Synthesis of nickel-tungsten sulfide hydrodearomatization catalysts by the decomposition of oil-soluble precursors

Article abstract of DOI:10.1134/S0965544115080174

Nickel-tungsten sulfide catalysts for the hydrogenation of aromatic hydrocarbons have been prepared by the in situ decomposition of an oil-soluble tungsten hexacarbonyl precursor in a hydrocarbon feedstock using oil-soluble nickel salt nickel(II) 2-ethylhexanoate as a source of nickel. The in situ synthesized Ni-W-S catalyst has been characterized by X-ray photoelectron spectroscopy. The activity of the resulting catalysts has been studied in the hydrogenation of bicyclic aromatic hydrocarbons and dibenzothiophene conversion in a batch reactor at a temperature of 350°C and a hydrogen pressure of 5.0 MPa. It has been shown that the optimum W: Ni molar ratio is 1: 2. Using the example of the hydrofining of feedstock with high sulfur and aromatics contents, it has been shown that the synthesized catalyst exhibits high activity in the hydrogenation of aromatic hydrocarbons.

Full text of DOI:10.1134/S0965544115080174

ISSN 0965ꢀ5441, Petroleum Chemistry, 2016, Vol. 56, No. 1, pp. 44–50. © Pleiades Publishing, Ltd., 2016.
Original Russian Text © I.A. Sizova, A.B. Kulikov, M.I. Onishchenko, S.I. Serdyukov, A.L. Maksimov, 2016, published in Neftekhimiya, 2016, Vol. 56, No. 1, pp. 52–58.
Synthesis of Nickel–Tungsten Sulfide Hydrodearomatization
Catalysts by the Decomposition of OilꢀSoluble Precursors
I. A. Sizovaa, A. B. Kulikova, M. I. Onishchenkoa, S. I. Serdyukova, b, and A. L. Maksimova, b
aTopchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, Moscow, Russia
eꢀmail: isizova@mail.ru
bFaculty of Chemistry, Moscow State University, Moscow, Russia
Received June 5, 2015
Abstract—Nickel–tungsten sulfide catalysts for the hydrogenation of aromatic hydrocarbons have been preꢀ
pared by the in situ decomposition of an oilꢀsoluble tungsten hexacarbonyl precursor in a hydrocarbon feedꢀ
stock using oilꢀsoluble nickel salt nickel(II) 2ꢀethylhexanoate as a source of nickel. The in situ synthesized
Ni–W–S catalyst has been characterized by Xꢀray photoelectron spectroscopy. The activity of the resulting
catalysts has been studied in the hydrogenation of bicyclic aromatic hydrocarbons and dibenzothiophene
conversion in a batch reactor at a temperature of 350°C and a hydrogen pressure of 5.0 MPa. It has been
shown that the optimum W : Ni molar ratio is 1 : 2. Using the example of the hydrofining of feedstock with
high sulfur and aromatics contents, it has been shown that the synthesized catalyst exhibits high activity in
the hydrogenation of aromatic hydrocarbons.
Keywords: tungsten hexacarbonyl, oilꢀsoluble precursors, nickel–tungsten sulfide catalyst, dehydrodearomꢀ
atization, light cycle oil
DOI: 10.1134/S0965544115080174
The use of heavy oil fractions with a high concenꢀ [5–9]. Oilꢀsoluble salts, such as transition metal naphꢀ
tration of sulfur and aromatic hydrocarbons (HCs) in
oil refining, along with tightening the requirements on
the amount of these compounds in fuels, has given an
impetus to increased interest in the study of new sulꢀ
furꢀresistant catalysts for the hydrogenation of aroꢀ
matic compounds. Owing to the exceptional resisꢀ
tance to catalyst poisons, transition metal sulfides
[1]—mostly tungsten and molybdenum sulfides proꢀ
moted with cobalt or nickel—are extensively used in
hydrotreating and hydrofining processes involving
purification of feedstocks for the removal of impurities
containing hetero atoms, such as sulfur, nitrogen, and
oxygen, in a hydrogen atmosphere, the hydrogen satꢀ
uration of unsaturated HCs, and the hydrogenation of
aromatic compounds [2].
thenates, carbonyls, 2ꢀethylhexanoates, and acetylacꢀ
etonates, can be used as precursors of sulfide catalysts
[10]. Oilꢀsoluble precursors are readily dispersed in a
HC feedstock and generate catalysts with high hydroꢀ
genation ability. The general scheme of synthesis of
sulfide catalysts from oilꢀsoluble precursors distribꢀ
uted in a HC phase includes the thermal decomposiꢀ
tion of the precursor in a HC medium with a sulfiding
agent [11].
Unlike the well documented Co(Ni)–Mo [3, 9]
and Co(Ni)–Mo–W sulfide systems [12, 13], unsupꢀ
ported Ni–W–S catalysts, which must exhibit a subꢀ
stantially higher hydrogenation activity, have been
examined to a lesser extent [14] and studies of disꢀ
persed catalysts focus on their behavior in the
hydrodesulfurization [13–15] and hydroconversion of
heavy feedstock [16, 17].
In recent years, unsupported sulfide catalysts have
attracted much attention owing to their high activity
in hydrotreatment reactions [3–4]. These catalysts
have exhibited higher catalytic activity than convenꢀ
tional supported catalysts [4]. The synthesis methods
for unsupported catalysts can be divided into two main
groups: the first group involves the synthesis of an
active catalyst outside of the reaction zone (ex situ),
while the second group is based on the formation of a
catalyst directly in a HC medium (in situ). The in situ
preparation of a catalyst in the reaction medium proꢀ
vides a high sulfur content in the resulting sulfide catꢀ
In this study, we propose a method for synthesizing
a nickel–tungsten sulfide catalyst by the in situ
decomposition of the oilꢀsoluble tungsten hexacarboꢀ
nyl precursor in a HC feedstock. The catalytic properꢀ
ties in the hydrogenation reaction were studied using
model systems (naphthalene and alkylꢀsubstituted
naphthalenes with one, two, and three methyl substitꢀ
uents) as an example and in the hydrofining of light
cycle oil (LCO), representative actual feedstock with
alyst and leads to the formation of stable fine particles high sulfur and aromatics contents.
44

SYNTHESIS OF NICKEL–TUNGSTEN SULFIDE HYDRODEAROMATIZATION CATALYSTS
45
EXPERIMENTAL
m(W(CO)6)M(W)
W = ꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀ × 106 [ppm],
M(W(CO)6)m(feedstock)
Catalyst Synthesis Procedures
where m(W(CO)6) is the mass of tungsten hexacarboꢀ
The nickel–tungsten sulfide catalyst was prepared
in situ in a HC feedstock using the oilꢀsoluble salt
tungsten hexacarbonyl W(CO)6 (99.99%, Aldrich) as a
precursor and the oilꢀsoluble salt nickel(II) 2ꢀethylꢀ
hexanoate Ni(С7H15СOO)2 (a 78% solution in 2ꢀethꢀ
ylhexanoic acid, Aldrich) as a source of nickel. To preꢀ
pare tungsten sulfide exhibiting activity in the hydroꢀ
genation of aromatic HCs, 2.5 wt % elemental sulfur
was admixed as a sulfiding agent to the HC feedstockꢀ
with.
nyl dissolved in the HC feedstock, g;
molar mass of tungsten, 183.8 g/mol;
the molar mass of tungsten hexacarbonyl,
М
(W) is the
М(W(CO)6) is
351.9 g/mol; and
feedstock, g.
m(feedstock) is the mass of the HC
Two milliliters of the resulting solution was placed
into the glass cartridge of the autoclave. After that,
the autoclave was filled with hydrogen to a pressure of
50 atm and held at a temperature of 350°С for 2–10 h;
the hydrogen/substrate molar ratio was 60 mol/mol.
Model feedstocks (10% solutions of bicyclic aroꢀ
matic HCs in benzene) and light gas oil produced on a
catalytic cracking unit (LCO) were used in the experiꢀ
ments.
Catalyst Investigation Procedures
Xꢀray photoelectron spectroscopy (XPS) studies of
the resulting samples were conducted using a Kratos
Axis Ultra DLD Xꢀray photoelectron spectrometer.
Photoemission was excited using nonmonochromaꢀ
Product Analysis
tized Al
K
α
radiation (
h = 1486.6 eV) with a power of
ν
The hydrogenation products of the model systems
were analyzed on a 4000 M Kristallyuks chromatoꢀ
graph equipped with a flame ionization detector and a
SPBꢀ1 capillary column coated with the polydimethꢀ
300 W. Photoelectron peaks were calibrated against
the carbon C 1s line with a binding energy of 285 eV.
The spectra were deconvoluted by the nonlinear leastꢀ
square method using the Gaussian–Lorentzian funcꢀ
tion.
ylsiloxane stationary liquid phase (dimensions, 30 m
×
0.25 mm; carrier gas, helium; split ratio, 1 : 90). Conꢀ
version was calculated as the degree of conversion of
the original aromatic compound to the hydrogenated
form. Selectivity was calculated as the ratio of the mass
Catalytic Testing Procedure
Catalytic hydrogenation tests were conducted in a of a given product to the total mass of the resulting
steel autoclave in a hydrogen atmosphere under a high products. In some cases, the activities of the catalyst
pressure and vigorous stirring of the reaction mixture. systems were compared in terms of specific catalytic
Tungsten hexacarbonyl and nickel(II) 2ꢀethylhexꢀ activity (SCA), which is a conventional quantity calꢀ
anoate were dissolved in the HC feedstock. The tungꢀ culated as the ratio of the amount of the reacted naphꢀ
sten content in the feedstock was calculated using the thalene to the charge of the catalytically active metal
following formula
(W), both in moles, per unit time:
(5Conv ⋅ S(C10H18) + 2Conv ⋅ S(C10H12))n(C10H8)
SCA = ꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀ [h–1],
τn(W)
where Conv is the naphthalene conversion;
reaction product selectivity; (C10H8) is the naphthaꢀ
lene content in the original feedstock, mol; (W) is the
is the reaction
S
is the
RESULTS AND DISCUSSION
n
n
Catalyst Characteristics
charge of the active metal, mol; and
time, h.
τ
XPS analysis of the synthesized catalyst has shown
that the spectra exhibit peaks characteristic of tungꢀ
sten, sulfur, carbon, nickel, nitrogen, and oxygen. The
tungsten is in three forms: sulfide (W 4f7/2, 32.2 eV;
W4f5/2 34.3 eV), oxysulfide (W4f7/2 33.4 eV; W4f5/2
35.3 eV), and oxide (W4f7/2 36.2 eV; W4f5/2 37.9 eV)
[18]. These data suggest that, on the catalyst surface,
more than 65% of the tungsten is in the sulfide form,
The total sulfur analysis of the LCO hydrofining
products was conducted on an EA 3100 instrument
equipped with an UV detector. The aromatic HC conꢀ
tent was determined by HPLC according to GOST R
EN 12916ꢀ06 (mobile phase,
umn, diasphereꢀ80ꢀamine).
nꢀheptane; amino colꢀ
PETROLEUM CHEMISTRY Vol. 56
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46
SIZOVA et al.
100
90
80
70
60
50
40
30
20
10
35
30
25
20
15
10
5
0
without Ni 3 : 1 2 : 1 1 : 1 1 : 2 1 : 3 1 : 4
W : Ni ratio, mol/mol
0
500
1000
1500
2000
2500
W content in feedstock, ppm
Fig. 2. Dependence of the SCA on the W : Ni molar ratio.
Reaction conditions: = 350°C; = 5.0 MPa; = 5 h;
and W content in feedstock, 680 ppm.
T
P
t
H2
Fig. 1. Dependence of the naphthalene conversion on the
W content in the feedstock. Reaction conditions:
350°C, = 5.0 MPa, and = 5 h.
T
=
P
t
H2
The dependence of the naphthalene conversion on
the reaction time was studied at a 680ꢀppm tungsten
content in the feedstock. As the reaction time
increases, the naphthalene conversion increases and
reaches 96% within 7.5 h. Accumulation of decalins is
observed after 7.5 h; after 10 h, the decalin content is
32% and the ratio between cisꢀ and transꢀdecalins is
1 : 1.7.
The addition of nickel (oilꢀsoluble salt nickel(II)
2ꢀethylhexanoate) has a positive effect on the activity
of the resulting catalyst. Even the addition of a small
amount of nickel (W : Ni molar ratio, 3 : 1; W content,
680 ppm; reaction time, 5 h) leads to an increase in the
naphthalene conversion from 62 to 88%. In addition,
the two stereoisomeric forms of decalin were identified
in the products; the amount of the stereoisomers is
about 7%; the ratio between cisꢀ and transꢀdecalins is
1 : 2.5.
while about 30% of the tungsten is in the oxygen enviꢀ
ronment.
The nickel present on the catalyst surface is also in
both the sulfide and oxygen environment. The deconꢀ
volution of the Ni 2p level has shown that the nickel is
in three states: the NiS sulfide (Ni2
869.5 eV), the Ni–W–S phase (Ni2p3/2 853.6 eV;
Ni2 1/2 870.9 eV), and the NiO oxide (Ni2 3/2 856.0 eV;
Ni2 1/2 873.8 eV) [18]. Seventy percent of the nickel is
p, 852.5 eV; Ni2p1/2
p
p
p
in the sulfide environment; as low as about 2% of the
nickel is the form of pure NiS sulfide, while more than
65% of the nickel is included in the Ni–W–S complex
sulfide, where the Ni atoms are in the environment of
tungsten atoms.
The deconvolution of the S2p level has shown that
the sulfur is in three states: S2⎯ (161.8 eV), oxysulfide
(163.0 eV), and sulfate (168.7 eV) [18, 19]; in addition,
the sulfur present on the catalyst surface is mostly in
the form of oxysulfide (48%).
With a further increase in the nickel content of the
HC feedstock, the naphthalene conversion became
96–99%; therefore, the catalytic activities of the
resulting systems were compared in terms of SCA,
which takes account of both the naphthalene converꢀ
sion and the product selectivity (Fig. 2).
Catalytic Properties
At a molar ratio of W : Ni = 1 : 2, the naphthalene
conversion is 99% to form 76% tetralin and 24% decaꢀ
lin with a cisꢀ to transꢀdecalin ratio of 1 : 1.6. An
increase in the nickel(II) salt concentration leads to a
decrease in SCA: even at a W : Ni molar ratio of 1 : 3,
the conversion decreases to 96% and the decalin selecꢀ
tivity is no more than 20%, while the ratio between cisꢀ
and transꢀdecalins remains unchanged (1 : 1.6).
As the nickel content in the feedstock is increased
The properties of the synthesized Ni–W–S catalyst
were studied in a batch reactor at a temperature of
350°C and a hydrogen pressure of 5.0 MPa using 10%
solutions of bicyclic aromatic HCs in benzene as
model systems.
It has been shown that the naphthalene conversion
increases with increasing tungsten content; at a tungꢀ
sten content of 2500 ppm, the naphthalene conversion
achieves 100%. The product is tetralin. A small to 1350 ppm (at a W : Ni molar ratio of 1 : 2), the naphꢀ
amount of decalins (cisꢀ and transꢀstereoisomers) is thalene conversion makes 99% within 2.5 h to form
formed at a tungsten content in the feedstock of 88% tetralin and 12% decalin. An increase in the reacꢀ
2500 ppm, yet no more than 5%. The ratio between tion time leads to an increase in the decalin content in
cisꢀ and transꢀdecalins is 1 : 1.1.
the system; by 10 h, decalins are the main reaction
PETROLEUM CHEMISTRY Vol. 56
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SYNTHESIS OF NICKEL–TUNGSTEN SULFIDE HYDRODEAROMATIZATION CATALYSTS
Table 1. Hydrogenation of methylnaphthalenes. Reaction conditions: W content, 1350 ppm; W : Ni = 1 : 2; = 10 h;
47
t
T =
350
°
C; and PH = 5 MPa
2
Selectivity, %
Aromatic compound
Conversion, %
decalins
tetralins
1ꢀMethylnaphthalene
87
92
40
60
66
59
62
55
13
8
100
99
2ꢀMethylnaphthalene
2,3ꢀDimethylnaphthalene
2,6ꢀDimethylnaphthalene
1,5ꢀDimethylnaphthalene
1,8ꢀDimethylnaphthalene
2,7ꢀDimethylnaphthalene
2,3,6ꢀTrimethylnaphthalene
60
40
34
41
38
45
99
93
100
99
100
100
products with a transꢀdecalin selectivity of 72%. An rings, the migration of the alkyl substituent occurs, as
increase in the reaction time also results in a change in evidenced by published data [21]. Thus, in addition to
the ratio between cisꢀ and transꢀdecalins from 1 : 1.3 to 5ꢀmethyltetralin and 1ꢀmethyltetralin, the hydrogeꢀ
1 : 2.6 (reaction time of 2.5 and 10 h, respectively). nation of 1ꢀmethylnaphthalene led to the formation of
This effect can be due to the fact that transꢀdecalin is 2ꢀmethyltetralin and 6ꢀmethyltetralin; however, the
the thermodynamically favored stereoisomer of decaꢀ amount of these products in the total methyltetralin
lin.
content does not exceed 4%.
It has been shown that the resulting catalyst is
In the hydrogenation of 2ꢀmethylnaphthalene, the
active in the hydrogenation of naphthalenes with one, methyldecalin selectivity is 92%. As in the case of
two, and three methyl substituents (Table 1).
hydrogenation of 1ꢀmethylnaphthalene, four stereoiꢀ
somers of both 2ꢀmethyldecalin and 1ꢀmethyldecalin
are formed in the hydrogenation of 2ꢀmethylnaphthaꢀ
lene. The total amount of 1ꢀmethyldecalins in the
reaction products is 17%; the main 1ꢀmethyldecalin is
The hydrogenation of bicyclic aromatic HCs bearꢀ
ing one methyl substituent was studied using 1ꢀmethꢀ
ylnaphthalene and 2ꢀmethylnaphthalene as an examꢀ
ple. In the hydrogenation of monomethylated naphꢀ
thalenes, the main products are methyldecalins. In the
hydrogenation of 1ꢀmethylnaphthalene, the methylꢀ
decalin selectivity is 87%; in this case, both 1ꢀmethylꢀ
decalins and 2ꢀmethyldecalins are formed; the formaꢀ
tion of the latter is caused by the migration of the alkyl
substituent. The two compounds are formed as four
trans
product of the hydrogenation of 2ꢀmethylnaphthalene
is trans synꢀ2ꢀmethyldecalin (the most thermodyꢀ
ꢀsynꢀ1ꢀmethyldecalin (11%). The main end
ꢀ
namically stable stereoisomer of 2ꢀmethyldecalin
[20]); the selectivity for this product is 44%. The ratio
between cisꢀ and transꢀmethyldecalins in the hydrogeꢀ
nation of 2ꢀmethylnaphthalene significantly differs
from the ratios between cisꢀ and transꢀdecalins in the
hydrogenation of naphthalene or 1ꢀmethylnaphthaꢀ
lene: it is 1 : 6 .
stereoisomers (trans
cis synꢀmethyldecalins). The total amount of 2ꢀmethꢀ
yldecalins in the reaction products is 19%; the main
2ꢀmethyldecalin stereoisomer is trans synꢀ2ꢀmethylꢀ
decalin (7%). The main end product of the hydrogeꢀ
nation of 1ꢀmethylnaphthalene is trans
ꢀantiꢀ, transꢀsynꢀ, cisꢀantiꢀ, and
ꢀ
ꢀ
In the hydrogenation of 2ꢀmethylnaphthalene, the
ꢀ
antiꢀ1ꢀmethꢀ amount of methyltetralins remaining in the system
yldecalin (the most thermodynamically stable 1ꢀmeꢀ does not exceed 8%. The main methyltetralin isomer
thyldecalin [20]); the selectivity for this product is formed during the hydrogenation of 2ꢀmethylnaphꢀ
35%. The cisꢀ to transꢀmethyldecalin ratio is 1 : 2.6.
The amount of methyltetralins remaining in the
system does not exceed 13%. The hydrogenation rate
of the unsubstituted ring is several times higher than
that of the ring with an alkyl substituent; thus, the
main methyltetralin isomer produced during the
hydrogenation of 1ꢀmethylnaphthalene is 5ꢀmethylteꢀ
tralin; the amount of this material in the total content
of methyltetralins is 50%. This fact is attributed to the
presence of steric hindrances to the adsorption of
methylnaphthalene by the substituted aromatic ring
thalene is 6ꢀmethyltetralin; the amount of this product
in total methyltetralins is 49%. It should also be noted
that the migration of the alkyl substituent is more
active than in the case of hydrogenation of 1ꢀmethylꢀ
naphthalene. Thus, in addition to the formation of 6ꢀ
methyltetralin and 2ꢀmethyltetralin, the formation of
5ꢀmethyltetralin and 1ꢀmethyltetralin was observed in
the hydrogenation of 2ꢀmethylnaphthalene; the
amount of these products in total methyltetralins is
more than 20%.
In a 10ꢀh reaction, the conversion of all these dimꢀ
on the catalyst surface [20]. It should also be noted ethylated naphthalenes is 93–100%. In [22] we noted
that in addition to the hydrogenation of aromatic that dimethylnaphthalenes can be conditionally
PETROLEUM CHEMISTRY Vol. 56
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48
SIZOVA et al.
Table 2. Effect of the sulfiding agent on the catalyst activity in the hydrogenation of naphthalene. Reaction conditions:
T
=
350
°
C; PH = 5.0 MPa;
t
= 5 h; W content, 680 ppm; W : Ni = 1 : 2; and S content, 25000 ppm
2
Selectivity, %
Solvent
Naphthalene
conversion, %
Sulfiding agent
decalins
tetralins
Elemental sulfur
DMDS
Benzene
24
24
20
14
45
30
12
76
76
80
86
55
70
88
99
100
100
100
98
Benzene
Benzene
Benzene
DMSO
DMDS + DMSO
DMDS
n
n
n
ꢀHexadecane
ꢀHexadecane
ꢀHexadecane
DMSO
13
DMDS + DMSO
92
divided into two groups depending on the number of which is slightly lower than that in the hydrogenation
isomeric forms of the product dimethyltetralin. The of monoꢀ and dimethylated naphthalenes; this differꢀ
hydrogenation of 1,8ꢀdimethylnaphthalene, 2,6ꢀdimꢀ ence can also be due to the steric hindrances created
ethylnaphthalene, 1,5ꢀdimethylnaphthalene, and 2,7ꢀ by the trimethylated aromatic ring to the adsorption of
dimethylnaphthalene results in the formation of a sinꢀ 2,6,7ꢀtrimethyltetralin on the catalyst surface.
gle appropriate form of dimethyltetralin owing to the
symmetric arrangement of the methyl substituents on
Selection of Sulfiding Agent
different aromatic rings. In the hydrogenation of these
dimethylnaphthalenes, the main products are dimethꢀ
yldecalins in different stereoisomeric forms.
The hydrogenation of 2,3ꢀdimethylnaphthalene
results in the formation of three isomeric forms of
In addition to elemental sulfur, dimethyl disulfide
(DMDS) and dimethyl sulfoxide (DMSO) were tested
as a sulfiding agent. In the case of using a DMDS–
DMSO mixture as a sulfiding agent, the DMDS :
DMSO ratio was 1 : 2. When a 10% naphthalene soluꢀ
tion in benzene was used as a model feedstock, all of
these sulfiding agents were soluble in the HC feedꢀ
stock. The naphthalene conversion was 99–100% in
all cases (Table 2). The main product was tetralin. The
lowest decalin yield (14%) was observed in the case of
a DMDS–DMSO mixture. The ratio between cisꢀ to
transꢀdecalin remained almost unchanged, being at
the level of 1 : 2 to 1 : 2.5 for all the sulfiding agents.
dimethyltetralin: 6,7ꢀdimethyltetralin, 2,3ꢀtrans
ꢀ
dimethyltetralin, and 2,3ꢀcisꢀdimethyltetralin
because the methyl substituents in this dimethylnaphꢀ
thalene are arranged on one aromatic ring. It should be
noted that the main form of the resulting dimethylteꢀ
tralin will be dimethyltetralin bearing substituents in
the 6ꢀ and 7ꢀpositions owing to the fact that the
unsubstituted aromatic ring undergoes hydrogenation
more readily. In this case, the selectivity of hydrogenaꢀ
tion for dimethyldecalins (40%) is lower than that of
the other discussed substrates; this feature can be
attributed to steric hindrances created by the dimethꢀ
ylated aromatic ring to the adsorption of 6,7ꢀdimethꢀ
yltetralin on the catalyst surface.
It is noteworthy that as in the case of hydrogenation
of monomethylnaphthalenes, in addition to the
hydrogenation of the aromatic rings, both the migraꢀ
tion of the methyl substituents the formation of
dealkylation products occurred to a small extent.
In the case of using a 10% naphthalene solution in
ꢀhexadecane as a model feedstock, a significant
effect of the sulfiding agent on the catalytic activity of
the resulting Ni–W–S particles was observed. Thus,
the catalyst synthesized using DMSO, which is immisꢀ
n
cible with nꢀhexadecane, as a sulfiding agent showed
the lowest activity. The naphthalene conversion was as
low as 13%. The highest catalytic activity was found
for the catalyst prepared using the sulfiding agent
DMDS, which is soluble in this feedstock. Thus, the
The 2,3,6ꢀtrimethylnaphthalene conversion is naphthalene conversion was 98%; the decalin selectivꢀ
100% and results in the formation of 2,6,7ꢀtrimethꢀ ity was 45%. This difference in the activity of the
yltetralin, 2,3,6ꢀtransꢀtrimethyltetralin, 2,3,6ꢀcisꢀtriꢀ resulting catalysts can be attributed to the presence of
methyltetralin, about 1% other trimethyltetralins due oxygen in DMSO, which can lead to a slowdown in
to the migration of the methyl groups, and a small the sulfide formation. The us of the mixed DMDS–
amount of dealkylation products. The main trimethꢀ DMSO agent dramatically increased the activity of the
yltetralin isomer is 2,6,7ꢀtrimethyltetralin (selectivity catalyst system. This finding suggests that in order to
of 26%); the selectivity for 2,3,6ꢀcisꢀtrimethyltetralin increase the activity of the catalyst synthesized from
and 2,3,6ꢀtransꢀtrimethyltetralin is 2 and 15%, DMSO solutions, it is necessary to use an additional
respectively. In the hydrogenation of 2,3,6ꢀtrimethylꢀ sulfiding agent (DMDS). It is noteworthy that the
naphthalene, the trimethyldecalin selectivity is 55%, ratio between cisꢀ and transꢀdecalins remains
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SYNTHESIS OF NICKEL–TUNGSTEN SULFIDE HYDRODEAROMATIZATION CATALYSTS
49
Table 3. Characterization of light cycle oil and hydrofining products
Hydrofining products
Characteristic
LCO
W content in feedstock, wt %
0.3
2.1
4.2
Sulfur, ppm
3320
34
27
99
57
99
40
2
98
29
2
Monocyclic aromatic HCs, wt %
Bicyclic aromatic HCs, wt %
Polycyclic aromatic HCs, wt %
7.5
0.5
65
5
0
0
Σ
aromatic HCs, wt %
66
42
31
unchanged at the level of 1 : 2 for all the sulfiding tion of monocyclic HCs contained in the feedstock
agents. occurs.
LCO Hydrofining
CONCLUSIONS
In this study, the possibility of applying the syntheꢀ
sized catalyst to the hydrofining of actual feedstock
with a high concentration of sulfur and aromatic HCs
has been explored using LCO as an example. Table 3
shows the data on the hydrodearomatization and
hydrodesulfurization of LCO as a function of the
weight fraction of the precursor in the feedstock.
The data show that the hydrodesulfurization of
LCO under these experimental conditions can result
in the formation of the hydrofining product with a
total sulfur content of 0.01%. The degree of hydrodesꢀ
ulfurization is 97% and does not change with increasꢀ
ing precursor content in the feedstock.
Thus, a nickel–tungsten sulfide catalyst has been
first prepared by the in situ decomposition of the oilꢀ
soluble tungsten hexacarbonyl precursor in a hydroꢀ
carbon feedstock using the oilꢀsoluble salt nickel(II)
2ꢀethylhexanoate as a source of nickel. It has been
revealed that the optimum W : Ni molar ratio is 1 : 2.
It has been shown that the synthesized catalyst exhibits
high activity in the hydrogenation of bicyclic HCs and
can be used in the hydrofining of a feedstock with high
sulfur and aromatics content, as evidenced by the
example of LCO.
ACKNOWLEDGMENTS
The features of the hydrodearomatization of LCO
hydrocarbons are similar to those of the hydrogenation
of the model systems. The total aromatics content of
the hydrofining products decreases with the increasing
precursor content in the feedstock. The amount of biꢀ
and polycyclic aromatic HCs significantly decreases;
at a W content in the feedstock of 2.1 wt %, the
amount of bicyclic polyaromatic HCs in the hydrofinꢀ
ing product is no more than 2%, while polycyclic aroꢀ
matic HCs are not identified at all. The hydrogenation
of aromatic HCs having two and more aromatic rings
leads to the formation of not only naphthenic HCs,
but also monocyclic aromatic HCs, as was shown for
the model systems. Thus, at a W content in the feedꢀ
stock of 0.3 and 2.1 wt %, the content of monocyclic
aromatic HCs in the hydrogenation products is higher
than that in the original LCO. However, with an
increase in the tungsten content in the feedstock, the
amount of monocyclic aromatic HCs decreases; this
fact indicates the occurrence of the hydrogenation of
monocyclic aromatic HCs produced during the
hydrodearomatization of biꢀ and polycyclic aromatic
HCs; at a W content in the feedstock of 4.2 wt %, the
amount of monocyclic aromatic HCs becomes lower
than that in the feed LCO, thereby suggesting that not
only the deep hydrogenation of biꢀ and polycyclic HCs
directly to naphthenic HCs, but also the hydrogenaꢀ
This work was supported by the Russian Science
Foundation of the Federation (contract no. 15ꢀ13ꢀ
00123).
The work was performed using the equipment of
the Center for collective use “New Petrochemical
Processes, Polymer Composites, and Adhesives.”
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LTranslated by M. Timoshinina
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