Composition of stacked bed for VGO hydrocracking with maximum diesel yield

• NiMo/Al2O3, NiMo/ASA-Al2O3, NiMo/Y-Al2O3 catalysts were prepared and studied using TEM, nitrogen adsorption, XRD and tested in hydrocracking of VGO.
• NiMo/ASA catalyst has the optimal activity and selectivity to diesel in hydrocracking of VGO.
• Stacked bed containing zeolite-based catalysts has the highest activity and the lowest selectivity to diesel.

Hydrocracking catalysts prepared by co-impregnation of three different supports with solutions containing Ni, Mo and citric acid were studied. Pure γ-Al2O3, 30% of zeolite Y/γ-Al2O3 and 70% of amorphous aluminosilicate ASA (Si/Al = 0.9)/γ-Al2O3 were used as supports. All the catalysts were shown to contain the particles of Ni-Mo-S phase with similar morphology after liquid phase sulfidation by DMDS. The active component is uniformly distributed on γ-Al2O3 and ASA surface in NiMo/Al2O3 and NiMo/ASA-Al2O3 catalysts. The main amount of Ni and Mo is localized on γ-Al2O3 surface in NiMo/Y-Al2O3 catalyst while the main part of zeolite Y surface is free of supported metals. Testing of stacked beds, which comprise different prepared catalysts, in hydrocracking of vacuum gasoil showed that the NiMo/Al2O3 catalyst had the maximum selectivity to diesel fuel, but its activity was insufficient. Diesel fuel yield did not exceed 50 wt.% for the stacked beds comprising NiMo/Y-Al2O3 independent on the process temperature. NiMo/ASA-Al2O3 had an optimal ratio of activity to selectivity for the production of diesel fuel and provided the diesel fuel yield by over 60 wt.% at 400 °C.

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