Very stable and highly regioselective supported ionic-liquid-phase (SILP) catalysis: Continuous-flow fixed-bed hydroformylation of propene

Article abstract of DOI:10.1002/anie.200461534

The advantages of heterogeneous catalysis and transition-metal catalysis in ionic liquids are combined in rhodium bisphosphine catalysts in an ionic-liquid phase on a silica support. These active, regioselective, and highly stable catalysts were applied in a fixed-bed reactor for the continuous-flow gas-phase hydroformylation of propene.

Full text of DOI:10.1002/anie.200461534

Angewandte
Chemie
Catalyst Development
Very Stable and Highly Regioselective Supported
Ionic-Liquid-Phase (SILP) Catalysis: Continuous-
Flow Fixed-Bed Hydroformylation of Propene**
Anders Riisager,* Rasmus Fehrmann, Stephan Flicker,
Roy van Hal, Marco Haumann, and Peter Wasserscheid*
[
1]
In the last decade the application of ionic liquids in catalysis
has been the subject of intensive research in academia and
[
2]
industry. A major reason for the growing interest is the use
[
3]
of ionic liquids as alternative solvents for many transition-
metal-catalyzed reactions. In particular, liquid–liquid biphasic
processes having an organic product phase have been
examined since the ionic catalyst phase often induces
excellent catalyst immobilization and also has low miscibility
with the organic reaction products. However, implementation
of these strategies in industrial processes is still hampered by
the fact that the biphasic methodologies rely on relatively
large amounts of ionic liquids. Even though ionic liquids have
[
4]
become commercially available they are still relatively
expensive compared to traditional solvents.
In many cases, liquid–liquid biphasic catalysis makes use
of only a fraction of the ionic-liquid solvent and of the catalyst
dissolved therein. In the case of a fast chemical reaction and
relatively slow mass transfer (caused by the relatively high
viscosity of the ionic liquid) the concentration of the reactant
in the bulk ionic-liquid phase is reduced significantly, and the
reaction occurs primarily at the interphase or in the diffusion
layer of the ionic-liquid catalyst phase rather than in the bulk
solvent. An ideal catalyst system would thus consist of a bulk
catalyst phase the same size as the diffusion layer. In this way
the solubilized catalyst complex and the ionic liquid are all
available. In addition, application of solid catalysts is pre-
[*] Dr. A. Riisager, Prof. R. Fehrmann, Dr. S. Flicker
Department of Chemistry and
Interdisciplinary Research Center for Catalysis (ICAT)
Technical University of Denmark
Building 207, 2800 Kgs. Lyngby (Denmark)
Fax: (+45)4525-2235
E-mail: ar@kemi.dtu.dk
Dipl.-Chem. R. van Hal, Dr. M. Haumann, Prof. P. Wasserscheid
Lehrstuhl fꢀr Chemische Reaktionstechnik
Universitꢁt Erlangen-Nꢀrnberg
Egerlandstrasse 3, 91058 Erlangen (Germany)
Fax: (+49)9131-852-7421
E-mail: wasserscheid@crt.cbi.uni-erlangen.de
[
**] This work was supported by the ConNeCat project “Smart ligands—
smart solvents” financed by the German Federal Ministry for
Education and Research (BMBF). Financial support (M.H.) by the
Deutsche Forschungsgemeinschaft (DFG) and by The Foundation
of Technical Chemistry, Technical University of Denmark (FTIR
equipment) are gratefully acknowledged. The authors thank Dr. A.
Kustov (Department of Chemistry, Technical University of Denmark)
and Prof. O. B. Lapina (Boreskov Institute of Catalysis, Novosibirsk,
Russia) for their contributions to this work.
Supporting information for this article is available on the WWW
under http://www.angewandte.org or from the author.
Angew. Chem. Int. Ed. 2005, 44, 815 –819
DOI: 10.1002/anie.200461534
ꢀ 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
815

Communications
ferred from a technical standpoint due to easy product
n-C H OSO )). These ionic catalyst solutions were physi-
8 17 3
separation and the potential for developing a continuous-flow
fixed-bed process.
sorbed on the unmodified silica support. However, these
systems were also deactivated after prolonged use (reaction
time > 24 h) regardless of the type of ionic liquid, the loading
a (defined as the volume of the ionic liquid divided by the
pore volume,) and the ligand/rhodium ratio.
Recently we and others introduced “heterogenized”
versions of homogeneous ionic-liquid catalyst systems, de-
scribed as supported ionic-liquid-phase (SILP) catalyst sys-
[
5–7]
[13]
tems, for olefin hydroformylation
(Rh-catalyzed), hydro-
Very recently, Han et al. demonstrated an interesting
[
8]
[9]
genation (Rh-catalyzed), Heck reactions (Pd-catalyzed),
variation of the SILP concept. They immobilized Pd nano-
particles with a lactate-based ionic liquid on molecular sieves
and used the resulting systems for the liquid-phase hydro-
genation of cyclohexene and 1-hexene.
[
10]
and hydroamination (Rh-, Pd-, and Zn-catalyzed). In these
systems the catalysts are composed of a transition-metal
complex dissolved in a thin film of the ionic liquid, which is
held on a porous solid with high surface area by physisorption,
tethering, or covalent anchoring. The SILP catalyst concept
results in a very efficient use of the ionic liquid and relatively
short diffusion distances for the reactants compared to those
in conventional two-phase systems with an ionic-liquid
catalyst phase. In addition, the negligible vapor pressure,
large liquid range, and thermal stability of ionic liquids ensure
that the solvent is retained on the support in its fluid state
even at elevated temperatures; this makes SILP catalysts
highly suitable for continuous processes. Moreover, the
solvent properties of the ionic liquid are tuneable by the
choice of the cation/anion combination. Further advantages
of the SILP concept are, for example, compatibility with
hydrolytically labile catalyst complexes and possible catalyst
In this communication we demonstrate the first use of a
SILP catalyst system in which the catalyst remains active,
highly selective, and stable over extended periods in a
continuous gas-phase process. The catalysts are composed of
Rh-1 in [bmim][n-C H OSO ] on a partly dehydroxylated
8
17
3
silica support (hereafter referred to as Rh-1/IL/SiO ). More-
2
over, we propose an explanation for the deactivation phe-
nomena previously observed with analogous nondehydroxyl-
ated SILP silica catalysts. Our proposal is based on FTIR
studies of the catalyst conducted in situ (syngas atmosphere at
elevated temperature), as well as characterization of the
3
1
support by MAS P NMR spectroscopy and temperature-
programmed desorption of ammonia (NH -TPD).
3
In our previous studies of silica-based Rh-1 SILP catalysts
[
11]
activation by interaction with the ionic liquid.
In rhodium-catalyzed olefin hydroformylation, Mehnert
on nondehydroxylated supports in the continuous-flow
[
6]
hydroformylation of propene (reaction times of 4–5 h), we
found that the catalyst performance was strongly influenced
by the ligand/rhodium ratio and the loading of the ionic
liquid, but less affected by the choice of ionic liquid (except
for the catalyst preformation, which appears to depend on the
solubility of the ligand and precursor). High selectivities
(n/iso > 20) were obtained only for Rh-1/IL/SiO2 catalyst
systems with an L/Rh ratio of more than 10; this is in contrast
to analogous reactions performed with an ionic-liquid catalyst
solution without a support where high selectivities were
[
7]
et al. examined the liquid-phase reaction of 1-hexene in a
batch reactor using unselective (n/iso ratios of 0.4–2.4) SILP
catalyst systems. The catalysts were composed of mono-
phosphines (PPh and TPPTS) dissolved in [bmim]X (bmim =
3
1
-n-butyl-3-methylimidazolium, X = PF or BF ) on a 1-n-
6 4
butyl-3-[3-(triethoxysilanyl)propyl]imidazolium-modified
silica gel support (average of 0.4 imidazolium fragments per
2
nm , corresponding to the involvement of approximately
3
5% of the silanol groups of the support). The SILP catalysts
[
14]
were found to have higher activity than analogous biphasic
systems; however, a significant amount of the metal catalyst
leached into the product phase at high conversions (rhodium
loss of up to 2.1 mol%), due to depletion of the ionic-liquid
phase from the support. Importantly, even at lower conver-
sion pronounced catalyst deactivation was observed during
recycling, which was independent of the presilylation of the
observed even at 1/Rh ratios of 2.
The results clearly
indicate a significant effect of the inorganic support. Accord-
ingly, we devised a suitable preparation for the support
(catalysts with an untreated support were not stable beyond
12–24 h).
In our continuous-flow gas-phase hydroformylation of
propene with a reaction time of 60 h, we applied a partially
dehydroxylated silica support (heating at 5008C in air for
[
12]
support.
This deactiviation shortened the lifetime and
[
6]
limited the applicability of the catalysts significantly.
15 h). In the earlier work support pretreatment implied only
drying the support in vacuo (1108C, 24 h). The thermal
pretreatment proved to be a crucial parameter for obtaining
Rh-1 silica-based catalysts with high stability during pro-
longed reactions (Figure 1).
Recently we have described a selective (n/iso ratios up to
2
3.7, that is, 96.0% linearity) SILP catalyst for the Rh-
catalyzed gas-phase hydroformylation of propene in a fixed-
[
6]
bed reactor. The rhodium catalyst contains the bisphosphine
ligand sulfoxantphos 1 and is dissolved in either a halogen-
The catalytic performance and catalyst stability, however,
still proved to be significantly influenced by the catalyst
composition, (loading a and 1/Rh ratio; Figures 2 and 3). In
reactions with catalysts having various 1/Rh ratios we found
that catalysts with low ligand contents (1/Rh = 3 and 5) were
initially very active compared to the catalyst with 1/Rh = 10
but less selective (Figure 2). In addition, the catalysts with low
ligand content were deactivated relatively quickly within the
containing or halogen-free ionic liquid ([bmim]X (X = PF or
6
À1
first 24 h; the turnover frequency (TOF) dropped to 4–5 h ,
and the selectivity fell to n/iso = 1–1.3). In contrast, the
816
ꢀ 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
Angew. Chem. Int. Ed. 2005, 44, 815 –819

Angewandte
Chemie
catalyst with 1/Rh = 10 retained the initial catalytic perform-
À1
ance over at least 60 h (TOF = 44 h , TON ꢀ 2600, n/iso >
2
0).
These results clearly indicate that a large excess of ligand
is required for a stable SILP catalytic system. Even when the
support is pretreated, reactions presumably occur between
the ligand and the support, rendering some of the ligand
inaccessible for complex formation. Evidence for the inter-
action of the ligand and the support was provided by solid-
3
1
state MAS P NMR spectra of Rh-1/IL/SiO2 (1/Rh = 10)
recorded prior to reaction (see the Supporting Information).
Here, the signals measured could be assigned to free ligand
(
5
d = À13 ppm, 27%), surface-bonded ligand (d = À21 ppm,
Figure 1. Hydroformylation of propene on untreated (~, ~) and partly
4%), and complexed ligand (d = 31 ppm, 19%).
dehydroxylated supports (*,*). Plots of activity (mol butanal
À1 À1
Moreover, in studies with catalysts having different
(
mol Rh)
h , closed symbols) and selectivity (n/isobutanal, open
loadings of the ionic liquid (a = 0–0.5), the catalyst systems
containing no ionic liquid were deactivated rapidly; after a
reaction time of 60 h only 30% of the initial activity and
selectivity remained (Figure 3). The slow deactivation of the
other catalysts can be explained by the slow surface diffusion
of the ligand from the initial Rh-coordinated active state to
the surface-bonded state, in which the metal atom is less
coordinated to the ligand but possibly more strongly coordi-
nated to the support and thus less active and selective.
Evidently the SILP catalysts require a certain amount of
ionic-liquid solvent—not only for high selectivities (n/iso >
symbols) of Rh-1/[bmim][n-C H OSO ] on silica (a=0.1, 1/Rh=10)
as function of reaction time.
8
17
3
2
0) as previously seen—but also for stability over longer
periods during continuous processes. Further, since the n/iso
selectivity in hydroformylation reactions is known to depend
[
15]
on the amount of ligand available for coordination, the
simultaneous decrease in selectivity along with activity lends
additional support to the hypothesis that deactivation is
closely related to a gradual degradation and removal of ligand
from the catalyst complex system.
To further explain the observed results, we studied the
catalyst in situ under conditions closely related to the reaction
conditions by FTIR spectroscopy (Figure 4). The FTIR
Figure 2. Hydroformylation of propene with catalysts having different
À1 À1
amounts of ligand. Plots of activity (mol butanal (mol Rh)
h ,
closed symbols) and selectivity (n/isobutanal, open symbols) of
Rh-1/[bmim][n-C H OSO ] on silica (a=0.1). Results for catalysts
8
17
3
with 1/Rh=3 (^, ^), 1/Rh=5 (~, ~), and 1/Rh=10 (*, *) are
shown.
spectra of the system Rh-1/IL/SiO (1/Rh = 10; 1008C) show
2
the relatively fast transformation of the red dimeric catalyst
[
16]
precursor [{Rh(m-CO)(1)(CO)} ] (2) —characterized by a
2
broad band for the terminal CO stretch at n˜ (CO) =
À1
1
990 cm —to the light-yellow monomeric compound
Figure 3. Hydroformylation of propene with catalysts having different
À1 À1
loadings a. Plots of activity (mol butanal (mol Rh)
h , closed sym-
bols) and selectivity (n/isobutanal, open symbols) of Rh-1/[bmim][n-
C H OSO ] on silica (1/Rh=10). Results for catalysts with a=0 (^,
Figure 4. Part of an FTIR spectra of Rh-1/IL/SiO catalysts (1/Rh=10,
a=0.5) at 1008C after: a) 15 min in nitrogen, b) 15 min in syngas, and
2
8
17
3
^) and a=0.1 (*, *) are shown.
c) 30 min in syngas.
Angew. Chem. Int. Ed. 2005, 44, 815 –819
www.angewandte.org
ꢀ 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
817

Communications
[
HRh(CO) (1)] (Scheme 1), which has two isomeric forms, 3-
2
À1
ea ( n˜ (CO) = 1994, 1948 cm ) and 3-ee ( n˜ (CO) = 2035 (w),
1
À1
964 cm ) coexisting in dynamic equilibrium. Reexposure of
the 3-ea/3-ee mixture to nitrogen slowly regenerates the
dimer 2 reversibly, while air treatment leads to irreversible
degradation of the complex and presumably to the oxidation
of excess ligand. This is supported by a significant change in
the color of the sample along with the appearance of a new
À1
broad CO band at n˜ (CO) = 1972 cm .
Importantly, the complex formation in the SILP Rh-1/IL/
SiO catalysts with 1/Rh = 10 (Scheme 1) is very similar to
2
that previously reported for Rh-1 and analogous rhodium–
[
16]
xanthene-based systems in organic and ionic-liquid solvents
Table 1). Thus, it seems reasonable to conclude that complex
Figure 5. Part of an FTIR spectra of Rh-1/IL/SiO catalysts (a=0.1,
1008C, after 15 min in syngas) containing different ligand/Rh ratios:
a) 1/Rh=10, b) 1/Rh=5, and c) 1/Rh=3.
2
(
formation in the SILP catalyst systems takes place in the
sponds to 26% of the original content present in the
untreated support (see the Supporting Information
for details). This is in relatively good agreement with
the remaining fraction of 35% Si-OH groups (Q3,
d ꢀ À100 ppm) relative to Si-O-Si groups (Q4, d ꢀ
2
9
À111 ppm) determined by solid-state MAS Si NMR
spectroscopy for analogous samples (see the Sup-
porting Information). Therefore, it seems reasonable
to assume that the pretreatment decreases the
amount of acidic OH groups on the support only by
dehydroxylation of surface silanol groups and not by, for
example, inducing structural changes in the support. This is
further affirmed by the identical Tmax values obtained for
ammonia desorption and by the practically unchanged BET
surface area and pore volume after dehydroxylation.
Scheme 1. Formation of Rh complexes in the Rh-1/IL/SiO catalyst systems (1/Rh=10) at
2
1
008C during various gas treatments.
Table 1: Comparison of n˜ (CO) bands of [HRh(CO) (L)] complexes in
2
different systems.
Solvent
ea isomer
n˜ (CO) [cm
ee isomer
n˜ (CO) [cm ]
À1
À1
]
SILP (Rh-1/IL/SiO2)
[bmim][n-
1994, 1948
2035, 1964
The amount of ligand 1 present in the Rh-1/IL/SiO2
C H OSO ]
8
17
3
[
16b]
[
[
[
RhH(CO) (1)]
[bmim][PF6] 1985, 1935
benzene 1991, 1941
cyclohexane 1999, 1953
2032, 1967
2036, 1969
2040, 1977
system during catalysis was determined for L/Rh = 3 to be
2
[
16b]
[
À1
À1
RhH(CO) (xantphos)]
58 mmol1g ; for L/Rh = 5, 97 mmol1g support; and for L/
2
16b]
RhH(CO) (thixantphos)]
À1
2
Rh = 10, 194 mmol1g support. These values can be corre-
lated to the measured OH content of the support, by assuming
that the ligand bonds irreversibly to one acidic OH group on
the surface of the support. Hence, very little ligand should be
available for complex formation in the case of a catalyst with
L/Rh = 3, 30% of the ligand should still be available with L/
Rh = 5 (i.e. effective 1/Rh ratio = 1.5), and 65% of the ligand
should still be available with L/Rh ratio = 10 (effective 1/Rh =
6.5). Consequently, highly selective and stable catalyst
systems can be obtained only when the amount of ligand is
sufficient to compensate for the loss induced by the surface
bonding, that is, when the effective 1/Rh ratio is greater than
1. This is in excellent agreement with the experimental data,
thus underlining the importance of the acidic OH groups of
the support for the long-term stability of SILP Rh–phosphine
catalysts.
ionic-liquid solvent, and consequently that the examined
SILP hydroformylation reactions are indeed homogeneously
catalyzed.
The FTIR spectra of the analogous catalysts with 1/Rh = 3
and 5 show that degraded catalysts formed irreversibly
regardless of the gas treatment. The decrease in the intensity
of the two characteristic absorption bands was more pro-
nounced for catalysts with 1/Rh = 3 than for catalysts having
1/Rh = 5 (Figure 5). For catalysts with 1/Rh = 10 no loss in
intensity was observed. This clearly suggests that catalysts
with 1/Rh = 10 contain a sufficient amount of ligand to
stabilize the monomeric, catalytically active monomers. Since
this is in excellent accordance with the relative catalyst
stabilities measured, the stability of the SILP catalyst is
directly related to the degradation of the catalytically active
complex, which in turn is correlated to the amount of ligand
available for complex formation.
This paper describes important progress in the very
promising field of SILP catalysis. We demonstrate for the
first time the long-term stability of Rh-1/[bmim][n-
C H OSO ] catalysts supported on partly dehydroxylated
8
17
3
silica in the selective, continuous, gas-phase hydroformylation
of propene. Clear spectroscopic evidence also indicates that
the catalysis in the supported ionic-liquid layer is homoge-
neous. Moreover, decreasing the number of surface silanol
The proportion of acidic OH groups (mostly Brønsted
sites) on the partly dehydroxylated silica support used was
À1
evaluated by NH -TPD to be 69 mmolOHg , which corre-
3
818
ꢀ 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
Angew. Chem. Int. Ed. 2005, 44, 815 –819

Angewandte
Chemie
groups on the support material by thermal treatment is a
crucial parameter in the preparation of stable hydroformyla-
tion systems that are selective and active for at least 60 h on
stream.
[
1] List of reviews: a) J. D. Holbrey, K. R. Seddon, Clean Prod.
Proc. 1999, 1, 223 – 236; b) T. Welton, Chem. Rev. 1999, 99,
2071 – 2083; c) P. Wasserscheid, W. Keim, Angew. Chem. 2000,
112, 3926 – 3946; Angew. Chem. Int. Ed. 2000, 39, 3772 – 3789;
We have found that the effect of the support is directly
related to the irreversible reaction of the ligand with the
acidic silanol surface groups before and during catalysis.
Therefore, the prerequisites for active, highly selective, and
long-term stable SILP catalysts are not only the ionic-liquid
solvent but also a relatively large excess of phosphine ligand
to compensate for some detrimental surface reactions.
We hope that the knowledge gained in this work will lead
to the development of new SILP catalysts for hydroformyla-
tions, hydrogenations, and CÀC coupling reactions. The
d) J. Dupont, C. S. Consorti, J. Spencer, J. Braz. Chem. Soc. 2000,
11, 337 – 344; e) R. Sheldon, Chem. Commun. 2001, 2399 – 2407;
f) C. M. Gordon, Appl. Catal. A 2001, 222, 101 – 117; g) D. Zhao,
M. Wu, Y. Kou, E. Min, Catal. Today 2002, 74, 157 – 189; h) H.
Olivier-Bourbigou, L. Magna, J. Mol. Catal. A: Chem. 2002, 182/
183, 419 – 437; i) J. Dupont, R. F. de Souza, P. A. Z. Suarez,
Chem. Rev. 2002, 102, 3667 – 3692; j) H. Zhao, S. V. Malhotra,
Aldrichimica Acta 2002, 35, 75 – 83.
[2] R. D. Rogers, K. R. Seddon, Science 2003, 302, 792 – 793, and
references therein.
[
3] a) Ionic Liquids in Synthesis, 1st ed. (Eds.: P. Wasserscheid, T.
Welton), VCH-Wiley, Weinheim, 2003; b) J. S. Wilkes, J. Mol.
Catal. A: Chem. 2004, 214, 11 – 17.
combination of well-defined catalyst complexes, nonvolatile
ionic liquids, and porous solid supports offers many advan-
tages over traditional catalysis with water (SAPC) or with
organic solvents with low vapor pressure (SLPC) on sup-
[
4] Selection of ionic liquid suppliers: a) Solvent Innovation
(
www.solvent-innovation.com); b) Sigma-Aldrich (www.sigma-
aldrich.com); Fluka (www.fluka.com); c) Merck (www.merck.-
com); d) Acros Organics (www.acros.com); e) Wako
(www.wako-chem.co.jp); f) Strem (www.strem.com).
[
17]
[18]
ports, which are clearly limited by solvent volatility. We
therefore consider the SILP catalysis concept to be a
significant contribution to the development of highly selec-
tive, heterogenized homogeneous catalysts.
[
5] A. Riisager, K. M. Eriksen, P. Wasserscheid, R. Fehrmann, Catal.
Lett. 2003, 90, 149 – 153.
[
6] a) A. Riisager, P. Wasserscheid, R. van Hal, R. Fehrmann, J.
Catal. 2003, 219, 252 – 255; b) A. Riisager, R. Fehrmann, P.
Wasserscheid, R. van Hal in Ionic Liquids III: Fundamentals,
Progress, Challenges, and Opportunities (Eds.: R. Rogers, K. R.
Seddon), ACS, Washington DC, 2004, in press.
Experimental Section
The SILP catalysts were prepared according to our previously
[
6]
reported method by impregnation of the partly dehydroxylated
silica support with an anhydrous methanolic solution of the ionic
[
7] C. P. Mehnert, R. A. Cook, N. C. Dispenziere, M. Afeworki, J.
Am. Chem. Soc. 2002, 124, 12932 – 12933.
[
19]
liquid [bmim][n-C H OSO ]
[
containing the catalyst precursor
8
17
3
[
20]
Rh(acac)(CO)2] (Aldrich, 98%) and bisphosphine ligand 1
[8] a) C. P. Mehnert, E. J. Mozeleski, R. A. Cook, Chem. Commun.
002, 3010 – 3011; b) A. Wolfson, I. F. J. Vankelecom, P. A.
under argon atmosphere using standard Schlenk techniques. The
partial dehydroxylation of the support (silica gel 100, Merck) was
performed by heating at 5008C in air for 15 h followed by storage in
2
Jacobs, Tetrahedron Lett. 2003, 44, 1195 – 1198.
9] H. Hagiwara, Y. Sugawara, K. Isobe, T. Hoshi, T. Suzuki, Org.
Lett. 2004, 6, 2325 – 2328.
10] S. Breitenlechner, M. Fleck, T. E. Mꢂller, A. Suppan, J. Mol.
Catal. A: Chem. 2004, 214, 175 – 179.
[
2
À1
vacuo over P O prior to use (BET surface area: 304 m g , pore
4
10
3
À1
volume: 1.01 cm g , mean pore diameter (monomodal): 132 ꢀ).
The continuous-flow gas-phase hydroformylation of propene was
[
performed at a total pressure of 10 bar (C H :CO:H = 1:1:1) and T=
3
6
2
[11] P. Wasserscheid, M. Eichmann, Catal. Today 2001, 66, 309 – 316.
1
008C with differential conversion (< 10% conversion) using a
[
12] C. P. Mehnert, R. A. Cook, E. J. Mozeleski, N. C. Dispenziere,
M. Afeworki, Supported ionic liquid catalysis for hydroformy-
lation and hydrogenation reactions, 226th ACS National Meet-
ing, New York, USA, 2003.
13] J. Huang, T. Jiang, H. Gao, B. Han, Z. Liu, W. Wu, Y. Chang, G.
Zhao, Angew. Chem. 2004, 116, 1421 – 1423; Angew. Chem. Int.
Ed. 2004, 43, 1397 – 1399.
14] R. van Hal, P. Wasserscheid, unpublished results.
15] Rhodium Catalyzed Hydroformylation, (Eds.: P. W. N. M. van
Leeuwen, C. Claver), Kluwer, Dordrecht, 2000.
16] a) A. J. Sandee, V. F. Slagt, J. N. H. Reek, P. C. J. Kamer,
P. W. N. M. van Leeuwen, Chem. Commun. 1999, 1633 – 1634;
b) S. M. Silva, R. P. J. Bronger, Z. Freixa, J. Dupont, P. W. N. M.
van Leeuwen, New J. Chem. 2003, 27, 1294 – 1296.
microcatalytic flow system. The solid SILP catalyst was used as a fixed
[
5,6]
bed in a stainless-steel tubular reactor, as previously described.
The activity (TOF) and selectivity (n/iso) of the catalysts were
determined directly from online FID-GC measurements (Shimadzu
GC-9A, Nukol capillary columm, 15 m ꢁ 0.53 mm ID, Supelco Inc.) of
the reaction products by comparison with authentic samples of
aldehydes.
[
[
[
FTIR spectra of the catalysts were recorded on a Perkin Elmer
Paragon 1000 FTIR spectrophotometer. Samples were prepared as
KBr catalyst wafers by pressing catalyst onto the KBr and mounted
for measurements in situ under various gas atmospheres at 1008C in a
stainless-steel variable-temperature transmittance IR cell (Infraspac
LB-100, Infraspac Ltd, Novosibirsk, Russia; Si optical windows)
having gas inlet and outlet ports and an adjustable sample holder.
With this setup each recording could be corrected for background
absorbance without changing the atmosphere.
[
[
17] a) K. T. Wan, M. E. Davis, Nature 1994, 370, 449 – 450;
b) Applied Homogeneous Catalysis with Organometallic Com-
pounds, 1st ed. (Eds.: B. Cornils, W. A. Herrmann), VCH,
Weinheim, 1996.
3
1
29
Experimental details and data from MAS P and Si NMR
spectroscopy and NH -TPD measurements are available in the
3
[18] A. Beckmann, F. J. Keil, Chem. Eng. Sci. 2003, 58, 841 – 847.
19] P. Wasserscheid, R. van Hal, A. Bꢃsmann, Green Chem. 2002, 4,
00 – 404.
Supporting Information.
[
4
Received: August 4, 2004
Published online: December 21, 2004
[20] M. S. Goedheijt, P. C. J. Kamer, P. W. N. M. van Leeuwen, J.
Mol. Catal. A: Chem. 1998, 134, 243 – 249.
Keywords: catalyst development · hydroformylation
.
ionic liquids · phosphine ligands · rhodium
Angew. Chem. Int. Ed. 2005, 44, 815 –819
www.angewandte.org
ꢀ 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
819