Study of magnesium-containing zeolite catalysts for the synthesis of lower olefins from dimethyl ether

Article abstract of DOI:10.1134/S096554411101004X

The catalytic properties of magnesium-containing zeolite catalysts in the synthesis of olefins from dimethyl ether (DME) were studied. The optimal concentrations of magnesium in the zeolite catalyst were found, and a procedure for its introduction was developed. The effect of the operation conditions of DME conversion into lower olefins on the catalyst activity and selectivity was studied. The stability of the catalytic properties of the synthesized catalyst after oxidative regeneration was examined.

Full text of DOI:10.1134/S096554411101004X

ISSN 0965ꢀ5441, Petroleum Chemistry, 2011, Vol. 51, No. 3, pp. 169–173. © Pleiades Publishing, Ltd., 2011.
Original Russian Text © T.I. Goryainova, E.N. Biryukova, N.V. Kolesnichenko, S.N. Khadzhiev, 2011, published in Neftekhimiya, 2011, Vol. 51, No. 3, pp. 181–185.
Study of MagnesiumꢀContaining Zeolite Catalysts for the Synthesis
of Lower Olefins from Dimethyl Ether
T. I. Goryainova, E. N. Biryukova, N. V. Kolesnichenko, and S. N. Khadzhiev
Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, Leninskii pr. 29, Moscow, 119991 Russia
eꢀmail: goryainova@ips.ac.ru
Received August 27, 2010
Abstract—The catalytic properties of magnesiumꢀcontaining zeolite catalysts in the synthesis of olefins from
dimethyl ether (DME) were studied. The optimal concentrations of magnesium in the zeolite catalyst were
found, and a procedure for its introduction was developed. The effect of the operation conditions of DME
conversion into lower olefins on the catalyst activity and selectivity was studied. The stability of the catalytic
properties of the synthesized catalyst after oxidative regeneration was examined.
DOI: 10.1134/S096554411101004X
Recently, we have found that in the DME converꢀ 34 wt % in the resulting catalyst. The extrudates were
sion into lower olefins ethanol is a primary precursor successively dried in air and in a drying cabinet and
of ethylene and is formed mainly via isomerization of calcined at 500 С for 4 h. Magnesium was introduced
°
dimethyl ether [1]. The introduction of ethanol forꢀ into the zeolite via ion exchange either before mixing
mationꢀpromoting components into the zeolite cataꢀ with the binder (Al2O3) or by impregnating the preꢀ
lyst should enhance the selectivity for lower olefins in pared НZSMꢀ5/Al2O3 extrudates with an aqueous
the DME conversion. Magnesium is well known to be solution of its salt.
an element that participates in the isomerization of
Experiments were carried out in a laboratory setup
hydrocarbons with functional groups [2–4]. In order
with a flow microreactor. Nitrogen was used as the
to develop a selective catalyst for the synthesis of lower
DME diluent. The fusedꢀsilica flow reactor was
olefins (ethylene, propylene, and butylenes) from
loaded with the catalyst (0.2–1.0 g, of a 0.4–0.6 mm
DME, we studied the catalytic properties of zeolite
and coarser fraction). The catalyst was activated in a
catalysts containing magnesium and the influence of
He stream at 400–450
space velocity (500–10000 h–1), temperature (320–
450 ), and pressure (~1 atm) were established. Liqꢀ
°С. The required reactant feed
the operation conditions on the activity, selectivity,
and stability of these catalysts.
°С
uid products were condensed in a receiver, and the gas
stream through a dosing valve was sent to a chromatoꢀ
graph for analysis. The DMA conversion products
were determined on the Kristallyuks 4000M chroꢀ
matograph with a flame ionization detector, a capilꢀ
EXPERIMENTAL
The chemical used as the feedstock was DME
(99.8%) produced at the OAO “Azot” Novomoskovsk
joint stock company.
lary column (27.5 m
×
0.32 mm
×
10 m), and the
µ
nonpolar CPꢀPoraPLOT Q phase as an adsorbent,
which is reasonably efficient for the separation of the
In the synthesis of lower olefins from DME, cataꢀ
lyst samples based on ZSMꢀ5 zeolite (the highꢀsilica
zeolite TsVM, the domestic analog of ZSMꢀ5, with a
SiO2/Al2O3 mole ratio of 37 (OAO Angarsk Catalyst
and Organic Synthesis Plant) containing at most
0.04 wt % sodium oxide) were studied. The hydrogen
form of the zeolite (HZSMꢀ5) with a given residual
content of sodium oxide is obtained via double cation
exchange of Na+ in a 1 N ammonium nitrate solution
with consequent drying and calcination for 4 h at
main groups of products (DME, СН3ОН
hydrocarbons). The analysis was carried out in the
temperatureꢀprogrammed mode (80–150 at a heatꢀ
ing rate of 30 C/min) with helium as a carrier gas
, С1–С6
°С
°
(30 ml/min). The chromatograms were processed
with the NetChromWin program.
RESULTS AND DISCUSSION
500
°
С.
The zeoliteꢀcontaining catalysts were obtained by
To select a procedure for the preparation of the
mixing the zeolite HZSMꢀ5 with a binder, alumina magnesiumꢀcontaining catalyst, we examined the catꢀ
suspension containing 23 wt % dry Al2O3 (ZAO Indusꢀ alytic properties of the samples prepared by various
trial Catalysts, Ryazan) and consequent formation of methods of magnesium introduction (Table 1). The
granules, (extrudates) with an Al2O3 content of 33– DME conversion is altered insignificantly by changing
169

170
GORYAINOVA et al.
Table 1. Effect of the procedure of magnesium introduction into the zeolite catalyst on the catalytic properties
Selectivity, wt %
Converꢀ
Magnesium introduction procedure
sion, %
C2=
C3=
C4=
C5=
Σ
C2–C=4
C=2 /C=3
C2+
CH4
Σ
Ion exchang
69.2
67.4
70.5
2.7
2.2
1.9
29.4
30.8
26.7
15.2
19.2
4.6
6.3
0.1
0.2
0.1
49.2
56.3
53.0
48.0
41.3
45.0
1.9
1.6
1.7
Ion exchange without zeolite washing
Impregnation of extrudates with zeolite
pretreatment with water
15.3 11.0
Impregnation of extrudates
69.3
0.7
33.1
29.3 1.2
0.8
63.6
34.9
1.1
–1
Note: Conditions: T = 320°C, P = 0.1 MPa, feed mixture: 20% DME + 80% N , v = 2000 h , magnesium content, 0.1 wt %.
2
0
Table 2. DME conversion under the olefin synthesis conditions
Selectivity, wt %
Converꢀ
Catalyst
C2=
C3=
C4=
C5=
Σ
C2–C=4 C=2 /C=3
sion, %
CH4
Σ
C2+
HZSM/Al2O3
94.3
70.0
85.6
1.1
2.5
21.6
26.0
33.6
23.3
44.4
21.6
11.5
6.4
6.8
3.6
2.4
35.8
17.1
30.4
56.4
76.8
67.2
0.9
0.6
1.6
LaꢀZr/HZSM/Al2O3
Mg/HZSM/Al2O3
weak
12.0
–1
Note: T = 340°C, P = 0.1 MPa, feedstock: DME + N , v = 2000 h
.
2
0
the procedure. However, the ratio between lower oleꢀ alkanes decreases pronouncedly with an increase in
fins components and their total yield substantially the magnesium concentration up to 1.0 wt %, and
depends on the procedure of magnesium introduction remains almost unchanged upon further increase in
into the zeolite catalyst. The ethylene/propylene ratio the magnesium content in the catalyst (Table 2). The
varies twofold from 1.9 to 1.1. In actual practice, it is observed enhancement of the selectivity for butylenes
possible to vary the output of ethylene, propylene, and and total alkanes and a simultaneous decline in the
butylenes depending on the demand. The best results selectivity for ethylene and propylene with an increase
with respect to the total yield of lower olefins were in the temperature from 320 to 360 С indicate that the
°
obtained in the case of magnesium deposition by activation energy of the ethylene and propylene forꢀ
impregnating the finished HZSM/Al2O3 extrudates. mation is lower than that of the formation of alkanes
The propylene yield was substantially higher on this and olefin polymerization.
sample, and the methane yield was the lowest.
Interestingly, the methane formation is low on the
Based on the obtained results, the further investigaꢀ magnesiumꢀcontaining zeolite catalysts, thus increasꢀ
tion was performed with the samples prepared by the ing substantially the selectivity of the process as a
impregnation of the finished catalyst extrudates, when whole.
magnesium modifies not only the zeolite component,
but also the alumina binder.
The comparison of the magnesiumꢀcontaining
zeolite catalysts with the lanthanum–zirconiumꢀproꢀ
The study of the effect of the magnesium concenꢀ moted [5] and the decationized catalysts (Table 3)
tration in the zeolite catalyst on its catalytic properties investigated in detail earlier shows that the introducꢀ
in DME conversion at various temperatures (Table 2) tion of magnesium in the zeolite catalyst enhances
has shown that the DME conversion decreases and the (relative to the decationized sample of the zeolite catꢀ
selectivity for С2–С4 olefins passes through a maxiꢀ alyst) the selectivity for lower olefins by more than
mum with an increase in the magnesium concentraꢀ 10 wt % with a decrease in the DME conversion from
tion in the catalyst. The best results were obtained on 94.3 to 85.6 wt %. Simultaneously, the ethylene/proꢀ
a catalyst containing 1.0 wt % magnesium. The overall pylene ratio increases drastically from 0.9 to 1.6; i.e.,
selectivity for С2–С4 olefins is ~80.8 wt %, of which the introduction of magnesium results in a preferential
almost 80 wt % is made by ethylene and propylene. A increase in the ethylene selectivity and the correꢀ
high yield of butylenes (up to 14.6 wt %) is observed for sponding decrease in the selectivity for butylenes and
the magnesiumꢀcontaining catalysts at 360 С, which amylenes. The relative amount of alkanes in the reacꢀ
°
may be of practical interest. The ethylene/propylene tion products decreases. Interestingly, the selectivity
ratio decreases insignificantly with an increase in the for ethylene and butenes is lower for the lanthanumꢀ
amount of magnesium introduced. The total yield of and zirconiumꢀcontaining zeolite catalyst than that
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STUDY OF MAGNESIUMꢀCONTAINING ZEOLITE CATALYSTS
171
Table 3. Effect of the superficial velocity of the feed gas mixture on the DME conversion and the distribution of reaction products
electivity, wt %
Superficial
m/V, g/ml
of catalys
Converꢀ
sion, %
velocity,
m/s
t
, h
C2=
C3=
C4=
C5=
Σ
C2–C=4
C=2 /C=3
CH4
Σ
C2+
1.0/2.0
0.5/1.0
0.3/0.6
2.5
1.2
7.4
×
×
×
10–2
10–2
10–3
1
5
1
5
1
5
100
100
100
100
100
100
0.7
0.7
0.6
0.7
0.6
0.7
15.5
15.2
14.5
14.7
15.1
15.1
30.6
32.4
29.0
31.7
30.7
32.3
14.5
15.8
16.0
18.2
15.3
17.1
4.6
4.8
7.1
4.9
4.5
4.7
60.6
63.4
59.5
64.5
61.2
64.5
34.1
31.1
32.8
29.9
33.7
30.0
0.51
0.47
0.50
0.46
0.49
0.47
–1
–1
Note: T = 450°C, P = 0.1 MPa, feedstock: 10% DME + N ,v = 2000 h = const, w
= 0.75 h = const.
2
0
DME
Table 4. Effect of the catalyst particle size on the DME conversion and the product distribution
Selectivity, wt %
Catalyst m/V, g/ml
fraction, ml of catalyst
Converꢀ
sion, %
t
, h
C2=
C3=
C4=
C5=
Σ
C2–C=4
C=2 /C=3
CH4
Σ
C2+
0.2–0.4
0.4–0.6
0.6–1.0
1.0–1.6
0.5/1.0
0.5/1.0
1
5
1
5
1
5
1
5
100
100
100
100
100
100
100
100
0.7
1.0
0.6
0.7
0.6
0.7
0.7
0.6
14.8
14.8
14.5
14.7
15.7
15.4
13.9
15.1
35.5
35.4
29.0
31.7
31.9
33.9
31.6
34.3
17.4
17.9
16.0
18.2
14.9
16.7
16.8
16.8
5.1
5.8
7.1
4.9
4.7
5.1
4.7
5.5
67.7
68.1
59.5
64.5
62.6
66.0
62.3
66.1
26.5
25.1
32.8
29.9
32.1
28.2
32.3
27.8
0.42
0.42
0.50
0.46
0.49
0.45
0.44
0.44
0.5/1.05
0.5/1.06
–1
–1
Note: T = 450°C, P = 0.1 MPa, feedstock: 10% DME + N , v = 2000 h = const, w = 0.8 h = const.
DME
2
0
for the magnesiumꢀcontaining sample by 7.6 and into olefins, the experiments at various superficial
5.6 wt %, respectively, whereas the propylene selectivꢀ velocities of the feedstock in the reactor at a constant
ity is substantially higher (by 22.8 wt %). Therefore, feed space velocity per catalyst unit volume were carꢀ
the selectivity for С2–С4 olefins increases by 76.8 wt %, but ried out (Table 3). In order to estimate the possible
the ethylene/propylene ratio decreases down to 0.6. effect of the internal diffusion limitation, the catalytic
Under conditions accepted for the comparison, the properties were studied for catalyst sample with variꢀ
yield of alkanes is lower on the lanthanum–zircoꢀ ous particle sizes (Table 4).
niumꢀcontaining zeolite catalyst than that on the
magnesiumꢀcontaining catalyst, but the yield of methꢀ
ane is significantly higher; i.e., the appearance of
strong acid sites characteristic of the lanthanumꢀ and
zirconiumꢀcontaining catalysts results in the
enhancement of methane formation.
The experiments were carried out at 450
С, the
°
highest temperature possible for this reaction, because
the external and internal diffusion retardation
increases with an increase in the temperature. One can
see from the data presented, the external and internal
diffusion retardation is insignificant even at the highꢀ
The comparison of the lanthanum–zirconiumꢀ est temperature, therefore, it can be concluded with
containing and magnesiumꢀcontaining zeolite cataꢀ certainty that the reaction proceeds in the kinetic
lysts shows that each of them is applicable in practice, region at the test temperatures.
depending on the plant demand for one or another
olefin.
In further experiments, the variable parameters of
the process were changed in the temperature range of
In view of the potential use of the magnesiumꢀconꢀ 320 to 450
°
С and the feed space velocity range from
taining zeolite catalyst, we studied the effect of certain 500 to 10000 h–1.
processing parameters on the DME conversion and
the selectivity for olefins.
The data on the DME conversion and the product
selectivity for the extreme values of the temperatures
First, in order to estimate the possible effect of the at different feed space velocities are given in Fig. 1 and
external diffusion limitation in the DME conversion Table 5. The DME conversion rate at 450 is so high
°С
PETROLEUM CHEMISTRY Vol. 51
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172
GORYAINOVA et al.
Table 5. Effect of the space velocity of the feed gas mixture on the DME conversion and the product distribution (T= 320°C,
P
= 0.1 MPa).
Selectivity, wt %
Space
Converꢀ
sion, %
velocity, h–1
C2=
C3=
C4=
C5=
Σ
C2–C=4
C=2 /C=3
CH4
Σ
C2+
2000
3000
4000
5000
6000
7000
94.0
57.9
48.2
32.0
26.1
28.0
0.6
48.7
38.2
37.5
35.5
35.5
35.2
27.0
40.5
41.0
41.9
41.6
42.0
2.2
1.7
2.2
1.7
1.4
1.7
0.1
0.6
1.1
1.6
1.7
1.8
77.9
80.5
80.7
79.1
78.5
78.9
21.4
18.9
18.2
19.2
19.7
19.3
1.8
0.9
0.9
0.9
0.9
0.8
weak
weak
weak
weak
weak
that the degree of conversion is 100 wt % over the ture is very complex. In fact, the product composition
entire spaceꢀvelocity range examined. However, an observed at high temperature is determined by the
increase in the feed weight hourly space velocity mechanism of the secondary transformation reactions
(WHSV) results in a substantial change of the product of olefins and alkanes that have been formed at a high
composition at the constant 100% DME conversion rate in the primary reactions, with the propylene
due to the change in the conditions of occurrence of selectivity being inversely proportional to the isobuꢀ
secondary reactions (Fig. 1). A decrease in the space tane selectivity (Fig. 2). A similar dependence is
time (growth of WHSV) is most likely unfavorable for observed in the catalytic cracking of hydrocarbons on
the secondary reactions. A regular increase in the proꢀ zeoliteꢀcontaining catalysts [12].
pylene yield accompanied by an almost equivalent
Unlike the case of the reaction temperature of
decrease in the ethylene yield is observed. The propyꢀ
450 С, the DME conversion decreases with a decrease
°
lene/ethylene ratio is 3.1 at the highest WHSV equivꢀ
alent to the liquid space velocity of 6 h–1 and varies
toward the value obtained in the Lurgi methanolꢀtoꢀ
propylene process [6–11].
in the space time, and the selectivity for alkanes is
independent of the space time at low temperatures
(Table 5). The selectivity for butylenes and amylenes is
very low and does not exceed 3–4 wt % in total. The
It should be pointed out that there is correlation selectivity for ethylene and propylene is high (75.7–
between the yield of isobutane and ethylene on one 78.5 wt %) and almost does not depend on the DME
hand and the yields of isobutene and nꢀbutene with conversion. This indicates strong differences in the
propylene on the other hand. Similarly, the yield of mechanism of the formation of olefins in the primary
amylenes decreases and that of alkanes increases with and secondary reactions. At a high DME conversion
an increase in the space time; i.e., there is interrelation corresponding to the feed space velocity (2000 h–1),
between the olefin formation stages and the hydrogen the contribution of the secondary reactions is maniꢀ
transfer stages yielding alkanes. This indicates that the fested and a rise in the ethylene yield and a fall in the
mechanism of the olefin formation at high temperaꢀ propylene yield are observed (Table 5).
45
40
ethylene
35
30
25
20
15
10
5
propylene
isobutane
isobutene
n
ꢀbutane
ꢀbutene
n
0
–1
DME weight hourly space velocity, h
Fig.1.Effect of the DME weight hourly space velocity on the distribution of the reaction products (DME conversion = 100 wt %,
= 0.1 MPa).
T = 450°C,
P
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STUDY OF MAGNESIUMꢀCONTAINING ZEOLITE CATALYSTS
173
temperature makes it possible to pass from the primary
to the secondary reactions and to control the ratio
between ethylene, propylene, and butenes over a wide
range. The synthesized catalyst retains a high activity
and selectivity after oxidative regeneration.
increase in the space velocity
45
43
41
39
37
35
33
31
29
27
25
ACKNOWLEDGMENTS
This work was supported by the Grant of the Presiꢀ
dent of the Russian Federation for the support of
young scientists no. MKꢀ1332.2009.3 (contract
no. 02.120.11.1332ꢀMK).
0
2
4
6
8
10
12 14
Selectivity for isobutane, wt %
REFERENCES
1. N. V. Kolesnichenko, T. I. Goryainova, E. N. Biryuꢀ
kova, et al., Neftekhimiya 51 (2011) [Pet. Chem. 51
(2011)].
Fig. 2. Interrelation between the formation of propylene
and isobutane in the DMA conversion into olefins (DMA
conversion = 100 wt %,
T = 450°C, P = 0.1 MPa).
2. D. A. Potapov, L. A. Tyurina, and V. V. Smirnov, Izv.
Akad. Nauk, Ser. Khim., No. 51155 (2005).
3. M. N. Shemanaeva, L. V. Mel’nik, S. I. Kryukov, et al.,
RU Patent No. 2,174,113 (2001).
4. V. Ya. Sosnovskikh, Soros. Obraz. Zh., Khim., No. 6,
47 (1999).
5. E. N. Biryukova, T. I. Goryainova, R. V. Kulumbegov,
et al., Neftekhimiya 51 (2011) [Pet. Chem. 51 (2011)].
The assumption that the contribution of secondary
reactions to the reaction mechanism, rather than the
decrease in the amount of DME adsorbed under the
reaction conditions, manifests itself at a high DME
conversion is confirmed by the fact that the selectivity
for olefins at the same conversion does not depend on
the DME concentration in the stream. In this case, a
rise in the olefin yield is observed even at a high DME
conversion.
6. Hydrocarbon Process. 82, 128 (2003).
7. M. Hack, U. Koss, R. Konig, et al., US Patent
No. 7015369 (2006).
The magnesiumꢀcontaining zeolite catalyst is relaꢀ
tively stable in operation after multiply repeated oxiꢀ
dative regeneration cycles. The data show that the oxiꢀ
dative regeneration of the catalyst almost does not
alter its catalytic properties; even a slight increment in
the DME conversion is observed.
8. R. Konig, M. Rothaemel, H.ꢀD. Holtmann, and
U. Koss, DE Patent No. 10027159 (2001).
9. M. Hack, U. Koss, P. Konig, et al., RU Patent
No. 2266885 (2004).
10. M. Scheidtr, F. Schmidt, G. Bugfels, et al., EP Patent
0448 000 (1991).
Thus, the introduction of magnesium into the zeoꢀ
liteꢀcontaining catalyst substantially enhances the
selectivity for С2–С4 olefins (80.8 wt %), of which ethꢀ
ylene and propylene make almost 80 wt %. A variation
in the space velocity of the feedstock and the reaction
11. Ch. Higman, R. Konig, F.ꢀW. Moller, et al., DE Patent
No. 119723363 (1972).
12. Cracking of Petroleum Fractions on Zeolite Catalysts, Ed.
by S. N. Khadzhiev (Khimiya, Moscow, 1982) [in Rusꢀ
sian].
PETROLEUM CHEMISTRY Vol. 51
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