Desulphurization of Athabasca petroleum coke by (a) chemical oxidation and (b) solvent extraction

Abstract

This study concerns the desulphurization of petroleum coke produced by delayed coking of Athabasca bitumen. The coke contains 7.5 wt % sulphur, 99.6% of the sulphur in coke being organic and the remainder pyritic. The coke was treated both with nitric acid and by solvent extraction. During nitric acid treatment, sulphur removal was found to increase with reaction time and the concentration of nitric acid, and to decrease slightly with increase in particle size. About 30% of organic sulphur was removed from −250 Tyler mesh coke particles by 6 N nitric acid for 4 h at 102 °C. The basic mechanism for this treatment is oxidation and solution of organic sulphur compounds by nitric acid. About 50% ash was also removed from the coke. For solvent extraction, o-chlorophenol was used. Sulphur removal was found to increase with extracting temperature and time, and to decrease with increase in particle size of coke. About 19% of the sulphur was removed from −250 mesh coke particles by o-chlorophenol at 160 °C in 2 h. When treated consecutively with nitric acid and o-chlorophenol, about 40% of sulphur was removed from the −250 mesh coke particles.