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Description:
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A rigorous kinetic model of hydrodesulfurization (HDS ) of complex mixtures such
as light cycle oil (LCO ) or diesel has been developed . An experimental setup was
constructed to investigate the hydrotreatment of complex mixtures . The
hydrodesulfurization of LCO on a commercial CoMo /Al2O3 (IMP ) catalyst was
investigated in a Robinson Mahoney perfectly mixed flow stationary basket reactor . An
experimental investigation of the HDS of the dibenzothiophene (DBT ) and substituted
dibenzothiophenes in the LCO was carried out at temperatures between 290 and 330°C ,
space time for dibenzothiophene (W /F0
DBT ) between 1000 and 6500 kgcat -h /kmol , and
H2 /HC molar ratio constant of 2 .8 . To avoid having to deal with a huge number of
parameters in the model , a methodology based on structural contributions was applied .
DENs and DENt are the denominators of the Hougen -Watson rate expressions for
hydrodesulfurization of dibenzothiophene (DBT ) and methyl -substituted
dibenzothiophenes contained in the LCO . Both denominators comprise the concentration of all adsorbing species of the LCO multiplied by their adsorption equilibrium constants .
The estimation of the denominators DENs and DENt was performed using the
Levenberg -Marquardt algorithm and the results in terms of conversion for DBT ,
biphenyl and cyclohexylbenzene obtained in the hydrodesulfurization of the LCO . The
evolution of DENs and DENt values with the composition was calculated for each LCO
experiment .
Structural contributions were taken from Vanrysselberghe and Froment for
hydrogenolysis and hydrogenation of methyl -substituted dibenzothiophenes with a
significant reduction in the number of parameters to be estimated in the HDS of the
LCO .
The multiplication factors , fsDBT , which are products of structural contributions for
hydrogenolysis and hydrogenation of the mono - and dimethyl -dibenzothiophenes were
also taken from Vanrysselberghe and Froment . These multiplication factors are based on
experimental results with model components such as DBT , 4 -Methyl dibenzothiophene
and 4 ,6 -Dimethyl dibenzothiophene .
The results obtained in the modeling are in good agreement with the experimental
data because the model reproduces very well the observed total conversions of DBT ,
conversions of DBT into biphenyl and conversions of DBT into cyclohexylbenzene as a
function of temperature . |