Preparation and application of Ba/ZSM-5 zeolite for reaction of methyl vinyl ether and methanol

Article abstract of DOI:10.1016/j.catcom.2015.03.012

Abstract The ZSM-5 zeolite is widely used to catalyze the reactions of methanol to olefins. Herein, we have prepared the H-ZSM-5 doped with barium (Ba/ZSM-5) using incipient wetness impregnation method. The Ba modified catalysts were used to catalyze a new reaction of methanol with methyl vinyl ether to improve the selectivity of ethylene and propylene (C₂⁼ + C₃⁼). The reaction catalyzed by Ba doped H-ZSM-5 shows higher propylene selectivity over H-ZSM-5. The reaction mechanism is discussed.

Full text of DOI:10.1016/j.catcom.2015.03.012

Catalysis Communications 66 (2015) 34–37
Contents lists available at ScienceDirect
Catalysis Communications
journal homepage: www.elsevier.com/locate/catcom
Short communication
Preparation and application of Ba/ZSM-5 zeolite for reaction of methyl
vinyl ether and methanol
Yang Wang a, Guixing Jian a, Zhihong Peng b, Jiaji Hu a, Xin Wang a, Wubiao Duan a, Bo Liu a,
⁎
a
Department of Chemistry, School of Science, Beijing Jiaotong University, Beijing 100044, PR China
b
State Key Laboratory of Solid Waste Reuse for Building Materials, Beijing Building Materials Academy of Science Research, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 2 January 2015
Received in revised form 17 February 2015
Accepted 12 March 2015
Available online 13 March 2015
The ZSM-5 zeolite is widely used to catalyze the reactions of methanol to olefins. Herein, we have prepared the
H-ZSM-5 doped with barium (Ba/ZSM-5) using incipient wetness impregnation method. The Ba modified
catalysts were used to catalyze a new reaction of methanol with methyl vinyl ether to improve the selectivity
of ethylene and propylene (C=2 + C3=). The reaction catalyzed by Ba doped H-ZSM-5 shows higher propylene
selectivity over H-ZSM-5. The reaction mechanism is discussed.
© 2015 Elsevier B.V. All rights reserved.
Keywords:
MTO
Ba/ZSM-5
Methyl vinyl ether
Propylene
C=2 + C=3 selectivity
1. Introduction
modified catalysts are expected to inhibit the formation of aromatic
hydrocarbons, increase the carbon deposition resistance, and lead to
Light olefins such as propylene and ethylene are important basic
chemicals and have extensive applications. Currently, light olefins
mainly come from steam cracking and catalytic cracking (FCCs).
However, the petroleum route is unable to meet the increasing demand
of olefins, especially for propylene. Therefore, other ways to prepare
light olefins have been studied, including the conversion from methanol
to olefin (MTO), the propane dehydrogenation (PDH) and the conver-
sion from methanol to propylene (MTP). Amongst the above methods,
turning methanol to C=2 + C3= (MTO) is regarded as the most econom-
ical way comparing with the conventional oil-based route [1–5].
MTO technology has focused on the development of the catalyst
with high selectivity, especially H-ZSM-5 [6,7]. Research on doping
metal atoms to H-ZSM-5 catalyst showed that even a trace amount of
the metal atoms in H-ZSM-5 could significantly influence the MTO
productions [8]. Sadegh et al. reported the use of the H-ZSM-5 powder
modified by iridium through impregnation. Results show that iridium
doped H-ZSM-5 leads to a decrease in strong acidic sides and improves
the selectivity of propylene [9]. Other groups have adopted a non-
metallic doping way to modify the zeolites, such as B and P, leading to
an improvement of the catalytic selectivity [10–14]. The same group
of alkali metal including Mg, Ca and Sr has been extensively investigat-
ed. It is found that the number of strong acid sites can be reduced and
the distribution of acid center is improved [15–18]. Therefore, the Ba
an increase of olefin yield.
Recently, researchers tried to enhance the MTO performance by co-
feeding. Mier et al. and others have studied the co-feeding of methanol
and n-butane or i-butane over the H-ZSM-5 catalyst [19–23]. They
found that there is an enhancement of the olefin formation selectivity
and the lifetime of the catalyst. Methyl vinyl ether is a kind of material
with special double bond structure; it is reasonable to expect to produce
vinyl fragments in the thermal decomposition. In addition, methoxy
fragments, the vital intermediate in the formation progress of olefins
[12,24,25], from the pyrolysis of methyl vinyl ether are also possible if
we consider the similarity of chemical structure between methyl vinyl
ether and vinyl ethyl ether which had confirmed the generation of
ethoxy in the pyrolytic reactions [26].
We are trying to combine the metal modification and co-feeding
strategies in order to improve the selectivity in MTO conversion. In
this paper, we will report the improved selectivity in MTO process
when Ba modified zeolites (Ba/ZSM-5) and co-feeding of methyl vinyl
ether are employed.
2. Experimental
2.1. Preparation and characterization of Ba/ZSM-5
The Ba/ZSM-5 zeolite was prepared by the incipient wetness im-
pregnation method. Briefly, a certain amount of Ba(NO3)2 in aqueous
solution was added dropwisely into 20 g H-ZSM-5 zeolite (SiO2/Al2O3
⁎
Corresponding author.
E-mail address: boliu@bjtu.edu.cn (B. Liu).
http://dx.doi.org/10.1016/j.catcom.2015.03.012
1566-7367/© 2015 Elsevier B.V. All rights reserved.

Y. Wang et al. / Catalysis Communications 66 (2015) 34–37
35
ratio = 38) suspended in an equal volume of deionized water. The
slurry was stirred at room temperature for 12 h, dried overnight at
110 °C, and then calcined in air at 550 °C for 6 h before being crushed
carefully. The content of Ba modified zeolites is calculated by the
following formula:
c
M1n
m þ M2n
X% ¼
ꢀ 100%:
b
In which “X” is the mass fraction of Ba in H-ZSM-5. “M1” and “M2”
represent the atomic mass of Ba and the relative molecular mass of
Ba(NO3)2, respectively. In addition, “m” is the quantity of H-ZSM-5
and “n” is moles of Ba(NO3)2. 3Ba/ZSM-5 denotes 3 wt.% content of Ba
in the catalysts, 5Ba/ZSM-5 for 5 wt.% of Ba.
a
a
XRD patterns of H-ZSM-5 sample data are acquired by Rigaku Ultima
IV. Scanning Electron Microscope (SEM) images of the H-ZSM-5 were
gotten by Hitachi 3400.
0
30
2-Theta-Scale
60
Fig. 2. XRD patterns of H-ZSM-5 (a), 3Ba/ZSM-5 (b) and 5Ba/ZSM-5 (c).
2.2. Catalytic reaction
The apparatus for catalytic reactions is shown in Fig. 1 schematically.
The experiments were conducted in a clean and dry quartz tube furnace.
Under atmospheric pressure, the reactor was purged with nitrogen
before heating. The accurate temperature controller was employed to
set temperature. Methanol mixed with methyl vinyl ether was added
to the reactor through Liquid inlet pump when the temperature is
stable. WHSV (weight hourly space velocity) is controlled by 1.8–
2.2 h−1. After the reactions were stable for certain time, the gaseous
products were collected with the gas pocket of aluminum foil. The
compositions of the products were identified by GC–MS.
The morphology and structure characteristics of H-ZSM-5
and Ba/ZSM-5 catalysts were shown in Fig. 3. No clear differences on
morphology of both the modified catalysts and unmodified one are ob-
served. The absence of conglomeration indicates that BaO1.3, converted
from the Ba(NO3)2, disperses well on H-ZSM-5.
3.2. Influence of methyl vinyl ether and content of Ba
In olefin forming process, dimethyl ether as primary product is
crucial which is related to superficial methoxy. Generally, methoxy is
catalyzed by the Brønsted acid on the surface of the catalyst which is a
complex process; therefore, extra methoxy is expected to simplify the
previous steps in order to make the reaction efficiently and participate
in the circulation of “hydrocarbon pool” to increase the yield of propyl-
ene. Using the H-ZSM-5 and Ba modified H-ZSM-5, we studied the
effect of the addition of methyl vinyl ether into methanol during the
MTO process at 450 °C and at atmospheric pressure. Fig. 4 shows the
yield of propylene in the reaction, when using H-ZSM-5, the addition
of methyl vinyl ether shows higher light olefin selectivity than metha-
nol feeding only. Moreover, as the reaction proceeds, the mixture of
the H-ZSM-5 showed a relatively stable trend compared with methanol.
As seen in Fig. 4, when the mixture is catalyzed by 3Ba/ZSM-5, the
yield of propylene reached up to 53%. However, it presents the opposite
trends and lower than expected when the contents of Ba are 5 wt.%, the
mixture catalyzed by 5Ba/ZSM-5 showed lower selectivity even com-
pared with H-ZSM-5, it is because the selectivity of propylene is affected
not only by the acid strength of catalyst, but also by the particle size and
the specific surface area, especially the specific surface area [17], we can
see that the peak intensity of BaO1.3 is strong in Fig. 1, which means the
content of Ba in H-ZSM-5 is excessive. The acid sites of the catalyst are
occupied by Ba which leads to the decreased specific surface area of
catalyst and reduces the number of active center that is negative for
the formation of propylene. In addition, the faster inactivation perfor-
mance illustrates that the activity center of the catalyst is blocked easily
and deactivated finally.
3. Results and discussion
3.1. Structure and morphology
XRD patterns of H-ZSM-5 and Ba/ZSM-5 zeolites are shown in Fig. 2.
It displays the same peaks as pure H-ZSM-5 zeolite at the range of
2θ = 23–25°, which indicates that the H-ZSM-5 crystal structure was
retained after Ba impregnation. Diffraction peak intensity of the
samples is almost the same, illustrating that the degree of crystallinity
is intact. However, It can be clearly seen that the differences at 2θ =
22.88, 37.37 and 29.77 respectively which represents the BaO1.3
(PDF#47-1488) formed in H-ZSM-5.
3.3. Influence of temperature
As reported [27,28], temperature is an important factor in influenc-
ing the performance of MTO catalyst, simultaneously, the degree of
thermal decomposition of methyl vinyl ether is also greatly controlled
by temperatures. Therefore, the performance of the joint reaction
could be different when changing in temperatures. When mixed with
5 wt.% methyl vinyl ether, using Ba/ZSM-5 as the catalyst, Table 1
Fig. 1. Apparatus for catalytic reactions. (1) High-purity nitrogen, (2) Shut-off valve,
(3) Tubular furnace, (4) Fixed bed reactor, (5) Gas–liquid separator, (6) GC–MS, (7) Liquid
inlet pump, (8) Temperature controller.

36
Y. Wang et al. / Catalysis Communications 66 (2015) 34–37
Fig. 3. SEM images of H-ZSM-5 (a, b), 3Ba/ZSM-5 (c, d) and 5Ba/ZSM-5 (e, f) zeolites.
shows the olefin yield at different temperatures (350 °C, 450 °C and
550 °C) under the conditions of atmospheric pressure and WHSV of
1.8–2.2 h−1. The corresponding changes in selectivity with reaction
time have been shown in Fig. 5. The selectivity of propylene and olefins
is enhanced as temperature increases, apparently, the yield of olefin is
60
40
20
0
CH3OH+H-ZSM-5
Mixture+5Ba/ZSM-5
Mixture+H-ZSM-5
Mixture+3Ba/ZSM-5
Table 1
MTO reaction results of different temperatures.
Temperature
(°C)
MVE
(wt.%)
Time
(min)
Selectivity (%)
C2=
C3=
C=2 + C=3
350
450
550
5
5
5
30
150
240
30
150
240
30
12.46
12.11
13.10
14.29
11.40
10.56
16.28
14.11
8.31
15.58
12.48
12.10
20.29
15.80
12.90
30.56
24.02
22.90
28.04
24.59
25.20
34.58
27.20
23.46
46.84
38.13
31.21
0
100
Time on stream (min)
200
150
240
(C=2 and C=3 mainly represent ethylene and propylene, respectively. MVE represents meth-
yl vinyl ether.)
Fig. 4. The evolution of C=3 yield with time on stream at different conditions.

Y. Wang et al. / Catalysis Communications 66 (2015) 34–37
37
4. Conclusions
a
32
24
16
350 C
450 C
550 C
The Ba modified H-ZSM-5 zeolite has been prepared by using the
incipient wetness impregnation method. H-ZSM-5 and Ba modified
H-ZSM-5 have been used to catalyze reaction of methanol with vinyl
methyl ether. It shows that the addition of methyl vinyl ether into
methanol can significantly enhance the yield of olefins on 3Ba/ZSM-5,
especially for propylene, however, the excess Ba in H-ZSM-5 could
reduce the zeolite specific surface area, leading to a decrease for the
yield of propylene.
Acknowledgments
We acknowledge the funding of this project by Beijing Building
Materials Academy of Science Research (BBMA).
0
100
200
Time on stream (min)
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