Effect of pre-oxidation of dispersed catalysts on heavy oil cracking

Abstract

Heavy and extra-heavy oils are characterized by a high content of resins, asphaltenes, and sulfur, which hinders oil refining. The purpose of this paper is to study the effect of NiCrWC catalyst surface pre-oxidation on the composition of products of heavy oil catalytic cracking. The optimal conditions for the pre-oxidation of the catalyst are a temperature of 450 °C and a duration of 2 hours in air. The products of catalytic cracking are analyzed by content of saturated and aromatic hydrocarbons, resins and asphaltenes, gas chromatography, X-ray diffraction, and scanning electron microscope spectrometry methods. Pre-oxidation of a NiCrWC catalyst at 450 °C leads to a decrease in the content of macromolecular components, sulfur, by-products, and an increase in the yield of a fraction with a boiling point up to 360 °C. The decrease in sulfur content in the course of heavy oil upgrading is caused both by the interaction of metal oxides on the surface of NiCrWC with S-containing compounds of the feedstock, and by the removal of sulfur in the form of gas. A hypothetical mechanism for the cracking of heavy oil components over pre-oxidized catalysts is proposed.