Hydroprocessing of Low-Temperature Coal Tar for the Production of Clean Fuel over Fluorinated NiW/Al₂O₃–SiO₂ Catalyst

Abstract

Hydroprocessing of low-temperature coal tar (LTCT) for the production of clean fuel was investigated over fluorinated NiW/Al2O3–SiO2 catalyst in a fixed bed reactor. A series of NiW/Al2O3–SiO2 catalysts with different F-loading were prepared by incipient wetness coimpregnation and characterized by various techniques such as nitrogen adsorption, FT-IR, XRD, SEM TPD-NH3, and XPS. The effects on the yield, properties of liquid products, and gas components from using fluorinated NiW/Al2O3–SiO2 catalysts were discussed. In addition, coke formation was also evaluated by TG-DTG. The result showed that the introduction of F influenced both acidity and active phase while have little effect on crystalline structure of NiW/Al2O3–SiO2 catalysts. Lower F-loading in the NiW/Al2O3–SiO2 catalysts not only improved catalytic performance but also was helpful to improve some of the physicochemical properties of liquid product including dynamic viscosity, density, distillation range and hydrocarbon content, and so on. The optimal F concentration to NiW/Al2O3–SiO2 is 1.0 wt %, at which the highest naphtha and diesel yield was obtained due to its appropriate acid distribution and more active phase. Meanwhile, liquid product produced displayed the lowest N content (78.6 ug/g) and density (0.8507 g/mL). Furthermore, compared with feedstock, phenols almost disappeared and phenyl cycloalkanes (PCA) and cycloalkanes (CA) are rich in hydrogenated product.