Experimental study on pre-hydrogenation of catalytic slurry oil and co-carbonization of middle distillate and high boiling point distillate

A catalytic slurry oil (SO) was treated by moderate pre-hydrotreating, and the structural compositions, the thermal stability, the distillate oil yield, and the coking behavior of SO before and after hydrotreating were analyzed. The carbonization performance as well as the co-carbonization performance of the middle distillate (350–500 °C) and the high boiling point distillate (500–550 °C) derived from the hydrogenated SO (HSO) were investigated. The results show that the content of naphthenes and hydrogenated aromatics of HSO increases, while the olefin content decreases, and the olefinic hydrogen content of HSO decreases from 2.71% to 0.97%. Thus, the thermal stability of HSO is fundamentally improved. Additionally, compared with SO, the yields of the middle distillate and the high boiling point distillate of HSO increased by 25.8% and 23.1%, respectively. More importantly, there is no significant coke formation during distillation of HSO. The carbonization experimental results show that the anisotropic textural structure of the coke obtained from the middle distillate derived from HSO is the large flow domain structure, and the coke has the lowest coefficient of thermal expansion (CTE) value of 2.25×10−6 °C−1. The carbonization performance of the high boiling point distillate derived from HSO is poor, while the co-carbonization with the middle distillate significantly improves the carbonization performance of the high boiling point distillate. The anisotropic textural structure of the coke derived from carbonization of combined fraction is the large flow domain structure and the CTE value is less than 2.30×10−6 °C−1, when the mass ratio of aromatic fraction to middle fraction is not higher than 2:1.