Alkylation of naphthalene with propylene catalyzed by aluminum chloride immobilized on Al-MCM-41

Article abstract of DOI:10.1016/S1872-2067(09)60080-2

AlCl₃ catalysts immobilized on mesoporous Al-MCM-41 were prepared by a two step vapor method and their catalytic performance was evaluated for the alkylation of naphthalene with propylene in a slurry bubble column reactor. The physico-chemical properties of the supports and catalysts were characterized by X-ray diffraction, N₂ adsorption, and pyridine adsorption infrared spectroscopy. The halide loadings of the catalysts were analyzed by a chemical method. For the alkylation of naphthalene with propylene over AlCl₃/Al-MCM-41, pore diameters that match the molecular dimensions of 2,6-diisopropylnaphthalene (2,6-DIPN) and an appropriate amount of [-O-AlCl₂] in the catalyst are key to controlling activity and selectivity. The AlCl₃ catalyst immobilized on mesoporous H/Al-MCM-41 with a Si/Al ratio of 15 exhibited high activity when the alkylation was carried out at 0.1 MPa and 85 °C for 5 h. A naphthalene conversion of 82.1 and a 2,6-DIPN selectivity of 32.2 were obtained.

Full text of DOI:10.1016/S1872-2067(09)60080-2

CHINESE JOURNAL OF CATALYSIS
Volume 31, Issue 7, 2010
Online English edition of the Chinese language journal
Cite this article as: Chin. J. Catal., 2010, 31: 725–728.
SHORT COMMUNICATION
Alkylation of Naphthalene with Propylene Catalyzed by
Aluminum Chloride Immobilized on Al-MCM-41
TANG Hua, JI Min*, WANG Xinkui, HE Min, CAI Tianxi
Department of Chemistry, Dalian University of Technology, Dalian 116012, Liaoning, China
Abstract: AlCl
formance was evaluated for the alkylation of naphthalene with propylene in a slurry bubble column reactor. The physico-chemical proper-
ties of the supports and catalysts were characterized by X-ray diffraction, N adsorption, and pyridine adsorption infrared spectroscopy. The
halide loadings of the catalysts were analyzed by a chemical method. For the alkylation of naphthalene with propylene over
AlCl /Al-MCM-41, pore diameters that match the molecular dimensions of 2,6-diisopropylnaphthalene (2,6-DIPN) and an appropriate
amount of [–O–AlCl ] in the catalyst are key to controlling activity and selectivity. The AlCl catalyst immobilized on mesoporous
3
catalysts immobilized on mesoporous Al-MCM-41 were prepared by a two step vapor method and their catalytic per-
2
3
2
3
H/Al-MCM-41 with a Si/Al ratio of 15 exhibited high activity when the alkylation was carried out at 0.1 MPa and 85 °C for 5 h. A naph-
thalene conversion of 82.1% and a 2,6-DIPN selectivity of 32.2% were obtained.
Key words: naphthalene; alkylation; propylene; immobilization; aluminium chloride; MCM-41; slurry bubble column reactor
The alkylation of naphthalene with propylene is a base re-
action for the valuable chemical products of 2,6-diisopropyl-
naphthalene (2,6-DIPN), which is a raw material used in the
production of advanced polyester fibers, films, and plastics
Aluminum chloride immobilized on A1 O and SiO can
2 3 2
form a new type of solid acid catalyst [5]. It has been reported
that this immobilized AlCl has comparable activity and higher
3
selectivity for the alkylation of benzene. The strong Lewis and
Brönsted acidity and the support pore structure of the catalysts
contribute to their excellent activity and selectivity [6]. Re-
cently, Zhao et al. [7] reported the liquid-phase isopropylation
such as thermotropic liquid crystalline polymers [1]. AlCl is
3
widely used in the chemical industry as an active catalyst at
reaction temperatures between 50 and 100 °C but it causes
environmental problems and severe corrosion, and it is often
difficult to separate from reaction mixtures [2]. Therefore,
plenty of attention has been given to the development of solid
acid catalysts because of their environmentally friendly prop-
erties. Many researchers have reported results based on the use
of a fixed-bed reactor or a batch reactor, and typical catalysts
are mordenite, Hβ, ZSM-5, MCM-41, MCM-48, or MCM-22
molecular sieves, which have special pore structures [3].
However, practical use of these catalysts is hampered by high
reaction temperatures (200–300 °C) and high reaction pres-
sures (0.5–4.6 MPa) and, additionally, zeolite acidity is low. Li
et al. [4] used Fe (SO ) /bentonite as a catalyst for the isopro-
of naphthalene with isopropanol over immobilized AlCl on
3
mesoporous Si-MCM-41 in a Parr batch reactor. They demon-
strated that the immobilized aluminum chloride catalysts are
highly active and reusable during the liquid-phase isopropyla-
tion of naphthalene.
In this work, we report the use of AlCl immobilized on
3
Al-MCM-41 as a catalyst for the alkylation of naphthalene
with propylene in a slurry bubble column reactor. The influ-
ence of pore size and catalyst surface acidity on the reaction
activity and selectivity is discussed.
The supports were Na/Al-MCM-41(x) and H/Al-MCM-
41(x) (x denotes the n /n ratios of the catalysts). Na/Al-
2
4 3
Si Al
pylation reaction of naphthalene in a slurry bubble column
reactor. Their reactor had a simple structure, good heat transfer
property, and low operating cost but a high reaction tempera-
ture and pressure are still required for zeolite catalysts.
MCM-41 with different n /n ratios were synthesized hydro-
Si Al
thermally based on a previous report [8]. Reactants with the
following compositions were prepared: 1.0DTAB (dodecyl
trimethyl ammonium bromide):xA1 O :7.5TEOS (tetraethyl
2
3
Received date: 20 March 2010.
*
Corresponding author. Tel: +86-411-39893637; Fax: +86-411-83631333; E-mail: jimin@dlut.edu.cn
Copyright © 2010, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier BV. All rights reserved.
DOI: 10.1016/S1872-2067(09)60080-2

TANG Hua et al. / Chinese Journal of Catalysis, 2010, 31: 725–728
orthosilicate):1.8NaOH:500H
2
O (molar ratio), where x = 0.25
and 0.3. Sodium aluminate was used as the aluminum source.
H/Al-MCM-41 was obtained by ion-exchange using ammo-
nium nitrate [9]. The immobilized AlCl catalysts were pre-
3
(1)
pared using a two-step method. All supports were calcined at
2
00 °C under a N stream for 2 h and then an AlCl stream,
2
3
(2)
which was produced in another reactor by reacting CCl with
4
Al O at 500 °C, was carried into the reactor containing the
2
3
(3)
pretreated support by N . The immobilization reaction between
2
the AlCl stream and the support was allowed to proceed at 200
3
°
C for 4 h. Excess and physically adsorbed AlCl was removed
3
(4)
1400
by flushing with N at 200 °C for 1 h. The immobilized catalyst
2
1600
1550
1500
Wavenumber (cm )
1450
was then cooled down to room temperature under a N stream.
−1
2
Powder X-ray diffraction (XRD) patterns were obtained
Fig. 1. XRD patterns of different samples. (1) Na/Al-MCM-41(15); (2)
using a D/MAX-2400 powder diffractometer with Cu K ra-
α
H/Al-MCM-41(15); (3) Na/Al-MCM-41(12.5); (4) H/Al-MCM-41(12.5).
diation and operating at 40 kV and 100 mA. The surface area
and pore distribution were measured by N adsorption at –196
2
°
C on a Micrometrics ASAP 2000. The catalyst samples were
the (100) peak decreases for Na/Al-MCM-41 as well as H/Al-
MCM-41. No (110) or (200) diffraction peaks are present. A
(100) diffraction peak is present between 2° and 7° for all four
samples. This phenomenon indicates that Al is incorporated
into the framework structure of MCM-41, resulting in the
distortion of long-range ordering in the hexagonal mesoporous
structures. In addition, we also found that the XRD patterns of
H/Al-MCM-41 are weaker and broader than that of
Na/Al-MCM-41, which is also caused by the incorporation of
small amounts of Al into MCM-41 [12].
evacuated at 250 °C for 3 h before N physisorption meas-
2
urements. Fourier transform infrared (FT-IR) spectra of the
chemically adsorbed pyridine were collected on an EQUI-
NOX55 FT-IR spectrometer. Catalysts were activated in an IR
cell at 150 °C under vacuum for 2 h, cooled to room tempera-
ture, and exposed to pyridine at this temperature for 30 min.
The sample was then evacuated at 150 °C for 1 h to remove the
physically adsorbed pyridine. Finally, the spectrum was re-
corded at 150 °C. The chloride content of the catalysts was
determined using the Volhard method [10].
Table 1 lists the physico-chemical properties of the supports
and the catalysts. We found that the pore size of Na/Al-
MCM-41 decreases with an increase in the amount of alumi-
num. Compared with Na/Al-MCM-41, the ion-exchanged
H/Al-MCM-41 materials have an increscent surface area, pore
The alkylation of naphthalene with propylene was carried
out in a glass test tube reactor, where the immobilized AlCl3
catalyst was added to a solution of naphthalene and cyclo-
hexane, and propylene gas was bubbled from the bottom of the
reactor. The reaction temperature was maintained at 85 °C by
an oil bath equipped with a thermostat and an electric stirrer.
The reaction pressure was 0.1 MPa. After 5 h, the reactor was
cooled to room temperature. The liquid products were analyzed
using a GC-FID with a HP-INNOWAX column (50 m × 0.2
mm) [11].
volume, and pore diameter. After the immobilization of AlCl
,
3
the surface area, pore volume, and pore diameter of the cata-
lysts decrease greatly. The largest pore diameter of 2.55 nm
was obtained for AlCl
was obtained for AlCl
diameter of only 1.74 nm.
The obtained AlCl loadings for the different Al-MCM-41
supports are shown in Table 1. The [–O–AlCl ] loadings on
AlCl /Na/Al-MCM-41(15) and AlCl /Na/Al-MCM-41(12.5)
were much higher than that on AlCl /H/Al-MCM-41(15) and
/H/Al-MCM-41(15) while the lowest
3
3
/Na/Al-MCM-41(12.5) with a pore
XRD patterns of the Al-MCM-41 supports with different
nSi/nAl ratios are shown in Fig. 1. All the samples show a main
diffraction in the 2θ range from 2.44° to 2.56°. With an in-
crease in the aluminum content of the samples, the intensity of
3
2
3
3
3
3
Table 1 Physico-chemical properties of the Al-MCM-41 supports and the AlCl /Al-MCM-41 catalysts
2
3
Sample
Surface area (m /g)
Pore volume (cm /g)
Pore diameter (nm)
w([–O–AlCl
—
2
]) (%)
Na/Al-MCM-41(15)
360
147
408
281
225
186
421
187
0.22
0.08
0.26
0.19
0.13
0.08
0.27
0.13
2.35
2.19
2.59
2.55
2.31
1.74
2.58
2.51
AlCl
H/Al-MCM-41(15)
AlCl /H/Al-MCM-41(15)
Na/Al-MCM-41(12.5)
AlCl /Na/Al-MCM-41(12.5)
H/Al-MCM-41(12.5)
AlCl /H/Al-MCM-41(12.5)
3
/Na/Al-MCM-41(15)
24.13
—
3
12.58
—
3
26.73
—
3
18.93

TANG Hua et al. / Chinese Journal of Catalysis, 2010, 31: 725–728
3 3
AlCl /H/Al-MCM-41(12.5), and the AlCl loadings are not
dependent on the surface area of the catalysts. The immobili-
zation of AlCl onto the surface of the support can occur by the
3
reaction of AlCl with the support’s surface hydroxyl groups,
3
(1)
accompanied by the release of HCl [6,12,13]. Over 90% of the
chloroaluminum species on the surface of the immobilized
(2)
catalyst’s support has a composition of [–O–AlCl ] [12].
2
Therefore, the different [–O–AlCl ] loadings of the catalysts
2
(3)
can be attributed to a difference in the surface hydroxyl group
concentrations of the supports.
FT-IR spectra of the chemically adsorbed pyridine were used
to characterize the catalyst acid types. They were recorded at
(
4)
1600
1550
1500
Wavenumber (cm )
1450
1400
−1
1
50 °C and are shown in Fig. 2. The band at 1 540 cm is
−1
−1
assigned to Brönsted acid sites and the band at 1 450 cm is
−1
Fig. 2. FT-IR spectra of pyridine adsorbed on different samples. (1)
AlCl /Na/Al-MCM-41 (15); (2) AlCl /H/Al-MCM-41(15); (3) AlCl /Na/
Al-MCM-41(12.5); (4) AlCl /H/Al-MCM-41(12.5).
assigned to Lewis acid sites while the band at 1 490 cm is
assigned to a combination signal associated with both Brönsted
and Lewis acid sites [14]. From Fig. 2, the intensity of the band
3
3
3
3
−1
−1
at 1 450 cm is much stronger than that at 1 540 cm for all
the catalysts, which indicates that the Lewis acid sites are the
MIPN was obtained. Combined with the results listed in Table
1 and illustrated in Fig. 2, we determined that the pore diameter
that matches the molecular dimensions of 2,6-DIPN and an
predominant acid species on the four AlCl catalysts that are
3
immobilized on Al-MCM-41. AlCl /Na/Al-MCM-41(12.5)
3
showed the least amount of acid sites among the four studied
catalysts.
appropriate amount of [–O–AlCl
controlling the activity and selectivity. We also found that with
a decrease in pore size from 2.55 nm for AlCl /H/Al-
MCM-41(15) to 1.74 nm for AlCl /Na/Al-MCM-41(12.5),
2
] in the catalyst are key to
The product distributions of all the catalysts after 5 h are
shown in Table 2. No product was detected over the
Al-MCM-41 supports under these reaction conditions while all
3
3
naphthalene conversion and 2,6-DIPN selectivity rapidly de-
creased from 82.1% to 4.8% and from 33.3% to zero, respec-
the AlCl /Al-MCM-41 catalysts were active for the alkylation
3
of naphthalene with propylene. Monoisopropylnaphthalene
tively. For AlCl /Na/Al-MCM-41(12.5), the DIPN selectivity
3
(
MIPN) and DIPN were the main products of the reaction.
of zero might be related to its smaller pore diameter of 1.74 nm,
which does not allow for diffusion of the products.
Other by-products such as tri- and tetra-isopropylnaphthalenes
were also present. From Table 2, the highest conversion of
Figure 3 shows the stability of AlCl immobilized on H/Al-
3
naphthalene was 82.6% when using AlCl as catalyst but the
MCM-41(15). After simply separating the reacted medium
from the reactor by sedimentation, the new reaction medium
was charged for a new reaction cycle without any regeneration
of the catalyst. From Fig. 3 we found that although the con-
version of naphthalene decreased with an increase in reaction
cycles, naphthalene conversion was still 60% after four cycles.
3
n(2,6-DIPN)/n(2,7-DIPN) ratio was only 0.8. This shows that
the selectivity of AlCl is very low even at high catalytic ac-
3
tivity. It is clear that AlCl /H/Al-MCM-41(15) and
3
AlCl /H/Al-MCM-41(12.5) have similar high catalytic activity
3
and selectivity at the low reaction temperature of 85 °C.
Naphthalene conversions as high as 80% with
a
In conclusion, this study demonstrates that AlCl /Al-
3
n(2,6-DIPN)/n(2,7-DIPN) ratio of almost 1 were also obtained.
The highest n(2,6-DIPN)/n(2,7-DIPN) = 1.2 was obtained over
MCM-41 has high catalytic activity for the alkylation of
naphthalene with propylene in a slurry bubble column reactor.
AlCl /Na/Al-MCM-41(15), which has a small pore size of 2.19
At 85 °C and 0.1 MPa, AlCl /H/Al-MCM-41(15) exhibits high
3
3
nm. AlCl /Na/Al-MCM-41(12.5) did not form DIPN, and only
naphthalene conversion (more than 82%) and a n(2,6-DIPN)/
3
Table 2 Catalytic performance of the immobilized AlCl
3
catalysts for alkylation of naphthalene with propylene
Naphthalene
Product distribution (%)
n(2,6-DIPN)
2,6-DIPN in
DIPN (%)
18.3
Sample
conversion (%)
Naphthalene
17.3
MIPN
27.8
12.7
37.4
4.8
DIPN
26.5
1.4
Others
28.2
0.2
/n(2,7-DIPN)
AlCl
AlCl
AlCl
AlCl
AlCl
3
3
3
3
3
82.6
14.3
82.1
4.8
0.8
1.2
0.9
0.0
0.9
/Na/Al-MCM-41(15)
/H/Al-MCM-41(15)
/Na/Al-MCM-41(12.5)
/H/Al-MCM-41(12.5)
86.6
20.5
16.8
33.3
0.0
12.3
0.0
32.2
95.1
0.0
80.1
19.8
41.5
29.6
9.0
28.0
o
Reaction conditions: naphthalene 0.05 mol, propylene 0.1 mol, cyclohexane 100 ml, catalyst 4.21 mmol [–O–AlCl
Others: tri- and tetra-isopropylnaphthalenes.
2
], 85 C, 5 h.

TANG Hua et al. / Chinese Journal of Catalysis, 2010, 31: 725–728
References
100
1
2
3
Song C S. CATTECH, 2002, 6: 64
8
6
4
2
0
0
0
0
Iwahara M, Aoki A, Saruwatari T, Imada S. EP 0 565 821. 1993
Zhang M J, Chen S Y, Shen Sh D, Sun Y H, Wu D. Chin J
Catal, 2000, 21: 440
4
Li K J, He G X, Jin H B, Zhao Zh. Chin J Process Eng, 2008, 8:
5
23
5
6
7
8
Wu L M, Ji M, He M, Cai T X. Chin J Catal, 2007, 28: 585
Getty E E, Drago R S. Inorg Chem, 1990, 29: 1186
Zhao X S, Lu M G Q, Song C. J Mol Catal A, 2003, 191: 67
Zhang W H, Shi J L, Wang L Z, Yan D S. Chem Mater, 2000, 12:
0
1
2
3
4
5
Reaction cycle
Fig. 3. Reusability of the AlCl /H/Al-MCM-41(15) catalyst. Reaction
1
408
3
9
0
1
2
3
Li X, Wang A J, Shun Z C, Li C, Ren J, Zhao B, Wang Y, Chen Y
Y, Hu Y K. Appl Catal A, 2003, 254: 319
conditions: naphthalene 0.05 mol, propylene 0.1 mol, cyclohexane 100
o
ml, catalyst 4.21 mmol [–O–AlCl
2
], 85 C, 5 h.
1
1
1
1
Gong W M, Li N, Liu Zh G, Zhu A M. Analysis Chemistry.
Dalian: Dalian Univ Technol Press, 2000. 87
n(2,7-DIPN) ratio of 0.9 was obtained. This catalyst is stable.
Tranke S, Grunenberg J, Schwarzbauer J. Intern J Environ Anal
Chem, 2007, 87: 437
Characterization of the pore property indicated that the im-
mobilization of AlCl leads to a decrease in the pore size of the
3
Luan Z H, Cheng C F, He H Y, Klinowski J. J Phys Chem, 1995,
catalysts and this influences the selectivity. Therefore, the pore
diameter that matches the molecular dimensions of 2,6-DIPN
9
9: 10590
Xu T, Kob N, Drago R S, Nicholas J B, Haw J F. J Am Chem
Soc, 1997, 119: 12231
and an appropriate amount of [–O–AlCl ] in the catalyst are
2
key to controlling its activity and selectivity.
14 Drago R S, Getty E E. J Am Chem Soc, 1988, 110: 3311