Zirconia-supporting iron oxide catalysts were developed for recovery of lighter fuels in a steam atmosphere from residual oils in petroleum refinery processes. In these processes, steam is first decomposed on zirconia, yielding active hydrogen and oxygen species. These oxygen species spill over to the surface of iron oxide and react with heavy oil molecules, producing lighter molecules and carbon dioxide. The remaining active hydrogen species are then added to the lighter molecules. This reaction therefore proceeds by oxidative degradation. It was found in the present study that the catalysts exhibited catalytic activity to decompose the residual oil without any carbonaceous residue. The catalysts were, however, deactivated when the sequence of reaction and regeneration was repeated, which is attributed to a change in the iron oxide, namely, between hematite and magnetite, and subsequent peeling of zirconia from the catalyst. To avoid this phase change, Al2O3 was added to the iron oxide lattice. The second-order reaction rate constant of this catalyst was almost the same value 0.16 as 0.18 of the catalyst without Al2O3 and increased to 0.22 after the third sequence of the reaction and regeneration, where the rate constant of the catalyst without Al2O3 decreased to 0.11.