde r of magnitude higher than those with the alloys containing other Pt g roup elements and produced only CH4. The less active Pd- and Ir-contai ning alloys produced CO as well as CH4. The addition of Nb to the high ly active Fe-70Zr-2Ru alloy led to a significant decrease in the activ ity for CH4 production, but only CH4 was produced, even if Nb was adde d. X-ray photoelectron spectroscopy analysis revealed that the Ru and Fe contents in the surface were not markedly changed by the addition o f Nb. However, the peak binding energy of Ru 3d5/2 electrons of metall ic Ru changes with the Nb content of the surface. The change in the el ectronic state of Ru by the addition of Nb seems to be one of the reas ons for the decrease in the activity for the methanation of CO2.