Journal of Natural Gas Chemistry 18(2009) –
Synthesis of dimethyl ether from methane mediated by HBr
Qin You1 , Zhen Liu1, Wensheng Li1 , Xiaoping Zhou1,2∗
1. Department of Chemical Engineering, Hunan University, Changsha 410082, Hunan, China;
2. College of Life Science and Pharmaceutical Engineering, Nanjing University of Technology, Nanjing 210009, Jiangsu, China
[ Received July 3, 2009; Revised July 13, 2009; Available online September 15, 2009 ]
Abstract
Dimethyl ether (DME) was synthesized from methane through a two-step process, in which CH3 Br was prepared from the oxidative bromination
reaction of methane in the presence of HBr and oxygen over a Rh-SiO2 catalyst and then, in the second step, CH3 Br was hydrolyzed to DME
over a silica supported metal chloride catalyst. 12 mol%ZnCl2 /SiO2 catalyst was found to be the most active, but it deactivated because of Cl−
losing.
Key words
dimethyl ether; methane oxidative bromination; methyl bromide; catalyst
1. Introduction
DME is an important chemical, which has potential applications in many fields, such as clean fuel, fuel additive [1,2],
and intermediate for olefin and aromatic compound synthesis [3−6]. DME is currently used as aerosol propellant and
environmental friendly refrigerant because of its low ozone
depletion potential [7,8].
In industry, DME is produced from the dehydration of
methanol [9−11], while methanol is synthesized from synthesis gas (syngas) [12,13]. There were investigations to synthesize DME directly from syngas over bifunctional catalysts
[3,14] or physically admixed methanol synthesis catalyst and
methanol dehydration catalyst [15,16]. The DME synthesis
process directly from syngas is still not commercialized because of the water-gas shifting reaction, which consumes stoichiometric amount of CO to form CO2 and hydrogen. Generally, the syngas process for DME synthesis is an energy consuming process, furthermore, the syngas process is a greenhouse gas emission process.
More energy efficient and clean process is desired for
DME synthesis. Olah et al. reported a DME synthesis reaction, in which DME was prepared from the hydrolysis of
CH3 Cl or CH3 Br over catalysts, meanwhile methanol was
formed as by-product [17]. Zhou et al. once reported a process to convert methane to DME mediated by HBr [18]. In
the process, DME and methanol were synthesized in a batch
model reaction through the hydrolysis of CH3 Br.
In this investigation, we report a HBr-mediated new process to synthesize DME from methane. The previous investigation of our laboratory proved that Rh-SiO2 was a good catalyst for the oxidative bromination of methane (OBM) to prepare CH3 Br [19]. A CH3 Br selectivity of 90.0% at methane
conversion of 30.0% was obtained over the catalyst. However, there was still about 10% of methane which was burned
to COx (CO and CO2 ). In order to reduce CO2 emission, CO2
and CO were co-fed with methane, oxygen, and HBr/H2 O in
the OBM to prepare CH3 Br. To synthesize DME from CH3 Br
hydrolysis, a new catalyst was developed.
2. Experimental
2.1. Catalyst preparation
2.1.1. Catalyst f or the OBM
The Rh-SiO2 catalyst (0.406 wt% Rh in SiO2 ) was prepared according to the following method. 6.300 g of oxalic
acid was dissolved in 100 ml of deionized water to prepare
a solution. 34.700 g of Si(OC2 H5 )4 and 0.0828 g of RhCl3
were added to the above oxalic acid solution and stirred at
room temperature for 4 h to obtain gel solution. The gel
∗
Corresponding author. Tel: 0731-88821017; Fax: 0731-88821017; E-mail: [email protected]
This work was supported by the Chinese Ministry of Education Project No.107132 and the Chinese Ministry of Science and Technology Project
No.2006BAE02B05, 2005CB221406.
Copyright©2009, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. All rights reserved.
doi:10.1016/S1003-9953(08)60122-X
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Qin You et al./ Journal of Natural Gas Chemistry Vol. 18 No. 3 2009
solution was dried at 120 ◦ C for 4 h to obtain a solid. The
solid sample was heated from room temperature to 900 ◦ C for
4 h, and then calcined at 900 ◦ C for 10 h to obtain the Rh-SiO2
catalyst. The catalyst was crushed and sieved to 20−60 mesh.
The specific surface area of the catalyst was 0.26 m2 /g.
water to obtain a solution. 69.33 g of Si(OC2 H5 )4 was added
into the ZnCl2 solution and stirred at room temperature for 8 h
to obtain a gel. The gel was dried at 120 ◦ C for 24 h to obtain
catalyst 10 mol%ZnCl2 -SiO2 . The catalyst was crushed and
sieved to 20−60 mesh for testing.
2.1.2. Catalyst f or CH3 Br hydrolysis
2.2. Reactions
The silica was prepared according to the method described below. 12.80 g of oxalic acid was dissolved in
200 ml of deionized water to obtain a solution. 216.02 g of
Si(OC2 H5 )4 was added into the above oxalic acid solution and
stirred at room temperature overnight to obtain a gel. The gel
was dried at 120 ◦ C for 4 h, and then calcined at 400 ◦ C for
4 h to obtain the silica. The silica was crushed and sieved
to 20−60 mesh for the preparation of the following catalysts.
The specific surface area of SiO2 was 726.3 m2 /g.
SiO2 supported metal chloride catalysts were prepared according to the following method. 10 mol%ZnCl2 /SiO2 catalyst was prepared by mixing 5.04 g of ZnCl2 , 20.00 g of SiO2
(20−60 mesh), and 200 ml of deionized water to obtain a mixture. The mixture was kept at room temperature for 3 h, and
then dried at 120 ◦ C for 16 h to obtain the catalyst. The catalysts with other compositions, such as 1 mol%ZnCl2 /SiO2 ,
3 mol%ZnCl2 /SiO2 , 5 mol%ZnCl2 /SiO2 , 8 mol%ZnCl2 /SiO2 ,
10 mol%ZnCl2 /SiO2 , 12 mol%ZnCl2/SiO2 , 13 mol%ZnCl2
/SiO2 , and 15 mol%ZnCl2/SiO2 were also prepared by the
same method. The amounts of precursors are listed in
Table 1.
2.2.1. Oxidative bromination of CH 4
Table 1. The amount of precursors for ZnCl2 /SiO2 catalyst preparation
Sample
1 mol%ZnCl2 /SiO2
3 mol%ZnCl2 /SiO2
5 mol%ZnCl2 /SiO2
8 mol%ZnCl2 /SiO2
10 mol%ZnCl2 /SiO2
12 mol%ZnCl2 /SiO2
13 mol%ZnCl2 /SiO2
15 mol%ZnCl2 /SiO2
ZnCl2 (g)
0.458
1.402
2.386
3.942
5.040
6.182
6.774
8.000
SiO2 (g)
20.00
20.00
20.00
20.00
20.00
20.00
20.00
20.00
H2 O (ml)
200
200
200
200
200
200
200
200
Other metal chloride catalysts (10 mol%MClx /SiO2 )
were also prepared by the same method. The amount of metal
chloride listed in Table 2 was mixed with 20.00 g of SiO2
(20−60 mesh) and 200 ml of deionized water to obtain a mixture. The mixture was kept at room temperature for 3 h, and
then dried at 120 ◦ C for 16 h to obtain the catalyst.
The 10 mol%ZnCl2 -SiO2 catalyst was prepared by sol-gel
method. 5.04 g of ZnCl2 was dissolved in 200 ml of deionized
Table 2. List of precursors for catalyst preparation
MClx
CuCl2 ·2H2 O
FeCl3 ·6H2 O
CoCl2 ·6H2 O
MnCl2 ·2H2 O
MgCl2 ·6H2 O
NiCl2 ·6H2 O
Weight (g)
6.31
10.01
8.81
7.33
7.53
8.80
The OBM reaction with CO2 and CO co-feeding was carried out in a quartz-tube reactor (ID 1.4 cm, length 60 cm,
hot zone 30.0 cm). 5.00 g of Rh-SiO2 catalyst (20−60 mesh)
was packed in the middle section of the reactor tube. The
empty spaces at the both ends of reactor tube were filled
with quartz sands (20−40 mesh). Mass flow controllers were
used to control the flows of CH4 , O2 , N2 , CO, and CO2 .
The flows of CH4 , O2 , N2 , CO, and CO2 were 20.0 ml/min,
5.0 ml/min, 5.0 ml/min, 3.0 ml/min, and 4.0 ml/min, respectively. 48 wt%HBr/H2 O solution was pumped into the evaporation zone of the reactor by a syringe pump. The flow rate of
liquid 48 wt%HBr/H2 O was 6.5 ml/h. The gas effluent of the
reactor was analyzed on a GC (Agilent 6890N) with thermal
conductivity detector and a GC/MS (6890N/5973N).
2.2.2. DME preparation reaction
The DME synthesis reaction was carried out in a glass
tube reactor (ID 1.8 cm, length 35 cm). The catalyst was
packed in the middle section of the reactor tube. CH3 Br and
H2 O were pumped into the catalyst bed to carry out reaction
at desired conditions. Nitrogen was used as internal standard
and carry gas. The flows of CH3 Br, N2 , and H2 O were given
in the corresponding sections. The gas effluent of reactor was
analyzed on Agilent 6890N and a GC/MS (6890N/5973N).
The liquid phase was analyzed on GC/MS (6890N/5973N) to
check if there were other organic products. In the present investigation, except DME, no other organic product was detected in the liquid phase.
3. Results and discussion
3.1. Preparation of CH 3 Br
In this work, CH3 Br was used as reactant for DME synthesis and was prepared from the OBM as shown in reactions (1) and (2). Except CH3 Br, reaction (1) also forms byproducts CH2 Br2 , CO, and CO2 . CH3 Br selectivity of 90% at
a methane conversion of more than 30% was reached over catalyst 0.41%Rh-SiO2 [19]. However, there was still about 10%
of methane converted to by-products (mostly CO and CO2 ). In
the present investigation, we found that when co-feeding CO
and CO2 with CH4 , O2 , and HBr into the OBM reactor, CO
and CO2 formation could be suppressed. As shown in Table 3,
when feeding CH4 , O2 , N2 , CO, CO2 , and 48 wt%HBr/H2 O
(liquid) with flows of 20.0 ml/min, 5.0 ml/min, 5.0 ml/min,
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Journal of Natural Gas Chemistry Vol. 18 No. 3 2009
Table 3. Methane oxidative bromination over 0.41wt%Rh-SiO2 (5.00 g) at 660 ◦ C
CH4
(ml/min)
20.0
20.0
O2
(ml/min)
5.0
5.0
N2
(ml/min)
5.0
5.0
HBr/H2 O
(ml/h)
6.5
6.5
CO
(ml/min)
3.0
5.0
CO2
(ml/min)
4.0
4.0
5.0 ml/min, 4.0 ml/min, and 6.5 ml/h into reactor (packed with
5.000 g of 0.41 wt%Rh-SiO2 ), respectively, at 660 ◦ C, CH3 Br
selectivity of 98.3% at a methane single-pass conversion of
34.7% was obtained. The by-product CH2 Br2 can be converted to CH3 Br by reacting with CH4 [20].
CH4 + O2 + HBr → CH3 Br + CH2 Br2 + CO + CO2 + H2 O
(1)
2CH3 Br + H2O = CH3 OCH3 + 2HBr
(2)
3.2. Hydrolysis of CH 3 Br
Previously, we reported a RuCl3 catalyst for DME synthesis from bromomethane hydrolysis in a batch model reaction [18]. In the process, bromomethane reacted with water
to form DME and CH3 OH. DME selectivity of 69% was obtained at a CH3 Br conversion of 98% under 180 ◦ C. However,
the space-time yield of batch process is lower and the catalyst
RuCl3 is expensive. Concerning on the problems, we intend to
develop a new process and new catalysts for DME synthesis.
In this investigation, silica supported metal chloride catalysts
were tested for DME synthesis from CH3 Br hydrolysis. The
results are shown in Figure 1. The reactions were carried out
at 180 ◦ C over 10.00 g of catalyst. Generally, 50% to 95% of
CH3 Br initial conversions were obtained over these silica supported metal chloride catalysts. DME and HBr were formed
Methane conversion
(%)
38.3
34.7
CH3 Br
83.1
98.3
Selectivity (%)
CH2 Br2
CO
0.6
16.3
0.7
0
CO2
0
1
as the products over 10 mol%ZnCl2 /SiO2 , 10 mol%CoCl2 /
SiO2 , 10 mol%MnCl2 /SiO2 , 10 mol%NiCl2 /SiO2 , and
10mol% MgCl2 /SiO2 catalysts, whereas Br2 was also formed
except DME and HBr over 10 mol%CuCl2 /SiO2 and 10 mol%
FeCl3 /SiO2 catalysts. The formation of Br2 indicates that
Fe3+ and Cu2+ ions could oxidize Br− anions. Among
the tested catalysts, ZnCl2 /SiO2 and MgCl2 /SiO2 showed
higher activities than CoCl2 /SiO2 , MnCl2 /SiO2 , NiCl2 /SiO2 ,
CuCl2 /SiO2 , and FeCl3 /SiO2 for CH3 Br hydrolysis reaction.
10 mol%ZnCl2 /SiO2 catalyst was found to be the most active.
Over all of these catalysts, the conversions of CH3 Br declined
with time on stream.
The investigation reveals that most of the silica supported metal chloride catalysts show high initial activity for
CH3 Br hydrolysis to prepare DME. However, they lost activity rapidly. In order to explore way to prolong the catalyst
life-time, we adopted sol-gel method to prepare the ZnCl2 SiO2 catalyst. As shown in Figure 2, the conversion of CH3 Br
over 10 mol%ZnCl2 -SiO2 catalyst also declined with time on
stream and the activity of sol-gel catalyst 10 mol%ZnCl2 -SiO2
is lower than the supported catalyst 10 mol%ZnCl2 /SiO2 .
Concerning on the catalyst life-time, the results of Figure 2 do
not show any improvement when the catalyst was prepared by
sol-gel method.
Figure 2. Dimethyl ether synthesis by hydrolyzing CH3 Br over 10 mol%
ZnCl2 /SiO2 catalyst prepared as supported catalyst and 10 mol% ZnCl2 -SiO2
catalyst prepared with sol-gel method. Reaction conditions: catalyst 10.00 g,
reaction temperature 180 ◦ C and the flow rates for CH3 Br, N2 , and H2 O (L)
are 10.0 ml/min, 10.0 ml/min, and 0.5 ml/h, respectively
Figure 1. The hydrolysis of CH3 Br over silica supported metal chloride catalysts. Reaction conditions: catalyst 10.00 g, reaction temperature 180 ◦ C, the
flows for CH3 Br, N2 and H2 O (L) are 10.0 ml/min, 10.0 ml/min, and 0.5 ml/h,
respectively
Since the silica supported ZnCl2 catalysts have the highest
activity in DME synthesis from the hydrolysis of CH3 Br, silica supported ZnCl2 catalysts were optimized based on ZnCl2
loading. The results are shown in Figure 3. It was found that
with the increase of ZnCl2 loading from 1.0 mol% to 12.0
mol%, the CH3 Br conversion increased and reached a maximum at 12.0 mol% of ZnCl2 loading. When ZnCl2 loading
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Qin You et al./ Journal of Natural Gas Chemistry Vol. 18 No. 3 2009
was higher than 12.0%, CH3 Br conversion decreased. When
ZnCl2 loading reached 15.0 mol%, the CH3 Br conversion
was almost equal to that of pure ZnCl2 . The decrease of
CH3 Br conversion at high ZnCl2 loading could be attributed
to the decrease of specific surface area of catalyst. As shown
in Figure 4, the specific surface area of catalyst decreases
with the increase of ZnCl2 loading on silica. The blank silica has a specific surface area of 726.3 m2 /g. When ZnCl2
loading reached 12.0%, the specific surface area reduced to
187.4 m2 /g. In this case, a surface area of 187.4 m2 /g might
be the minimum value to maintain a high CH3 Br conversion.
This explains the decrease of CH3 Br conversion over higher
ZnCl2 loading (>12.0%) catalysts.
(higher than 90%, see Figure 5). At elevated reaction temperature, the CH3 Br conversion increased and reached a maximum at 170 ◦ C. At a reaction temperature higher than 170 ◦ C,
CH3 Br conversion decreased (Figure 5 in the cases of 200
to 220 ◦ C). Our investigation also showed that high reaction temperature accelerated the coke formation. Hence, the
preferred reaction temperature for DME synthesis is 160 to
170 ◦ C.
Figure 5. The hydrolysis of CH3 Br over 12.0 mol%ZnCl2 /SiO2 catalyst in
the reaction temperature range from 130 to 220 ◦ C. Reaction conditions: catalyst 10.00 g and the flows for CH3 Br 10.0 ml/min, N2 10.0 ml/min and H2 O
(L) 0.5 ml/h
Figure 3. Hydrolysis of CH3 Br over silica supported ZnCl2 catalyst with
different ZnCl2 loadings. Reaction conditions: catalyst 10.00 g, reaction temperature 180 ◦ C, and the flows for CH3 Br 10.0 ml/min, N2 10.0 ml/min and
H2 O (L) 0.5 ml/h
Figure 6 shows the relation of CH3 Br conversion versus the mol ratio of CH3 Br to H2 O over catalyst 12.0 mol%
ZnCl2 /SiO2 . It was found that, at the feeding flows of
10.0 ml/min of CH3 Br (in gas phase) and 0.50 ml/h of H2 O
(in liquid phase), corresponding to the mol ratio of H2 O to
CH3 Br was about 1 : 1, the CH3 Br conversion reached the
highest level.
Figure 4. The specific surface areas of ZnCl2 /SiO2 catalysts with different
ZnCl2 loadings
12.0 mol%ZnCl2 /SiO2 catalyst was further tested in the
reaction temperature ranging from 130 to 220 ◦ C. It was
found that the catalyst had very high initial activity at 130 ◦ C
Figure 6. The hydrolysis of CH3 Br over 12.0 mol%ZnCl2 /SiO2 catalyst with
different feeding rates of CH3 Br (in gas) and H2 O (in liquid). Reaction conditions: catalyst 10.00 g, the flow of N2 10.0 ml/min, and reaction temperature
160 ◦ C
Journal of Natural Gas Chemistry Vol. 18 No. 3 2009
3.3. The sequential reaction mode
As mentioned previously, CH3 Br could be directly synthesized from the OBM in the presence of HBr and O2 . The
gas effluent (after passing through a liquid-gas isolator) of
OBM reaction was directly fed into the CH3 Br hydrolysis reactor (the second reactor). Together with the gas phase from
the OBM reaction, 0.50 ml/h of liquid water was also fed
into the second reactor. The reactions were carried out in a
sequential model. The reactant mixture and the effluent of
the second reactor were analyzed to calculate the conversion
of CH3 Br. When feeding CH4 , O2 , N2 (internal standard),
CO, CO2 , and 48wt%HBr/H2 O (liquid) into the first reactor
(loaded with 5.00 g of 0.41%Rh-SiO2) at 660 ◦ C, as shown
in Table 3, CH3 Br was produced. The gas from the first reactor with water (0.50 ml/h, liquid) was directly fed into the
second reactor loading ZnCl2 /SiO2 catalyst. The CH3 Br conversions are shown in Figure 7. The CH3 Br initial conversions varied from 61.0% to 71.0%. The CH3 Br conversion
in the sequential reaction mode is lower than that in pure
CH3 Br/H2 O feeding mode. The decreasing trend of CH3 Br
conversion in the sequential reaction mode is similar to that
in the pure CH3 Br/H2 O feeding mode. The probable reason
for the relatively lower CH3 Br conversions in the sequential
reaction mode than that in the pure CH3 Br/H2 O feeding mode
is due to the short contacting time in the sequential reaction
mode. As the data listed in Table 3, if the H2 O flow rate was
not counted in, the gas flow rate in the second reactor was
about 30−40 ml/min, which was higher than that in the pure
CH3 Br/H2 O feeding model (the gas flow rate is 20.0 ml/min).
Hence, the reactant-catalyst contacting time might be an important factor, which influences the CH3 Br conversion. In order to prove this hypotheses, the CH3 Br hydrolysis reactions
Figure 7. The CH3 Br hydrolysis with CH3 Br synthesized directly from
the oxidative bromination of methane. (1) The first reactor was fed with
20.0 ml/min of CH4 , 5.0 ml/min of O2 , 5.0 ml/min of N2 , 3.0 ml/min of CO,
4.0 ml/min of CO2 , and 6.5 ml/h of HBr/H2 O (in liquid) and the second reactor was fed with 0.50 ml/h of H2 O (in liquid). (2) The first reactor was fed
with 20.0 ml/min of CH4 , 5.0 ml/min of O2 , 5.0 ml/min of N2 , 5.0 ml/min
of CO, 4.0 ml/min of CO2 , and 6.5 ml/h of HBr/H2 O (in liquid) and the second reactor was fed with 0.50 ml/h of H2 O (in liquid). The first reactor was
loaded with 5.0 g of catalyst 0.41%Rh-SiO2 and run at 660 ◦ C. The second
reactor was loaded with 10.00 g of 12.0 mol%ZnCl2 /SiO2 catalyst and run at
160 ◦ C
5
were run at constant flows of CH3 Br (10.0 ml/min) and H2 O
(0.50 ml/h), but changing N2 flow. The results are shown in
Figure 8. With the increase of N2 flow from 10.0, 20.0, 30.0,
to 40.0 ml/min, the CH3 Br initial conversion (measured at 1 h
of time on stream reaction) decreased from 91.2%, 62.6%,
44.2%, to 20.2%, respectively. The investigation indicated
that the catalyst-reactant contacting time has significant impact on CH3 Br conversion.
Figure 8. The hydrolysis of CH3 Br over 10.00 g of 12.0 mol%ZnCl2 /SiO2
catalyst at constant flows of CH3 Br (10.0 ml/min) and H2 O (0.50 ml/h in liquid). The reaction temperature was 160 ◦ C. The flow rates of N2 were: (1)
10.0 ml/min, (2) 20.0 ml/min, (3) 30.0 ml/min, and (4) 40.0 ml/min
3.4. Regeneration of catalyst
In the DME synthesis reaction, all of the silica supported
metal chloride catalysts lost activities with time on stream.
We thought that Cl− ion losing might be the reason of catalyst
deactivation.
In the reaction, metal chlorides could be converted to
metal bromide, which may not be active for the hydrolysis reaction of CH3 Br. The silica supported ZnCl2 catalyst
was taken as an example for investigation. We prepared
a 10 mol%ZnBr2 /SiO2 catalyst and carried out CH3 Br hydrolysis reaction at 200 ◦ C. Our investigation proved that
10 mol%ZnBr2 /SiO2 was not active for CH3 Br hydrolysis to prepare DME. In another experiment, the deactivated
10 mol%ZnCl2 /SiO2 catalyst was dissolved in water and
filtrated out silica to obtain a solution. The solution was dried
at 200 ◦ C in nitrogen to obtain a solid. The XRD spectrum
of the solid is shown in Figure 9. The XRD characterization
shows that the deactivated catalyst contains ZnBr2 as the major component. The investigations show that ZnCl2 is the active component for DME synthesis.
Since the losing of Cl− ions led to the deactivation of
ZnCl2 /SiO2 catalyst, we tried to regenerate the exhausted
catalyst by HCl. The exhausted 12 mol%ZnCl2 /SiO2 catalyst was regenerated at 300 ◦ C for 8 h in HCl/H2 O (20wt%,
2.0 ml/h). The data are shown in Figure 10. The fresh catalyst
has a CH3 Br initial conversion of 90% (measured after 1 h of
online reaction). After 30 h of on line reaction, the catalyst
lost activity completely. After the first regeneration cycle of
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Qin You et al./ Journal of Natural Gas Chemistry Vol. 18 No. 3 2009
the catalyst, the CH3 Br initial conversion was 78.91%. After the second regeneration cycle of the catalyst, the CH3 Br
initial conversion was 73.60%. After the third and fourth regeneration cycles of catalyst, the CH3 Br initial conversions
were 66.9% and 57.8%, respectively. It seems that although
there was recovery in CH3 Br initial conversion after the catalyst was regenerated in HCl, the catalyst activity can not be
fully recovered.
pared from the OBM. Silica supported ZnCl2 , MgCl2 , CoCl2 ,
MnCl2 , NiCl2 , CuCl2 , and FeCl3 catalysts showed high initial activities in the hydrolysis of CH3 Br to prepare DME.
Almost 100% of DME selectivities were obtained over these
catalysts. 12%ZnCl2 /SiO2 catalyst was found to be the most
active. However, all of the silica supported metal chloride catalysts lost their activities because of Cl− anion losing. The
activity of ZnCl2 /SiO2 catalyst could be partially recovered
by regenerating it in HCl/H2 O, and the catalytic activity can
not be fully recovered. Our current investigation only shows
the possibility to prepare DME through CH3 Br hydrolysis. In
order to make this approach practical, the development of a
long life-time catalyst for CH3 Br hydrolysis reaction is necessary. Investigations in this area are in progressing in our
laboratory.
References
Figure 9. X-ray diffraction spectra. (1) ZnCl2 , (2) pure ZnBr2 , and (3)
sample obtained from the deactivated catalyst after dissolving, filtrating, and
drying
Figure 10. CH3 Br hydrolysis to prepare dimethyl ether over fresh and regenerated 12 mol%ZnCl2 /SiO2 catalyst. In each regeneration cycle, deactivated
catalyst was regenerated in HCl/H2 O (20%, 2.0 ml/h) at 300 ◦ C for 8 h. Reaction conditions of CH3 Br hydrolysis: the flow rates for CH3 Br, N2 and H2 O
(L) are 10.0 ml/min, 10.0 ml/min, and 0.5 ml/h, respectively, and the reaction
temperature was 160 ◦ C
4. Conclusions
Our investigation shows that DME could be formed
from the catalytic hydrolysis of CH3 Br, which could be pre-
[1] Wang H W, Zhou L B. Proceedings of the Institution of Mechanical Engineers Part D-Journal of Automobile Engineering,
2003, 217(D9): 819
[2] Arkharov A M, Glukhov S D, Grekhov L V, Zherdev A A,
Ivashchenko N A, Kalinin D N, Sharaburin A V, Aleksandrov
A A. Chem Petro Eng, 2003, 39(5-6): 330
[3] Ge Q J, Huang Y M, Qiu F Y, Li S B. Appl Catal A, 1998,
167(1): 23
[4] Kaeding W W, Butter S A. J Catal, 1980, 61(1): 155
[5] Spivey J J. Chem Eng Commun, 1991, 110: 123
[6] Cai G Y, Liu Z M, Shi R M, He C Q, Yang L X, Sun C L, Chang
Y J. Appl Catal A, 1995, 125(1): 29
[7] Berkhour H. Aerosol Spray Rep, 1994, 33(7-8): 385
[8] Heide R, Lippold H, Schenk J. DE 4 338 029. 1995
[9] Vishwanathan V, Jun K W, Kim J W, Roh H S. Appl Catal A,
2004, 276(1-2): 251
[10] Yaripour F, Baghaei F, Schmidt I, Perregaard J. Catal Commun,
2005, 6(2): 147
[11] Yaripour F, Baghaei F, Schmidt I, Perregaard J. Catal Commun,
2005, 6(8): 542
[12] Chang C D, Bell W K. US 4 423 155. 1983
[13] Xia J C, Mao D S, Zhang B, Chen Q L, Tang Y. Catal Lett, 2004,
98(4): 235
[14] Sun K P, Lu W W, Qiu F Y, Liu S W, Xu X L. Appl Catal A,
2003, 252(2): 243
[15] Li J L, Zhang X G, Inui T. Appl Catal A, 1996, 147(1): 23
[16] Takeguchi T, Yanagisawa K, Inui T, Inoue M. Appl Catal A,
2000, 192(2): 201
[17] Olah G A, Gupta B, Farina M, Felberg J D, Ip W M, Husain A,
Karpeles R, Lammertsma K, Melhotra A K, Trivedi N J. J Am
Chem Soc, 1985, 107(24): 7097
[18] Xu H F, Wang K X, Li W S, Zhou X P. Catal Lett, 2005, 100(12): 53
[19] Liu Z, Huang L, Li W S, Yang F, Au C T, Zhou X P. J Mol Catal
A: Chem, 2007, 273(1-2): 14
[20] Lorkovic I M, Sun S L, Gadewar S, Breed A, Macala G S, Sardar A, Cross S E, Sherman J H, Stucky G D, Ford P C. J Phys
Chem A, 2006, 110(28): 8695