To reduce the consumption of hydrogen when converting heavy oil to light oil, the catalytic cracking of a heavy oil (residue of atmospheric distillation) with steam was examined. Two iron oxide-based catalystsshematite (R-Fe 2 O 3 ) and goethite (FeOOH, denoted herein as FeO X catalyst)swere used. It was found that the heavy oil was converted to a mixture of useful light hydrocarbons (i.e., gasoline, kerosene, and gas-oil) over iron oxide-based catalysts. Moreover, because the FeO X catalyst possessed mesopores with diameters of 6-10 nm, it exhibited higher activity than the R-Fe 2 O 3 catalyst without the production of carbonaceous residue. The catalytic activity could be enhanced by loading ZrO 2 on the FeO X catalyst. From the X-ray diffraction analysis and Mössbauer measurement, it was considered that the active oxygen species generated from H 2 O over ZrO 2 particles spilled over the FeO X surface, where the oxidized decomposition of heavy oil occurred.

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This study investigated the transfer of oxygen and hydrogen species from steam to product during the catalytic cracking of heavy oil with iron oxide-based catalysts containing zirconia and alumina. Light oil and carbon dioxide were produced in the catalytic oxidative cracking of petroleum residual oil in the presence of steam. The alkene/alkane ratio of light aliphatic hydrocarbons decreased and carbon dioxide yield increased with higher flow rate ratio of steam to feedstock. The steam catalytic cracking of dodecylbenzene as a model compound of heavy oil showed lower alkene/alkane ratio and generation of a small amount of oxygen-containing compounds. The oxygen species derived from steam reacted with heavy oil and were transferred to carbon dioxide and a small amount of oxygen-containing compounds, producing hydrogen species from the steam. The hydrogen species were transferred to light hydrocarbons, thus suppressing alkene generation. The alkene/alkane ratio decreased with higher supporting zirconia content in the catalyst because zirconia promotes hydrogen generation from steam.

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, Al 2 O 3 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 Al 2 O 3 and increased to 0.22 after the third sequence of the reaction and regeneration, where the rate constant of the catalyst without Al 2 O 3 decreased to 0.11.

This paper describes catalytic cracking, with zirconia-supporting iron oxide catalysts in a steam atmosphere, of heavy oil, such as petroleum residual oil, to recover as much lighter fuel as possible. In this process, the heavy oil reacts with active oxygen species generated from steam over the iron oxide catalyst and significant amounts of lighter fractions and carbon dioxide are produced with almost no coke. Active hydrogen species generated from steam are added to the heavy and middle fractions, producing gasoline, kerosene, and gas oil (boiling points less than 350 °C). Large amounts of these lighter fuels (48 mol % C) were produced by the catalytic cracking of residual oil, which contained 93 mol % C of heavy oil fraction (boiling points above 350 °C), with a zirconia-alumina-iron oxide catalyst at 500 °C, with lesser amounts (20 mol % C) at 450 °C. More alumina was mixed to the catalyst to promote the cracking of heavy oil at lower temperatures. This modified catalyst was found to be better for cracking heavy oil, even at 450 °C, and the total amount of lighter fuels was as large as that obtained at 500 °C.