New Heterogeneous Alkylation Catalysts Based on Niobium Pentachloride

Article abstract of DOI:10.1134/S0023158418050026

New active catalysts based on niobium pentachloride immobilized on the surface of silica gel or aluminum oxide for the alkylation of aromatic compounds were prepared. The reaction occurs with a high rate at room temperature. Thus, the conversion of 1-hexene in the alkylation of benzene or toluene was close to 100% only 5 min after the onset of the reaction.

Full text of DOI:10.1134/S0023158418050026

ISSN 0023-1584, Kinetics and Catalysis, 2018, Vol. 59, No. 5, pp. 688–689. © Pleiades Publishing, Ltd., 2018.
Original Russian Text © V.I. Bykov, B.A. Belyaev, T.A. Butenko, 2018, published in Kinetika i Kataliz, 2018, Vol. 59, No. 5, pp. 667–668.
LETTER
TO THE EDITOR
New Heterogeneous Alkylation Catalysts
Based on Niobium Pentachloride
V. I. Bykova, *, B. A. Belyaeva, and T. A. Butenkoa
aTopchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, Moscow, 119991 Russia
*e-mail: bykov@ips.ac.ru
Received April 19, 2018
Abstract—New active catalysts based on niobium pentachloride immobilized on the surface of silica gel or
aluminum oxide for the alkylation of aromatic compounds were prepared. The reaction occurs with a high
rate at room temperature. Thus, the conversion of 1-hexene in the alkylation of benzene or toluene was close
to 100% only 5 min after the onset of the reaction.
Keywords: alkylation, aromatic compounds, heterogeneous catalysts, niobium pentachloride
DOI: 10.1134/S0023158418050026
INTRODUCTION
in the reactor. The catalyst support (KSK silica gel or
γ-Al2O3 (Ssp = 220 m2/g) with a particle diameter of
0.31–0.34 mm) was calcined at 300°C in a vacuum
(5 × 10–4 Torr) for 4 h. A weighed portion of finely dis-
persed powder of NbCl5 (99.5%) was added to a
The production of ethylbenzene by the alkylation
of benzene with ethylene is among the largest scale
processes. About 70 units for its production are cur-
rently in operation on a global scale; 17 of these units
use a solution of aluminum chloride as a homoge- weighed portion of the support in an atmosphere of
argon, and the mixture was evacuated (5 × 10–4 Torr)
for 8 h at room temperature or for 4 h at 80°C with agi-
tation at regular intervals. The completeness of NbCl5
immobilization was monitored based on the amount
of released HCl. The purity of the initial compounds
and the course of reactions were monitored by gas–
liquid chromatography (GLC) with the use of an
LKhM-8MD chromatograph (Russia) with a flame-
ionization detector (quartz capillary column, 40 m ×
0.2 mm) and SKTFP stationary phases. Hydrogen was
a carrier gas. Analyses were carried out under the con-
ditions of linear temperature programming (2 K/min)
from 35 to 200°C. The mass spectra (EI) were
recorded on a Finnigan MAT 95 XL 70 instrument
(Thermo Finnigan, the United States; 70 eV). All of
the reactions were carried out and the initial com-
pounds were prepared in an atmosphere of high-purity
argon with the use of LiAlH4 and Na as desiccants.
According to the GLC data, the purity of the initial
compounds was higher than 99.0%.
neous catalyst until now, and approximately 53 units
use zeolite catalysts. At these latter, 28 and 25 use gas-
phase and liquid-phase technologies, respectively [1].
Either of these technologies has its advantages and dis-
advantages. The homogeneous process proceeds at
low temperatures; however, difficulties related to the
separation of a catalyst and a large amount of wastewa-
ter outweigh the advantages, and high-temperature
heterogeneous technologies mainly based on zeolites
are preferable [1].
Earlier, we found [2–4] that molybdenum penta-
chloride reacts with the surface hydroxyl groups of sil-
ica gel at 80°C to form two covalent bonds. This cata-
lyst in combination with organotin or organosilicon
compounds as cocatalysts exhibits high activity in ole-
fin metathesis reactions.
Here, we report the synthesis of active catalysts
based on niobium pentachloride supported on the sur-
face of carrier (silica gel or aluminum oxide) for the
alkylation of aromatic compounds (benzene and tolu-
ene) with olefins (1-hexene).
RESULTS AND DISCUSSION
EXPERIMENTAL
Niobium pentachloride reacts with the surface
hydroxyl groups of the support to form one (at 25°C)
or two (at 80°C) covalent bonds with the release of one
Alkylation was performed in a thermostatically
controlled glass reactor with a magnetic stirrer. The
initial compounds (benzene or toluene and 1-hexene)
and then a weighed portion of the catalyst were loaded or two equivalents of HCl, respectively (Scheme 1).
688

NEW HETEROGENEOUS ALKYLATION CATALYSTS
689
O
O
NbCl4
H
SiO2
or
Al2O3
+HCl
25°C
80°C
O
O
H
H
SiO2
or
Al2O3
+NbCl5
O
SiO2
or
Al2O3
NbCl3 + 2HCl
O
Scheme 1. Immobilization of niobium pentachloride on the surface of a support.
Table 1. Composition of the products of catalytic benzene
alkylation with 1-hexene at a temperature of 25°C
The alkylation of benzene or toluene occurs with
the formation of mono- and dihexyl derivatives of
benzene or toluene, respectively.
Composition of the products
Concentration,
of catalytic benzene alkylation
wt %
Note that the support does not exert a considerable
effect on the rate and selectivity of the process. In the
case of benzene, two position isomers, 2-phenylhex-
ane (48.8%) and 3-phenylhexane (28.4%), and seven
disubstituted hexylbenzene isomers (in total, 22.8%)
are formed (Table 1). The reaction of toluene with
1-hexene under the same conditions leads to the for-
mation of 4 position isomers of monosubstituted tol-
uenes (in total, 88%) and 14 position isomers of disub-
stituted toluenes (in total, 12%) (Table 2). In both of
the experiments, the complete conversion of 1-hexene
was achieved only 5 min after the onset of the reaction.
with 1-hexene
3-phenylhexane
2-phenylhexane
Total monosubstituted derivatives
28.4
48.8
77.2
ortho-(3-hexyl),(3-hexyl)benzene
para-(3-hexyl),(3-hexyl)benzene
ortho-(2-hexyl),(3-hexyl)benzene
para-(2- hexyl),(3-hexyl)benzene
ortho-(2-hexyl),(2-hexyl)benzene
para-(2-hexyl),(2-hexyl)benzene
meta-(2-hexyl),(2-hexyl)benzene
Total dihexylbenzenes
0.4
1.8
2.6
7.4
3.0
6.8
0.9
22.8
Thus, we developed new highly active heteroge-
neous catalysts based on niobium pentachloride for
the alkylation of aromatic compounds with olefins.
Total
100.0
Molar ratio NbCl : benzene : 1-hexene = 1 : 200 : 40. Conversion
5
ACKNOWLEDGMENTS
of 1-hexene, 100%. Reaction time, 5 min. Amount of NbCl ,
5
14 wt % on a SiO or Al O basis.
2
2 3
This work was supported by the Russian Founda-
tion for Basic Research (project no. 17-03-00107).
Table 2. Composition of the products of catalytic toluene
alkylation with 1-hexene at a temperature of 25°C
REFERENCES
Composition of the products
Concentration,
1. Meyers, R.A., Handbook of petrochemicals production
process, McGraw-Hill professional, 2005.
of catalytic toluene alkylation
wt %
with 1-hexene
2. Bykov, V.I., Khmarin, E.M., Belyaev, B.A., Butenko, T.A.,
and Finkel’shtein, E.Sh., Kinet. Catal., 2008, vol. 49,
p. 11.
ortho-3-tolylhexane
para-2-tolylhexane
para-3-tolylhexane
ortho-2-tolylhexane
Total monosubstituted toluenes
Total disubstituted toluenes
Total
20.9
28.8
17.1
3. Bykov, V.I., Belyaev, B.A., Butenko, T.A., and Fin-
kel’shtein, E.Sh., Proc. NATO ASI Green Metathesis
Chemistry: Great Challenges in Synthesis, Catalysis and
Nanotechnology, 2010, p. 115.
21.2
88.0
12.0
100.0
4. Bykov, V.I., Belyaev, B.A., Butenko, T.A., and Fin-
kel’shtein, E.Sh., Pet. Chem., 2016, vol. 56, no. 2,
p. 140.
Molar ratio NbCl : toluene : 1-hexene = 1 : 200 : 40. Conversion
5
of 1-hexene, 100%. Reaction time, 5 min. Amount of NbCl ,
5
Translated by V. Makhlyarchuk
14 wt % on a SiO or Al O basis.
2
2 3
KINETICS AND CATALYSIS Vol. 59 No. 5 2018