Dimethyl disulfide conversion into dimethyl sulfide in the presence of sulfidized catalysts

Article abstract of DOI:10.1134/S0023158410050149

The conversion of dimethyl disulfide in the presence of various supported sulfidized metal-containing catalysts at atmospheric pressure and T = 150-350°C was studied. Sulfidized transition metals supported onto aluminum oxide were more active than catalysts based on a carbon support, silicon dioxide, amorphous aluminosilicate, and zeolite ZSM-5. The most active catalyst was 10% Co/Al₂O₃ prepared with the use of cobalt acetate as an active component precursor and treated with a mixture of hydrogen sulfide with hydrogen at T = 400°C. From kinetic data, it follows that all of the reaction products were formed simultaneously at a temperature of <200°C, whereas a consecutive reaction scheme took place at higher temperatures. In the presence of a sulfidized alumina-cobalt catalyst, the output of dimethyl sulfide was higher than that reached with the use of other well-known catalysts.

Full text of DOI:10.1134/S0023158410050149

ISSN 0023ꢀ1584, Kinetics and Catalysis, 2010, Vol. 51, No. 5, pp. 724–730. © Pleiades Publishing, Ltd., 2010.
Original Russian Text © A.V. Mashkina, L.N. Khairulina, 2010, published in Kinetika i Kataliz, 2010, Vol. 51, No. 5, pp. 750–756.
Dimethyl Disulfide Conversion into Dimethyl Sulfide
in the Presence of Sulfidized Catalysts
A. V. Mashkina and L. N. Khairulina
Boreskov Institute of Catalysis, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia
eꢀmail: amash@catalysis.ru
Received April 8, 2009
Abstract—The conversion of dimethyl disulfide in the presence of various supported sulfidized metalꢀconꢀ
taining catalysts at atmospheric pressure and
T = 150–350°C was studied. Sulfidized transition metals supꢀ
ported onto aluminum oxide were more active than catalysts based on a carbon support, silicon dioxide,
amorphous aluminosilicate, and zeolite ZSMꢀ5. The most active catalyst was 10% Co/Al2O3 prepared with
the use of cobalt acetate as an active component precursor and treated with a mixture of hydrogen sulfide with
hydrogen at
T = 400°C. From kinetic data, it follows that all of the reaction products were formed simultaꢀ
neously at a temperature of <200°C, whereas a consecutive reaction scheme took place at higher temperaꢀ
tures. In the presence of a sulfidized alumina–cobalt catalyst, the output of dimethyl sulfide was higher than
that reached with the use of other wellꢀknown catalysts.
DOI: 10.1134/S0023158410050149
INTRODUCTION
EXPERIMENTAL
The samples of
ꢀAl2O3
SBET = 200–275 m2/g),
γ
(
Lower dialkyl disulfides are formed in considerable
amounts upon the demercaptanization of fuels and
gases [1]. In the presence of a number of catalysts, they
can be converted into valuable substances, such as
dialkyl sulfides and alkanethiols. In an atmosphere of
γ
ꢀAl2O3 ꢀAl2O3 ꢀAl2O3
SBET = 250 m2/g),
BET = 300 m2/g), SiO2 (SBET = 300 m2/g), amorꢀ
phous AlSi (SBET = 360 m2/g), zeolite HZSMꢀ5
(Si/AL = 17;
BET ~ 500 m2/g), and Sibunit activated
carbon (
BET = 560 m2/g) were used as supports. The
+
χ
(
η
(
S
S
S
hydrogen at
Р = 0.1 MPa and Т = 180–260°С in the
supported catalysts were prepared by the incipient
wetness impregnation of precalcined supports with
aqueous solutions of sodium hydroxide; potassium
tungstate; tungstophosphoric acid; chromium nitrate;
cobalt acetate, chloride, or nitrate; nickel chloride or
nitrate; ammonium perrhenate; ruthenium hydroxyꢀ
chloride; palladium chloride; and ammonium heptaꢀ
molybdate. Bimetallic catalysts based on nickel
(cobalt) and molybdenum were prepared by the
impregnation of aluminum oxide with aqueous soluꢀ
tions containing a mixture of nickel (cobalt) nitrate or
chloride and ammonium heptamolybdate. All of the
samples after impregnation were kept in air at room
temperature for 12 h and dried at 110°С (5 h). The
samples based on cobalt, nickel, ruthenium, and palꢀ
ladium chlorides were not calcined; the samples conꢀ
taining potassium tungstate and cobalt acetate were
calcined at 400°С for 5 h, and the other samples were
calcined at 500°С. In the text and the tables, element
concentrations in weight percent are given before the
symbols of the elements. Reagentꢀgrade DMDS was
used in the experiments.
presence of supported sulfidized catalysts containing
Pd, Rh, Ru, Ni, Co, Mo, W, and Ni(Co)Mo, the
hydrogenolysis of dimethyl disulfide (DMDS) and
diethyl disulfide occurred at the S–S bond followed by
the predominant formation of alkanethiols and dimeꢀ
thyl sulfide or diethyl sulfide in 0.2–10 mol % yields
[2–7]. The yield of dialkyl sulfides considerably
increased upon the conversion of dialkyl disulfides on
oxide catalysts containing surface acid and basic sites
in an inert atmosphere at
Т = 190–350°С. Previously
[8], we found that catalysts on the surface of which
mediumꢀstrength basic sites, strong protic acid sites,
and strong aprotic acid sites occurred simultaneously
were most active and selective in the conversion of
DMDS into dimethyl sulfide. The sulfidization of the
active component of an oxide catalyst and a change in
its activity can occur in the course of reaction. The forꢀ
mation of dimethyl sulfide, which is a valuable thio
compound, by the conversion of DMDS in an inert
atmosphere in the presence of sulfidized catalysts was
not studied previously.
In this work, we studied the regularities of the conꢀ
version of DMDS into dimethyl sulfide in the presꢀ
ence of sulfidized catalysts of various compositions in
order to find an active and selective catalyst.
The catalytic experiments were performed in a flow
setup at atmospheric pressure. Helium from a gas cylꢀ
inder was supplied to a thermostated saturator filled
with DMDS. Then, the gas saturated with DMDS
724

DIMETHYL DISULFIDE CONVERSION INTO DIMETHYL SULFIDE
725
Table 1. Comparison between oxide and sulfide catalysts in terms of activity and selectivity in the conversion of dimethyl disulꢀ
fide (T = 190 and 250°C; X = 60%)
Oxide catalyst
Sulfide catalyst
Catalyst
mmol h–1
(g Cat)–1
×
w
,
mmol h–1
(g Cat)–1
×
wS,
mmol h–1
(g Cat)–1
×
wS
,
mmol h–1
×
w,
S, %
S, %
(g Cat)–1
T
= 190°C
0.3 Na/Al2O3
1.1
2.0
0.5
0.2
0.2
0.4
0.3
20
46
8
0.22
0.92
0.04
0.06
0.02
0.16
0.03
2.0
3.7
2.3
2.7
0.8
3.2
2.4
48
54
26
50
25
26
28
1.0
2
γꢀAl2O3
2.5 Cr/Al2O3
5 Mo/Al2O3
0.6
1.3
0.2
1.2
0.56
30
10
14
10
10 W/Al2O3
10 Co/Al2O3
5 Ni 10 Mo/Al2O3
T
= 250
°
C
Al2O3
8.2
4.2
40
16
15
26
36
3
3.3
16.3
18.9
17.4
13.8
32
54
30
44
40
40
6
8.8
5.2
2.5 Cr/Al2O3
5 Mo/Al2O3
10 W/Al2O3
10 Co/Al2O3
5 Co/C
0.7
1.7
0.26
1.7
7.6
6.4
5.5
18.4
0.4
6.6
12.8
0.1
0.01
0.16
1.2
5 Ni 10 Mo/Al2O3
1.6
10
10.3
35
3.6
arrived at a heated reactor with a catalyst. In the activꢀ
Y/Х ratio, and the rates of the overall reaction of DMDS
ity measurements, a fresh catalyst sample with a partiꢀ at a specified DMDS conversion (w) and the formation
cle size of 0.25–0.5 mm was used in each particular of dimethyl sulfide (wS) in mmol h–1 (g Cat)–1 were calꢀ
experiment. The catalysts were either not activated culated.
additionally or treated with a mixture of 15% H2S +
85% H2 at
T = 400°С for 1 h (except for specified
RESULTS AND DISCUSSION
cases) and then purged with helium at the experiment
temperature for 30 min before activity measurements.
A mixture of DMDS with helium (the initial concenꢀ
The preliminary experiments were performed at
= 190 and 250°С in the presence of a number of
T
tration of DMDS in the mixture was 1.6 0.2 vol %) oxide and sulfidized catalysts. Dimethyl sulfide, methꢀ
was passed through the reactor with the catalyst at a anethiol, Н2S, СS2, and С1–С2 hydrocarbons were the
required temperature. Within 30 min after the onset of reaction products on all of the catalysts. Table 1 sumꢀ
passing the mixture to the reactor, the initial mixture marizes experimental results. At the same concentraꢀ
and reaction products were sampled for analysis; in the tion of an active component, catalysts in the oxide
determination of catalyst stability, the samples were form were much less active (by a factor of 2–14) in the
taken at regular intervals for 3 h.
formation of dimethyl sulfide than the sulfidized samꢀ
ples. The introduction of sodium hydroxide or transiꢀ
tion metal (Mo, Cr, Co, and W) oxides into ꢀAl2O3
resulted in a decrease in the rate of dimethyl sulfide
formation, as compared with that observed on pure
aluminum oxide. This may be due to a difference in
the acid properties of catalyst surfaces [9, 10]. As we
found previously [8], the presence of both mediumꢀ
The reaction products were identified by gas chroꢀ
matography–mass spectrometry. The quantitative
analysis was performed on an LKhMꢀ8MD chroꢀ
γ
matograph with a katharometer (a column of 2 m
mm packed with Porapak Q and Porapak R (1 : 1);
helium was a carrier gas).
×
3
The ratio of the catalyst volume to the gas flow rate strength basic sites and strong acid sites on the surface
in cm3/s at room temperature and atmospheric presꢀ is required for the formation of dimethyl sulfide from
sure was taken as the contact time (
results of analysis, the conversion of DMDS (
the yields of reaction products (
, mol %), the selecꢀ and a small number of strong proton sites with РАk
tivity of dimethyl sulfide formation ( DMS, %) as the 1300 kJ/mol. In pure ꢀAl2O3
Al3+ cations are Lewis
τ
, s). Based on the DMDS. The majority of the test catalysts contained
Х
, %), mediumꢀstrength basic sites (РА° = 800–900 kJ/mol)
Y
<
S
γ
,
KINETICS AND CATALYSIS Vol. 51
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726
MASHKINA, KHAIRULINA
X
, %; y, mol %
(a)
(b)
100
100
1
1
60
60
2
2
3
4
5
3
20
20
4
5
60
120
180
60
120
180
, min
t
Fig. 1. Dependence of (
1
) DMDS conversion and the yields of (
2
) dimethyl sulfide, (
3
) methanethiol, (
4
) CS , and (
5
) H S on
2
2
experiment time at = 250°С. Catalyst: (a) oxide and (b) sulfidized forms of 10% Co/Al O .
T
2
3
S, %
(a)
(b)
60
60
20
1
2
1
2
20
3
3
4
4
60
120
180
60
120
180
, min
t
Fig. 2. Dependence of the selectivity of formation of (
1) dimethyl sulfide, (2) methanethiol, (3) CS , and (4) H S on experiment
2 2
time at = 250°С. Catalyst: (a) oxide and (b) sulfidized forms of 10% Co/Al O .
T
2
3
acid sites (LASs). Upon the introduction of sodium conversion of DMDS and the yields of dimethyl sulꢀ
hydroxide or transition metal oxides into ꢀAl2O3, the
γ
fide and H2S on oxide catalysts increased and the yield
of methanethiol decreased as the experiment time was
increased from 0.5 to 3 h. These characteristics
remained unchanged as the reaction time was further
increased. It is likely that oxides were sulfidized in the
course of reaction under the action of the reaction
atmosphere. This partially sulfidized oxide was much
superior to the starting oxide catalyst in catalytic activꢀ
ity; however, even in a steady state, it was inferior to
LASs of alumina were blocked with the cations of Na,
Mo, Co, Cr, and W oxides, which are weaker aprotic
acids than Al3+ [9, 10]. This can result in a decrease in
the rate of reaction and the selectivity of dimethyl sulꢀ
fide formation. Upon the treatment of oxides with a
mixture of H2S + H2 at an elevated temperature, the
dissociative chemisorption of hydrogen sulfide
occurred and the concentration of strong proton sites
on the surface increased [9]. In addition, metal oxides
under the action of H2S can be partially converted
unto sulfides and reduced at an elevated temperature
with the formation of coordinatively unsaturated catꢀ
ions (strong acceptor sites), which participate in the
activation of disulfide. Therefore, on sulfidized cataꢀ
lysts, the reaction of dimethyl sulfide formation
occurred at an elevated rate, as compared with oxide
catalysts.
the sample treated with a mixture of H2S + H2 at
T =
400°С, which was stable in operation (for example,
see Figs. 1, 2).
The increase in the conversion of DMDS on variꢀ
ous sulfidized catalysts at
T = 250°С resulted in an
increase in the selectivity of dimethyl sulfide and H2S
formation and a decrease in the selectivity of methꢀ
anethiol formation at the constant selectivity of CS2
and C1–C2 hydrocarbon formation. The selectivity of
In the course of reaction at
stant (contact time) on catalysts in oxide and sulfide
forms, the values of and the selectivity of product
formation remained unchanged for 3 h. At 250°С, the rence of side reactions (for example, see Table 2).
T = 190°С and a conꢀ
hydrogen sulfide formation was lower than
SDMS; this
τ
was likely due to the participation of H2S in the occurꢀ
Х
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DIMETHYL DISULFIDE CONVERSION INTO DIMETHYL SULFIDE
727
Table 2. Selectivity of reaction product formation at various
dimethyl disulfide conversions in the presence of the sulꢀ
These results allow us to hypothesize that dimethyl
sulfide is formed in accordance with a consecutive
reaction scheme: DMDS interacts with surface proꢀ
tons and decomposes with the release of methanethꢀ
iol, which then condenses with the formation of dimꢀ
ethyl sulfide and H2S.
fidized 5 Cr/Al2O3 catalyst at
T
= 250
°
C
S
, %
Х, %
dimethyl methaꢀ
sulfide
Н2S
CS2
At DMDS conversions of <100%, the sulfidized
catalysts differed in the selectivity of dimethyl sulfide
nethiol
formation; however, at
majority of the catalysts.
Table 3 summarizes the results of the experiments
performed on the sulfidized catalysts at = 250°С and
Х
~ 100%
,
S
≈
45–50% on the
40
61
83
95
27
33
44
47
51
49
38
26
20
15
10
14
15
18
20
12
14
13
14
13
T
various contact times. The catalysts based on Al2O3
exhibited higher activity and selectivity of dimethyl
sulfide formation than the samples based on aluminoꢀ
100
silicate, silica gel, or activated carbon. The
support treated with a mixture of H2S + H2 at
400°С was active in the formation of dimethyl sulfide:
γ
ꢀAl2O3
T
=
Table 3. Activity and selectivity of sulfidized catalysts in the
conversion of dimethyl disulfide into dimethyl sulfide (
250 C; = 70%)
at
Х = 70% w S = 50%, and
= 12.2 mmol h–1 (g Cat),
T
=
wS = 6.1 mmol h–1 (g Cat)–1. The activity of the
2.3% Na/Al2O3 sample decreased by a factor of ~16,
as compared with that of the parent support. After the
°
X
w
S, mmol
×
w
, mmol
×
Catalyst
S, %
h–1 (g Cat)–1
introduction of Ru, Re, Ni, and Pd, the value of
w
h–1 (g Cat)–1
decreased by a factor of 2.5–5. The activity of the samꢀ
ples containing Cr, Mo, and W differed only slightly
γ
ꢀAl2O3
12.2
0.7
50
25
30
38
12
46
42
40
32
15
46
44
35
14
32
32
46
46
35
35
20
27
35
30
6.1
0.18
0.6
4.7
0.1
7.0
5.4
4.3
4.5
0.3
2.8
5.7
2.2
0.1
1.0
1.1
9.7
13.8
1.7
1.2
0.24
2.0
4.2
2.0
from the activity of ꢀAl2O3. Changes in the concenꢀ
γ
2.3 Na/Al2O3
10 K2WO4/Al2O3
2.5 Cr/Al2O3
2.5 Cr/SiO2
5 Mo/Al2O3
10 Mo/Al2O3
20 Mo/Al2O3
10 Mo/C
trations of Mo, Re, and Ru did not result in a noticeꢀ
able increase in the rate of dimethyl sulfide formation.
It is important that sulfidized alumina–cobalt cataꢀ
lysts were the most active species. The formation of
dimethyl sulfide also occurred under the action of sulꢀ
fidized bimetallic Ni(Co)Mo/Al2O3 catalysts; in this
case, NiMo/Al2O3 was more active than CoMo/Al2O3
by a factor of almost 2; however, both of the catalysts
were inferior to the monometallic sulfidized Co/Al2O3
and Mo/Al2O3 samples.
The S–S bond in dialkyl disulfides, in particular, in
DMDS, is easily ruptured under the action of catalysts
with the formation of СН3S fragments. The methꢀ
anethio fragments decompose to sulfur and surface
СН3 groups, the interaction of which can result in
dimethyl sulfide [11]. In this case, the activity of sulꢀ
fidized catalysts can depend on the binding energy of
2.0
12.4
0.8
15.2
12.9
10.8
1.4
10 Mo/SiO2
5 W/ Al2O3
2.1
6.1
10 W/Al2O3
18 W/Al2O3
12.9
6.2
sulfur on the catalyst surface (the mobility of sulfur). 10 W/C
0.7
We compared the mobility of surface sulfur, which was
determined from the temperature of the onset of H2S
5 Re/Al2O3
2.4
20 Re/Al2O3
3.4
release on catalyst treatment with hydrogen (qS, 1/Т,
104 K) [9], with the found rates of dimethyl sulfide forꢀ
mation in the presence of a number of sulfidized cataꢀ
lysts containing 5 wt % metal on aluminum oxide:
5 Co/Al2O3
21.0
30.0
4.7
10 Co/Al2O3
10 Ni/Al2O3
A2О3 Co Cr Mo
W
Pd Ni Re
5 Ru/Al2O3
3.3
wS
,
6.1 9.7 4.7 7.0 2.8 2.0 1.7 1.0
10 Ru/Al2O3
5 Pd/Al2O3
1.2
mmol/h (g Cat)
7.5
qS, 1/Т, (К)
12.9 22.1 18.9 19.1 19.1 27.9 19.5 34.1
2.5 Ni 10 Mo/Al2O3
2.5 Co 10 Mo/Al2O3
12.5
6.7
Sulfur is most strongly bound to the surface of aluꢀ
mina; the value of qS for a cobalt catalyst is smaller by
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728
MASHKINA, KHAIRULINA
Table 4. Effect of the nature of an active component precursor on the activity and selectivity of sulfidized cobalt catalysts
in the conversion of dimethyl disulfide into dimethyl sulfide (
T
= 250°C; X = 70%)
wS
,
w
,
Catalyst
5 Co/AlSi
10 Co/Al2O3
Precursor
CoCl2
S, %
mmol h–1 (g Cat)–1
mmol h–1 (g Cat)–1
3.5
6.4
26
27
43
42
46
0.9
1.7
Со(С2Н3О2)2
CoCl2
5.2
2.2
Co(NO3)2
Со(С2Н3О2)2
21.6
30.0
9.1
13.8
Table 5. Effect of the nature of a support on the activity and selectivity of sulfidized cobalt catalysts in the conversion of
dimethyl disulfide into dimethyl sulfide ( = 250°С, = 70%)
Т
Х
w
S, mmolh–1
(g Cat)–1
×
w
S, mmol h–1
(g Cat)–1
×
w
, mmol h–1
(g Cat)–1
×
w
, mmol h–1
(g Cat)–1
×
Catalyst
10% Co/C
S
, %
Support
S, %
2.4
4.5
10
6
0.24
0.3
C
0.3
0.15
3.7
10
7
0.03
0.01
1.2
10% Co/SiO2
SiO2
10% Co/AlSi
6.5
22
41
46
45
48
1.4
AlSi
32
40
47
48
44
10% Co/HZSMꢀ5
8.0
3.3
HZSMꢀ5
14.1
12.2
7.2
5.6
10% Co/
γ
ꢀAl2O3
ꢀAl2O3
)ꢀAl2O3
30
13.8
9.8
γ
ꢀAl2O3
ꢀAl2O3
)ꢀAl2O3
5.7
10% Co/
η
21.8
10.2
η
3.4
10% Co/(
γ
+
χ
4.9
(γ
+
χ
6.4
2.8
a factor of 1.7, and it is more active than Al2O3 in the their higher activity in the formation of dimethyl sulꢀ
fide, as compared with that of the oxide samples.
formation of dimethyl sulfide by a factor of 1.6. The
mobility of sulfur on the surface of samples containing
Cr, W, Ni, and Pd is higher than that on aluminum
oxide by a factor of 1.5–2; however, they are inferior to
Al2O3 in the value of wS by a factor of 1.3–3.6. The
mobility of sulfur in the sulfidized Mo/Al2O3 catalyst
is higher than that in Al2O3 treated with a mixture of
H2S + H2; however, these catalysts differ only slightly
in terms of activity. Sulfur is least strongly bound to the
surface of rhenium sulfide; however, the 5% Re/Al2O3
catalyst is less active than Al2O3 by a factor of 6.1.
Thus, the observed difference in the activities of sulꢀ
fidized catalysts cannot be explained by different
mobility of sulfur on their surfaces. It is likely that the
reaction scheme of DMDS conversion into dimethyl
sulfide on sulfidized catalysts is analogous to the
scheme proposed previously for oxide catalysts [8].
Upon the chemisorption of DMDS on a catalyst, the
sulfur atom of a СН3S group is bound to a surface proꢀ
ton, the sulfur atom of the second СН3S group is
bound to an acceptor site (a coordinatively unsaturꢀ
ated metal sulfide cation), and the carbon atom of the
СН3 group is bound to a basic site. The decomposition
of the surface complex leads to the release of sulfur and
the formation of dimethyl sulfide. The increased conꢀ
centration of coordinatively unsaturated cations on
Among the test catalysts, the sulfidized cobalt catꢀ
alysts exhibited the highest activity in the formation of
dimethyl sulfide. The nature and concentration of a
cobalt precursor, the type of the support, and the conꢀ
ditions of treatment with a mixture of H2S + H2 can
affect their catalytic properties.
To reveal the effect of the nature of a catalyst preꢀ
cursor on process characteristics at
T = 250°С, we
determined the activity of cobalt samples prepared by
the impregnation of supports with the solutions of
cobalt chloride, nitrate, or acetate followed by sulꢀ
fidization at
T = 400°С (Table 4). The 5% Co/AlSi
catalyst, which was prepared with the use of cobalt
chloride, was inferior to the catalyst prepared from
cobalt acetate by a factor of 1.9 in terms of wS. The
10% Co/AlSi catalyst (cobalt chloride as an active
component precursor) was less active than that preꢀ
pared with the use of cobalt nitrate by a factor of 4.1;
however, the latter was inferior to the catalyst prepared
from cobalt acetate by a factor of 1.5. The higher activꢀ
ity of the sulfidized alumina–cobalt catalysts prepared
from cobalt acetate was due to a small size of cobaltꢀ
containing precursor particles on the support surface
(1.5–2 nm). After the activation of supports impregꢀ
nated with a solution of cobalt acetate, finely dispersed
the surface of sulfidized catalysts is responsible for cobalt sulfide particles can be formed on the surface.
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DIMETHYL DISULFIDE CONVERSION INTO DIMETHYL SULFIDE
729
The effect of the nature of a support on the activity
of cobalt catalysts sulfidized at 400°С was determined
in experiments on the conversion of DMDS into dimꢀ
ethyl sulfide in the presence of catalysts prepared from
cobalt acetate and containing 10 wt % Co on various
supports: aluminum oxide, aluminosilicate, silica gel,
activated carbon, and zeolite ZSMꢀ5. As follows from
data given in Table 5, the values of wS on Co/C and
Co/SiO2 samples were lower than those in the presꢀ
ence of catalysts based on amorphous AlSi and zeolite
HZSMꢀ5 by a factor of 5–10. However, the latter catꢀ
w
,
mmol h–1 (g Cat)–1
S
, %
40
20
40
20
2
6
10
14
18
Co concentration, wt %
alysts were less active than the Co/
γ
ꢀAl2O3 catalyst by
ꢀAl2O3 or ꢀAl2O3
ꢀAl2O3 as supports, which are structurally different
a factor of 4–10. With the use of
η
γ
+
Fig. 3. Dependence of (
and ( ) the selectivity of dimethyl sulfide formation at
70% on sulfidized alumina–cobalt catalysts upon the
cobalt content of the catalyst at = 250°С
1) the rate of DMDS conversion
χ
2
X =
from ꢀAl2O3 [6], less active cobalt catalysts were preꢀ
γ
T
.
pared. To determine the contribution of a support to
the activity of sulfidized cobalt catalysts, we performed
experiments on aluminum oxide, silica gel, activated
carbon, aluminosilicate, and zeolite ZSMꢀ5, which
catalyst demonstrated that, as the experiment temperꢀ
ature was increased, the rate of formation of dimethyl
sulfide at
were pretreated with a mixture of H2S + H2 at
T =
X = 70% increased, whereas selectivity,
400°С. The carbon support and silica gel did almost
not accelerate the reaction of DMDS conversion into
dimethyl sulfide, whereas the sulfidized catalysts conꢀ
taining cobalt on these supports exhibited a noticeable
activity. This fact allowed us to hypothesize that the
reaction on these catalysts occurs under the action of
cobalt sulfide rather than the support. Amorphous
AlSi and zeolite HZSMꢀ5 were equal in terms of activꢀ
ity or even somewhat superior to catalysts containing
cobalt on these supports. It is likely that, on these catꢀ
alysts, the reaction occurs on the support. In the presꢀ
ence of pure alumina, the reaction of dimethyl sulfide
formation occurred at a sufficiently high rate (Fig. 3).
which depends on contact time, decreased:
Т
,
°
С
150 170 200 220 250 300 330 350
0.6 1.3 2.8 5.9 13.8 24.8 46.2 53.1
wS
mmol h–1 (g Cat)–1
,
S, %
58 54 48 47 46 40 35 30
The kinetic experiments showed that the selectivity
of product formation remained unchanged as the conꢀ
version of DMDS was increased at a constant initial
concentration of DMDS and
T
≤
200°С. It is likely
that the products are formed from DMDS in indepenꢀ
dent reaction paths; that is, the reactions occur in parꢀ
allel directions. At a higher temperature, the selectivꢀ
ity of dimethyl sulfide formation increased with
DMDS conversion, whereas the selectivity of methꢀ
anethiol formation decreased (Fig. 4). It is likely that,
as on the other sulfidized samples, a consecutive reacꢀ
At a Co concentration of
activity of the sulfide catalyst was only slightly higher
than that observed on the support. On ꢀAl2O3 conꢀ
taining from 0.5 to 10 wt % Co, the values of were
≤
0.5 wt % on Al2O3, the
γ
w
higher than that on the pure support by a factor of 2–
3. This fact suggests the occurrence of the formation of
dimethyl sulfide mainly under the action of cobalt sulꢀ
fide at an insignificant contribution from the support.
At a cobalt sulfide content of >10 wt %, the activity of
the catalyst decreased; this was likely due to a change
in the dispersity of the active component.
tion scheme occurs on the 10% Co/ ꢀAl2O3 catalyst at
γ
an elevated temperature: the decomposition of
DMDS to methanethiol, which subsequently conꢀ
densed to form dimethyl sulfide and hydrogen sulfide.
The sulfidization temperature affected the activity
of alumina–cobalt catalysts (Table 6). The rate of
dimethyl sulfide formation on the 10% Co/Al2O3 catꢀ
Table 6. Effect of the temperature of treatment of the 10%
Co/Al2O3 catalyst with a mixture of H2S + H2 on its activity
alyst prepared with the use of cobalt acetate without and selectivity the conversion of dimethyl disulfide into
dimethyl sulfide (
T
= 250°C; X = 70%)
the treatment with a mixture of H2S + H2 was low; the
value of wS increased by a factor of ~3.5 or 7 after sulꢀ
, mmolh–1
(g Cat)–1
×
w
S, mmol h–1
(g Cat)–1
×
Т, °C catalyst treatꢀ
ment with H2S + H2
w
fidization at
T = 190–250 or 400°С, respectively. A
S, %
further increase in the temperature to 450°С resulted
in a dramatic decrease in the activity of the catalyst.
–
5.0
16.6
18.7
30.0
11.6
38
38
39
46
44
1.9
6.3
Thus, the sulfidized 10% Co/ ꢀAl2O3 catalyst preꢀ
γ
190
250
400
450
pared with the use of cobalt acetate as an active comꢀ
ponent precursor and treated with a mixture of H2S +
7.3
H2 at
formation of dimethyl sulfide from DMDS at
250°С. The variation of reaction conditions on this
T = 400°С exhibited the highest activity in the
13.8
5.1
T
=
KINETICS AND CATALYSIS Vol. 51
No. 5
2010

730
MASHKINA, KHAIRULINA
S, %
60
(a)
(b)
60
20
1
1
2
2
3
4
20
3
4
60
100
60
100
, %
X
Fig. 4. Dependence of the selectivity of formation of (
1) dimethyl sulfide, (2) methanethiol, (3) CS , and (4) H S on DMDS
2 2
conversion. = (a) 170 or (b) 250°С
T
.
4. Mashkina, A.V. and Khairulina, L.N., Kinet. Katal.
2005, vol. 46, no. 6, p. 921 [Kinet. Catal. (Engl. Transl.),
vol. 46, no. 6, p. 873].
5. Mashkina, A.V. and Khairulina, L.N., Kinet. Katal.
2007, vol. 48, no. 1, p. 132 [Kinet. Catal. (Engl. Transl.),
vol. 48, no. 1, p. 125].
6. Mashkina, A.V., Krivoruchko, O.P., and Khairuliꢀ
,
Based on the experimental data, we can conclude
that sulfidized metal oxide catalysts and ꢀAl2O3 are
active in the reaction of dimethyl sulfide formation
from DMDS. The 10% Co/ ꢀAl2O3 catalyst prepared
with the use of cobalt acetate and treated with a mixꢀ
ture of H2S + H2 at = 400°С was especially efficient.
The formation of dimethyl sulfide in the presence of
this sulfide catalyst occurred at a higher output, as
compared with published data [8]; this allowed us to
conclude that this catalyst is promising for the develꢀ
opment of a new process for the synthesis of dimethyl
sulfide.
γ
,
γ
T
na, L.N., Kinet. Katal., 2008, vol. 49, no. 1, p. 110
[Kinet. Catal. (Engl. Transl.), vol. 49, no. 1, p. 103].
7. Cadot, E., Lacroix, M., and Breysse, M., J. Catal.
,
1996, vol. 164, no. 1, p. 490.
8. Mashkina, A.V. and Khairulina, L.N., Kinet. Katal.
,
2009, vol. 50, no. 3, p. 434 [Kinet. Catal. (Engl. Transl.),
vol. 50, no. 3, p. 414].
REFERENCES
9. Mashkina, A.V., Kataliz reaktsii organicheskikh
soedinenii sery (Catalysis in Reactions of Organosulfur
Compounds), Novosibirsk: Sib. Otd. Ross. Akad.
Nauk, 2005.
10. Paukshtis, E.A., Infrakrasnaya spektroskopiya v geteroꢀ
gennom kislotnoꢀosnovnom katalize (Infrared Spectrosꢀ
copy in Heterogeneous Acid–Base Catalysis), Novosiꢀ
birsk: Nauka, 1992.
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,
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,
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KINETICS AND CATALYSIS Vol. 51
No. 5
2010