Abstract
This contribution deals with about selective conversion of heavy gas oils into middle distillates fuels that meet ultra-low sulfur and aromatic compound quality standards by using a novel NiWRu/TiO2–γAl2O3catalyst under typical hydrotreatment conditions. A diesel fuel fraction having sulfur, nitrogen and aromatics compound content of about 50 ppm, 10 ppm and 15 v%, respectively, was obtained when the reactor was operated atT = 370 °C,P = 12.4 MPa, LHSV = 0.5 h−1and H2/hydrocarbon ratio = 800 Nm3/m3. Titanium and ruthenium additives used in the preparation of the NiWRu/TiO2–γAl2O3catalyst, remarkably improved the catalytic activities for the hydrogenolysis, hydrogenation and hydrocracking reactions compared to the reference NiW/γAl2O3catalyst. The coprecipitation of titanium and aluminum hydroxides produced a catalyst support having greater surface area, pore volume and surface acidity. An improvement in mechanical properties of the support extrudates was also observed. Characterization analysis by XPS, AUGER and XRD techniques of the TiO2–γAl2O3support suggested the formation of an aluminum-titanate mixed phase (AlxTiyOz) having a non-well-defined stoichiometry. The NiW/TiO2–γAl2O3and NiWRu/TiO2–γAl2O3exhibited a greater surface dispersion of the supported nickel and tungsten species compared to the NiW/γAl2O3catalyst. The promoter effect of ruthenium on the NiW bimetallic system caused a strong increase in both hydrogenolysis and hydrogenation reactions. Hydrodenitrogenation and hydrocracking reactions were also favored by the increase in the hydrogenation capacity and in the surface acidity of the catalyst. The highest conversion levels for all investigated reactions were obtained when the NiWRu/TiO2–γAl2O3catalyst was prepared by co-impregnation of Ni and Ru in a second step. This catalyst showed sulfur tolerance properties when the reaction was conducted in the presence of different H2S partial pressures. The catalytic behavior of the NiWRu/TiO2–γAl2O3catalyst was explained by the existence of a promoting effect between separated Ni and Ru sulfides species and the NiWS phase (dual mechanism).
Highlights
The continued depletion of light crude reserves has made oil refineries to process larger amounts of heavy crudes
When the support was prepared by co-precipitation of Ti and Al hydroxides, significant in surface area and pore volume was observed
The conclusions that emerge from this work are the following: We have successfully demonstrated the selective conversion of heavy gasoil into middle distillates fuels that meet with the ultra-low sulfur and aromatic standards by using a NiWRu/TiO2–cAl2O3 based catalyst under typical hydrotreating operating conditions
Summary
The continued depletion of light crude reserves has made oil refineries to process larger amounts of heavy crudes. Very few refineries in the world are configured to process heavy crudes This is the reason behind large oil corporations for making significant capital investments to develop new catalytic processes and modernize their process units. The oil refining industry has been forced to produce cleaner fuels and operate their units more efficiently to meet with strict environmental restrictions imposed by. To fulfill these requirements, oil companies have been making important capital investment for modernizing their refineries through the acquisition of new technologies, supporting research projects for the development of new catalytic materials and optimizing their operations for producing gasolines and diesel fuels having very low level of sulfur and aromatic compounds.
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More From: Oil & Gas Science and Technology – Revue d’IFP Energies nouvelles
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