Catalytic Cracking of Heavy Oil with Iron Oxide-based Catalysts Using Hydrogen and Oxygen Species from Steam

Abstract

Upgrading of heavy oil is an important process in the petroleum industry to produce light oil for transportation fuels. The conventional processes of treating heavy oil, such as petroleum residual oil, include thermal cracking, residue fluidized catalytic cracking (RFCC), and hydrocracking1). Gas, liquid, and coke are produced by the thermal cracking of heavy oil in a coking process. Large amounts of light oil are generated at high temperature with long residence time, but the coke yield increases. The process requires hydrogenation of light oil to stabilize the product through the addition of hydrogen to the double bonds of the components. Hydrocracking is useful for producing stabilized light oil with low coke yield, but the use of hydrogen gas is expensive. The use of water as a hydrogen source has good potential for upgrading heavy oil. Several studies have reported the use of steam and supercritical water2)~7). Supercritical water can dilute the heavy oil, although the process requires high pressure and high temperature2),3). Aquaconversion is a catalytic steam conversion process to upgrade heavy oil into transportable oil, in which hydrogen is transferred from steam to hydrocarbons4). Catalytic cracking of heavy oil was achieved with iron oxide-based catalyst using steam5)~7). Oxidative decomposition of heavy oil occurred over the iron oxide-based catalysts containing zirconia and alumina to produce light oil. After the lattice oxygen of iron oxide reacted with the heavy oil, the oxygen species derived from steam were incorporated into the iron oxide lattice and reacted with the heavy oil. Zirconia promoted the generation of oxygen species from steam, and alumina suppressed the phase change of iron oxide. Generation of oxygen species from steam occurs simultaneously with generation of hydrogen species. One previous study briefly reported that hydrogen species could be incorporated into light oil7). The present study further investigated the transfer of hydrogen species from steam to product using a model compound and petroleum residual oil, and examined the effect of the flow rate ratio of steam to feedstock, as well as the effect of the zirconia content of the catalyst on hydrogen transfer. 329 Journal of the Japan Petroleum Institute, 58, (5), 329-335 (2015)