Aromatization of butane over zirconium-containing and zinc-zirconia-zeolite catalysts

Article abstract of DOI:10.1134/S1070427211070159

Comparative researches were conducted of zinc-, zirconia, and zinc-zirconia-ziolite catalysts for n-butane aromatization.

Full text of DOI:10.1134/S1070427211070159

ISSN 1070-4272, Russian Journal of Applied Chemistry, 2011, Vol. 84, No. 7, pp. 1213−1216. © Pleiades Publishing, Ltd., 2011.
Original Russian Text © D.B. Tagiev, S.B. Agaeva, S.I. Abasov, R.V. Starikov, F.M. Nasirova, 2011, published in Zhurnal Prikladnoi Khimii, 2011, Vol. 84,
No. 7, pp. 1141−1144.
ORGANIC SYNTHESIS
AND INDUSTRIAL ORGANIC CHEMISTRY
Aromatization of Butane over Zirconium-containing
and Zinc-zirconia-zeolite Catalysts
D. B. Tagiev, S. B. Agaeva, S. I. Abasov, R. V. Starikov, and F. M. Nasirova
Institute of Petrochemical Processes, National Academy of Sciences of Azerbaijan, Azerbaijan, Baku
Received July 28, 2010
Abstract—Comparative researches were conducted of zinc-, zirconia, and zinc- zirconia-ziolite catalysts for
n-butane aromatization.
DOI: 10.1134/S1070427211070159
The process of catalytic processing of individual paraf-
fin hydrocarbons, particularly n-butane, to highly market-
able products, aromatic hydrocarbons, is in the center of
attention of researchers [1–5]. In [5] it was demonstrated
the advantage of Sn-Zn-zeolite catalyst developed byA.L.
Lepidus et al. for aromatization of propane–butane faction
zirconium dioxide obtained by hydrolysis of ZrOCl ·8H O
2 2
in the presence of NH OH at elevated temperatures were
4
used as the initial supports (Table 1). Zirconium salt
ZrO(NO ) · 2H O and zinc salt Zn (CH COO) ·2H O
3
2
2
3
2
2
were used as a source of active ingredients.
Application of zirconium and zinc salts on the zeolite
HZSM-5 of an H-form was performed by soaking for
(PBF) for a flow installation in comparison with those
of foreign firms. At present, special attention is given to
researches with use of zirconium-containing samples, in
particular with high activity for isomerization of n-alkanes
2
4 hours with further evaporation, drying at room tem-
perature, mixing with the binder, Al O , and subsequent
2
3
heat treatment at 120, 350 and 500°C for 4 h.
[6–8]. However, the published papers on the use of nano-
Testing the catalytic activity of the synthesized
sized powders of zirconium in the aromatization of n-
butane do not show aromatizing activity without modifying
agents [9, 10].Accounting for that the process of aromatiza-
tion of n-paraffins proceeds at elevated temperatures and,
apparently, through a stage of intermediate formation of the
isomeric intermediate [11], the introduction of zirconium in
the NZSM-5 zeolites allows more effective aromatization
of lower alkanes. Therefore, it is promising to increase the
efficiency of conventional zeolite catalysts by zirconium
modifying to determine the possibility of carrying out the
process in a more favorable energy conditions.
Table 1. Composition of synthesized catalysts
Active com- Catalyst composi-
Original support
ponent
tion, %
HZSM-5a
Zr
Zr
Zr
Zr
0.5Zr/HZSM-5
2.5Zr/HZSM-5
5Zr/HZSM-5
5Zn/HZSM-5
ZrO2/HZSM-5
In the study we examined the activity of zirconium
catalysts for aromatization of n-butane, component of
casing-head and fume refinery manufacture gases, into a
mixture of aromatic hydrocarbons: benzene–toluene–xy-
lene fraction (BTX).
Zirconium hydrogel,
HZSM-5
Zirconium hydrogel
Zirconium hydrogel,
HZSM-5
Zn
Zn
5Zn/ZrO2
5Zn /ZrO +
HZSM-5
2
EXPERIMENTAL
a
To prepare the catalysts zeolite HZSM-5 hydrogel and
All samples contain 25% Al2O3 as binder.
1
213

1214
TAGIEV et al.
tion of aromatic hydrocarbons is not observed, since the
conversion of butane is in the direction of decomposition
of n-butane and its conversion is 28.5%. On a sample
containing as a carrier zirconium dioxide and zeolite
NZSM-5 in a weight ratio of 1 : 1 with a deposited zinc
in an amount of 5% butane undergoes transformation
into a mixture of BTX at 550°C with the conversion of
n-butane 86.1% and the yield of aromatic hydrocarbon
3
2.6% at xylene content 12.9%.
To determine the role of zirconium in the aromatiza-
tion of n-butane it was entered in various amounts in
the NZSM-5 zeolite composition. As can be seen from
Table 2 an increase in the concentration of zirconium
from 0.5 to 5% enhances the growth of butane conversion
more than 3 times. The distribution of reaction products
varied: aliphatic hydrocarbons yield decreased from 5.2
to 0.4%, the yield of benzene in this case increased by 2.5
times, yield of toluene and xylene isomers, from 30.2 to
52.6 and from 3.4 to 22.0%, respectively. Figure 2 shows
the dependencies of conversion of butane and distribu-
tion of products of its transformation on the catalyst 5%
Zr/NZSM-5 on temperature. The data obtained on the
5% Zr/NZSM-5 exhibit that even at 350°C the yield of
aromatic hydrocarbons is 30.8% at the conversion of n-
butane 49.1%, the total content of isomeric xylenes in the
aromatic hydrocarbons attains 25.9% with a significant
output of aliphatic hydrocarbons. Though further increase
in temperature to 450°C increased the conversion of n-
butane up to 81.5%, the yield of isomeric xylenes was not
changed.Agrowth in the yield of benzene and decrease in
yield of aliphatic hydrocarbons from 13.5 to 4.2% occur.
Fig. 1. Effect of the original support on the aromatizing activity
–1
in the butane conversion. V = 500 h , Т = 500°С. (I) butane
conversion, %, (II) yield of aromatic hydrocarbons, wt %, (III)
yield of xylenes, wt %. (1) HZSM-5, (2) 5% Zn/HZSM-5, (3)
5
% Zn/ZrO + HZSM-5 (550°С), (4) 5% Zn/ZrO .
2 2
samples was carried out on a catalytic setup with a flow
type reactor described in [4]. For the analysis of aro-
matic hydrocarbons (AHC) we used tricresyl phosphate
10%) applied over Polysorb (column length 3 m, d = 3
mm, 125°C), analyzed hydrogen on a column filled with
molecular sieves NaX (column length 1.5 m, d = 4 mm,
(
2
0°C) and C –C hydrocarbons, on a column filled Sep-
1 5
aron BD (column length 2 m, d = 3 mm, 70°C).
As it is seen from Fig. 1, the initial H-form of ZSM-5
shows the aromatizing activity and transforms the n-bu-
tane into a mixture of aromatic hydrocarbons (BTX) with
the conversion of 80.7% and an amount of output aro-
–
1
matic hydrocarbons of 31.6% at 500°C and V = 500 h .
Introduction of 5% Zn increases the conversion of
butane by 16.5%, a total yield of isomeric xylenes is
approximately 2-fold and is accompanied by the forma-
tion of unsaturated and higher molecular alkanes, and
also leads to the total growth of output of alkyl aromatic
hydrocarbons and polyalkyl benzene compounds . When
used zinc oxide as a catalyst deposited on the zirconium
dioxide prepared in laboratory conditions, the forma-
Comparative data on the transformation of n-butane
on the synthesized samples under optimal conditions
are listed in Table 3. As can be seen the introduction of
5% zirconium into HZSM-5 leads to significant changes
in the distribution of reaction products. Thus, there is
a significant (13.2%) decrease in the yield of benzene
Table 2. An effect of zirconium concentration on n-butane aromatization product distribution on zeolite catalysts. Support
–
1
HZSM-5, 500°С, V = 125 h , τ = 1 h
Zirconium con-
centration,
Composition of the reaction products, wt %
benzene toluene m+p-xylene о-xylene ethylbenzene
Conver-
sion, %
aliphatic hydro-
ΣС9
wt%
carbons
0
.5
.5
5.2
60.0
30.2
2.2
1.2
0.8
0.4
23.5
2
5
4.3
0.4
48.4
24.7
37.2
52.6
7.6
1.6
2.7
0.7
0.2
0.2
0.1
43.5
78.5
19.3
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 84 No. 7 2011

AROMATIZATION OF BUTANE
1215
and hydrocarbons ΣC . In this way the amount of xylene
9
isomers is increased almost 2-fold, while the values of
conversion differ by 5%. On the catalyst 5% Zn/ZrO +
2
HZSM-5 the conversion reaches 78% at the output of
xylenes about 21 wt%
Table 4 shows the performance of the developed
zirconium-zeolite sample in comparison with commer-
cial catalysts [5]. Despite the slightly lower total yield of
aromatic hydrocarbons (45.2%), the redistribution of the
outputs of the liquid fraction is observed with a marked
increase in the total yield of xylenes at the process tem-
perature 500°C that is by 100° lower than for known
catalysts.
CONCLUSIONS
Fig. 2. Effect of temperature Т (°С) on the butane conver-
sion on the catalyst 5% Zr/HZSM-5. V = 500 h , τ = 1 h. (1)
n-butane conversion, %) (2) yield of aromatic hydrocarbons,
–1
(
1) Zirconium-containing samples of zeolite HZSM-5
exhibits the significant aromatizing activity even at 623 K
with 50% conversion of raw materials and the total yield
of isomeric xylenes 35%.
%
; content in aromatic hydrocarbons of (%): (3) toluene, (4)
benzene, (5) isomeric xylenes, (6) aliphatic hydrocarbons, (7)
ethylbenzene + С9.
–
1
Table 3. n-Butane aromatization on zeolite HZSM-5 modified by zirconium and zinc. V = 500 h , τ= 1h
Composition of the products in catalysate, wt %
Yield of aro-
matic hydrocar-
bons, wt %
Conversion,
Catalyst
%
benzene
18.0
toluene
48.3
Σ xylene ethylbenzene
ΣС9
0.1
1.3
0.6
5
5
% Zr/HZSM-5 (773 K)
% Zn/HZSM-5 (873 K)
34.0
18.3
21.0
0.1
2.8
92.0
97.2
78.0
45.2
35.8
30.8
31.2
46.4
Zn/ZrO + HZSM-5 (823 K)
21.5
54.1
30
2
Table 4. Comparative indices of catalyst efficiency of aromatization of low molecular alkanes (PBF)
Cyclar
Z-Forming (according to data
of “Mitsubishi Oil”)
Parameter
Zr-Catalysta Sn–Zr-Catalyst
(
according to data of UOP)
Temperature, °С
500
5.2
600
47.1
33.1
600
63.5
25
600
59.5
28
Yield of aromatic hydro-
carbons, %
4
Composition of aromatic
hydrocarbons, %:
benzene
18.0
toluene
48.3
34.0
41.6
14.9
43
23
39
31
С9
С9+
0.1
10.4
9
12
a
Raw material was n-butane.
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 84 No. 7 2011

1216
TAGIEV et al.
(
2) Reduce in aromatization temperature was
4. Abasov, S.I.,Agayeva, S.B., Tagiyev, D.B. et al., Catalysis
in Application, Cambridge, UK, 2003.
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action of a catalyst at the introduction of the zirconium
component.
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KhTTM., 2010, no. 2, pp. 52–56.
6
7
. Jentoft, F.C., Hahn, A., Wild, U. et al., 13th Int. Congr. on
Catalysis, Paris, 2004.
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