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

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 degrees 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 degrees 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 degrees 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.