Barbara BROWNING^a, Pavel AFANASIEV^a,
Isabelle PITAULT^b, Françoise COUENNE^b, Melaz
TAYAKOUT-FAYOLLE^a*

Institut de
Recherches sur la Catalyse et l?Environnement de Lyon (IRCELyon)^a ,
LAGEP^b,

CNRS, Université
Claude Bernard Lyon 1, 2 Avenue Albert Einstein, 69626 Villeurbanne cedex,
France

*Corresponding
author: +33.(0)4.72.44.54.26, melaz.tayakout@ircelyon.univ-lyon1.fr

A model for
hydrocracking a VGO over a bifunctional catalyst at 400°C and 120 bar in a
semi-batch reactor has been constructed based on the experimental work of Henry
et al. [1].   In this work liquid phase composition was analysed by two
dimensional gas chromatography (GC x GC) and, to model these results, the
reaction mixture is lumped into pseudo-components by both molecular structure
and carbon number.  The rate constants are represented using probability
distributions including the product distribution published by Weitkamp for
ideal hydrocracking [2].  Reactivity is calculated as a function of carbon
number. 

The model uses the
Grayson-Streed activity coefficient model combined with the Peng-Robinson
equation of state to represent the vapour-liquid equilibrium in the reactor [3]
and also takes into account internal and external mass transfer resistances. 

The results of this
model show that the assumptions regarding the molecular structure of the
naphthenes and aromatics are important to successfully represent the
experimental data and, in particular, to simulate

the over-cracking
observed experimentally for the iso-paraffins.   The same effect could not be
achieved by adjusting only the mass transfer coefficients. 

Figure 1- Comparison between model results and experimental data

Keywords:
Hydrocracking, kinetic model, vacuum gas oil, bifunctional
catalyst

1.     R. Henry, M.
Tayakout-Fayolle, P. Afanasiev, C. Lorentz, G. Lapisardi, G. Pirngruber,
Catalysis Today 220-222 (2014) 159-167

2.     J. Weitkamp, ChemCatChem 4(2012) 292

3.B. Browning,
R. Henry, P. Aanasiev, G. Lapisardi, G. Pirngruber, M. Tayakout-Fayolle,