Hydroconversion of 2-methylnaphtalene and dibenzothiophene over sulfide catalysts in the presence of water under CO pressure

Article abstract of DOI:10.1007/s11172-020-2757-z

Unsupported highly dispersed nanosized catalysts based on transition metal sulfides were prepared insitu, in water-oil emulsions, by high-temperature decomposition of oil soluble metal precursors using elemental sulfur as sulfiding agent. Their catalytic activity was tested in hydroconversion of 2-methylnaphtalene and dibenzothiophene at 380 °C under H₂ pressure of 5 MPa. In addition, the catalysts were tested in the same reactions in the CO?H₂O medium (p(CO) = 5 MPa, the CO: H₂O molar ratio was 2: 1, ω(H₂O) = 20 wt.%) in which hydrogen is formed through a water gas shift reaction (WGSR). Unsupported Ni?Mo-sulfide catalysts were found to be the most active compared to catalysts supported on alumina. Transmission electron microscopy served to investigate the structure and determine general geometric characteristics of Ni?Mo?S particles formed in toluene—water medium by decomposition of transition metal naphthenates and hexacarbonyls in the presence of elemental sulfur under CO pressure. The method described in this study enables one to synthesize nanosized catalysts with a high content of active sulfide phase.

Full text of DOI:10.1007/s11172-020-2757-z

Russian Chemical Bulletin, International Edition, Vol. 69, No. 2, pp. 280—288, February, 2020
280
Hydroconversion of 2-methylnaphtalene and dibenzothiophene
over sulfide catalysts in the presence of water under CO pressure*
А. V. Vutolkina,а А. P. Glotov,а,b А. L. Maximov,а,c and E. А. Karakhanovа
аM. V. Lomonosov Moscow State University, Chemistry Department,
Build.3, 1 Leninskiye Gory, 119991 Moscow, Russian Federation.
E-mail: annavutolkina@mail.ru
bI. M. Gubkin Russian State University of Oil and Gas (National Research University),
65 Leninsky prosp., 119991 Moscow, Russian Federation
cA. V. Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences,
29 Leninsky prosp., 119991 Moscow, Russian Federation
Unsupported highly dispersed nanosized catalysts based on transition metal sulfides were
prepared insitu, in water-oil emulsions, by high-temperature decomposition of oil soluble
metal precursors using elemental sulfur as sulfiding agent. Their catalytic activity was tested in
hydroconversion of 2-methylnaphtalene and dibenzothiophene at 380 °С under Н2 pressure of
5 MPa. In addition, the catalysts were tested in the same reactions in the СО—H2О medium
(р(СО) = 5 MPа, the CO : H2O molar ratio was 2 : 1, ω(Н2О) = 20 wt.%) in which hydrogen
is formed through a water gas shift reaction (WGSR). Unsupported Ni—Mo-sulfide catalysts
were found to be the most active compared to catalysts supported on alumina. Transmission
electron microscopy served to investigate the structure and determine general geometric char-
acteristics of Ni—Mo—S particles formed in toluene—water medium by decomposition of
transition metal naphthenates and hexacarbonyls in the presence of elemental sulfur under CO
pressure. The method described in this study enables one to synthesize nanosized catalysts with
a high content of active sulfide phase.
Key words: sulfide catalysts, dispersed unsupported catalysts, 2-methylnaphthalene, di-
benzothiophene, water gas shift reaction, carbon monoxide.
The depletion of reserves of fossil fuels (oil, gas, coal),
genation of aromatic and organosulfur compounds. At the
same time, it is necessary that both water gas shift and
hydrogenation reactions proceed at the active sites of the
same catalyst. Catalytic systems including transition metal
sulfides, mainly molybdenum and tungsten, and pro-
moted with cobalt or nickel3—5 satisfy these requirements.
Alumina or zeolites are mainly used as supports for
hydroprocessing catalysts.6—10 However, in processing of
heavy petroleum feedstock, the conversion of large hydro-
carbon molecules in the presence of conventional catalysts
can be complicated by steric and diffusion restrictions that
arise when bulky molecules are adsorbed in the pores of
a support.11 In this regard, unsupported nanosized catalysts
distributed in a hydrocarbon medium are of a great inter-
est.12 Despite the relatively high cost, such catalysts have
a number of attractive advantages over traditional catalytic
systems. They are characterized by a high content of active
sites and can be readily converted into the sulfide form.13—15
In the case of their usage, the influence of steric restric-
tions caused by diffusion of substrate molecules to the
active component of the catalyst is negligible. Thus, appli-
cation of unsupported sulfide catalysts distributed in
along with a constant increase in energy consumption,
promotes an increase in contribution of unconventional
sources of hydrocarbons to the overall structure of pro-
cessed raw materials. In addition to highly viscous and
bituminous oils, bio-oil and renewable organic raw mate-
rials (biomass) are among these sources. These raw mate-
rials contain saturated, aromatic, heteroatomic com-
pounds, and, in some cases, water, the separation of which
requires additional technical solutions and is associated
with significant energy and resource costs.1,2 One of the
approaches designed to eliminate the stage of dehydration
is to involve water directly in the processing raw materials.
In particular, water can be a source of hydrogen generated
in the reaction medium. The water gas shift reaction, in
which water reacts with carbon monoxide to form carbon
dioxide and hydrogen, is an example of such a process.
The formed hydrogen can additionally be used in hydro-
* Based on the materials of the 18th International Symposium
IUPAC "Macromolecular Metal Complexes" (June 10—13, 2019,
Tver´, Russia).
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 0280—0288, February, 2020.
1066-5285/20/6902-0280 © 2020 Springer Science+Business Media LLC

Sulfidecatalysts
Russ. Chem. Bull., Int. Ed., Vol. 69, No. 2, February, 2020
281
Yield (%)
a hydrocarbon medium seems promising for the hydro-
processing of hydrocarbon feedstock containing water
which can be a source of hydrogen produced in situ by the
water gas shift reaction.
The ratio of metal to promoter in the case of traditional
sulfide catalysts used for hydroprocessing is 3 : 1.6,9
Herewith, depending on the nature of the metals, the
activity of sulfide catalyst systems in hydroconversion of
aromatic and organosulfur compounds is different. Thus,
Ni—Mo- and Ni—W-sulfide catalysts are the most active
in the hydrogenation of aromatic substrates,9,14,16 while
Co—Mo is used in hydrodesulfurization.6,7
a
6-Methyltetraline
2-Methyltetraline
trans-Decalines
cis-Decalines
100
90
80
70
60
50
40
30
20
10
Much investigations on the activity of unsupported
sulfide systems in hydrogenation of aromatic and organo-
sulfur substrates under hydrogen pressure have been re-
ported in the literature. At the same time, the effect of the
nature of the active metal and the promoter on the per-
formance of dispersed catalytic systems formed in situ,
i.e., in the reaction medium, is rarely discussed. Moreover,
in the literature, there are no studies on the functional
properties of such catalysts in processes carried out under
the pressure of carbon monoxide in the presence of water
as a source of hydrogen. In this regard, the aim of the
present work was to investigate the features of dispersed
catalytic systems consisting of transition metal sulfides
formed in situ from water-oil emulsions via the high-
temperature decomposition of oil-soluble metal salts in
the presence of a sulfiding agent. Activity of these catalysts
was estimated in hydroconversion of 2-methylnaphthalene
and dibenzothiophene at 380 °C and increased H2 pres-
sure, as well as in the СО—H2О system in which hydrogen,
as a reactant, is formed via the water gas shift reaction.
Mo Ni—Mo Co—Mo
W
Ni—W Co—W
Catalyst
Yield (%)
b
62
58
6-Methyltetraline
2-Methyltetraline
24
22
8
6
4
2
Mo Ni—Mo Co—Mo
W
Ni—W Co—W
Catalyst
Fig. 1. Distribution of products of hydrogenation of 2-methyl-
naphtalene over unsupported sulfide catalysts of different com-
position in the media of Н2 (а) and СО (b). Reaction conditions:
Т = 380 °С, t = 6 h, ω(Mo or W) = 1.5 wt.%: р(Н2) = 5 MPa (a),
p(СО) = 5 MPa (b), ω(Н2О) = 20 wt.%, CO : H2O = 1.5 (mol.).
Results and Discussion
To evaluate the effect of the nature of the metal and
the promoter on the activity of unsupported sulfide cata-
lysts, we selected 2-methylnaphthalene and dibenzothio-
phene, which is one of the most difficult to remove com-
pounds contained in hydrocarbon feedstock, as model
compounds in hydrogenation reactions.
Fig. 1, a). Their promotion with cobalt and nickel increases
the activity and, in the presence of the Ni—Mo catalyst,
conversion reaches 100%.
The Co—Mo catalyst demonstrates slightly lower activ-
ity: the conversion of the aromatic substrate reaches 80%
after 6 h run. At the same time, a reverse dependence is
observed for the W-containing systems. When Mo-based
catalyst is promoted, the activity increases by a factor of
1.3—1.5 and, in the case of W-based systems, it increases
about 2.4—2.6-fold. The main reaction products, comprise
in equimolar mixture of 2- and 6-methyltetralins. In the
presence of bimetallic systems, cis- and trans-decalins are
found, a fraction of which reaches 9% in the case of
Ni—Mo catalyst.
Figure 1 demonstrates the product distribution of
2-methylnaphthalene hydrogenation in the presence of
catalysts with various compositions. The total yield of the
products can be used to estimate the overall conversion of
the substrate. Fig. 1, a shows the data obtained in the
process carried out in hydrogen and Fig. 1, b shows the
data obtained in the reaction conducted under the pressure
of carbon monoxide in the presence of water as a source
of hydrogen, which is formed in situ by the water gas shift
reaction. In hydrogenation of 2-methylnaphthalene under
hydrogen pressure, molybdenum and tungsten sulfide
monometallic systems dispersed in a hydrocarbon medium
were the least active; in the case of the W-containing
catalyst, the substrate conversion did not exceed 34% (see
In hydrogenation of 2-methylnaphthalene in the pres-
ence of water under СО pressure, the series of activity of
the catalysts is different (see Fig. 1, b). Specifically when

Vutolkina et al.
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Russ. Chem. Bull., Int. Ed., Vol. 69, No. 2, February, 2020
unpromoted W- and Mo-sulfide catalysts are used, the
conversion of 2-methylnaphthalene at 380 °C and a pres-
sure of CO of 5 MPa after 6 h time-on-stream does not
exceed 1—2%. The introduction of cobalt improves the
activity of such catalysts; as evidenced by a significantly
higher activity of Co—Mo catalyst compared to W-containing
sample. Nickel promotion can greatly increase the activ-
ity of the Mo-containing catalyst in the hydrogenation of
2-methylnaphthalene, the conversion of which reaches
61%. As in the reaction under hydrogen pressure, hydro-
genation under CO pressure proceeds with high selectiv-
ity to 2- and 6-methyltetralines. Decalins, were not found
among the reaction products because the conditions were
not severe enough for their formation.
sulfide catalysts, when the reaction is performed under
hydrogen pressure, decreases in the presence of the cata-
lysts arranged in the following raw: Ni—Mo > Co—W >
> Co—Mo > Ni—W > Mo > W (see Fig. 2, а); and in the
СО—H2О reaction media, the catalyst order is different:
Ni—Mo >> Co—Mo ≥ Mo ≈ Co—W ≈ Ni—W ≈ W (see
Fig. 2, b).
When dibenzothiophene transforms in hydrogen at-
mosphere, the conversion of the substrate decreases in the
presence of the catalysts arranged as follows: Ni—Mo >
> W > Ni—W ≈ Co— Mo ≈ Mo > Co—W (see Fig. 2, c);
and in the СО—H2О reaction media, the catalytic activity
is in the following order: Ni—Mo >> Co—Mo > Mo >
> Ni—W ≈ Co—W ≈ W (see Fig. 2, d).
Figure 2 illustrates the conversions of 2-methylnaph-
thalene and dibenzothiophene in the presence of the
catalysts with various compositions when the reactions are
carried out under hydrogen pressure or in CO atmosphere.
Conversion of 2-methylnaphthalene over unsupported
Figure 3 shows the distribution of the products of
hydrotransformation of dibenzothiophene over the studied
catalysts in hydrogen atmosphere (Fig. 3, a) as well as that
under the pressure of carbon monoxide in the presence of
water (Fig. 3, b). The total yield of the substrate can be
Y (%)
Y (%)
70
a
b
100
90
80
70
60
50
40
30
60
8
7
6
5
4
3
2
1
W
Mo Ni—W Co—Mo Co—W Ni—Mo
Catalyst
W
Mo Ni—W Co—Mo Co—W Ni—Mo
Catalyst
Y (%)
Y (%)
c
d
74
72
70
100
90
80
70
60
50
40
30
20
10
16
12
8
4
W
Mo Ni—W Co—Mo Co—W Ni—Mo
Catalyst
W
Mo Ni—W Co—Mo Co—W Ni—Mo
Catalyst
Fig. 2. Conversion (Y) of 2-methylnaphtalene (a, b) and dibenzothiophene (c, d) over unsupported sulfide catalysts of different com-
position in the media of Н2 (а, c) and СО (b, d).

Sulfidecatalysts
Yield (%)
Russ. Chem. Bull., Int. Ed., Vol. 69, No. 2, February, 2020
283
conversion of which reaches 97—98%. The high activity
of the Ni—Mo catalyst can also be evidenced from the
formation of dicyclohexyl, the product of complete hydro-
genation of dibenzothiophene.
a
Biphenyl
Tetrahydrodi-
benzothiophene
Bicyclohexyl
Cyclohexylbenzene
100
90
80
70
60
50
40
30
20
10
In the СО—H2О medium, W-containing catalysts are
significantly less active than the Mo-containing analogs.
Thus the conversion of dibenzothiophene does not exceed
4% in the presence of the Ni—W catalyst, even after 8 h
run at 380 °C. At the same time, in the presence of the
Ni—Mo systems, the conversion of the substrate is 72%,
and the content of dicyclohexyl is 6% (see Fig. 3, b). In
the presence of the Co—Mo systems, the conversion of
dibenzothiophene decreases by a factor of more than 3.5.
In the presence of unsupported sulfide catalysts either
under hydrogen pressure or in the СО—H2О medium, the
hydroconvertion of dibenzothiophene proceeds generally
through hydrogenation of the thiophene ring with follow-
ing breakage of the C—S bond, as evidenced by the high
reaction selectivity to cyclohexylbenzene (Table 1). Here-
with, tungsten-containing catalysts have a higher hydro-
genating activity than molybdenum-containing systems.
Among Mo-containing systems, the Co—Mo catalyst is
the most active in hydrogenation of the thiophene ring. It
should be noted, that the hydrogenating activity of the
Ni—Mo catalyst is slightly lower in the CO—Н2О medium
and the fraction of biphenyl formed through direct hydro-
genolysis of the C—S bond increases in the reaction
products. One reason of this experimental result can be
the rearrangement of the active sites of the catalyst that
involves the change in the length and number of layers in
the multilayer agglomerate of molybdenum disulfide. In
addition, its transformation to the oxide form due to the
contact with water can be considered. This transformation
includes a decrease in the content of molybdenum sulfide
or mixed Ni—Mo—S phase and a decrease in promotion
of MoS2 crystallites with nickel. Another reason can be
a lack of hydrogen in the system that changes the reaction
mechanism and, as a consequence, the selectivity to the
product. At the same time, hydrogen sulfide acting as
Mo Ni—Mo Co—Mo
W
Ni—W Co—W
Catalyst
Yield (%)
b
Tetrahydrodi-
benzothiophene
Bicyclohexyl
Biphenyl
Cyclohexylbenzene
80
60
40
15
10
5
Mo Ni—Mo Co—Mo
W
Ni—W Co—W
Catalyst
Fig. 3. Distribution of products of hydroconversion of di-
benzothiophene over unsupported sulfide catalysts of different
composition in the atmospher of Н2 (a) and СО (b). Reac-
tion conditions: Т = 380 °С, t = 8 h, ω(Mo or W) = 1.5 wt.%:
р(Н2) = 5 MPa (a), p(СО) = 5 MPa (b), ω(Н2О) = 20 wt.%,
CO : H2O = 1.5 (mol.).
Table 1. The reaction selectivity to cyclohexylbenzene
(SCHB) and the selectivity of unsupported sulfide cata-
lysts to hydrogenation (SHYG), calculated from the
distribution of the products of hydroconversion of
dibenzothiophene
estimated from the total yield of products. As derived from
the experiments, when comparing the monometallic sys-
tems, the tungsten-based catalyst is the most active: the
conversion of the organosulfur substrate reaches 80% (see
Fig. 3, a). Its promotion with Co and Ni decreases the
conversion to 56 and 33%, respectively. However, the
reaction is highly selective to cyclohexylbenzene (58%
over Co—W and 79% over Ni—W). It is noteworthy that
desulfurization activities of Mo and Co—Mo catalysts are
comparable. The Co—Mo system is significantly more
active than the tungsten-containing analog. Nickel promo-
tion can significantly increase the activity of the Mo-sulfide
catalyst in hydrotransformation of dibenzothiophene, the
Catalyst
SCHB (%)
SHYG (%)
Н2 СО—Н2О
Н2 СО—Н2О
Mo
66
64
85
95
96
88
75
56
63
54
81
88
89
79
69
51
Ni—Mo
Co—Mo
W
84
79
100
100
100
100
100
100
Ni—W
Co—W

Vutolkina et al.
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Russ. Chem. Bull., Int. Ed., Vol. 69, No. 2, February, 2020
a sulfiding agent may also be insufficient for the regen-
eration of catalytic active sites which finally results in
a partial loss of the catalyst activity.
distribution of sulfide particles (Fig. 5, a). An average
particle length of the active component with the number
of layers of 3.2 is 54.0 Å (Table 2), and a fraction of
40—69 Å particles is ~78%. In the case of the catalysts
formed in the СО—Н2О medium, particles ranged from
40 to 79 Å in length (71%) with an average number of
active component layers of 2.8 are dominant. At the same
time, the curved molybdenum sulfide packages longer than
10 nm are found, the content of which does not exceed
7.5% (Fig. 5, b).
The total number of molybdenum atoms in an average
catalyst particle synthesized in the СО—Н2О medium is
slightly greater than that in sulfide particles formed in the
reaction under hydrogen pressure. At the same time, the
dispersion of the catalysts is comparable (see Table 2)
and the active sites are located mainly on the edges of
nanosized crystallites of the sulfide phase.
The activation of water and carbon monoxide on dis-
persed unsupported catalysts leads to the formation of
slightly longer MoS2 nanoplates with fewer layers of the
active component. This could be a reason for a high activ-
ity of Ni—Mo systems in hydrodesulfurization of di-
benzothiophene proceeding via the direct hydrogenoly-
sis route. We should note that water does not impede
the formation of nanosized particles of highly dispersed
sulfides.
The formation of active phase of the catalysts occurs
in situ in the course of the high-temperature (~300—320 °C)
decomposition of naphthenates and hexacarbonyls to the
corresponding metal oxides in the presence of a substrate
and elemental sulfur, which reacts with hydrogen forming
hydrogen sulfide in the system. The latter is needed to
transform the catalyst into its active sulfide form. After
the reaction, the obtained catalyst was isolated from the
reaction mixture, washed with toluene and then with
hexane. The elemental composition was determined by
X-ray fluorescence analysis. The geometric parameters of
the active sulfide phase were calculated based on the results
of a statistical evaluation of the size characteristics of more
than 300 particles of the active component in various im-
ages of the catalysts obtained by transmission electron
microscopy (TEM). From X-ray fluorescence analyses,
the sulfur content in the catalysts synthesized in hydrogen
and carbon monoxide atmosphere is 12.7 and 12.2 wt.%,
respectively. The TEM micrographs of sulfide catalysts
clearly show the typical layered structure of the MoS2
phase with an interlayer distance of 4.3—5.2 Å (Fig. 4).17
The catalysts formed in the reaction mixture under
hydrogen pressure, are characterized with a narrow size
a
b
MoS2
MoS2
20 nm
20 nm
c
d
MoS2
MoS2
20 nm
20 nm
Fig. 4. TEM images of unsupported Ni—Mo-sulfide catalysts prepared in water-oil emulsion insitu by high-temperature decomposi-
tion of oil soluble metal salts in the presence of sulfiding agent under pressure of Н2 (a, b) and in the СО—Н2О system (c, d). Reaction
conditions: Т = 380 °С, t = 6 h, р(Н2) = 5 MPa (a, b), p(СО) = 5 MPa (c, d), ω(Н2О) = 20 wt.%, CO : H2O = 2.0 (mol.).

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Russ. Chem. Bull., Int. Ed., Vol. 69, No. 2, February, 2020
285
N (%)
a
In hydrogenation of 2-methylnaphthalene, unsup-
ported Ni—Mo-sulfide catalysts are more active than their
alumina supported analogs, especially when the reaction
is performed in the СО—Н2О medium (Table 3). Thus in
the presence of unsupported catalyst, the conversion of
2-methylnaphthalene is 61 %, while it is 15% in the pres-
ence of Ni—Mo/Al2O3 (3.5% Ni, 11.7% Mo). At the same
time, in hydrogenation of dibenzothiophene under hydro-
gen pressure, alumina supported catalysts are as active as
unsupported systems and nearly all substrate is converted.
However, when the reaction is carried out in the СО—Н2О
medium, the conversion of dibenzothiophene is less than
38%, while it is nearly doubled in the presence of unsup-
ported catalyst.
30
In the CO—H2O medium
Under H2 pressure
25
20
15
10
5
20-29 40-49 60-69 80-89100-109120-129 Particle length/Å
N (%)
b
40
35
30
25
20
15
10
5
In the CO—H2O medium
Under H2 pressure
Similar behavior is observed in hydrogenation of
dibenzothiophene, the conversion of which in the presence
of supported systems proceeds via direct hydrodesulfuriza-
tion, as evidenced by the low content of cyclohexylbenzene
in the reaction products.
Thus, an approach to the catalyst synthesis based on
high-temperature decomposition—sulfidation of oil-sol-
uble metal precursors in the presence of water under the
pressure of carbon monoxide ensures the formation of
highly dispersed nanosized sulfide particles. The greatest
activity in the hydrotransformation of substrates both
under H2 pressure and in the СО—H2О medium was shown
by unsupported Ni—Mo-sulfide catalysts. In hydrogena-
tion in water under elevated pressure of carbon monoxide,
the conversion of 2-methylnaphthalene and dibenzothio-
1
2
3
4
5
6
Number of layers in MoS2 crystallites
Fig. 5. Distribution of sulfide particles along their length (a) and
the number of layers (b) for unsupported Ni—Mo-sulfide catalysts
obtained insitu in water-oil emulsions in the course of high-
temperature decomposition of oil-soluble metal salts in the
presence of a sulfiding agent under H2 pressure and in the
СО—Н2О system. Reaction conditions: Т = 380 °С, t = 6 h,
р(Н2) = 5 MPa (a), p(СО) = 5 MPa (b), ω(Н2О) = 20 wt.%,
CO : H2O = 2.0 (mol.).
Table 2. Main characteristics* of unsupported Ni—Mo-sulfide catalyst particles
prepared in situ in the media of hydrocarbons
Synthesis method
L/Å
N
ni
Moe Moc Mot
D
fe/fc
In СО—Н2О
Under Н2 pressure
64.9
54.0
2.8
3.2
10.6 146.6 17.0 872.4 0.19
18.9 131.6 19.0 675.8 0.22
8.6
6.9
* L is a mean size of the particle of active phase; N is the mean number of layers in
MoS2 crystallite; ni is a number of Mo atoms along one side of an average crystallite;
Moe is a number of Mo atoms on the edge of an average crystalline; Moc is a number
of Mo atoms at the angle of an average crystallite; Mot a total number of Mo atoms
in an average particle; D is dispersity of an active phase particle; fe/fc is the ratio of the
Mo atoms located on the edges to the Mo atoms located at the angles of crystallites.
a
Table 3. Comparison of activities of unsupported Ni—Mo-sulfide catalyst and its analogue supported on Al2O3
Catalyst
In Н2
In СО
SCHB (%) SHYG (%)
Conversion (%)
2-MNb DBTc
SCHB (%)
SHYGd (%)
Conversion (%)
2-MN
DBT
No support
Supported on Al2O3
97
73
100
198
54
33
36
63
61
15
72
38
51
30
44
72
a Reaction conditions: Т = 380 °С, t = 6 h, р(Н2) = 5 MPa, p(СО) = 5 MPa, ω(Н2О) = 20 wt.%, CO : H2O = 2.0 (mol.).
b 2-Methylnaphtalene. c Dibenzothiophene. d Selectivity to hydrodesulfurization.

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X-ray fluorescence analysis. The sulfur content in the catalysts
was measured in vacuum on a Thermo Fisher Scientific ARL
Quant´X energy dispersive X-ray fluorescence analyzer. The
results were processed using the UniQuant non-standard method.
Gas-liquid chromatography (GLC). To analyze the reaction
products, a Crystal-Lux 4000M gas-liquid chromatograph equipped
with a flame ionization detector and a Petrocol TM Supelco
capillary column (50 m × 0.25 mm) with programmed heating
was used. The temperature of the evaporator and detector were
330 and 320 °C, respectively. The flow rate of a carrier gas
(helium) was 30 mL min–1. To effectively separate the individ-
ual components of the reaction mixture, the chromatograph
column was stepwise heated. When analyzing the products of
hydrogenation of 2-methylnaphthalene, the column was heated
from 120 to 160 °C (at the rate of 5 °C min–1), kept at this tem-
perature for 5 min, then heated to 180 °C (at the rate of 2 °C
min–1), again kept for 5 min, heated to 230 °C (at the rate of
5 °C min–1) and kept for 25 min. In the reaction of dibenzothio-
phene, the column was kept at the initial temperature (100 °C)
for 2 min, after which it was heated to 230 °C at the rate of
20 °C min–1 and set on a temperature plateau for 40 min.
Chromatograms were processed using NetChrom 2.1 software.
The conversion of DBT (Y, %) was determined by the dif-
ference between the relative area (Srel, %) of the peaks of the
substrate and products according to the following equation:
phene at 380 °C is 61 and 72%, respectively, after 6—8 h
run. In the presence of alumina supported catalysts, the
conversion under the indicated conditions is 32 and 38%,
respectively, with a half content of substrates in the reac-
tion mixture.
Experimental
Instruments and methods. Transmission electron microscopy
(TEM). Micrographs of sulfide catalysts were performed on
a JEOLJEM-2100 transmission electron microscope at magni-
fication ranged from 80 to 500 000 and an image resolution of
10 nm. For the statistical evaluation of the dimensional charac-
teristics, more than 300 particles of the active components in
various TEM images were used; the distribution of sulfide par-
ticles by their length and the number of layers in multilayer ag-
glomerates were determined. The geometric characteristics of
the particles of the active component of the sulfide catalysts were
calculated using the equations18 given below.
An average length of the Ni—Mo—S active phase (L):
L = Σli/n,
where li is the length of the ith crystallite, n is the total number
of the crystallites;
a mean number of layers in MoS2 crystallite (N):
Y = (SrelBP + SrelCHB + SrelBCH + SrelTHDBT)/
/(SrelDBT + SrelBP + SrelCHB + SrelBCH + SrelTHDBT)•100%,
N = ΣniNi/n,
where BP is biphenyl, CHB is cyclohexylbenzene, THDBT is
tetrahydrodibenzothiophene.
where ni is the number of particles with Ni layers;
the number of Mo atoms along one side of an average crystallite
(ni):
The catalyst selectivities to hydrogenation (SHYD, %) and
hydrodesulfurization (SHDS, %) of dibenzothiophene were cal-
culated as the ratio of the amount of products (C) formed by the
hydrogenation of aromatic rings with ensuing breakage of the
C—S bond (CHB, THDBT) to the amount of products formed
via direct hydrogenolysis (BP), according to the following
relations:
ni = 5L/3.2 + 0.5;
the number of Mo atoms along edges of an average MoS2 crystal-
lite (Moe):
Moe = (6ni – 12)N;
SHDS = СBP/(CCHB + СBP + СTHDBT)•100%,
the number of Mo atoms at the corner of an average crystallite
(Moc):
SHYD = (CCHB + CTHDBT)/(CCHB + CBP + CTHDBT)•100%.
Moc = 6N;
Synthesis of sulfide catalyst supported on alumina oxide.
Metals were deposited on alumina γ-oxide, prepared by calcina-
tion of boehmite (AlOOH, Sasol, PURALSB) at 550 °С, by si-
multaneous precipitation of the support with aqueous solutions
of ammonium heptamolybdate ((NH4)6Mo7O24 •4H2O, Alfa
Aesar, 99%) and nickel nitrate (Ni(NO3)2•6H2O, Sigma—
Aldrich, ≥97%) using citric acid (C6H8O7, Khimreactiv, reagent
grade) as a chelate agent (the citric acid : molybdenum mole
ratio was 1 : 1).19 The amount of each salt was adjusted so as to
achive the target total metal content of 15 mol.% at the Mo : Ni
molar ratio of 3 : 1. The support was preliminary calcined for 2 h
in a muffle furnace at 380—400 °С to remove physically adsorbed
water, cooled in argon to 200 °С and then in air to 40—50 °С,
and weighted. The total amount of the precipitating solution was
given to provide a 2 mm liquid layer over the alumina oxide
powder after adding the solution to the support. The precipitat-
ing solution was added to the support at stirring and then kept
for 24 h. During first two hours the suspension was periodically
the total amount of Mo atoms in an average particle (Mot):
Mot = (3ni2 – 3ni + 1)N;
dispersion of the MoS2 active phase(D):
D = (Moe + Moc)/Mot;
the ratio between Mo atoms located on the edges and at the
corners (fe/fc):
fe/fc = 5L/3.2 – 1.5.
Inductively coupled plasma atomic emission spectroscopy (ICP
AES). The metal content in samples of sulfide catalysts sup-
ported on aluminum oxide was determined on an IRIS Interpid
II XPL atomic emission spectrometer (Thermo Electron Corp.,
USA) with radial and axial registration at a wavelength of 343.49 nm.

Sulfidecatalysts
Russ. Chem. Bull., Int. Ed., Vol. 69, No. 2, February, 2020
287
Table 4. Reactant ratios in catalytic experiments
b
Parametera
Unsupported catalyst
In СО
2-MN
Catalyst supported on Al2O3
In H2 In СО
2-MN 2-MN
In H2
2-MN
DBT
DBT
DBT
DBT
ω
Mo(W) (wt.%)
0.15
3.9
0.15
3.9
3 : 1
10
2.9
0.15
3.9
3 : 1
20
5.8
0.15
3.9
3 : 1
10
2.9
0.15
1.2
2.7 : 1
20
5.1
0.15
1.2
2.7 : 1
10
2.6
0.15
1.2
2.7 : 1
20
5.1
100
1 : 114
20
55.6
0.15
1.2
2.7 : 1
10
2.6
100
1 : 57
20
55.6
νS/mmol
Mo(W) : Ni(Co) (mol.) 3 : 1
ωSub(wt.%)
νSub/mmol
νg/mmol (25 °С)
20
5.8
100
100
1 : 65
—
100
1 : 130
20
100
1 : 65
20
100
1 : 114
—
100
1 : 57
—
Mo(W) : Sub (mol.) 1 : 130
ωH2O (wt.%)
—
—
νH2O/mmol
—
55.6
55.6
—
—
a Sub is substrate. b Calculated from the data of X-ray fluorescence analysis and ISP-AES (%): Mo, 11.5; Ni, 3.2; S, 11.3.
mixed. After one day, the water was removed by decantation.
The obtained catalyst (in its oxide form) was dried stepwise: 1 h
at 60—70 °С, 2 h at 80—85 °С, 2 h at 110 °C, 3 h at 350 °C, and
then calcined for 3 h in air at 550 °C. Catalyst samples were
converted into their active sulfide form in a 50 mL steel autoclave
in toluene (Khimmed, special purity grade) in the presence of
elemental sulfur (Khimreactiv, reagent grade) taken in a 3-fold
excess with respect to the molar content of metals in the catalyst.
Sulfidation was carried out at 350 °C, a hydrogen pressure of
5 MPa, and at vigorous stirring of the reaction mixture for 5 h.
The obtained sulfide catalyst was filtered off, then dried for 2 h
in argon at 60 °C. The procedure was performed just before the
catalytic test.
ms is the solution weight, g; ms = m(H2O) + msolv + mS, msolv is
the weight of the solvent, mS is the sulfur weight.
The weight of the preliminarily obtained alumina supported
catalyst was calculated considering that the Mo content in the
reaction is 0.15 wt.% taking into account the elemental compo-
sition of the sample measured by X-ray fluorescence analysis and
ICP-AES.
This work was financially supported by the Russian
Science Foundation (Project No. 19-79-00259).
References
Catalyst test procedure. The activities of sulfide catalysts
supported on aluminum oxide and dispersed catalysts in the
hydroconversion of 2-methylnaphthalene (Sigma—Aldrich, 99%)
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sion), in the course of the high-temperature decomposition of
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(W) content in the reaction system is 0.15 wt.% and the
Mo(W) : Co(Ni) molar ratio is 3 : 1.
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in revised form December 5, 2019;
accepted December 9, 2019