Hydroconversion of Oxidation Products of Sulfur-Containing Aromatic Compounds

Article abstract of DOI:10.1134/S1070427218060162

Hydroconversion of benzo- and dibenzothiophene sulfone on a Ni–Mo sulfide catalyst based on mesoporous aluminosilicate Al-HMS and on unsupported catalysts prepared in situ in the course of decomposition of poorly soluble precursors (molybdenum hexacarbonyl, nickel naphthenate) was investigated. Hydrogenation of sulfones was performed at 250°С, 340°С, and 380°С and elevated СО pressure in the presence of H₂O ensuring in situ generation of H₂ via water-gas shift reaction. The products that are formed by oxidation of organic sulfur compounds and remain in the hydrocarbon medium (mainly sulfones) will not significantly affect the subsequent hydrotreatment since under the conditions of hydroprocesses, they transform into the corresponding benzo- and dibenzothiophenes, which undergo the subsequent hydrodesulfurization to form mono- and diaromatic hydrocarbons.

Full text of DOI:10.1134/S1070427218060162

ISSN 1070-4272, Russian Journal of Applied Chemistry, 2018, Vol. 91, No. 6, pp. 981−989. © Pleiades Publishing, Ltd., 2018.
Original Russian Text © A.V. Vutolkina, A.V. Akopyan, A.P. Glotov, M.S. Kotelev, A.L. Maksimov, E.A. Karakhanov, 2018, published in Zhurnal Prikladnoi Khimii,
2018, Vol. 91, No. 6, pp. 850−858.
ORGANIC SYNTHESIS AND INDUSTRIAL
ORGANIC CHEMISTRY
Hydroconversion of Oxidation Products
of Sulfur-Containing Aromatic Compounds
a,
a
b
b
A. V. Vutolkina *, A. V. Akopyan , A. P. Glotov , M. S. Kotelev ,
a,c
a
A. L. Maksimov , and E. A. Karakhanov
a
Moscow State University, Moscow, 119991 Russia
b
Gubkin Russian State University of Oil and Gas (Natural Research University), Moscow, 119991 Russia
Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, Moscow, 119991 Russia
c
*
e-mail: annavutolkina@mail.ru
Received June 5, 2018
Abstract—Hydroconversion of benzo- and dibenzothiophene sulfone on a Ni–Mo sulfide catalyst based on
mesoporous aluminosilicate Al-HMS and on unsupported catalysts prepared in situ in the course of decomposi-
tion of poorly soluble precursors (molybdenum hexacarbonyl, nickel naphthenate) was studied. Hydrogenation
of sulfones was perfpormed at 250, 340, and 380°С and elevated СО pressure in the presence of water ensuring
in situ generation of hydrogen via water-gas shift reaction.
DOI: 10.1134/S1070427218060162
Environmental standards prohibiting sale of motor
their oxidation to the corresponding sulfoxides and
sulfones [8, 9]. The oxidation products are removed
by adsorption or extraction with polar organic solvents
[10, 11].
fuels with high sulfur content become more and more
stringent, which stimulates the improvement of oil
refining technologies with the aim of considerably
reducing the sulfur content of hydrocarbon fractions.
In the past several years, there has been a great deal of
interest in the development not only of high-performance
catalysts, but also of novel complex, economically
efficient, and highly productive technologies for
reducing the total sulfur content (down to 0.001 wt %
inclusive) in oil refining products and in the pretreatment
steps without using hydrogen.
The key problem in performing oxidative desulfur-
ization is the influence exerted by oxidation products
remaining in the hydrocarbon fraction after the adsorp-
tion or extraction treatment on the properties of the frac-
tion being treated and on the subsequent processes, in
particular, on those involving hydrogen. To determine
how “residual” sulfones affect the subsequent hydro-
processing, we prepared model hydrocarbon mixtures
containing benzo- and dibenzothiophene sulfones, after
which we performed desulfurization using Ni–Mo sul-
fide catalysts, both supported and formed in the course
of thermal decomposition of poorly soluble precursors,
Oxidative desulfurization seems to be the most
promising procedure for removing sulfur compounds.
The following oxidants can be used: H O , HNO , N O,
2
2
3
2
NaClO, NaClO , NaBrO, C H NO , NaIO , various
2
5
11
2
4
alkyl hydroperoxides, molecular oxygen, or air [1, 2].
These reactions are catalyzed, as a rule, by transition
metal compounds such as vanadium pentoxide, sodium
molybdate and tungstate, or peroxotungstate complexes,
with lower carboxylic acids as cocatalysts [3–7].
Oxidative desulfurization allows reaching very low
sulfur content of petroleum products with the removal
of benzothiophene and dibenzothiophene, which exhibit
low reactivity under the hydrotreating conditions, by
in the CO/H O system.
2
As support for Ni–Mo sulfide catalysts we used
mesoporous aluminosilicate Al-HMS-10. Catalysts
based on it have high specific surface area and the
pore size ensuring the substrate access to the active
component. Unsupported dispersed catalysts formed
by thermal decomposition of metal salts in the presence
of sulfiding agent are characterized by high content of
9
81

982
VUTOLKINA et al.
Al(sec-OBu) +
Si(OEt) +
3
4
i-PrOH
xH O
(1) Keeping at
2
(
1) Impregnation
room tempera-
ture for 24 h
with solutions
of metal salts in
citric acid
(1) Sulfiding in
the presence of
elemental sulfur
(2.5 wt %), 350°C,
p(H2) = 5 MPa
(2) Filtration
Solution of
template in
isopropyl
alcohol
SiO2·xAl2O3×
ySurfactant×
Mesoporous
alumino-
silicate
(
(
2) Filtration
3) Drying at
xH O
(2) Drying at
2
1
10°C for 3 h
4) Calcination
at 550°C for 6 h
8
(
5
0–110°C
3) Calcination at
50°C
(
(3) Drying in inert
atmosphere
Fig. 1. Scheme of the synthesis of mesoporous aluminosilicate Al-HMS and of the Ni–Mo sulfide catalyst based on it.
the active phase. In addition, the use of these catalytic
systems virtually eliminates the effect of steric and
diffusion factors hindering the substrate access to the
catalyst active component, which makes these systems
highly active in hydrogenation.
The following chemicals were used for preparing
mesoporous aluminosilicate Al-HMS-10 (here 10 is the
Si/Al atomic ratio): tetraethoxysilane (TEOS, 98%, Sig-
ma–Aldrich), hexadecylamine (HDA, 90%, Sigma–Al-
drich), aluminum sec-butoxide (97%, Sigma–Aldrich),
and isopropyl alcohol (IPA, Komponent-Reaktiv). The
synthesis procedure and characteristics of the material
are described elsewhere [12].
EXPERIMENTAL
Preparation of benzo- and dibenzothiophene sul-
fones. As starting compounds we used toluene (ultra-
pure grade, Reakhim, Russia), benzothiophene (98%,
Alfa Aesar), dibenzothiophene (98%, Sigma–Aldrich),
hydrogen peroxide (50%, Prime Chemicals Group), and
formic acid (88%, chemically pure grade, Komponent-
Reaktiv, Russia).
The metals were applied by impregnation of the
support with a solution of their salts in aqueous citric
acid (chemically pure grade, Khimreaktiv, Russia). As
starting transition metal compounds we used ammo-
nium paramolybdate tetrahydrate (NH ) Mo O ·4H O
4
6
7
24
2
(99%, Alfa Aesar) and nickel nitrate hexahydrate
Ni(NO ) ∙6H O (97%, Sigma–Aldrich). The salts for
3
2
2
A temperature-controlled reactor was charged with
n-octane. The starting benzothiophene or dibenzothio-
phene was added in an amount corresponding to the
preparing the solutions were taken in an amount cor-
responding to the Ni and Mo content of the catalyst of
7 and 24 wt %, respectively. The thickness of the liquid
layer over the support after adding the impregnation so-
lution did not exceed 2 mm. The samples were left over-
night for the impregnation, after which the solution was
decanted. The materials were dried in the temperature
interval 80–110°С (for 1 h at each temperature) and then
were calcined in a muffle furnace in air for 2 h at 350°С
and for 4 h at 550°С. As a result, we obtained a catalyst
5
000 ppm concentration. After its dissolution, a 50%
hydrogen peroxide solution was added in an amount
corresponding to the molar ratio Н О : S = 10 : 1. For-
2
2
mic acid taken in the molar ratio HCOOH : S = 5 : 1
was used as a catalyst. The mixture was stirred for 2 h at
6
0°С. The precipitate was filtered off, washed with ex-
cess n-hexane, and dried on a rotary evaporator to con-
stant weight. The benzo- and dibenzothiophene sulfones
of the composition NiO–MoO /Al-HMS-10.
3
1
obtained were analyzed by GLC and Н NMR.
The catalyst was converted to the sulfide form by
Synthesis of catalysts supported on mesoporous
aluminosilicate Al-HMS. Figure 1 shows the scheme
of the synthesis of the Ni–Mo sulfide catalyst based on
mesoporous aluminosilicate Al-HMS-10.
treatment with elemental sulfur (chemically pure grade,
Khimreaktiv) at 350°С and H pressure of 5 MPa for 5 h.
2
The catalyst of the composition NiS–MoS /Al-HMS-10
2
was filtered off, washed with toluene (ultrapure grade,
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HYDROCONVERSION OF OXIDATION PRODUCTS
983
Table 1. Reactant ratios and amounts
Mo :
ω(substrate),
Catalyst
ω(S), wt %
Mo : Ni
3 : 1
СО/Н О
ω(H O), wt %
2
2
substrate
wt %
Unsupported Ni–Mo sulfide
1 : 14
2.5
10
1.5
20
catalyst
NiS–MoS /Al-HMS-10
1 : 12
–
2
Khimmed, Russia), and dried for 2 h at 60°С in an inert
atmosphere.
determined by low-temperature adsorption/desorption
of nitrogen with a Micromeritics Gemini VII 2390t
device at 77 K. Prior to measurements, the samples were
degassed at 310°С for 6 h. The specific surface area was
calculated by the Brunauer–Emmett–Teller method from
Catalytic experiments. The catalytic experiments
on hydrogenation of sulfones were performed in a
steel autoclave with continuous stirring of the reaction
mixture. The temperature in the reactor was maintained
with a resistance furnace equipped with a thermocouple
and a temperature controller.The reaction was performed
in the presence of Ni–Mo sulfide catalysts supported on
mesoporousaluminosilicateAl-HMSandofunsupported
catalysts prepared in situ by thermal composition of
poorly soluble precursors. As such precursors we chose
the adsorption data in the relative pressure interval p/p0
=
0.04–0.20. The pore volume and size distribution were
determined from the adsorption branch of the isotherms
using the Barrett–Joyner–Halenda model. The specific
pore volume was calculated from the amount of the
adsorbed nitrogen at a relative pressure p/p = 0.99. The
0
normalized specific surface area of the oxide form of the
catalyst was calculated from the formula
molybdenum hexacarbonyl Mo(CO) (99.99%, Sigma–
6
Aldrich) and nickel(II) naphthenate Ni(С H СOO)
1
0
7
2
(5–12 wt % Ni, Sigma–Aldrich). In the case of
unsupported systems, the catalytically active particles
were formed directly in the course of hydrogenation.
To form the active phase of the catalyst (molybdenum
sulfide), 2.5 wt % elemental sulfur (chemically pure
grade, Khimreaktiv) was additionally introduced into
the reaction mixture. The molybdenum content of the
reaction mixture was calculated using the formula
where y is the content of the metals (wt %).
The metal content of the samples was determined
quantitatively by inductively coupled plasma atomic
emission spectroscopy (AES-ICP) with an IRIS Interpid
II XPL (Thermo Electron, the United States) with radial
and axial observation at a wavelength of 343.49 nm.
The structure and morphology of the catalyst surfaces
were examined with a Jeol Jem analytical electron
microscope at magnifications from 80 to 500000 and
image resolution of 0.2–0.34 nm.
where m[Mo(CO) ] is the molybdenum hexacarbonyl
6
weight (g); М(Мо), molybdenum molar weight
The acidity of the materials was determined with a
Micromeritics AutoChem HP chemisorption analyzer.
The samples was crushed to a particle size of 1–2 mm,
placed in a reactor, and calcined in a helium flow at
400°C for 30 min, after which the temperature was
decreased to 100°C and the sample was saturated with
ammonia for 30 min. Physically adsorbed ammonia
was removed in a helium stream until the baseline drift
stopped. Then, the reactor was heated to 750°C at a rate
–1
(
96 g mol ); M[Mo(CO) ]; molybdenum hexacarbonyl
6
–
1
molar weight (264 g mol ); and m(solution), solution
weight(g),m(solution)=m(H O)+m(solvent)+m(sulfur).
2
Hydrogenation of sulfones was performed at elevated
СО pressure in the presence of water ensuring in situ
generation of hydrogen via water-gas shift reaction
[13], with toluene (ultrapure grade, Khimmed) used as
solvent. The reactant ratios and amounts are given in
Table 1.
–1
of 20 deg min . The amount of ammonia desorbed in
Methods for studying the catalysts. The specific
surface area and the pore volume and diameter were
the course of TPD was calculated using the AutoChem
HP V2.04 program.
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 91 No. 6 2018

984
VUTOLKINA et al.
Table 2. Textural characteristics of mesoporous aluminosilicate and catalyst based on it
2
–1
3
–1
Sample
SBET, m g
Dpore, Å
Vpore, cm g
Al-HMS-10
NiO–MoO /Al-HMS-10
773
456
45
42
0.88
0.76
3
Analysis of reaction products. The sulfone hy-
drogenation products were analyzed with a Kristall-
Lyuks4000М gas–liquid chromatograph equipped with
a flame ionization detector and a PetrocolTM (Supelco)
pregnation of the support with solutions of their salts. In
this step, the Ni and Mo compounds interact with the po-
rous system of the support, which determines their mor-
phology and composition of the active phase of the cata-
lyst. The use of chelating agents favors uniform distribu-
tion of the metals on the support surface and formation
of the catalytically active Ni–Mo–S phase [14]. Citric
acid was used as a chelating agent. Bimetallic complex-
es of the composition [Ni(H O) ] [Mo O (C H O ) ]
0
.25 mm × 30 m capillary column under the conditions
of programmed heating. The carrier gas was helium.
RESULTS AND DISCUSSION
2
2 2
4
11
6
5
7 2
Hydroconversion of sulfones was performed in the
presence of Ni–Mo sulfide catalysts based on mesopo-
rous aluminosilicate or of catalysts formed in situ in
the reaction medium. Mesoporous aluminosilicate Al-
HMS-10 was used as a support for Ni–Mo sulfide cata-
lysts. The preparation procedure, structure, and charac-
teristics of the material are described elsewhere [12].
Catalysts on this support have high specific surface area
and the pore size ensuring the substrate access to the ac-
tive component. Therefore, they show high performance
in hydrogenation.
are formed in the impregnation system when using so-
lutions of Ni and Mo salts in citric acid. In the course
of subsequent drying and calcination, these complexes
decompose with the formation of oxides of the corre-
sponding metals on the support surface.
As found by AES-ICP, the content of NiO and MoO3
in terms of the metal is 6 and 22 wt %, respectively,
which is close to the calculated values.
According to the low-temperature nitrogen
adsorption/desorption data, the specific surface area of
the materials and the pore diameter decrease on applying
the metals (Table 2).
The standard procedure for applying metals is im-
3
–1
Vpore, cm g Å–1 × 10–3
3
–1
N, cm g
(a)
(b)
Dpore, Å
Fig. 2. (a) Nitrogen adsorption/desorption isotherms and (b) pore size (Dpore) distribution for mesoporous aluminosilicate and Ni–Mo
catalyst based on it. (N) Amount of desorbed nitrogen, (Vpore) pore volume, and (p/p ) relative pressure.
0
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HYDROCONVERSION OF OXIDATION PRODUCTS
985
The support strongly influences the catalyst
morphology. For example, Mo–O–Al bonds can be
formed in the mesoporous aluminosilicate, leading to the
predominant formation of monolayer MoS sheets in the
2
course of sulfiding. In the case of supported catalysts,
smaller number of sulfide layers in the stack may also
be due to weak interaction of metal sulfides with silicon
present in the support [15–17]. In the case of dispersed
unsupported catalysts, the catalytically active phase
is formed directly in the reaction medium. Therefore,
the reaction parameters influence its composition and
structure.
T, °C
Fig. 3. Profiles of NH TPD curves for aluminosilicate Al-
HMS and oxide form of the Ni–Mo catalyst. (T) Temperature.
3
The layered packing of MoS particles is clearly
2
seen in the TEM images of the NiS–MoS /Al-HMS-10
2
However, the mesoporous structure of the materials
is preserved, as indicated by the hysteresis loop of type
IV in the nitrogen adsorption/desorption curves (Fig. 2).
The mesoporous structure of the materials is confirmed
by capillary adsorption of nitrogen in pores at the
catalyst and catalyst formed in situ by decomposition
of insoluble precursors and separated from the reaction
mixture immediately after the reaction (Figs. 4a, 4b,
respectively).
The active component in the samples of the sulfide
catalysts obtained consists of multilayer bent stacks of
molybdenum sulfide. Its formation is also proved by the
interplanar spacing of 4.4 Å, corresponding to the basal
relative pressure p/p = 0.35.
0
The quantity NSBET for the catalyst exceeds 0.8,
suggesting that the pores on applying the metals are
blocked insignificantly.
(
002) plane of МоS crystallites. Statistical analysis of
2
The acidity of the aluminosilicate and catalyst based
the TEM images of sulfide catalysts shows that the mean
length of the active phase particles on the surface of the
catalyst supported on Al-HMS-10 is 3–5 nm, and the
mean number of layers in the stack is 3.
on it were evaluated by TPD of NH (Fig. 3).
3
All the curves were analyzed using the Gauss–Lo-
rentz approximation method. The acid sites were subdi-
vided with respect to the temperature range of ammonia
desorption into weak (Т < 300°С), medium-strength (Т =
00–500°С), and strong (T > 500°С). The concentrations
of the acid sites, expressed in micromoles of the desorbed
Unsupported Ni–Mo sulfide catalysts formed in
situ in the reaction medium are characterized by high
content of the active phase and, as a consequence,
by high activity in hydrogenation. In such catalytic
systems, the effect of steric and diffusion factors
hindering the access of the substrate to the active
component of the catalyst is virtually fully eliminated.
The choice of oil-soluble precursors is governed by
the fact that they readily dissolve in hydrocarbons and
form highly catalytically active nanoparticles in the
3
NH per gram of the catalyst, are given in Table 3.
3
According to the TPD-NH data, the amount of
3
medium-strength acid sites decreases upon application
of the metals with an increase in the fraction of strong
acid sites. The total acidity of the materials decreases by
–
1
6
0 μmol g .
Table 3. NH TPD data for samples of aluminosilicates and catalysts based on them
3
Weak acid sitesa
Medium-strength and strong
Total ammonia amount
b
acid sites
Sample
μmol g–1
Al-HMS-10
NiO–MoO /Al-HMS-10
95
318
238
413
353
115
3
a
Amount of ammonia desorbed up to 300°С.
Amount of ammonia desorbed above 300°С.
b
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986
VUTOLKINA et al.
c, %
c, %
(b)
(a)
L, Å
L, Å
1
0 nm
20 nm
Fig. 4. TEM images and length (L) distribution of sulfide particles for the (a) NiS–MoS /Al-HMS-10 catalyst and (b) unsupported
2
Ni–Mo sulfide catalyst. (c) Content.
course of thermal decomposition in the presence of a
sulfiding agent. The mean length of active component
particles in the unsupported dispersed Ni–Mo sulfide
catalyst prepared in the reaction medium is 6–9 nm,
and the mean number of active component layers in
the multilayer agglomerate is 4.0. Molybdenum sulfide
crystallites of length larger than 10 nm are also formed;
their fraction is about 22%.
can also be formed via hydrogenation or desulfurization
of benzothiophene.
Thermal cracking of dibenzothiophene sulfone (Т >
3
00°С) yields biphenyl. The occurrence of the reaction
along the sulfone hydrogenation pathway leads to the
accumulation of dibenzothiophene in the reaction
mixture. This compound undergoes hydrogenolysis of
the C–S bond with the formation of biphenyl or takes
up hydrogen to form tetrahydrodibenzothiophene and
cyclohexylbenzene (Scheme 2).
Under the conditions of hydroprocesses, sulfones
can undergo thermal cracking or hydrogenation to the
corresponding benzothiophenes [18]. Hydroconversion
of the latter compounds can occur as hydrogenation of
the benzene ring, followed by elimination of hydrogen
sulfide, or as direct hydrogenolysis of the C–S bond
Hydrogenation of benzothiophene sulfone in the
presence of unsupported Ni–Mo sulfide catalyst at 250
and 350°С for 4 h leads to the formation of benzothio-
phene whose yield does not exceed 30%. An increase in
the reaction time to 6 h leads to the formation of trace
amounts (no more than 7%) of ethylbenzene (Fig. 5).
(Scheme 1). In the case of benzothiophene, thermal
cracking leads to the formation of ethylbenzene, which
Scheme 1. Benzothiophene sulfone transformations under the conditions of hydroprocesses.
Benzothiophene
Dihydrobenzothiophene
O
O
Ethylbenzene
Ethylcyclohexane
Benzothiophene sulfone
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HYDROCONVERSION OF OXIDATION PRODUCTS
987
Scheme 2. Dibenzothiophene sulfone transformations under the conditions of hydroprocesses.
Tetrahydrodibenzothiophene
Cyclohexylbenzene
Dibenzothiophene
S
Dicyclohexyl
Dibenzothiophene sulfone
Biphenyl
Further temperature elevation to 350°С allows reach-
ing quantitative conversion of benzothiophene sulfone.
The ethylbenzene content increases to 47 and 70%
when performing the reaction for 4 and 6 h, respectively.
Throughout the examined temperature interval, no ethyl-
cyclohexane, which could be formed by complete hydro-
genation of benzothiophene, was detected in the reaction
products.
The catalyst supported on mesoporous alumino-
silicate Al-HMS-10 is less active at 250°С: The ben-
zothiophene sulfone conversion does not exceed 15%
even after the 6-h reaction. The temperature eleva-
tion leads to a significant increase in the conversion,
which at 380°С becomes quantitative already in 4 h.
In this case, ethylcyclohexane is formed with 20% se-
lectivity.
(a)
(b)
Y, %
T, °C
Y, %
T, °C
τ, h
Benzothiophene
τ, h
Benzothiophene
Ethylcyclohexane
Ethylbenzene
Ethylbenzene
Fig. 5. Distribution of products of benzothiophene sulfone hydrogenation in the presence of (a) unsupported Ni–Mo sulfide catalyst and
(b) catalyst based on mesoporous aluminosilicate Al-HMS-10. (Y) Yield, (Т) temperature, and (τ) time; the same for Fig. 6.
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 91 No. 6 2018

988
VUTOLKINA et al.
(a)
(b)
Y, %
Y, %
T, °C
T, °C
τ, h
τ, h
Dibenzothiophene Cyclohexylbenzene
Biphenyl
Tetrahydrodibenzothiophene
Dibenzothiophene Cyclohexylbenzene
Biphenyl
Tetrahydrodibenzothiophene
Fig. 6. Distribution of products of dibenzothiophene sulfone hydrogenation in the presence of (a) unsupported Ni–Mo sulfide catalyst
and (b) catalyst based on mesoporous aluminosilicate Al-HMS-10.
Lower activity of catalysts supported on Al-HMS
sulfide catalyst, the quantitative conversion is reached at
350°С, with 10–15% yield of biphenyl (Fig. 6).
in hydrogenation of benzothiophene may be due
to partial blocking of pores upon application of the
metals (according to the calculations of the normalized
BET specific surface area for the oxide form of the
catalyst), so that the active sites of the catalyst become
less accessible to substrate molecules. Furthermore,
introduction of aluminum into the silicate structure can
lead to the formation of Mo–O–Al bridging bonds and,
as a consequence, to the formation of NiMoS of type
I. However, this phenomenon is leveled out by high
specific surface area of the mesoporous material and its
high adsorption capacity for sulfur compounds, caused
by the presence of aluminum atoms bound to the surface
hydroxy groups.
An increase in the temperature to 380°С leads to
the appearance of tetrahydrodibenzothiophene in the
reaction products. Its content reaches 11%. This fact
suggests that the reaction occurs along the pathway of
the aromatic ring hydrogenation followed by hydrogen
sulfide elimination. In the process, trace amounts (≤6%)
of cyclohexylbenzene are formed.
The catalysts supported on mesoporous Al-HMS
exhibit higher activity. For example, at 250°С the
conversion of benzothiophene sulfone reaches 35% in
6
h, whereas with the unsupported dispersed catalysts the
conversion does not exceed 18%. However, at 380°С the
activity of both kinds of catalysts becomes comparable,
with the fraction of dibenzothiophene hydrogenation
products reaching 39 and 36%, respectively.
The catalyst activity in dibenzothiophene hydroge-
nation is determined by the number of molybdenum
sulfide layers in the agglomerate. This characteristic de-
termines the steric hindrance to adsorption of a substrate
molecule on active sites of the catalyst. An increase in
CONCLUSIONS
the number of layers in the MoS packing leads to an
increase in the number of edge and vertex sites and, as
a consequence, to high activity of the catalyst. Because
2
Hydroconversion of sulfones to the corresponding
benzo-anddibenzothiophenesoccursconsiderablyfaster
than the subsequent hydrogenation of these products.
Therefore, the products that are formed by oxidation of
organic sulfur compounds and remain in the hydrocarbon
medium (mainly sulfones) will not significantly affect
the subsequent hydrotreatment because under the
conditions of hydroprocesses they transform into the
corresponding benzo- and dibenzothiophenes, which
the numbers of sulfide layers in the MoS crystallite in
2
the catalysts used is virtually equal, their activities are
comparable.
Hydrogenation of dibenzothiophene sulfone under
these conditions occurs with high selectivity with respect
to dibenzothiophene. With the unsupported Ni–Mo
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HYDROCONVERSION OF OXIDATION PRODUCTS
vol. 16, no. 1, pp. 211–220.
989
undergo the subsequent hydrodesulfurization to form
mono- and diaromatic hydrocarbons.
7. Lu, M.-C., Biel, L.C.C., Wan, M.-W., et al., Int. J. Green
Energy, 2014, vol. 11, no. 8, pp. 833–848.
ACKNOWLEDGMENTS
8
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Presas, P., and Fierro, J.L.G., J. Chem. Technol.
Biotechnol., 2010, vol. 85, no. 7, pp. 879–890.
The study was financially supported by the Ministry
of Education and Science of the Russian Federation
within the framework of the Federal Target Program
9. Akopyan, A.V., Ivanov, E.V., Polikarpova, P.D., et al.,
Petrol. Chem., 2015, vol. 55, no. 7, pp. 571–574.
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