Hydrotreatment of Middle Distillate from Pyrolysis Tar by Using Fixed Bed Reactor

Abstract

Hydrotreatment is a crucial operation in the modern oil refining industry, used for removing heteroatoms and hydrogenating aromatic compounds. Middle distillates of coal tar can serve as an alternative feed for producing diesel fuel after heteroatom reduction. Coal tar was obtained through the pyrolysis of Mongolian brown coal at 700°C. The middle distillate, with a boiling range of 220–350°C, was separated from the tar by vacuum distillation, yielding 36.09 wt.%. Hydrotreatment of the middle distillate was carried out at temperatures of 340 and 360°C using a continuous flow, fixed bed reactor filled with a commercial NiMo/Al₂O₃ catalyst. The hydrogen pressure was 6MPa, and the hydrogen flow rate was 0.54 ml/min. The results showed that decreasing the liquid hourly space velocity (LHSV) from 1.55 to 1.03 h^–1 significantly reduced the content of heteroatoms in products from 6.16 to 2.60% and 4.36 to 0.52% for 340 and 360°C, respectively. The total removal of heteroatomic compounds from the middle distillate was highest at 92.36% for the product obtained at 360°C temperature using LHSV 1.03 h^–1.