Research On Hydrogenation Catalysts For Inferior Heavy Oil And Production Of Light Fraction

With the increasingly heavy&inferior quality of crude oil and the demand of environmental protection,how to utilize the inferior heavy oil sources for production of ultra-clean transportation fuels has become research hotspot in petrochemical industry fields.Due to the"rich coal,deficient oil,lean gas"energy structure in China,extensive studies have been focused on coal-to-liquids（CTL）technology,resulting in large amounts of coal tar byproduct.As one of the byproducts from fluid catalytic cracking unit,light cycle oil（LCO）with poor quality cannot be directly used for fuel blending components.Hydrotreatment process could convert coal tar&LCO into light fraction and high value-added products,which cannot only relieve the growing crisis in oil energy but also realize the clean utilization of coal tar&LCO.In current work,Zr O₂ was blended into Si O₂,Al₂O₃ materials,respeactively,and USY into Al₂O₃ materials by employing the coating-precipitation method.Meanwhile,Al₂O₃-USY（AYx）support was prepared by mechanical mixing approach.And then the Co Mo hydrogenation catalysts were acquireed.The surface acidity,porous structure and the reducing ability of active metals over the composite supports and the supported Co Mo catalysts were analyzed.The effects of physicochemical properties of Co Mo catalysts on the product distribution were investigated by combining the hydrogenation performance of low-temperature coal tar on the 200 m L fixed-bed apparatus and the characterization results.The gas chromatography was employed to analyze the yield of gaseous organic compounds.The oil phase from hydrogenated product was separated into gasoline fraction（≤180℃）,diesel fraction（180-300℃）,and residue fraction（>300℃）.Zr O₂species in the composite materials of Zr O₂-Si O₂（ZSx）and Zr O₂-Al₂O₃（ZAx）were presented with high dispersion or amorphous condition.The aggregation and phase transition of Zr O₂species were suppressed due to the presence of Si-O-Zr bond or Al-O-Zr bond.The metal-support interaction was modulated with the introduction of Zr O₂,thus enhanced the dispersion of active metals.Comparing with the Co Mo/ZAx samples,the Co Mo species were higher dispersed on the ZSx composite support due to the addition of Zr O₂.With the increase in Zr O₂ content,the acid amount of ZSx,ZAx,and the supported Co Mo catalysts were enhanced,and the reducing ability of active metal components was modulated.The intensive large mesoporous structure of Co Mo/ZS24 and Co Mo/ZA24 samples was beneficial to the reaction for the huge molecules.The introduction of Zr O₂ significantly improved the hydrogenation performance of Co Mo catalysts.However,the excessive amounts of Zr O₂in Co Mo/ZAx catalysts will induce the over-cracking,thus reduced the yield of middle distillate.After the introduction of USY zeolites of high specific surface area into Co Mo/Al₂O₃,the active metals were well dispersed.As the content of USY increased,the acid amount of composite carriers and supported catalysts was enhanced.And the surface acidity of samples which obtained by coating-precipitation method was lower than those samples by mechanical mixing approach.Meanwhile,the active metals of Co Mo/CAY70 catalysts were easier to reduce.Co Mo/AYx catalysts exhibited higher hydrogenation activity than Co Mo/Al₂O₃catalyst.However,after the content of USY above 30 wt%,the yield of middle distillate declined.Co Mo catalysts with equivalent USY content which prepared by mechanical mixing approach,displayed lower yield of middle distillate than those ones which obtained by coating-precipitation method.Co Mo/CAY70 catalyst exhibited relatively higher middle distillate selectivity and hydrogenation performance among the Co Mo/AYx samples.The hydrocarbon composition of gasoline&diesel fraction from hydrogenated low-temperature coal tar over Ni Mo/Beta-KIT-6 and Co Mo/CAY70 catalysts was analyzed,respectively.The results demonstrated that Ni Mo/Beta-KIT-6 possessed high hydrocracking performance,and Co Mo/CAY70 in possession of high selectivity to cycloalkanes and hydrogenation activity.Besides,the hydrogenation process of LCO was preliminarily conducted over the hydrogenation catalysts for low-temperature coal tar,with the conversion rate of residue fraction up to 86.7 wt%and low yield of middle distillate.Due to the meaningful process of LCO hydro-converting into transportation fuels or high value-added products,there still need some in-depth efforts to explore the effects of various catalysts and process conditions on the LCO hydrogenation performance.