Thermal behaviour of oxidized Boscan atmospheric residue

Abstract

Controlled and progressive chemical oxidation was performed on Boscan atmospheric residue, then the thermal behaviour of the samples was examined. Hydrogen peroxide-methanol gave specific sulphoxidation, while stronger oxidation of sulphur and large viscosity and solubility changes were observed with hydrogen peroxide-acetic acid and m-chloroperbenzoic acid. Thermal cracking sensitivity was reduced and coke production increased steadily with the strength of oxidation. Efficient visbreaking only occurred with H 2O 2-methanol from low temperature decomposition of sulphoxides to active radicals. In no case was the sulphur elimination at the level expected from model compound pyrolysis. Except with H 2O 2-methanol, carbonization of the oxidized residues followed by transmission electron microscopy showed deep degradation of the microstructural organization (decrease in the extent of the local molecular orientation). This altered the graphitization capacity, as confirmed by the sulphur concentration in the pre-graphites. All the results suggest that sulphone entities are mainly responsible for profound physical and thermochemical changes, with rapid destruction of the microstructural organization.