Effects of bifunctional catalyst geometry on Vacuum Gas Oil Hydrocracking Conversion and Selectivity for Middle Distillate.

A kinetic model for the hydrocracking of a real vacuum gas oil feedstock (VGO) with 217 discrete lumps defined by carbon number and structure was extended from the model published by our group. A model with two additional parameters, taking into account catalyst composition and geometrical properties, was developed. The 17-parameter estimation was performed from 1332 experiment data points obtained in a semi batch reactor at 120 bar and 400 degrees C at various reaction times (0-338 min) for 3 bifunctional catalysts and is validated against 8 catalysts with different zeolite and metal loadings (respectively, 0.5-1.5 and 0.6-0.7) based on a statistical analysis. A macroscale relation for cracking rates, dependent on zeolite loading and catalyst internal geometry, was proposed. This interpretation gives good agreement between calculated and measured mass fractions, VGO conversion and middle distillate, and naphtha and LPG selectivities. Critical analysis of the estimated kinetic constants confirms the well-known bifunctional mechanism derived from model molecules.