Aromatization of a C3-C4 alkane mixture over Zn-pentasil modified with tin and lead

Article abstract of DOI:10.1007/s11172-011-0090-2

Modification of Zn-containing H-ZSM-5 pentasil by tin and lead reduces the yield of C₁₀₊ aromatic hydrocarbons from alkanes C₃-C ₄. The high selectivity of formation of the aromatization products is retained.

Full text of DOI:10.1007/s11172-011-0090-2

Russian Chemical Bulletin, International Edition, Vol. 60, No. 3, pp. 585—586, March, 2011
585
Aromatization of a C —C alkane mixture over Znꢀpentasil
3
4
modified with tin and lead
A. L. Lapidus, A. M. Kozlov, D. S. Khudyakov, and A. A. Dergachevb
a
a
a
aI. M. Gubkin Russian State University of Oil and Gas,
6
5 Leninsky prosp., 119991 Moscow, Russian Federation.
Fax: +7 (499) 135 8895. Eꢀmail: akozlov@pochtam.ru
b
N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences,
4
7 Leninsky prosp., 119991 Moscow, Russian Federation.
Fax: +7 (499) 135 5328
Modification of Znꢀcontaining HꢀZSMꢀ5 pentasil by tin and lead reduces the yield of
C10+ aromatic hydrocarbons from alkanes C —C . The high selectivity of formation of the
3
4
aromatization products is retained.
Key words: aromatization, alkanes C —C , pentasil, modified zeolites, zinc, lead, tin.
3
4
Aromatic hydrocarbons С —С
are formed from alꢀ
10+
containing 5 wt.% Zn introduced by the impregnation method
from zinc nitrate. Lead and tin chlorides were used to modify
Znꢀcontaining pentasil. Experiments were carried out at atꢀ
6
kanes C —C over Znꢀcontaining zeolites of the pentasil
3
—4
4
family.1
Hydrocarbons С —С8 are the most valuable
6
–
1
mospheric pressure, at 600 °С, and with a flow rate of 300 h
.
products. In addition, the presence of condensed comꢀ
pounds in the aromatization products can deactivate the
catalysts due to coke formation. Therefore, the problem of
decreasing the fraction of heavy hydrocarbons is imporꢀ
tant for the development of efficient zeolite catalysts of
aromatization of low alkanes. Literature data on the
role of tin and lead as components of zeoliteꢀbased cataꢀ
lytic systems are so far unavailable.
Gaseous aromatization products were analyzed on a Khromatekꢀ
Kristall 500 chromatograph using packed columns with zeolite
1
3X and alumina modified with Nuiol. Liquid aromatization
products were analyzed using a capillary column with the nonꢀ
polar phase OVꢀ1. The results obtained are presented in Table 1.
Results and Discussion
In the present work we attempted to directly change
the composition of aromatization products over Znꢀpenꢀ
tasil by doping the catalysts with tin and lead.aa
It follows from the data in Table 1 that with an inꢀ
crease in the lead or tin content in ZnꢀZSMꢀ5 the selecꢀ
tivity of formation of aromatic hydrocarbons remains rathꢀ
er high, although their yield decreases insignificantly. The
yield of aromatic hydrocarbons С10+ decreases more than
threefold, whereas the yield of methane on modified penꢀ
tasils varies from 10 to 16 wt.%. Benzene, toluene, and
Experimental
The conversion of a mixture of propane and butanes (ratio
2
.5 : 1) was studied over pentasil HꢀZSMꢀ5 (SiO /Al O = 90)
2 2 3
Table 1. Dependence of the main parameters of alkane С —С aromatization at 600 °C and a flow
3
4
rate of 300 h–1 on the additive (M) content in the catalyst ZnꢀZSMꢀ5
M
Ratio
М/Zn (mol.)
Conversion
Selectivity
Yield (%)
С10+
%
С —С9
СН4
6
Sn
0
89.3
82.1
80.5
80.8
52.4
79.2
78.5
73.6
64.8
56.9
56.7
58.6
54.0
60.0
56.2
59.4
50.9
61.2
40.3
41.4
42.9
39.7
30.0
38.3
44.2
34.7
36.8
10.5
5.2
4.2
3.9
1.4
6.2
2.4
2.8
2.9
13.8
16.0
15.3
16.0
13.1
15.5
13.4
12.7
10.2
0
0
0
0
.05
.10
.15
.25
Pb
0.05
0
0
0
.10
.15
.25
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 572—573, March, 2011.
066ꢀ5285/11/6003ꢀ585 © 2011 Springer Science+Business Media, Inc.
1

586
Russ.Chem.Bull., Int.Ed., Vol. 60, No. 3, March, 2011
Lapidus et al.
xylenes prevail in the aromatization products due to modꢀ
ification.
2. G. Caeiro, R. H. Carvalho, X. Wang, M. A. N. D. A. Lemos,
F. Lemos, M. Guisnet, F. Ramôa Ribeiro, J. Mol. Catal. A:
Chem., 2006, 255, 133.
Thus, the possibility of controlling the composition of
products of aromatization of alkanes С —С by doping
3
. A. L. Lapidus, A. A. Dergachev, V. A. Kostina, A. A. Silaꢀ
3
4
kova, Neftekhimiya, 2008, 48, No. 2, 83 [Petroleum Chem.
Znꢀpentasils with tin or lead was shown for the first time.
The optimum concentration of the dopant (Sn/Zn = 0.15,
Pb/Zn = 0.1) was found, which causes a 2—4 fold deꢀ
crease in the yield of condensed aromatic hydrocarbons
(
Engl. Transl.), 2008, 48, No. 2, 83].
4
. V. B. Kazansky, J. Catal., 2003, 216, 192.
(
naphthalene and its derivatives).
References
1
. A. L. Lapidus, A. A. Dergachev, Proc. GKMKꢀConference,
Munich, Germany, 2004, 193.
Received February 25, 2011;
in revised form March 29, 2011