Steam reforming of ethylene over nickel based spinel oxides

Spinel oxides containing Ni cations can be present in the barrier layers of ethane steam cracker tubes. As Ni is known to catalyze steam reforming side reactions as well as coke deposition, the catalytic performance of Ni spinel catalysts was investigated. A series of NiM2O4 spinel catalysts (M = Al, Cr, Fe) was synthesized from a solgel method and thoroughly characterized. The NiAl2O4 and NiCr2O4 catalysts were active for ethylene steam reforming at 873 K without degradation of the spinel structure. The NiFe2O4 catalyst was the least stable because of partial reduction of Fe3+ to form Fe3O4, which facilitated Ni-Fe alloy particle formation and severe coking. The reforming activity and the coke deposited on the NiAl2O4 and NiCr2O4 catalyst both increased after oxidative regeneration at 873 K, suggesting a slow reduction of Ni2+ to Ni metal particles during steam reforming that subsequently sinter into larger NiO particles during oxidative regeneration.