Hydrotreatment of model compounds with catalysts of NiW/Al₂O₃ and NiWP/Al₂O₃ to simulate low temperature coal tar oil

Eight characteristic model compounds were employed as hydrotreatment feedstocks to simulate low temperature coal tar oil. A series of NiW/Al₂O₃ catalysts with different Ni/W ratio and NiWP/Al₂O₃ catalysts with different phosphorus content were prepared by incipient wetness co-impregnation. Both catalysts were characterized by N₂ adsorption-desorption, X-ray diffraction, HRTEM, H₂-TPR, NH₃-TPD and FT-IR. The heteroatom removal and polyaromatic hydrogenation conversions were more than 90% over these catalysts. Ni₆W₂₀ showed the highest conversion among the NiW/Al₂O₃ catalysts due to the presence of relatively short, thick slabs when compared to the other Ni/W ratios. Phosphorus was added to adjust the acid concentration of NiW sulfides. The best hydrotreatment performance was seen with the 0.8 wt% phosphorus catalyst, which was attributed to the highest medium strength acid concentration. The results suggested the medium acid on the NiW sulfide was probably the active site for the hydrogenation of the aromatic ring in the coal tar oil hydrotreatment process. The self-prepared catalyst showed higher HDS and HDN activity than a commercial catalyst.