Visbreaking reaction of atmospheric residue. Part 5. Structural analysis and reaction mechanism for Khafji atmospheric residue.

Abstract

Atmospheric residue from Khafji crude was subjected to thermal cracking at 420-460°C in the presence of a diluent, namely, nitrogen, hydrogen, or tetralin as a hydrogen donor. The feed and the product residues were separated into six fractions. The Khafji feed has the larger share of asphaltenes and the smaller share of saturates and monoaromatics, compared with the three other feeds, namely, Arabian Heavy, Iranian Heavy and Taching. The yield and structural change of the six fractions by thermal cracking were accounted for by the mechanism consisting of unimolecular decomposition and radical chain reaction.