Enhanced Carbon-Resistant Dry Reforming Fe-Ni Catalyst: Role of Fe

A series of bimetallic Fe-Ni/MgAl2O4 catalysts with Fe/Ni ratios between 0 and 1.5 have been examined for methane dry reforming at 923-1073 K, atmospheric pressure, and a CH4/CO2 ratio of 1. The evolution of the catalyst structure during H-2 temperature-programmed reduction (TPR), CO2 temperature-programmed oxidation (TPO), and dry reforming is examined using time-resolved in situ X-ray diffraction (XRD). During H-2-TPR up to 973 K, Fe2O3 and NiO are reduced to Fe and Ni. Higher temperatures lead to Fe-Ni alloy formation. The alloy remains stable up to 900 K under CO2-TPO and is decomposed to Ni and Fe3O4 at higher temperatures. The Fe-Ni alloy is the active phase while Fe partially segregates from the alloy forming FeOx during dry reforming. This is beneficial as it reduces the surface carbon accumulation through interaction with FeOx lattice oxygen, producing CO. Alternate CH, and CO2 pulse experiments over Ni, Fe, and Ni-Fe samples showed that dry reforming over Fe-Ni catalysts can follow a Mars-van Krevelen mechanism. A molar Fe/Ni ratio of 0.7 provides the most active and least deactivated catalyst. All studied catalysts can be regenerated by CO2 carbon removal.