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oxygenates such as phenol, guaiacol, decanoic acid inhibi-
ted the HDS transformation of dibenzothiophene (DBT) and
4,6-dimethyldibenzothiophene (4,6-DMDBT) when these
compounds were not totally converted. However, when
phenol or guaiacol was totally converted, i.e. to water and
hydrocarbons, no effect in HDS was noticed showing that
water had no impact on HDS performances. Conversely, the
decomposition of decanoic acid to CO led to a strong
inhibiting effect [20]. In that respect, density functional
theory (DFT) studies have also shown that CO must be
considered as a much stronger inhibitor than guaiacol [21],
alcohol or carboxylic acid [22e24]. In HDS of a model feed
representative of FCC gasoline under various operating
conditions, Pelardy et al. [25] confirmed the strong impact
of CO on the HDS of 2-methylthiophene and the hydroge-
nation of 2,3-dimethylbut-2-ene in mixture. The authors
explained these results by the mutual competitive
adsorption on the catalyst surface and the higher adsorp-
tion energy of CO compared to other compounds (sulfur
compounds and alkenes) determined by density functional
theory (DFT) calculations. CO adsorption is indeed ther-
modynamically favored on mixed CoMoS sites on the S-
edge and M-edge, which explains the loss in HYD and HDS
activities.
The present paper summarizes and compares the main
results on the impact of CO presence on the transformation
of two model feeds of petroleum fractions (FCC gasoline
and Straight-Run gas oil). We focus more specifically on the
different impact of CO depending on the operating condi-
tions (T, P), the feed (gasoline or gas oil) and the catalysts
(CoMoS/Al2O3 or CoMoPS/Al2O3). The model compounds
chosen for describing the petroleum fractions were 2-
methylthiophene (2 MT) and 2,3-dimethylbut-2-ene (2,3-
DMB2N) for the model FCC gasoline and dibenzothio-
phene (DBT) and 4,6-dimethyldibenzothiophene (4,6-
DMDBT) for the model SR gas oil.
and phenol (>99% purity) from Aldrich Chemicals. They
were used without further purification. Carbon monoxide
and carbon dioxide (1 or 10 vol% in mixture with H2) have
been purchased from Air Liquide.
2.2. Reaction conditions
Reaction conditions are those described in previous
papers respectively for HDS of gasoline [25] and for HDS of
gas oils [19,20], only the main conditions are reported
herein. We report coherent operating conditions with usual
industrial ones given in Table 1
For HDS of FCC gasoline, catalytic activity measure-
ments were carried out in a fixed bed reactor at 250 ꢀC
under a total pressure of 2 MPa with a ratio H2/feed of
360 NL/L. Using these conditions, all the components are in
the gas phase. The model feed FCC gasoline containing
0.3 wt% of 2 MT, 20 wt% of 2,3-DMB2N, and 30 wt% of o-
xylene (representing aromatics) diluted in n-heptane was
injected in the reactor by a HPLC Gilson pump (307 series,
pump's head: 5 cm3) (Table 2).
The impact of CO on the transformation of the model
feed has been evaluated according to the experimental
procedure reported in a previous paper [25]. The amount of
CO varied from 0 to 1.31 kPa.
For HDS of gas oil, the HDS of 4,6-DMDBT (or DBT) wꢀas
carried out also in a fixed bed microflow reactor at 340 C
and 4.0 MPa of total pressure after an in situ sulfidation of
the catalyst according to the procedure described above
[19,20]. In these conditions, all reactants and products are
totally vaporized. 4,6-DMDBT or DBT (500 wt ppmS) were
dissolved in a mixture of toluene to which dimethyl di-
sulfide (DMDS) (9500 wt ppmS) was added to generate
H2S. To examine the effect of oxygenates on the 4,6-DMDBT
or DBT transformation, the partial pressure of the latter was
maintained constant at the standard 1.9 kPa (Table 3) while
the pressure of CO varied from 0 to 6 kPa.
2. Experimental part
2.1. Catalysts and chemicals
Table 2
Partial pressures (MPa) of the different compounds for the sulfidation step
and the transformation of the model FCC gasoline feed.
As reported previously [19,29,25], catalysts used are a
CoMo catalyst containing 3 wt% CoO and 10 wt% MoO3
supported on alumina for the HDS of FCC gasoline and a
CoMoP/Al2O3 catalyst containing 4 wt% CoO, 19 wt% MoO3
and 2.6 wt% of phosphorus for the HDS of SR gas oil. These
catalysts were provided by IFPEN. Both catalysts have been
Pressure (MPa)
Sulfidation
Model FCC gasoline
Polefin
0
0.01
0
0
0.09
0
0.150
0
PH
2 S
P2MT
Po-xyl
0.003
0.190
1.31
0.347
2
PH
crushed and sieved to a 250e315 mm size range.
2
PnC7
PTOT
The catalysts were sulfided in situ under H2S/H2 flow
(10 mol% H2S) for 10 h at 673 K at atmospheric pressure
before gasoline HDS measurements [24] or using a sulfid-
ing feed made of 4.75% by volume of dimethyl disulfide
(DMDS) in toluene as a solvent under a 4.0 MPa of total
pressure before gas oil HDS measurements [19,20].
0.1
Table 3
Partial pressures of the different compounds for the sulfidation step and
the transformation of 4,6-DMDBT or DBT.
2-methylthiophene (98% purity) and decanoic acid
(>98% purity) have been purchased from Alfa Aesar, 2,3-
dimethylbut-2-ene (98% purity) from Acros Organics, o-
xylene (>99% purity), dimethyl disulfide (>98% purity),
toluene (>99% purity) from Fluka, n-heptane (>99% purity)
from Carlo Erba, 4,6-dimethyldibenzothiophene (>95%
purity) from Eburon Organics and guaiacol (>98% purity)
Pressure (MPa)
Sulfidation
DBT or 4,6-DMDBT feed
PDBT or 4,6-DMDBT
0
0.002
0.036
1.299
2.627
4.0
PH and PCH
2 S
0.12
1.16
2.6
4.0
4
Ptoluene
PH
2
PTOT
Pelardy, Florian
