Poisoning effect of nitrogen compounds on the performance of CoMoS/Al2O3 catalyst in the hydrodesulfurization of dibenzothiophene, 4-methyldibenzothiophene, and 4,6-dimethyldibenzothiophene
C. Kwak et al., Poisoning effect of nitrogen compounds on the performance of CoMoS/Al2O3 catalyst in the hydrodesulfurization of dibenzothiophene, 4-methyldibenzothiophene, and 4,6-dimethyldibenzothiophene, APP CATAL B, 35(1), 2001, pp. 59-68
Citations number
34
Categorie Soggetti
Physical Chemistry/Chemical Physics","Environmental Engineering & Energy
The poisoning effect of carbazole and quinoline on the performance of sulfi
ded CoMo/Al2O3 in the hydrodesulfurization (HDS) of dibenzothiophene (DBT),
4-methyidibenzothiophene (4-MDBT), and 4,6-dimethyldibenzothiophene (4,6-D
MDBT) has been examined. The HDS of 4-MDBT or 4,6-DMDBT is retarded by the
presence of the nitrogen compounds in the reaction stream even at low conce
ntrations, e.g. 50 ppm, while the HDS of DBT remains nearly unaffected by t
hese compounds unless the concentrations are high, in excess of 500 ppm. Th
e nitrogen compounds suppress the ring-hydrogenation step (HYD) more than t
he direct desulfurization step (DDS) in the HDS of DBT, while an opposite t
rend is observed in the HDS of 4-MDBT or 4,6-DMDBT, i.e. DDS is suppressed
to a greater extent than HYD. The nitrogen compounds poison acidic sites on
the catalyst, as confirmed by the reduced amounts of pyridine adsorbed and
by the suppressed isomerization of 2,2 ' -dimethylbiphenyl on the poisoned
catalyst. Quinoline exhibits a stronger poisoning effect than carbazole. T
he HDS of the three DBT compounds studied in this work are suppressed to di
fferent extents by the nitrogen compounds because the extent of steric hind
rance to the C-S-C bond by methyl groups attached to the ring structure is
different depending on the DBT compounds. (C) 2001 Elsevier Science B.V. Al
l rights reserved.