Thermal treatment of FCC slurry oil under hydrogen: Correlation of hydrogen transfer ability with carbonization performance of the fractions

Hydrogen transfer property is of great importance in the carbonization of heavy oils. Thermal treatment under hydrogen was performed on a raw slurry oil (SO) from FCC process. The theoretical hydrogen-donating property of SO fractions before and after treatment was predicted by comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry. The hydrogen-transfer experiments using anthracene (ANT) and 9,10-dihydroanthracene (DHA) as chemical probes were carried out to determine the hydrogen transfer ability (HTA) of SO fractions, the effect of which was examined by subsequent carbonization experiments. Results show that the donatable hydrogen contents of SO fractions are increased after thermal treatment under hydrogen. A modified method for calculating the hydrogen-donating ability (HDA) of the fractions is proposed on the basis of the 1H NMR data of the reacted mixtures derived from the hydrogen-donating experiments. The results calculated with this method are more accurate with inherent ANTs and DHAs considered. The HDA is found to be closely related to the composition of hydroaromatics in terms of the content and hydrogen-donating activity. The hydrogen-accepting ability (HAA) of the fractions is also calculated with similar method proposed accordingly, and thus the hydrogen-donating index that quantitatively describes the HTA is obtained. Thermal treatment under hydrogen improves the HTA of the fractions considering the increased HDA and decreased HAA after treatment, and also improves the morphology of derived semi-cokes as indicated by subsequent carbonization experiments. The correlation between the HTA of SO fractions and the morphology of derived semi-cokes reveals that the quality of derived cokes improves as the HTA of carbonization feedstocks improves, not necessarily in positive correlation with the HDA of SO fractions nor necessarily in negative correlation with the HAA of SO fractions.