Study on suspension bed hydrocracking of medium temperature pyrolytic heavy tar fraction

The medium temperature pyrolytic coal tar was used as raw material and was analyzed, in which the fraction with boiling point > 350 ℃ that contains the resin of 30.88%, the asphaltene of 37.27% and the tetrahydrofuran insolubles of 3.36% is difficult to hydrocrack directly by conventional fixed bed. A Mo-based ultra-dispersed catalyst was synthesized, and characterized by FT-IR, XPS, XRD, SEM and TEM, etc. The catalyst contains Mo=O and Mo-S characteristic structure and has an excellent dispersibility in the reaction system, and the vulcanization ratio of molybdenum reaches 84.34%. The catalyst can be decomposed into hyper dispersive MoS₂ particle in the reaction system. The suspension bed hydrocracking experiments were carried out in a 0.25 t/d continuous unit with heavy fraction of tar. Moreover, the effects of reaction conditions on product distribution and coking rate were investigated. The optimum reaction conditions were 19 MPa, 440 ℃ and 300 mg/kg of catalyst addition. Under these conditions, the naphtha yield is 24.47%, the diesel fraction yield is 49.71%, and the coking rate is 1.32%.