Catalytic synthesis of dimethyl sulfi de from dimethyl disulfi de and methanol

Article abstract of DOI:10.1134/S1070427212050158

The reaction of dimethyl disulfi de with methanol was studied at atmospheric pressure and temperature of 350°C in the presence of catalysts containing acid and basic sites.

Full text of DOI:10.1134/S1070427212050158

ISSN 1070-4272, Russian Journal of Applied Chemistry, 2012, Vol. 85, No. 6, pp. 926−932. © Pleiades Publishing, Ltd., 2012.
Original Russian Text © A.V. Mashkina, L.N. Khairulina, 2012, published in Zhurnal Prikladnoi Khimii, 2012, Vol. 85, No. 6, pp. 945−952.
ORGANIC SYNTHESIS
AND INDUSTRIAL ORGANIC CHEMISTRY
Catalytic Synthesis of Dimethyl Sulfide
from Dimethyl Disulfide and Methanol
A. V. Mashkina and L. N. Khairulina
Boreskov Institute of Catalysis, Siberian Division, Russian Academy of Sciences, Novosibirsk, Russia
e-mail: amash@catalysis.ru
Received November 22, 2011
Abstract—The reaction of dimethyl disulfide with methanol was studied at atmospheric pressure and temperature
of 350°C in the presence of catalysts containing acid and basic sites.
DOI: 10.1134/S1070427212050158
Oxidation processes are extensively used today for re-
moving mercaptans from hydrocarbon mixtures at oil- and
gas-processing plants. These processes give a mixture of
lower dialkyl disulfides dominated by dimethyl disulfide
(DMDS) [1] suitable for synthesis of a number of valu-
able thio compounds. In this context, of particular interest
is preparation of dimethyl sulfide (DMS), an important
organosulfur compound which is used for preparation
of dimethyl sulfoxide and also serves as extractant and
gas odorant.
Here, we studied the reaction of DMDS with methanol
in the presence of catalysts possessing different surface
acid-base properties with a view to obtaining active cata-
lysts for selective formation of DMS.
EXPERIMENTAL
In our experiments we used chemically pure-grade
methanol and pure-grade DMDS. As support and
catalyst served off-the-shelf γ-Al2O3 material with
Ssp = 275 m2 g–1; also we used off-the-shelf SiO2 with
Ssp = 310 m2 g–1 as support. As catalysts served zeolites
NaX, HNaY (Ssp = 800 m2 g–1), HZSM-5 (Si/Al 17 and
35; Ssp = 500 m2 g–1), and HZSM-5 (Si/Al 17) with 20%
binder, as well as massive Cr2O3.
Solid-catalyzed conversion of DMDS in an inert me-
dium at atmospheric pressure and T = 190–350°C leads
to DMS and also to large quantities of byproducts [2–4].
Previously [2] we studied this reaction in the presence
of acid-base catalysts and presumed that formation of
DMS requires that the catalyst surface contain strong
acid sites and medium-strength basic sites. They cause
disruption of the S–S and C–S bonds in disulfide, with the
resulting CH3 and CH3S groups reacting to form DMS.
The appearance of the surface CH3 groups originated
from decomposition of DMDS is accompanied by forma-
tion of sulfur, hydrogen sulfide, carbon disulfide, C1–C2
hydrocarbons, and resins. As a result, DMS is produced
with a low selectivity of ≤50%. As found earlier [5, 6],
it is possible to suppress the side processes and increase
the DMS yield by introducing into the reaction system
of methanol able of more efficient, compared to DMDS,
methoxylation of the alumina surface.
The supported catalysts were prepared by impregna-
tion of precalcined supports with aqueous solutions of
phosphoric, sulfuric, and tungstosilicic (HSiW) acids,
as well as chromic acid anhydride, sodium hydroxide,
ammonium tungstate, potassium tungstate, cobalt acetate,
and ammonium heptamolybdate. Bimetallic catalyst
NiMo/Al2O3 was obtained by impregnating alumina with
an aqueous solution containing a mixture of nickel nitrate
and ammonium heptamolybdate. Catalyst CoHZSM-5
was prepared by the procedure described in [3].
After impregnation, all the samples were maintained in
air at room temperature for 12 h and dried at 110°C (5 h).
The samples based on phosphoric and tungstophosphoric
926

CATALYTIC SYNTHESIS OF DIMETHYL SULFIDE
927
acids were calcined for 5 h at 300°C in a helium stream,
and other samples, at 500°C in a dry air stream for 5 h.
The content of active ingredient in the catalyst, wt%, was
as follows: H3PO4 30, K2WO4/Al2O3 25, K2WO4/SiO2 20,
Co/Al2O3 10, Mo/Al2O3 10, Cr/SiO2 2.5, CoHZSM-5 2.5,
Na/Al2O3 0.2 and 1.7, and Cr/Al2O3 1.5 and 0.12–15. For
some of the samples, the numbers preceding the element
symbols in the tables and the text represent their weight
per cent concentrations.
following results were obtained for γ-Al2O3 at X = 70%:
0.2 0.6 1.2 1.7 2.0 2.4 2.6
М
Yield of DMS, mol% 60 76 106 118 126 134 136
Methanol primarily reacts with DMDS to form
DMS, but a certain amount (15–25%) of methanol is
decomposed into dimethyl ether (DME) and carbon
oxides. The largest yield of DMS was obtained at M >
2 (approximately 2 times the degree of DMDS conver-
sion). In further experiments the activity and selectivity
of the catalysts of different compositions in the reaction
of methanol with DMDS were determined at 350°C and
M = 2.4–2.6.
The acid-base properties of the catalysts were exam-
ined by IR spectroscopy of adsorbed probe molecules
[7–9]. The strength of the sites, kJ mol–1, was estimated
from the heat of adsorption of CO QCO for Lewis acid sites
(L-sites), from the affinity of deuterium in CDCl3 for basic
sites (BSs) PAb which is 800–900 kJ mol–1 for medium-
strength BSs, and from the proton affinity of pyridine for
protic sites (PSs) PAa which is 1170–1200 kJ mol–1 for
strong PSs. The concentration of active sites c is expressed
in units of micromoles per squared meter.
Based on the difference between the concentration of
methanol in the initial reaction mixture and the sum of the
concentrations of unchanged methanol and the resulting
DME and carbon oxides we calculated the concentration
of methanol that could enter into the reaction with DMDS
to form DMS. For most of the catalysts examined this
concentration was equal, within the experimental error,
to that of the resulting DMS. Some of the relevant data
are presented in Table 1.
The catalytic experiments were carried out in a flow
setup at atmospheric pressure. Helium from a gas cyl-
inder was supplied to saturators filled with DMDS and
methanol and placed into thermostats. Upon mixing, the
gas saturated with DMDS and methanol was fed into a
reactor heated to a certain temperature and charged with
0.25–0.5-mm catalyst grains. After 45 min from the start
of supply of the mixture to the reactor the first sample of
the initial mixture and the reaction products was taken
for analysis. Sampling was repeated in regular intervals
during the subsequent 2.5 h.
The conversion of DMDS mixed with methanol in
the presence of the catalysts of interest gave DMS and
methanethiol (MT) as organosulfur products; a small
amount of H2S was also formed (in a 0.02–6 mol%
yield); the reaction on some of the catalysts at different
contact times gave methane in a 0.1–5 mol% yield as
calculated for the initial DMDS. Decomposition of neat
DMDS gave these compounds in larger quantities; DMS
was obtained in a ~50% yield [2–4]. Minor amounts
of sulfur and carbon were deposited onto the catalyst
surface in the initial period, e.g., 0.44 and 0.27 wt %,
respectively, onto Cr/Al2O3 after 45 min of the experi-
ment (first sampling run). During the subsequent 2.5 h
of the reaction the sulfur and carbon content remained
virtually constant (0.46 and 0.30 wt%, respectively), and
the activity of the catalyst remained unchanged. The yield
of water was equal, within the experimental error, to the
degree of methanol conversion; DME and carbon oxides
were formed. Figures 1 and 2 demonstrate the results of
the experiments on Cr/γ-Al2O3-catalyzed conversion of
methanol, both neat and mixed with DMDS.
The reaction products were analyzed on an LKhM-
8MD chromatograph equipped with a katharometer
[a 2 m × 3 mm column packed with Porapak phase Q +
R (1 : 1), carrier gas helium].
The contact time τ, s, was determined as the ratio of
the catalyst volume to the gas flow rate, cm3 s–1, at room
temperature and atmospheric pressure. Based on the re-
sults of the analysis we calculated the degree of reactant
conversion X, %, the yield of the reaction products from
the ratio of the concentration of the resulting product to
the initial substrate concentration, mol%, and the reaction
rate, mmol h–1 per gram of catalyst.
We carried out preliminary experiments on conver-
sion of DMDS mixed with methanol in the presence of
γ-Al2O3 at atmospheric pressure, temperature of 350°C,
and different contact times and methanol to DMDS mole
ratios M. These experiments showed that, with increasing
M, the yield of DMS tends to increase. For example, the
Figure 1a shows that, within a brief contact time, neat
methanol undergoes dehydration solely, with DME being
formed; at longer contact times the reaction products also
include carbon oxides (2–12 mol% yield). For methanol
mixed with DMDS (Fig. 1b) the yield of DME at a brief
contact time τ is approximately equal to the degree of
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 85 No. 6 2012

928
MASHKINA, KHAIRULINA
(a)
(b)
Fig. 1. (1) Degree of methanol conversion X, %, and (2–4) yield Y, mol%, of (2) DME, (3) CO, and (4) CO2 on Cr/γ-Al2O3 catalyst at
350°C vs. contact time τ, s. Conversion of methanol: (a) neat and (b) mixed with DMDS at M = 2.4–2.6.
methanol conversion, like in the case of dehydration of
neat methanol; with increasing τ the yield of DMS tends
to increase, that of DME, to sharply decrease, and those
of CO and CO2, to slightly increase.
Table 1. Concentration of methanol reacted with dimethyl
disulfide against the concentration of the resulting dimethyl
sulfide. Temperature 350°C, dimethyl disulfide conversion
60–80%
Concentration, mM, of indicated
compound
In the case of conversion of DMDS mixed with
methanol (Fig. 2), an increase in the contact time causes
the degree of DMDS conversion and the DMS yield to
increase, with the latter parameter being approximately
twice the former. Similar results were obtained in the
presence of other catalysts of interest. In the reactions
carried out on the acid catalysts under identical condi-
tions the rate of conversion for neat DMDS differed in-
Catalyst
resulting
reacted methanol
dimethyl sulfide
H3PO4/SiO2
HSiW/SiO2
HZSM-5: Si/Al = 17
Si/Al = 35
0.56
0.62
0.70
0.60
0.64
0.59
0.65
0.15
0.21
0.18
0.42
0.39
0.75
0.88
0.86
0.33
0.58
0.74
0.62
0.65
0.77
0.66
0.62
0.65
0.68
0.18
0.15
0.14
0.45
0.22
0.79
0.83
0.91
0.39
0.62
0.81
HZSM-5 + binder
HNaY
CoHZSM-5
NaX
1.7Na/Al2O3
K2WO4/Al2O3
K2WO4/SiO2
Cr/SiO2
γ-Al2O3
H2SO4/γ-Al2O3
W/γ-Al2O3
Co/γ-Al2O3
Mo/γ-Al2O3
Cr/γ-Al2O3
Fig. 2. (1) Degree of conversion X, %, of DMDS mixed with
methanol and (2, 3) yield Y, mol%, of (2) DMS and (3) MT
vs. contact time τ, s. Catalyst Cr/γ-Al2O3, 350°C, M = 2.4–2.6.
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 85 No. 6 2012

CATALYTIC SYNTHESIS OF DIMETHYL SULFIDE
929
significantly from that for DMDS mixed with methanol.
For example, at 350°C and X = 70% on Cr/Al2O3, these
rates were estimated at 37 and 24 mmol h–1 per catalyst
gram, respectively.
Table 2. Activity of zeolites and supported acids and bases in
the reaction of dimethyl disulfide with methanol. Temperature
350°C; dimethyl disulfide and methanol conversion 70 and
50%, respectively
Thus, we found that the DMS yield is twice the de-
gree of DMDS conversion; deep cracking products are
lacking for DMDS; there is no CS2, and small quantities
of H2S, methane, and sulfur are produced; the yield of
DMS is at a maximum at M > 2; and the concentrations
of the methanol reacted with dimethyl disulfide and of
the resulting DMS are identical. These data suggest the
DMS formation from the reaction between two methanol
molecules and one DMDS molecule:
Yield, mol%, of
Formation rate, mmol
indicated compound h–1per catalyst gram
Catalyst
dimethyl
sulfide
dimethyl dimethyl
methanethiol
82
sulfide
ether
1.7% Na/γ-
Al2O3
K2WO4/SiO2
9.8
0.15
2.1
5.6
7.0
63
65
0.08
0.16
0.13
0.15
[H]
K2WO4/γ-
Al2O3
(CH3)2S2 + 2CH3OH → (CH3)2S + 2H2O.
NaX
28
0
55
43
3.5
14
6.4
0
0.60
0.21
This process probably involves surface protons which
are continuously reproduced on the surface via methanol
decomposition.
H3PO4/SiO2
HSiW/SiO2
HNaY
132
112
5.0
24.8
14.8
In the reaction of methanol with DMDS we applied
catalysts differing in the type, strength, and concentration
of the acid and basic sites. For each of the catalysts we
estimated the degree of DMDS conversion and the yield
of the products in relation to the contact time. Using the
kinetic plots we determined the contact time correspond-
ing to 70% conversion of DMDS and calculated the yield
of MT, as well as the yield and formation rate for DMS
(Tables 2 and 3). The DMS formation rate served as the
measure of activity of the catalyst.
36.3
HZSM-5:
Si/Al=17
126
132
118
106
4.2
4.2
8.4
8.1
32.4
34.6
37.4
28.1
92.7
60.5
29.5
53.4
Si/Al=35
CoHZSM-5
HZSM-5 +
binder
1300 kJ mol–1, c = 1.2 μmol m–2) and weak BSs solely
(PAb < 800 kJ mol–1) is inactive in formation of DMS.
The catalysts characterized by high content of
alkaline promoters (1.7 Na/Al2O3, K2WO4/SiO2, and
K2WO4/Al2O3) do not contain PSs; there are weak
L-sites (QCO = 18–20 kJ mol–1, c = 2–3 μmol m–2) and
strong BSs (PAo = 830–960 kJ mol–1, c ~ 3 μmol m–2) in
them. In their presence DMS was obtained in a 5–10%
yield, with MT being the main reaction product. On the
zeolite NaX surface there are no PSs either, and there are
weak L-sites (QCO = 20 kJ mol–1, c = 3.0 μmol m–2) and
medium-strength BSs (c = 0.5 μmol m–2). The DMDS
conversion catalyzed by NaX zeolite led predominantly to
MT; DMS was obtained in a 28 mol% yield, and the rate
of its formation exceeded that observed in the presence of
supported alkaline catalysts. Thus, in formation of DMS,
weakly acidic catalysts containing medium-strength BSs
surpass in activity the catalysts containing strong BSs.
In HSiW/SiO2, L-sites are lacking; there are strong
PSs (PAa = 1170–1180 kJ mol–1, c = 1.0 μmol m–2) and
weak BSs (PAb < 800 kJ mol–1), and this catalyst exhibits
a noticeable activity in formation of DMS.
Hydrogen forms of HNaY and HZSM-5 zeo-
lites (Si/Al 17 and 35), containing strong PSs (PAa =
1170–1190 kJ mol–1, c = 0.16–0.33 μmol m–2) and
medium-strength BSs (c = 1.1 μmol m–2) are highly
active in formation of DMS. This activity may be as-
sociated not only with the occurrence of strong PSs but
also with simultaneous presence in zeolites of L-sites
(QCO = 28–32 kJ mol–1, c = 0.3–1.1 μmol m–2 and QCO
37–54 kJ mol–1, c = 0.04–0.1 μmol m–2) and medium-
strength BSs (c = 1.1 μmol m–2).
=
With 20% binder added to HZSM-5 (Si/Al 17) the
activity of the catalyst slightly decreases. Upon adding
The H3PO4/SiO2 catalyst containing weak PSs (PAa =
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MASHKINA, KHAIRULINA
Table 3. Activity of the oxide catalysts in the reaction of
dimethyl sulfide formation from dimethyl sulfide and methanol
and of dimethyl ether formation from dehydration of methanol.
Temperature 350°C; M = 2.4–2.6; X = 70%; dimethyl disulfide
and methanol conversion 70 and 50%, respectively
PSs, as well as a decrease in the strength of the L-sites
to QCO = 33 kJ mol–1 and a certain increase in basicity
of the surface (to PAb = 850–930 kJ mol–1, c = 3 μmol
m–2). The DMS formation rate decreases by a factor of
1.8 relative to unpromoted γ-Al2O3. Addition of sulfuric
acid to γ-Al2O3 leads to increases in the concentration
of strong PSs (to 0.5 μmol m–2) and in the strength of
L-sites (QCO = 37–43.5 kJ mol–1); the activity of the
catalyst increases by a factor of 1.6. An insufficiently
high activity is apparently associated with blocking of
the BSs by sulfuric acid [7].
Formation rate,
Yield, mol%, of
indicated compound per catalyst gram
mmol h–1
Catalyst
dimethyl
disulfide
dimethyl dimethyl
methanethiol
sulfide
ether
Promotion of γ-Al2O3 by transition metal oxides
leads to appearance on the surface of strong PSs (c =
0.1–0.2 μmol m–2); there is a sufficient number of L-
sites (QCO = 34–37 kJ mol–1, c = 1.0–1.2 μmol m–2) and
medium-strength BSs (c = 1.3–2.8 μmol m–2). In forma-
tion of DMS from DMDS and methanol the promoted
γ-Al2O3 catalysts are close in activity to the hydrogen
forms of zeolites and surpass unpromoted alumina. The
bimetallic catalyst Ni, Mo/Al2O3 has no advantages over
monometallic catalysts in terms of activity in DMS forma-
tion. The silica-supported oxide catalysts exhibit a lower
activity. For example, Cr/SiO2 containing strong PSs (c =
0.25 μmol m–2), weak L-sites (QCO = 28 kJ mol–1, c =
0.4 μmol m–2), and weak BSs on the surface exhibits a
lower, compared to chromium-alumina catalyst, activity
in DMS formation.
Cr/SiO2
24
134
137
5.2
0.7
1.6
3.6
3.3
68
γ-Al2O3
γ-Al2O3 + H2S
0.3
5.2
237
61
0.2% Na/γ-Al2O3 133
2.8
2.0
H2SO4/γ-Al2O3
W/Al2O3
126
136
95
4.9
5.7
113
68
1.4
11.2
28.6
37.2
49.6
16.0
Со/γ-Al2O3
Mo/γ-Al2O3
Cr/γ-Al2O3
18.9
12.6
4.2
32
112
130
91
42
54
Ni,Mo/γ-Al2O3
21
38
2.5 mol% cobalt into zeolite HZSM-5 the Lewis acidity
of the surface increases (QCO = 35.7–59.5 kJ mol–1, c =
0.78 μmol m–2); the catalyst also contains strong protic
sites (c = 0.2 μmol m–2) and is close in activity to neat
zeolite.
Our results suggest that, in order that catalysts exhibit
a high activity in formation of DMS from DMDS and
methanol, they should contain a combination of strong
PSs and L-sites and medium-strength BSs on their surface.
In the presence of all the catalysts examined, methanol
was dehydrated to DME. To determine whether the acid-
basic sites affect the rate of methoxylation of the surface
of the catalysts during interaction with methanol, we
carried out experiments on converting neat methanol at
T = 350°C, [CH3OH]0 ~3.5 vol%, and different contact
times. From the kinetic plots we determined the contact
time τ corresponding to 50% conversion of methanol
(with methanol dehydration being the sole process) and
calculated the DME formation rate. Some researchers
[10–12] believe that, when methanol contacts the catalyst,
methoxy groups appear on the catalyst surface, which
are intermediate in formation of DME. The rate of DME
formation can indirectly characterize the rate of surface
methoxylation with methanol. Tables 2 and 3 list the
DME formation rates for different catalysts. It was found
that the trends in variation of the rate of methoxylation
The surface of neat γ-Al2O3 calcined at T = 500°C
contains a very small amount of strong PSs (c =
0.03 μmol m–2); there are L-sites due to Al3+ (QCO
=
32–34 kJ mol–1, c = 2.2 μmol m–2 and QCO = 41–
56 kJ mol–1, c = 0.2 μmol m–2) and medium-strength
BSs (c = 4 μmol m–2). The activity exhibited by γ-Al2O3
in formation of DMS is of the same order as that of the
proton-donating HSiW/SiO2 catalyst. A low activity
of γ-Al2O3 is evidently due to insufficient number of
strong PSs on its surface. It was found that, upon treat-
ment of γ-Al2O3 with an H2S + H2 mixture at T = 400°C
for 1 h, a certain number of strong PSs (c = 0.08 μmol
m–2) appear on the surface; the strength of the L-sites
remains unchanged but their concentration decreases.
The activity of the catalyst increases by a factor of 1.4
compared to neat γ-Al2O3. Promotion of γ-Al2O3 by
adding 0.2 wt % Na caused significant suppression of
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CATALYTIC SYNTHESIS OF DIMETHYL SULFIDE
931
by methanol with the catalyst composition are qualita-
tively identical to those in the case of DMS formation.
Probably, both reactions proceed under the action of
the same surface sites. As to quantitative correlation, it
was unsatisfactory, probably due to the fact that, in the
reaction of DMS formation from DMDS and methanol,
the rate of surface methoxylation by methanol is not the
limiting factor.
Table 4. Influence of the chromium content in the catalyst on
the conversion rate of dimethyl disulfide in the presence of
methanol and the yields of dimethyl sulfide and methanethiol.
Temperature 350°C, M = 2.4–2.6, dimethyl disulfide conversion
70%
Dimethyl disulfide
conversion rate,
mmol h–1 per gram of
indicated compound
Yield, mol%, of indicated
compound
Chromium
content on
γ-Al2O3,
wt%
The data on how the activity of the catalysts is affected
by the acid-base properties of their surface suggest that,
similar to methanol dehydration to DME, the reaction of
DMS formation from DMDS and methanol follows a het-
erolytic mechanism with the acid-basic sites on the cata-
lyst surface involved.According to [11, 12], the methanol
dehydration proceeds via surface methoxylation, followed
by formation of a surface complex comprising one CH3O
group and gaseous methanol or a second CH3O group.
In this complex, the oxygen atom from one CH3O group
is linked to the L-sites, and that from the second CH3O
group, to the PSs on the surface, occurring in the initial
catalyst or originated from methanol decomposition. We
found that, over a broad range of variation of the degree
of DMDS conversion, the yield of MT changes insignifi-
cantly (Fig. 2) and presumed that MT is not the primary
product and does not participate in formation of DMS.
dimethyl
methanethiol
sulfide
catalyst chromium
0
2.4
6.3
–
136
137
129
132
131
130
132
120
120
98
1.4
2.1
0.12
5040
4160
2340
2060
1600
977
0.25 10.4
2.8
0.5
1.0
11.7
20.6
24.0
29.3
32.1
38.0
28.2
3.3
3.5
4.9
1.5
5.0
3.0
4.2
5.0
640
8.4
10.0
15.0
68.4*
380
7.7
187
21.0
60.1
4.8
13
The weak S–S bond in DMDS is ruptured at elevated
temperature, which process is facilitated by catalysts;
DMDS decomposition gives CH3S and CH3 groups
which undergo various transformations [13–15]. It can
be presumed that, in the case of DMDS mixed with
methanol, the DMS synthesis proceeds via formation of
a surface complex which comprises bonds linking the
acid-basic sites to the CH3O and CH3S groups arising
from methanol and dimethyl disulfide. Formation of such
a complex is the most probable in the case of catalysts
simultaneously containing strong protic and aprotic acid
sites and medium-strength basic sites on their surface.
This concerns, in particular, the hydrogen form of zeolites
and γ-Al2O3-supported transition metal oxide catalysts.
In their presence, surface methoxylation with methanol is
more facile than in the case of DMDS. Methanol hinders
coordination of the CH3S groups of DMDS to the L-sites
and BSs, thereby preventing the rupture of the C–S bond
in disulfide and, consequently, the formation of byprod-
ucts. As a result, DMS is formed in a high yield.
a Massive Cr2O3 sample.
are affected by the content of the active ingredient. The
experimental data (Table 4) suggest that promotion of
γ-Al2O3 with 0.12 wt% Cr caused the DMDS conversion
rate to increase by a factor of ~2.6; with further increase
in the chromium content it tends to increase and approxi-
mately 17 times exceeds the rate of the reaction catalyzed
by γ-Al2O3; on the massive Cr2O3 sample the DMDS con-
version rate is 10 times lower than that on γ-Al2O3. The
specific surface area of the chromium-alumina catalysts of
interest was by a factor of no larger than 1.3 smaller than
that of neat γ-Al2O3. Enhanced activity of the supported
chromium catalysts is probably due to the fact that, as
known [16], chromium in γ-Al2O3 occupies only a portion
(~18%) of its surface area, and the acidity of the cata-
lyst surface is determined by those of both unpromoted
γ-Al2O3 and Cr/γ-Al2O3. With increasing chromium con-
centration in the catalyst the reaction rate per gram of Cr
tends to decrease, probably due to a change in the grain
size characteristics of the active ingredient. The yields of
DMS in the reactions catalyzed by 0.12–3.0 Cr/γ-Al2O3
In the presence of Cr/Al2O3, which is one of the most
active catalysts at T = 350°C, we examined how the
conversion parameters for DMDS mixed with methanol
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MASHKINA, KHAIRULINA
Table 5. Influence of temperature on the dimethyl disulfide
conversion rate and yields of dimethyl sulfide and methanethiol
at 70% conversion of dimethyl disulfide
(2) It was found that this reaction proceeds only in the
presence of catalysts having medium-strength basic sites
and strong protic or aprotic sites.
(3) The highest activity in formation of dimethyl
sulfide is exhibited by the catalysts containing simultane-
ously medium-strength basic sites and strong protic and
strong Lewis acid sites on the surface. With γ-Al2O3-
supported chromium oxide, the yield of dimethyl sulfide is
nearly doubled relative to the degree of dimethyl disulfide
conversion and reaches 95 mol%.
Yield, mol%, of indicated
Dimethyl disulfide
Т, °С conversion rate, mmol
h–1 g–1
compound
dimethyl
sulfide
methanethiol
300
325
350
380
400
8.7
12.2
24.0
40.6
55.0
86
24
10
5
113
130
129
132
REFERENCES
5
1 Mazgarov,A.M. and Vil’danov,A.F., Neftekhimiya, 1999,
vol. 39, no. 5, pp. 371–378.
4
2. Mashkina, A.V. and Khairulina, L.N., Kinet. Katal., 2009,
vol. 50, no. 3, pp. 434–439.
3. Mashkina, A.V. and Khairulina, L.N., Kinet. Katal., 2010,
are nearly identical, but at higher chromium content the
yield decreases and gets particularly low in the case of
massive chromium oxide. In the reactions on the catalysts
promoted with up to 3% Cr, methanethiol is formed in a
low yield (2–5 mol%) which, however, tends to increase
with increasing chromium content and reaches 60% in
the massive sample.
vol. 51, no. 4, pp. 603–607.
4. Mashkina, A.V. and Khairulina, L.N., Kinet. Katal., 2010,
vol. 51, no. 5, pp.750–756.
5. Mashkina, A.V., Zh. Org. Khim., 2011, vol. 47, no. 5,
pp. 677–679.
6. RF Patent 2402529.
7. Paukshtis, E.A., Infrakrasnaya spektroskopiya v geterogen-
nom kislotno-osnovnom katalize (Infrared Spectroscopy in
HeterogeneousAcid-Base Catalysis), Novosibirsk: Nauka,
1992.
In the presence of 1.5 Cr/γ-Al2O3 we examined the
DMS formation parameters in relation to temperature
(Table 5). It is seen that, with the temperature increas-
ing from 300 to 400°C, the DMDS conversion rate and
the DMS yield tend to increase, and the MT yield, to
decrease. From the plot of the logarithm of the reaction
rate vs. reciprocal temperature we estimated the apparent
activation energy at 67 kJ mol–1.
8. Mashkina,A.V., Kataliz reaktsii organicheskikh soedinenii
sery (Catalysis of Reactions of Organosulfur Compounds),
Novosibirsk: Sib. Otd. Ross. Akad. Nauk, 2005.
9. Mashkina,A.V., Sulfur Rep., 1991, vol. 10, no. 4, pp. 279–
388.
10. Krylov, O.V. and Matyshak, V.A., Usp. Khim., 1994,
Our experimental data suggest that the supported
oxide catalysts are promising for development of a new
process for selective synthesis of DMS from DMDS and
methanol. The process should be carried out at atmo-
spheric pressure and temperature of 350–400°C with total
conversion of disulfide. Under these conditions, DMS can
be obtained in a yield of ≥95 mol %.
vol. 63, no. 7, pp. 585–600.
11. Kazanskii, V.B., Usp. Khim., 1988, vol. 57, no. 12,
pp. 1937–1962.
12. Matyshak,V.A., Berezina, L.A., Sil’chenkova, O.N., et al.,
Kinet. Katal., 2009, vol. 50, no. 1, pp. 120–126.
13. Kang, D.H. and Friend, C.M., Langmuir, 2004, vol. 20,
no. 26, pp. 11443–11449.
CONCLUSIONS
14. Halevi, B. and Vohs, J.M., J. Phys. Chem. B, 2005, vol. 109,
no. 50, pp. 23976–23982.
(1) It was shown that, in the presence of acid-base
catalysts at atmospheric pressure and temperature of
350°C, dimethyl disulfide reacts with methanol to form
dimethyl sulfide and a small amount of methanethiol.
15. Huang, T.P., Lin, T.H., Teng, T.F., and Hung, W.H., Surf.
Sci., 2009, no. 9, pp. 1244–1252.
16. Skrigan, E.A., Gorbatsevich, M.F., and Sen’kov, G.M., Izv.
Akad. Nauk Bel. SSR, Ser. Khim., 1990, no. 4, pp. 36–39.
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 85 No. 6 2012