Selective hydrocracking of light cycle oil into high-octane gasoline over bi-functional catalysts

Abstract

Serial catalyst systems were evaluated on naphthalene, tetralin and light cycle oil (LCO) hydrocracking reactions. The CoMo-AY/NiMo-AY grading catalysts system presented the highest BTX content, yield and octane number of gasoline fraction. • CoMo/AY catalyst presented high selectivity of saturating naphthalene to tetralin. • NiMo/AY catalyst showed high activity of cracking tetralin into light aromatics. • A novel lumping kinetic model of naphthalene was proposed and calculated. • CoMo-AY/NiMo-AY grading catalysts was the best choice to convert LCO to gasoline. • CoMo-AY/NiMo-AY grading catalysts showed good stability and low carbon deposition. Light cycle oil (LCO) with high content of poly-aromatics was difficult to upgrade and convert, which had hindered upgrading fuel quality to meet with the standard of automotive diesel for the purpose of sustainable development. The hydrocracking behaviors of typical aromatics in LCO of naphthalene and tetralin were investigated over NiMo and CoMo catalysts. Several characterization methods including N 2 -adsoprtion and desorption, ammonia temperature-programmed desorption (NH 3 -TPD), Pyridine infrared spectroscopy (Py-IR), CO infrared spectroscopy (CO-IR), Raman and X-ray photoelectron spectroscopy (XPS) were applied to determine the properties of different catalysts. The results showed that CoMo catalyst with high concentration of S-edges could hydrosaturate more naphthalene to tetralin but exhibit lower yield of high-value light aromatics (carbon numbers less than 10) than NiMo catalyst. NiMo catalyst with high concentration of Mo-edges also presented a higher selectivity of converting naphthalene into cyclanes than CoMo catalyst. Subsequently, the naphthalene and LCO hydrocracking performances were also investigated over different catalysts systems. The activity evaluation and kinetic analysis results showed that the naphthalene hydrocracking conversion and the yield of light aromatics for CoMo-AY/NiMo-AY grading catalysts were higher than NiMo-AY/CoMo-AY grading catalysts at same condition. A stepwise reaction principle was proposed to explain the high efficiency of CoMo-AY/NiMo-AY grading catalysts. Finally, the LCO hydrocracking evaluation results confirmed that CoMo-AY/NiMo-AY catalysts grading system with low carbon deposition and high stability could remain high percentage of active phases, which was more efficient to convert LCO to high-octane gasoline.