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

A series of bimetallic Fe-Ni/MgAl 2 O 4 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 CH 4 /CO 2 ratio of 1. The evolution of the catalyst structure during H 2 temperature-programmed reduction (TPR), CO 2 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, Fe 2 O 3 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 CO 2 -TPO and is decomposed to Ni and Fe 3 O 4 at higher temperatures. The Fe-Ni alloy is the active phase while Fe partially segregates from the alloy forming FeO x during dry reforming. This is beneficial as it reduces the surface carbon accumulation through interaction with FeO x lattice oxygen, producing CO. Alternate CH 4 and CO 2 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 CO 2 carbon removal.