Oligomerisation of isobutene with silica supported ionic liquid catalysts

Article abstract of DOI:10.1039/c1gc15989e

Bronsted acidic ionic liquids, supported on silica gel, have been used effectively in oligomerisation of isobutene. The supported catalysts could be used several times without loss of activity or change in selectivity. The ratio of the products could be influenced by the proper choice of the ionic liquid component of the catalyst and the reaction temperature.

Full text of DOI:10.1039/c1gc15989e

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PAPER
Oligomerisation of isobutene with silica supported ionic liquid catalysts†
Csaba Fehe´r,a Eszter Kriva´n,b Jeno˝ Hancso´kb and Rita Skoda-Fo¨ldes*a
Received 10th August 2011, Accepted 3rd November 2011
DOI: 10.1039/c1gc15989e
Brønsted acidic ionic liquids, supported on silica gel, have been used effectively in oligomerisation
of isobutene. The supported catalysts could be used several times without loss of activity or
change in selectivity. The ratio of the products could be influenced by the proper choice of the
ionic liquid component of the catalyst and the reaction temperature.
nate ionic liquids and nickel catalysts, known as the Difasol
1. Introduction
process, was commercialised.38 Oligocyclisation of 1-hexene
The oligomerisation of light olefins is an important alternative
was performed in similar ionic liquids using Ti-complexes as
for the production of higher molecular weight hydrocarbon
catalysts.39
mixtures, useful as fuels (e.g. gasoline or diesel). Both Brønsted
and Lewis acids have been used as oligomerisation catalysts in
Seddon observed that chloromaluminate ionic liquids with
Lewis acidic character catalyzed oligomerisation themselves,
either a homogeneous (H2SO4, organometallic complexes, etc.)
or heterogeneous (mixed oxides, zeolites, clays, ion exchange
resins etc.) phase.1 Solid phosphoric acid catalysis has been
applied industrially since the early 1930s for the production of
gasoline through the oligomerisation reaction.2
without the addition of transition metal complexes or salts.40
These catalysts were proved to be very efficient for the oligomeri-
sation of linear 1-olefins.41–43 Similar ionic liquids prepared with
anhydrous iron(III) chloride, instead of AlCl3, were shown to
catalyze isobutene oligomerisation with high selectivity toward
diisobutene and triisobutene.44
The main challenges in the design of catalysts for this reaction
are focused on reaching high conversion and high selectivity.
Consequently, several solid acid catalysts of different types
have been developed for the oligomerisation of lower alkenes,
such as isobutene.3 These include cation exchange resins,4–7
sulfated zirconia8 and titania,9 SiO2-Al2O3,10 zeolites,11–18 zeolites
modified with Lewis acids,19 zeolites doped with nickel,20–24 silica
supported heteropolyacids25–27 and mixed metal oxides.28,29
Several Ni-based homogeneous catalysts containing phos-
phine ligands30,31 have also been introduced. However, a great
drawback of homogeneous catalytic reactions is the problem
of catalyst recovery and recycling. The use of a two-phase
solvent system, together with a transition metal complex,
is an attractive alternative, as it enables catalyst separation
and reuse. This methodology was found to be very efficient
in alkene oligomerisation32 by cationic nickel complexes in
chloroaluminate33–36 or hexafluorophosphate37 ionic liquids as
solvents. In 1998, an industrial process based on chloroalumi-
Selective dimerisation of a-methystyrene, producing 4-
methyl-2,4-diphenyl-1-pentene in high yields, was carried out in
3-alkyl-1-methylimidazolium ionic liquids with acid additives.45
Imidazolium ionic liquids with SO3H functionalized side chains
were also found to be excellent and reusable catalysts in
oligomerisation of various alkenes.46 The selectivity of the
reaction was greatly dependent on the length of the side chains.
The use of an ionic liquid with imidazolium cations with smaller
side chains led to higher selectivity for dimeric products.
Generally, ionic liquids (ILs) have gained increasing attention
because they can be considered as environmentally friendly
solvents with multiple applications in synthesis and catalysis.47
Despite their advantages, there are also some drawbacks,
including the difficulties in product purification or IL recycling
and the problems for application in fixed bed reactors. Also,
biphasic ionic liquid–organic systems require large amounts of
the expensive ILs, which hinders industrial applications. These
difficulties can be overcome by the use of supported ionic liquid
phases (SILPs) prepared by the immobilization of ionic liquids
on solid supports.48
aUniversity of Pannonia, Institute of Chemistry, Department of Organic
Chemistry, Egyetem. u. 10., Veszpre´m, Hungary.
E-mail: skodane@almos.uni-pannon.hu; Fax: +36-88-624469;
Tel: +36-88-624719
Based on these findings, we decided to explore the possibility
of the use of silica-supported SO3H-functionalised ILs as
catalysts in the oligomerisation of isobutene. In this paper, we
report on our results concerning the effects of the changes in the
catalytic system and reaction conditions (the nature of the cation
and the anion of the IL, the reaction time and temperature) on
the outcome of the oligomerisation reaction.
bUniversity of Pannonia, Department of MOL Hydrocarbon and Coal
Processing, Egyetem. u. 10., Veszpre´m, Hungary.
E-mail: hancsokj@almos.uni-pannon.hu; Fax: +36 88 624520;
Tel: +36 88 624217
† Electronic supplementary information (ESI) available: 1H NMR
spectra of 4 and 5 and a representative gas chromatogram. See DOI:
10.1039/c1gc15989e
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Scheme 1 Synthesis of ionic liquids IL-1 and IL-2 and supported ionic liquids SILP-1—SILP-7.
trifluoromethanesulfonate (IL-2) (11.93 g, 97%). Water content:
1.25% (IL-1), 1.92% (Il.-2).
2. Experimental
2.1. Synthesis of the ionic liquids
1-(4-Sulfobutyl)-3-alkylimidazolium hydrogensulfates (IL-3:
alkyl = methyl, IL-4: alkyl = butyl).50 A mixture of the 1-
(4-sulfobutyl)-3-alkylimidazolium betaine 4 or 5 (15 mmol)
and sulfuric acid (1.47 g, 15 mmol) was stirred at 150 ◦C
for 5 h under argon. After being allowed to cool to room
temperature, the ionic liquid was washed repeatedly with toluene
(3 ¥ 10 ml) and diethylether (3 ¥ 10 ml) to remove non-ionic
The ionic liquids were synthesized by methods analogous to
literature procedures (Scheme 1).49,50
1-(4-Sulfobutyl)-3-alkylimidazolium betaine (4: alkyl = methyl,
5: alkyl = butyl).49 1,4-Butanesultone (3) (2.72 g, 20 mmol)
was added slowly to 1-alkylimidazole 1 or 2 (20 mmol). The
mixture was stirred at room temperature for 48 h. The product
was washed with toluene (3 ¥ 10 ml) and diethylether (2 ¥
10 ml) to remove any unreacted starting material. Evaporation
of any volatiles in vacuo at 60 ◦C gave 3.62 g (83%) of 1-(4-
sulfobutyl)-3-methylimidazolium betaine (4) or 4.06 g (78%) of
1-(4-sulfobutyl)-3-butylimidazolium betaine (5).
◦
residues, and dried in vacuo at 110 C to give 1-(4-sulfobutyl)-
3-methylimidazolium hydrogensulfate (IL-3) (4.55 g, 96%) or 1-
(4-sulfobutyl)-3-butylimidazolium hydrogensulfate (IL-4) (5.21
g, 97%). Water content: 2.05% (IL-3), 2.91% (Il.-4).
Spectroscopic data for 4: 1H-NMR d (D2O) 8.64 (s, 1H); 7.40
(m, 1H); 7.34 (m, 1H); 4.15 (t, 7.3 Hz, 2H); 3.79 (s, 3H); 2.85 (t,
7.3 Hz, 2H); 1.93 (quint., 7.3 Hz, 2H); 1.65 (quint., 7.3 Hz, 2H).).
IR (KBr): 1575 (C C), 1177 (SO), 1042 (SO) cm-1. Analysis
calculated for C8H14N2O3S (218.28): C, 44.02; H, 6.46; N, 12.83;
found: C, 43.87; H, 6.61; N, 12.99. Water content: 0.68%.
Spectroscopic data for 5: 1H-NMR d (D2O) 8.72 (s, 1H); 7.40–
7.43 (m, 2H); 4.15 (t, 7.3 Hz, 2H); 4.10 (t, 7.3 Hz, 2H); 2.84 (t,
7.3 Hz, 2H); 1.93 (quint., 7.3 Hz, 2H); 1.76 (quint., 7.3 Hz,
2H); 1.64 (quint, 7.3 Hz, 2H); 1.21 (sext, 7.3 Hz, 2H); 0.82 (t,
7.3 Hz, 3H). IR (KBr): 1556 (C C), 1183 (SO), 1041 (SO) cm-1.
Analysis calculated for C11H20N2O3S (260.36): C, 50.75; H, 7.74;
N, 10.76; found: C, 50.59; H, 7.81; N, 10.56. Water content:
0.53%.
2.2. Preparations of supported ionic liquids (SILP-1—SILP-7)
Supported ionic liquids were prepared by a method analogous
to a literature procedure.51
Silica gel (Kieselgel 60 (0.040–0.063 mm), Merck) was pre-
treated by heating for 5 h at 150, 250 or 450 ◦C (see Table 1). After
that it was allowed to cool to room temperature in a desiccator
and was stored under argon. A mixture of silica gel (10 g), the
ionic liquid (IL-1, IL-2, IL-3 or IL-4) (10 mmol) and 25 ml
Table 1 Supported ionic liquid catalysts used in oligomerisation of
isobutene
Temp. of silica
Catalyst
Ionic liquida
pre-treatment [◦C]
1-(4-Sulfobutyl)-3-alkylimidazolium
trifluoromethanesul-
SILP-1
SILP-2
SILP-3
SILP-4
SILP-5
SILP-6
SILP-7
IL-1
IL-1
IL-1
IL-2
IL-2
IL-3
IL-4
150
250
450
150
250
250
250
fonates (IL-1: alkyl = methyl, IL-2: alkyl = butyl).49 A mixture
of the 1-(4-sulfobutyl)-3-alkylimidazolium betaine 4 or 5
(30 mmol) and trifluoromethanesulfonic acid (4.50 g, 30 mmol)
was stirred at 150 ◦C for 5 h under argon. After being allowed to
cool to room temperature, the ionic liquid was washed repeatedly
with toluene (3 ¥ 20 ml) and diethylether (3 ¥ 20 ml) to remove
non-ionic residues, and dried in vacuo at 110 ◦C to give 1-(4-
a IL-1: 1-(4-sulfobutyl)-3-methylimidazolium trifluoromethanesul-
fonate, IL-2: 1-(4-sulfobutyl)-3-butylimidazolium trifluoromethanesul-
fonate, IL-3: 1-(4-sulfobutyl)-3-methylimidazolium hydrogensulfate,
IL-4: 1-(4-sulfobutyl)-3-butylimidazolium hydrogensulfate.
sulfobutyl)-3-methylimidazolium
trifluoromethanesulfonate
(IL-1) (10.82 g, 98%) or 1-(4-sulfobutyl)-3-butylimidazolium
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Table 2 Oligomerisation of isobutene in the presence of ionic liquid
based catalystsa
MeOH was stirred at room temperature for 24 h. MeOH was
removed in vacuo and the catalyst was dried at 60 C in vacuo
◦
for 1 h to produce the supported ionic liquids.
Ratio of products [%]b
Entry Catalyst Conv. [%]b TON TOF [h-1] C8
C12
C16
C20
2.3. Oligomerisation of isobutene
1
2
3
4
5
6
7
8
9
IL-1
IL-2
98
99
5.6 1.13
5.7 1.14
57.5 11.5
57.5 11.5
57.5 11.5
57.5 11.5
57.5 11.5
48.9 9.8
75
33
19
16
14
32
54
83
82
24
60
46
54
60
48
35
17
18
1
7
—
—
1
1
2
1
1
—
—
The reactions were carried out in an autoclave under argon.
The autoclave was cooled to -15 ◦C and isobutene (5 ml,
57.5 mmol) was charged into the reactor, which contained the
catalyst (10 mmol of IL-1 or IL-2 or 1 g of the supported ionic
liquids SILP-1—SILP-7). The autoclave was pressurised with
argon (22 bar, room temperature). In a typical reaction, the
mixture was stirred at 100 ◦C for 5 h. The autoclave was cooled
to -15 ◦C, the organic phase was separated and analysed by gas
chromatography. The SILP catalysts were washed with pentane
(3 ¥ 5 ml), dried in vacuo and reused.
SILP-1 100
SILP-2 100
SILP-3 100
SILP-4 100
SILP-5 100
SILP-6 85
SILP-7 92
34
29
24
19
10
—
—
52.9 10.6
a Reaction conditions:100 ◦C, 5 h. b Determined by GC.
selectivity of oligomerisation in some cases (compare entries 1,
3, 4, 5 and 2, 6, 7). (It should be mentioned that silica gel itself
had no catalytic activity in this reaction.) The use of SILP-1,
SILP-2 or SILP-3 (entries 3–5) led to the C12 compounds as
the main products, instead of C8, obtained with good selectivity
in IL-1 (entry 1). On the contrary, in the presence of SILP-5
(entry 7), an increase in C8 selectivity was observed, compared
to the results obtained with IL-2 (entry 2). The temperature of
pre-treatment of the silica gel also seems to affect selectivity. A
shift toward lighter oligomers was observed with catalysts pre-
treated at higher temperature (C16 → C12 with supported IL-1,
entries 3–5 and C12 → C8 with supported IL-2, entries 6, 7).
The catalysts containing ionic liquids with hydrogensulfate
anion showed somewhat lower activity, but excellent selectivity
toward the dimers (entries 8, 9).
2.4. Physical measurements
1H- spectra were recorded on a BRUKER AVANCE 400
spectrometer in D2O. Elemental analyses were measured on a
1108 Carlo Erba apparatus. Water content was determined by
a Mettler DL35 Karl Fischer Titrator. The specific surface area
and pore size distribution in the micropore (0–2 nm), mesopore
(2–50 nm), and the macropore (50–300 nm) diameter ranges
were determined by nitrogen adsorption/desorption isotherms
measured with a Micromeritics ASAP 2000-type instrument on
samples previously out gassed overnight in a vacuum at the
temperature of 150 ◦C. The surface areas of the samples (SBET
)
were determined by the BET method from the corresponding
nitrogen adsorption isotherm.52 The meso- and macropore
volume values were calculated from the nitrogen desorption
isotherms using the BJH (Barret–Joyner–Halenda) theory.53 The
pore volume of pores have 1.7–300 nm in diameter range were
determined by mercury penetrance method using Carlo Erba
Porozimetro’70 device.
These results show that the selectivity of oligomerisation
is affected by several factors, such as the substituent on the
imidazolium cation, the nature of the anion and the pre-
treatment of the solid support.
BET surface area, pore volume and pore diameter of pre-
treated silica gels and SILP catalysts were measured (Table 3).
BET surface area of SILP catalysts obtained from IL-1 are
higher than those prepared from IL-2. A decrease in the BET
surface was observed with an increase in the temperature of
pre-treatment in both cases. The pore volume values showed a
similar tendency.
The above mentioned changes of selectivity using the same
ionic liquid (supported IL-1 or supported IL-2) but with
different pre-treatment temperature may be partly due to the
change in the BET surface area. At the same time, no detectable
difference in the selectivity of oligomerisation was observed
3. Results and discussion
Four Brønsted acidic ionic liquids (IL-1—IL-4) were prepared
and were immobilised on silica gel by adsorption to give catalysts
SILP-1—SILP-7 (Scheme 1, Table 1).
IL-1 and another ionic liquid with a longer side chain (1-(4-
sulfobutyl)-3-hexylimidazolium trifluoromethanesulfonate) had
been proved to be efficient oligomerisation catalysts by Deng et
al. before.46 They found, that isobutene oligomerisation could be
carried out with excellent selectivity toward C8 + C12 products.
Besides, the use of the ionic liquid with the longer side chain led
to an increase in the ratio of C12 products, probably due to the
higher solubility of C8 in this ionic liquid.
Our main goal was to test the efficiency of the immobilised
catalysts. Nevertheless, in order to compare the selectivity of
immobilised and non-immobilised ionic liquids, oligomerisation
was carried out first in IL-1 and IL-2 under our conditions
(100 ◦C, 5 h). Almost total conversion was obtained in both
cases and the ratio of C12 products was higher in IL-2 than in
IL-1, as it had been expected (Table 2, entries 1,2).
Table 3 BET surface area, pore volume and pore diameter of the SILP
catalysts
BET surface
area [m2 g-1]
Pore volume
[cm3 g-1]
Pore diameter
[nm]
Catalyst
SILP-1
SILP-2
SILP-3
SILP-4
SILP-5
SILP-6
SILP-7
261
238
233
224
195
269
188
0.41
0.38
0.38
0.33
0.31
0.43
0.29
6.1
6.3
6.4
5.9
6.3
6.2
6.0
All of the supported ionic liquid catalysts (SILP-1–SILP-
7) were found to be active (Table 2, entries 3–9). Interestingly,
immobilisation of the ionic liquids resulted in a change in the
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using SILP-6 and SILP-7 in spite of the difference in the BET
surface area values between the two catalysts.
The possibility of reusing the SILP catalysts was also in-
vestigated. SILP-1 (Fig. 1), SILP-2 (Fig. 2), SILP-3 (Fig. 3),
SILP-4 (Fig. 4) and SILP-5 (Fig. 5) were reused several times
without loss of activity or a remarkable change in selectivity.
At the same time, a considerable drop of activity was observed
even in the second run when either of the catalysts with ILs
with the hydrogensulfate anion (SILP-6 and SILP-7) were used
(Fig. 6).
Fig. 4 Oligomerisation of isobutene in the presence of SILP-4 (100 ◦C,
5 h).
Fig. 1 Oligomerisation of isobutene in the presence of SILP-1 (100 ◦C,
5 h).
Fig. 5 Oligomerisation of isobutene in the presence of SILP-5 (100 ◦C,
5 h).
Fig. 2 Oligomerisation of isobutene in the presence of SILP-2 (100 ◦C,
5 h).
Fig. 6 Oligomerisation of isobutene in the presence of (a) SILP-6 and
(b) SILP-7 (100 ◦C, 5 h).
Combined product mixtures of subsequent runs with catalysts
SILP-2 (eight runs) and SILP-7 (six runs) were evaporated and
the residues were examined by 1H NMR and were identified as
ionic liquids IL-1 and IL-4, respectively. Total catalyst leaching
of the eight runs was 2.0% of the original load in the case of
SILP-2 and 4.8% in the case of SILP-7. A higher rate of catalyst
leaching might be one of the factors that led to inactivation of
the catalysts with ILs with hydrogensulfate anion (SILP-6 and
SILP-7) upon reuse.
In the presence of ionic liquids immobilised on silica gel pre-
treated at 150 ◦C (SILP-1 and SILP-4), the main products were
the C12 oligomers, irrespective of the length of the alkyl chain
Fig. 3 Oligomerisation of isobutene in the presence of SILP-3 (100 ◦C,
5 h).
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of the imidazolium cation (Fig. 1 and 4). At the same time,
considering the minor components, the use of SILP-1 led to C16
oligomers in yields comparable to those of C12 products, while
with SILP-4 C8 compounds prevailed over C16 oligomers.
This difference was even more apparent when the ionic liquids
were immobilised on silica gel pre-treated at 250 ◦C (SILP-2
and SILP-5). SILP-2 showed good selectivity toward C12 + C16
products, resulting in oligomeric mixtures with C12 as the main
components (Fig. 2). On the contrary, in the presence of SILP-5,
dimers were obtained in yields higher than 50% and the ratio of
C16 products was only around 10% (Fig. 5).
Only a small difference in the composition of reaction
mixtures, produced with SILP-2 and SILP-3 catalysts (obtained
with silica gel pre-treatment at 250 ◦C and 450 ◦C, respectively),
was observed.
Fig. 8 Oligomerisation of isobutene in the presence of SILP-5
(100 ◦C).
Although immobilisation of ionic liquids slightly affects the
selectivity of oligomerisation, these catalysts can efficiently be
used and recycled in this reaction. By the proper choice of the
catalyst, either C8 + C12 or C12 + C16 products can be obtained
with good selectivity.
The turnover numbers and frequencies of the SILP catalysts
are ten times higher than those of the ILs (see Table 2). When
using the SILP catalysts, a smaller amount of the relatively
expensive ionic liquid was sufficient for the reaction. Due to
the high viscosity of the ionic liquids, the mass transport into
the ionic liquid phase can be rate limiting. By dispersing the
ILs on support materials this drawback can be circumvented.
Furthermore, the solid catalysts are easier to handle than the
ionic liquids themselves, so separation and recovery of even small
amounts of catalyst are simple.
The effect of the reaction conditions on the outcome of the
oligomerisation was explored with supported catalysts prepared
from IL-1 and IL-2. The use of SILP-2 (Fig. 7) resulted in total
conversion of isobutene even after 1 h (TOF: 57.5 h-1). With
SILP-5 (Fig. 8), conversion was above 98% after 1 h (TOF: 28.1
h-1) and reached 100% after 5 h. With the increase in the reaction
time, a slight change in selectivity toward heavier oligomers was
observed in both cases.
Fig. 9 Oligomerisation of isobutene in the presence of SILP-2 at
different temperatures (average values of three subsequent runs at the
given temperature, reaction time: 5 h).
Fig. 10 Oligomerisation of isobutene in the presence of SILP-4 at
different temperatures (average values of three subsequent runs at the
given temperature, reaction time: 5 h).
Fig. 7 Oligomerisation of isobutene in the presence of SILP-2 (100 ◦C).
obtained with each catalyst at 100 ◦C, but with the exception of
the use of SILP-2, conversions were above 90% even at 60 C.
◦
The effect of the change of the reaction temperature was
also investigated using three of the supported ionic liquid
catalysts (SILP-2 (Fig. 9), SILP-4 (Fig. 10) and SILP-5 (Fig.
11). The data depicted in the figures are average values of three
subsequent runs at the given temperature). Total conversion was
At 60 ◦C, very good selectivity toward C8 products was obtained
in each case. With an increase in the temperature, an increase of
the ratios of higher oligomers was observed. The best selectivity
for C8 and C12 products can be reached by using SILP-5 at 60 ◦C
and SILP-2 at 100 ◦C, respectively.
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6 K. Hauge, E. Bergene, D. Chen, G. R. Fredriksen and A. Holmen,
Catal. Today, 2005, 100, 463.
7 (a) M. Di Girolamo and M. Marchionna, J. Mol. Catal. A: Chem.,
2001, 177, 33; (b) R. Alca´ntara, E. Alcantara, L. Canoira, M. J.
Franco, M. Herrera and A. Navarro, React. Funct. Polym., 2000, 45,
19.
8 F. J. Tzompantzi, M. E. Manr´ıquez, J. M. Padilla, G. D. Angel, R.
Go´mez and A. Mantilla, Catal. Today, 2008, 133, 154.
9 A. Mantilla, G. Ferrat, A. Lo´pez-Ortega, E. Romero, F. Tzompantzi,
M. Torres, E. Ort´ız-Islas and R. Go´mez, J. Mol. Catal. A: Chem.,
2005, 228, 333.
10 B. Chiche, E. Sauvage, F. D. Renzo, I. I. Ivanova and F. Fajula, J.
Mol. Catal. A: Chem., 1998, 134, 145.
11 M. Golombok and J. D. Bruijn, Appl. Catal., A, 2001, 208, 47.
12 J. W. Yoon, J. H. Lee, J. S. Chang, D. H. Choo, S. J. Lee and S. H.
Jhung, Catal. Commun., 2007, 8, 967.
13 M. Bjørgen, K. P. Lillerud, U. Olsbye, S. Bordiga and A. Zecchina,
J. Phys. Chem. B, 2004, 108, 7862.
Fig. 11 Oligomerisation of isobutene in the presence of SILP-5 at
different temperatures (average values of three subsequent runs at the
given temperature, reaction time: 5 h).
14 J. W. Yoon, J. S. Chang, H. D. Lee, T. J. Kim and S. H. Jhung, J.
Catal., 2007, 245, 253.
15 L. M. T. Ngandjui and F. C. Thyrion, Ind. Eng. Chem. Res., 1996, 35,
1269.
Conclusions
16 J. A. Martens, R. Ravishankar, I. E. Mishin and P. A. Jacobs, Angew.
Chem., Int. Ed., 2000, 39, 4376.
Supported Brønsted acidic ionic liquids were proved to be
efficient catalysts in isobutene ologomerisaton. The use of the
solid phase catalysts ensures easy separation and recycling. The
catalysts comprising the trifluoromethanesulfonate anion could
be reused several times without loss of activity.
The selectivity of oligomerisation is influenced by various fac-
tors, such as the length of the N-alkyl chain of the imidazolium
cation, the nature of the anion, the pre-treatment of the support
and the reaction temperature. Best C8 selectivity was achieved
with imidazolium hydrogensulfate type catalysts (SILP-5 and
SILP-6), but a great drop of activity was observed upon reuse.
Excellent C8 selectivity (87%) was obtained with SILP-5 at
60 ◦C, while the use of SILP-2 resulted in good C12+ selectivity
(above 84%) at 100 ◦C.
17 J. W. Yoon, S. H. Jhung, D. H. Choo, S. J. Lee, K. Y. Lee and J. S.
Chang, Appl. Catal., A, 2008, 337, 73.
18 J. P. G. Pater, P. A. Jacobs and J. A. Martens, J. Catal., 1999, 184,
262.
19 J. W. Yoon, J. S. Lee, S. H. Jhung, K. Y. Lee and J. S. Chang, J. Porous
Mater., 2009, 16, 631.
20 B. Nkosi, F. T. T. Ng and G. L. Rempel, Appl. Catal., A, 1997, 161,
153.
21 A. Bru¨ckner, U. Bentrup, H. Zanthoff and D. Maschmeyer, J. Catal.,
2009, 266, 120.
22 X. Zhang, J. Zhong, J. Wang, L. Zhang, J. Gao and A. Liu, Fuel
Process. Technol., 2009, 90, 863.
23 J. K. Jeon, S. K. Park and Y. K. Park, Catal. Today, 2004, 93–95,
467.
24 G. G. Podrebarac, F. T. T. Ng and G. L. Rempel, Appl. Catal., A,
1996, 147, 159.
25 G. Chen, J. Li, X. Yang and Y. Wu, Appl. Catal., A, 2006, 310, 16.
26 J. Zhang, R. Ohnishi, T. Okuhara and Y. Kamiya, Appl. Catal., A,
2009, 353, 68.
These results clearly show that this type of supported catalyst
can be applied flexibly to follow the changing demands of fuel
production.
27 G. Chen, J. Li, X. Yang and Y. Wu, Appl. Catal., A, 2006, 310, 16.
28 J. S. Lee, J. W. Yoon, S. B. Halligudi, J. S. Chang and S. H. Jhung,
Appl. Catal., A, 2009, 366, 299.
29 F. Tzompantzi, A. Mantilla, G. Del Angel, J. M. Padilla, J. L.
Ferna´ndez, J. A. I. D´ıaz-Go´ngora and R Go´mez, Catal. Today, 2009,
143, 132.
30 G. A. Foulds, A. M. A. Bennet, M. L. Niven, D. A. Thornton, K.
J. Cavell, S. Desjardins and E. J. Peacock, J. Mol. Catal., 1994, 87,
117.
Acknowledgements
The authors thank TAMOP-4.2.1/B-09/1/KONV-2010-0003
(Mobility and Environment: Research in the fields of motor
vehicle industry, energetics and environment in the Central- and
Western-Transdanubian Regions of Hungary) for the financial
support. The Project is supported by the European Union and
co-financed by the European Social Fund. The help of G.
Ne´meth (Univ. of Pannonia, Research Inst. of Bioengineering,
Membrane Technology and Energetics) in determination of
water content of ILs and J. Kova´cs (Inst. of Environmental
Eng.) in measurement of physical properties of SILPs is kindly
acknowledged.
31 K. Nomura, M. Ishino, M. Hazama and G. Suzukamo, J. Mol. Catal.
A: Chem., 1997, 126, L93.
32 F. A. Nasirov, F. M. Novruzova, A. M. Aslanbeili and A. G. Azizov,
Pet. Chem., 2007, 47, 309.
33 (a) Y. Chauvin, S. Einloft and H. Olivier, Ind. Eng. Chem. Res., 1995,
34, 1149; (b) Y. Chauvin, H. Olivier, C. N. Wyrvalski, L. C. Simon
and R. F. de Souza, J. Catal., 1997, 165, 275; (c) V. Lecoq and H.
Olivier-Bourbigou, FR2835447 A1, 2003 (IFP).
34 (a) L. C. Simon, J. Dupont and F. R. dDe Souza, Appl. Catal., A,
1998, 175, 215; (b) R. F. de Souza, D. Thiele and A. L. Monteiro,
J. Catal., 2006, 241, 232; (c) D. Thiele and R. F. de Souza, J. Mol.
Catal. A: Chem., 2007, 264, 293.
35 (a) B. Ellis, W. Keim and P. Wasserscheid, Chem. Commun., 1999,
337; (b) P. Wasserscheid and M. Eichmann, Catal. Today, 2001, 66,
309; (c) M. Eichmann, W. Keim, M. Haumann, B. U. Melcher and
P. Wassserscheid, J. Mol. Catal. A: Chem., 2009, 314, 42.
36 K. M. Song, H. Y. Gao, F. S. Liu, J. Pan, L. H. Guo, S. B. Zai and
Q. Wu, Catal. Lett., 2009, 131, 566.
37 P. Wasserscheid, C. Hilgers and W. Keim, J. Mol. Catal. A: Chem.,
2004, 214, 83.
38 H. Olivier, J. Mol. Catal. A: Chem., 1999, 146, 285.
39 A. H. Azizov, R. V. Aliyeva, E. S. Kalbaliyeva and M. J. Ibrahimova,
Appl. Catal., A, 2010, 375, 70.
Notes and references
1 G. A. Olah, A. Molna´r, Hydrocarbon Chemistry (2nd edition). John
Wiley & Sons, Inc., Hoboken, New Jersey, 2003, pp. 723.
2 J. H. Coetzee, T. A. Mashap, N. M. Prinsloo and J. D. Rademan,
Appl. Catal., A, 2006, 308, 204.
3 S. H. Jhung and J. S. Chang, Catal. Surv. Asia, 2009, 13, 229.
4 M. L. Honkela, A. Root, M. Lindblad and A O. I. Krause, Appl.
Catal., A, 2005, 295, 216.
5 J. W. Yoon, S. H. Jhung and J. S. Chang, Bull. Korean Chem. Soc.,
2008, 29, 339.
408 | Green Chem., 2012, 14, 403–409
This journal is
The Royal Society of Chemistry 2012
©

View Online
40 A. K. Abdul-Sada, P. W. Ambler, P. K. G. Hodgson, K. R. Seddon
and N. J. Stewart, WO9521871, 1995 (BP Chemicals Ltd).
41 O. Stenzel, R. Bru¨ll, U. M. Wahner, R. D. Sanderson and H. R.
Raubenheimer, J. Mol. Catal. A: Chem., 2003, 192, 217.
42 (a) D. R. Johnson, T. V. Harris and M. S. Driver, US20050245778 A1,
2005 (Chevron USA Inc); (b) E. Saleh and K. Russell, US 2007142691
A1 (Chevron USA Inc).
43 M. J. Ibragimova, F. I. Samedova, R. Z. Gasanova, N. G. Azmame-
dov and E. Z. Eivazov, Pet. Chem., 2007, 47, 64.
44 S. Yang, Z. Liu, X. Meng and C. Xu, Energy Fuels, 2009, 23,
70.
47 H. Olivier-Bourbigou, L. Magna and D. Morvan, Appl. Catal., A,
2010, 373, 1.
48 A. Riisager, R. Fehrmann, M. Haumann and P. Wasserscheid, Top.
Catal., 2006, 40, 91.
49 K. Funabiki, T. Komeda, Y. Kubota and M. Matsui, Tetrahedron,
2009, 65, 7457.
50 T. L. T. Bui, W. Korth, S. Aschauer and A. Jess, Green Chem., 2009,
11, 1961.
51 M. K. Munshi, S. T. Lomate, R. M. Deshpande, V. H. Rane and A.
A. Kelkar, J. Chem. Technol. Biotechnol., 2010, 85, 1319.
52 S. Brunauer, P. H. Emmett and E. Teller, J. Am. Chem. Soc., 1938,
60, 309.
45 Z. L. Shen, X. J. He, B. X. Hu, N. Sun and W. M. Mo, Catal. Lett.,
2008, 122, 359–365.
53 P. Barrett, L. G. Joyner and P. P. Halenda, J. Am. Chem. Soc., 1951,
73, 373.
46 Y. Gu, F. Shi and Y. Deng, Catal. Commun., 2003, 4, 579.
This journal is
The Royal Society of Chemistry 2012
Green Chem., 2012, 14, 403–409 | 409
©