Kinetic Model for Catalytic Cracking of Heavy Oil with a Zirconia-Alumina-Iron Oxide Catalyst in a Steam Atmosphere

A kinetic model was proposed to represent the catalytic cracking of heavy oil with a zirconia-alumina-iron oxide catalyst in a steam atmosphere. The model includes four lumps: heavy oil (boiling point above 350 degrees C), gas oil (boiling point of 250-350 degrees C), gasoline + kerosene (boiling point less than 250 degrees C), and gas. In this reaction, heavy oil fractions reacted with lattice oxygen in iron oxide and the active oxygen species, which were incorporated from the steam into the iron oxide lattice. Hence, lighter fractions, such as gasoline, kerosene, and gas oil, and carbon dioxide were produced with almost no coke. Kinetic parameters were determined using a nonlinear least-squares regression of the experimental results obtained under the reaction conditions of 450-500 degrees C and a time factor, W/F-R, of 3.8-28 h. The evaluated activation energy of heavy oil cracking was lower than those reported in the literature on the hydrocracking process. Accordingly, it is supposed that active oxygen species generated from steam and the lattice oxygen in iron oxide promoted the cracking of heavy oil.