Multiphasic aqueous hydroformylation of 1-alkenes with micelle-like polymer particles as phase transfer agents

Article abstract of DOI:10.1039/C8RA04022B

Micelle-like polymer particles have been applied in aqueous multiphasic hydroformylation reactions of long chain alkenes. These colloids act as phase transfer agents for the nonpolar substrates and as carriers for the catalyst bearing sulfonated ligands by electrostatic attraction. The catalyst performance and the phase separation were optimized with special focus on the conversion, selectivity and catalyst recovery, as those are key points in multiphasic systems to achieve a feasible industrial process. The effect on the catalyst performance of the number of sulfonate groups and electron withdrawing trifluoromethyl groups in the ligand has been studied. The approach was successfully demonstrated for 1-alkenes from 1-hexene to 1-dodecene. For 1-octene, a TOF of more than 3000 h^?1 could be achieved at a substrate to catalyst ratio of 80?000, while keeping the rhodium and phosphorous leaching below 1 ppm. In repetitive batch experiments the catalyst was recycled four times, yielding an accumulated TON of more than 100?000 for 1-octene.

Full text of DOI:10.1039/C8RA04022B

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PAPER
Multiphasic aqueous hydroformylation of 1-alkenes
with micelle-like polymer particles as phase
Cite this: RSC Adv., 2018, 8, 23332
transfer agents†
a
Bachir Bibouche,
Daniel Peral,a Dmitrij Stehl,b Viktor Soderholm,c
¨
Reinhard Schomacker,a Regine von Klitzingb and Dieter Vogt
¨
c
*
Micelle-like polymer particles have been applied in aqueous multiphasic hydroformylation reactions of long
chain alkenes. These colloids act as phase transfer agents for the nonpolar substrates and as carriers for the
catalyst bearing sulfonated ligands by electrostatic attraction. The catalyst performance and the phase
separation were optimized with special focus on the conversion, selectivity and catalyst recovery, as
those are key points in multiphasic systems to achieve a feasible industrial process. The effect on the
catalyst performance of the number of sulfonate groups and electron withdrawing trifluoromethyl
groups in the ligand has been studied. The approach was successfully demonstrated for 1-alkenes from
1-hexene to 1-dodecene. For 1-octene, a TOF of more than 3000 hꢀ1 could be achieved at a substrate
to catalyst ratio of 80 000, while keeping the rhodium and phosphorous leaching below 1 ppm. In
repetitive batch experiments the catalyst was recycled four times, yielding an accumulated TON of more
than 100 000 for 1-octene.
Received 11th May 2018
Accepted 21st June 2018
DOI: 10.1039/c8ra04022b
rsc.li/rsc-advances
this process is limited to short chain alkenes with sufficient
water solubility to enable rapid mass transfer to the aqueous
Introduction
catalyst phase.
On an industrial scale, the separation and reuse of homoge-
neous catalysts is a very important issue. As this is oen not easy
to achieve, heterogeneous catalysts are being applied in about
80% of industrial catalytic processes.1 However, molecular
catalysts oen show superior selectivity and activity under
milder conditions. One of the biggest homogeneously catalyzed
processes is the hydroformylation of olens with an annual
production of 12 Mt. One way to combine easy separation of
catalyst and product mixture and the advantages of molecular
catalysts is the use of a multiphasic reaction system. This is
One strategy to separate and recycle the homogeneous
catalyst is to carry out the reaction in a completely homoge-
neous medium that can be switched into two phases for easy
product separation aer the reaction. This can be achieved by
adding cosolvents4,5 or additives with cosolvents that can be
switched in polarity by addition of CO2.6 The homogeneous
catalyst itself can also be switched from a nonpolar to a polar
state by using special ligands that react with CO2, changing the
phase in which the catalyst is dissolved.7,8 In thermomorphic
multiphase-systems (TMS) a homogeneous reaction medium is
generated at higher (reaction) temperature, while at lower
temperature a miscibility gap allows to separate the catalyst
phase from the product phase. A mixture of water and 1-butanol
has recently been used to carry out the hydroformylation of
methyl 10-undecenoate in a continuous miniplant process with
efficient catalyst recycling.9,10 Another strategy used for the
hydroformylation of long chain alkenes catalyzed by a water
soluble molecular catalyst is the use of phase transfer agents
(PTA). These additives reduce the mass transfer limitation
during reaction and are ideally recycled together with the
catalyst. Surfactants11–14 and cyclodextrins15–17 have been used as
phase transfer agents for multiphase hydroformylation
reactions.
ˆ
being applied in the Ruhrchemie–Rhone-Poulenc process for
the hydroformylation of short chain alkenes with a molecular
rhodium catalyst.2,3 In that process, the substrates and products
form a nonpolar phase, while the rhodium catalyst resides in an
aqueous phase due to the water soluble, trisulfonated triphenyl-
phosphine ligand (TPPTS). This indeed combines most of the
advantages of homogeneous catalysis with simple product
separation at very low Rh leaching in the ppb range. However,
a
¨
Department of Chemistry, Technische Universitat Berlin, Straße des 17. Juni 124,
TC-8, 10623 Berlin, Germany
b
¨
Department of Physics, Technische Universitat Darmstadt, Alarich-Weiss-Straße 10,
64287 Darmstadt, Germany
cDepartment of Biochemical and Chemical Engineering, Technische Universitat
¨
Dortmund, Emil-Figge-Straße 66, 44227 Dortmund, Germany. E-mail: dieter.vogt@
tu-dortmund.de
An alternative to a classical phase transfer agent, like
a surfactant, is the use of colloidal dispersions with covalently
attached ligands. This enables multiphasic reactions with
† Electronic supplementary information (ESI) available. See DOI:
10.1039/c8ra04022b
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moderate to low leaching of metal to the product phase.18–21 The
difference to the before mentioned systems is that the ligands
are covalently bound, making the catalyst less similar to a truly
homogeneous catalyst. It should be mentioned, that the selec-
tivity does not necessarily suffer from this, and in some cases
even increases.18,19
Colloidal, micelle-like polymer particles have been shown to
be viable phase transfer agents for multiphasic hydro-
formylation reactions, although their role in enabling mass
transfer has not been fully understood yet.22–24 The particles
have a cross-linked polystyrene core, a polyethylene glycol (PEG)
shell, making them water soluble, and are functionalized with
cationic ammonium salts. This means that any anionic ligand
will interact with them, making them exible in terms of
applicability. Although the particles successfully worked as
phase transfer agents for the aqueous multiphasic hydro-
formylation of 1-octene, only moderate turnover frequencies
(TOF) could be obtained (350 hꢀ1). Moreover, the formation of
stable emulsions aer the catalytic reactions prevented easy
separation of the aqueous catalyst phase and the organic
product phase. The products were extracted with diethylether,
which enabled the recycling of the particles and catalyst but still
required an undesired cosolvent.22
In this work, the performance of functionalized polymer
particles as phase transfer agents and catalyst carriers has been
further investigated for the hydroformylation of long chain
alkenes. Ligands with different stereoelectronic properties have
been evaluated. The focus of this work has been the combina-
tion of yield of desired products, catalyst efficiency and ease of
recyclability.
Fig. 1 Molar composition and reaction conditions for the synthesis of
the polymer particle suspensions by emulsion polymerization.
as shown by TEM (30 nm) and SEM images (32 nm), where only
the polystyrene core could be observed. By AFM the particles
showed diameters of 72 nm and the core and the shell could be
differentiated in the phase mode images. The hydrodynamic
diameter of the particles in aqueous suspension found by DLS
was 95 nm.
The functionalization of the polymer particles with
ammonium salts stabilizes the particles in water, as indicated
by the zeta potential of +48 mV. Moreover, the cationic
ammonium salts have been proven to electrostatically interact
with anionic ligands, rendering the particles catalyst carriers.
This was conrmed by membrane ltration experiments with
mixtures of polymer particles, anionic ligand (L), and the
rhodium-precursor in the concentration regime of the actual
catalytic reaction conditions ([Rh] : [L] : [S] ¼ 1 : 20 : 40 000,
35 mg mlꢀ1 polymer particles, where S stands for substrate).
The ltrate did not contain any particles and no detectable
amounts of functionalized ligand (TPPTS, TPPMS, TPPDS,
Danphos, Dan2phos, see Fig. 5).
Results and discussion
Colloidal polymer particles
Hydroformylation of 1-octene
The colloidal polymer particles used in this work as phase
transfer agents for the multiphasic hydroformylation of longer
chain 1-alkenes were described in a recent publication.22 They
are comprised of a nonpolar cross-linked polystyrene core and
a hydrophilic shell based on PEG-modied styrene and
ammonium salt-modied styrene monomers. The polymer
particles were designed to act as microreactors in aqueous
liquid–liquid catalytic reactions, as they are similar to micelles
and can solubilize non polar solvents. In this approach, the
particles are dispersed in the aqueous catalyst phase. Unlike the
The multiphasic hydroformylation of 1-octene was performed
using [Rh(acac)(CO)2] as catalyst precursor and 6 equivalents of
the trisulfonated triphenylphosphine (TPPTS) as water soluble
ligand. The reactions were carried out in high pressure auto-
claves equipped with a mechanical gas-impeller stirrer to have
better control over the mass-transfer processes between the
nonpolar substrate phase and the aqueous catalyst phase. As
standard reaction conditions 100 bar of syngas (CO : H2 ¼ 1 : 1),
ꢁ
a stirring rate of 700 rpm at 80 C reaction temperature were
chosen (Scheme 1). The concentration of the polymer particles
in the aqueous phase was 25 mg mlꢀ1 and n-dodecane was used
as internal standard for GC analysis. Hydroformylation of 1-
octene was carried out at a scale of 150 mmol, where the
amount of catalyst was successively decreased from a substrate
to catalyst ratio of 5000 to 80 000 (Table 1).
polymer particles carrying
a
covalently bound ligand,
mentioned in the introductory part, our particles are function-
alized with cationic groups. This allows to attach any ligand
carrying anionic groups, like the common sulfonated TPPTS-
ligand, by electrostatic interaction (ion-exchange). The
colloidal suspensions have been synthesized by emulsion
polymerization in water. The molar monomer composition and
the reaction conditions for the polymer particles used in this
work are depicted in Fig. 1.
The polymer particles were characterized by dynamic light
scattering (DLS), atomic force microscopy (AFM), transmission
electron microscopy (TEM) and scanning electron microscopy
(SEM). The cores of the particles have diameters around 30 nm, Scheme 1 Multiphasic hydroformylation of 1-octene.
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Table 1 Multiphasic hydroformylation of 1-octene with increasing
separation, in order to achieve effective catalyst separation and
reuse. The reaction optimization was carried out at a substrate
to catalyst ratio of 40 000, since the selectivity of the reaction
signicantly dropped at a ratio of 80 000. For the optimization,
the amount of ligand and phase transfer agent, as well as the
stirring rates were varied systematically (Table 2 and Fig. 2).
An increase of the L : Rh ratio from 6 to 20 gave the expected
increase of chemo- and regioselectivity towards the linear
aldehyde, although the conversion and rate of the reaction
dropped signicantly (entries 1 and 2, Table 2). Moreover, the
formation of a stable Pickering emulsion was observed under
these conditions, hampering the phase separation. In order to
minimize the formation of stable emulsions, the stirring rate
was decreased to 350 rpm. The phase separation improved,
although both the conversion and the rate of the reaction
further dropped (entry 3, Table 2). To increase the performance
of the catalytic reaction while keeping a good phase separation,
the amount of particles was increased from 25 mg mlꢀ1 to
35 mg mlꢀ1. Under these conditions, a satisfying combination
of phase separation, rate, selectivity and conversion was ob-
tained (entry 4, Table 2). Under these conditions simple
decantation of the product phase enabled catalyst recycling
without the need for an extraction with a cosolvent (Fig. 3).
An increase of stirring rate or particle concentration leads to
faster conversion, as mass transfer is improved. The formation
of these Pickering emulsions could suggest that an important
feature of the particles is the ability to lead to a locally high
catalyst concentration in the interphase between the aqueous
phase and the substrate droplets. Therefore, mass transfer
limitations are reduced. Under catalytic conditions, both,
carrying the catalyst to the interphase and acting as a micro-
reactor might be relevant (Fig. 4).
substrate to catalyst ratioa
TOF at 10%
Entry [S] : [C] Conversion (%) Chemosel. (%) l : b conv. (hꢀ1
)
1
2
3
4
5
5000
87
99
98
96
90
85
2.6 347
2.5 541
2.4 1200
2.3 2024
2.1 3280
10 000 86
20 000 90
40 000 93
80 000 96
a
Reaction conditions: [Rh(acac)(CO)2], TPPTS, [L] : [Rh] ¼ 6, 150 mmol
1-octene, 15 mmol n-dodecane as internal standard. 500 mg of polymer
particles, 20 ml H2O. 80 ꢁC, 700 rpm, 100 bar CO : H2 (1 : 1), 22 h.
Fig. 2 Catalytic performance of the multiphasic hydroformylation of
1-octene using different ratios of substrate to catalyst, conditions see
Table 1.
Lower amounts of catalyst lead to higher rates. However, as
expected, lower amounts of rhodium precursor and ligand,
while keeping their ratio constant, lead to lower selectivities, as
the lower ligand concentration is expected to lead to less
phosphine ligands coordinating to the metal center (Table 1
and Fig. 2). Furthermore, when using half of the amount of
catalyst, the conversion stayed similar, but the TOF roughly
doubled, indicating a mass transfer limitation of substrate to
the catalyst.
The excellent activity obtained at very high substrate : Rh
ratio led us to perform further optimization studies in order to
counteract the simultaneous drop in linear selectivity. At the
same time, we monitored and strove for efficient and fast phase
Ligand effect
In order to further improve the catalyst performance, different
sulfonated ligands were tested using the optimized conditions
previously described: [Rh] : [L] : [S] ¼ 1 : 20 : 40 000, using
35 mg mlꢀ1 of polymer particles as phase transfer agents and
a stirring rate of 350 rpm, to minimize the formation of stable
Pickering emulsions.
Triphenylphosphines with fewer sulfonate groups than
TPPTS (TPPDS and TPPMS) were tested. Moreover, two different
sulfonated phosphines bearing electron withdrawing tri-
uoromethyl groups were used (Danphos and Dan2phos,
Fig. 5). The incorporation of electron withdrawing groups in the
Table 2 Optimization of the multiphasic hydroformylation of 1-octenea
TOF at 10%
Entry
[L] : [C]
[PTA] (mg mlꢀ1
)
Stirring (rpm)
Conv. (%)
Chemo-sel. (%)
l : b
conv. (hꢀ1
)
1
2
3
4
6
25
25
25
35
700
700
350
350
93
59
50
73
90
98
98
97
2.3
2.5
2.5
2.5
2024
1240
1076
1600
20
20
20
a
Reaction conditions: [Rh(acac)(CO)2], TPPTS, 150 mmol 1-octene, 15 mmol n-dodecane as internal standard, [S] : [Rh] ¼ 40 000, 20 ml H2O. 80 ꢁC,
100 bar CO : H2 (1 : 1), 22 h.
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the shell of the polymer particles interacts with the sulfonated
ligands, rendering the particles catalyst carriers. A reasonable
explanation for the inferior performance of the lower
sulfonated ligands TPPDS and TPPMS is the decreasing
number of binding sites of the catalyst at the particles.
The triuoromethylated and sulfonated phosphines, Dan-
phos and Dan2phos increased the activity of the system,
compared to TPPDS and TPPMS, respectively (entries 4 and 5,
Table 3). It is well-known that triuoromethyl groups have
a very strong electron withdrawing effect on phosphines,
leading to a signicant decrease of the electron density at the
metal center.26,27 This can change the rate determining step of
the reaction in certain cases, improving the catalytic activity. It
has been previously reported that for the unmodied rhodium
carbonyl catalyst and for catalysts modied with electron-poor
ligands, the rate determining step of the reaction is the
hydrogenolysis of the acyl species,28 in contrast to electron-
rich phosphines, where the reaction rate is controlled by the
rst step of the catalytic cycle, CO dissociation.29
Fig. 3 Aldehyde yield vs. time in the multiphasic hydroformylation of
1-octene, end point from GC-results and the graph by gas uptake
conditions see Table 2.
Moreover, the triuoromethylated phosphines improved the
regioselectivity towards the linear aldehyde. Especially with the
Dan2phos ligand, which contains two bis(3,5-triuoromethyl)
phenyl rings in its structure, linear to branched ratios of 4.6
could be obtained (Table 3, entry 5). The improvement of regio-
selectivity by p-accepting ligands like uorinated phosphines has
been reported previously for the hydroformylation of 1-alkenes.27,30
Recycling experiments
The aqueous catalyst phase obtained aer the hydroformylation
of 1-octene with the ligands TPPTS and Danphos (entries 1, 2,
Table 4) were recycled three times for consecutive reactions.
Although under those conditions the phase separation aer the
reaction was satisfactory, the reaction mixtures were centri-
fuged for 15 min at 3000 rpm in order to quantitatively recover
the catalyst together with the polymer particles.
Fig. 4 Schematic representation of the role of the polymer particles
under catalytic conditions. Left as microreactor and right as catalyst
carriers to the interphase (S: substrate, P: product, C: catalyst).
The recycling experiments with TPPTS were successful, and
the yield dropped by only 5% from the rst to the forth run. The
regioselectivity did drop towards the last runs, but this can
easily be explained by partial oxidation of the phosphine
ligands, since phase separation and centrifugation were carried
out under non inert conditions. ICP-MS measurements of the
organic phase aer the rst and the fourth reaction with TPPTS
indicated that the loss of rhodium in the oil phase was 1.6 and
1.8% of the initial amount of rhodium, respectively. However,
since the substrate to catalyst ratio is 40 000, the product phase
contains less than 0.3 ppm of rhodium.
phosphine structure both decreases the s-donating and the p-
accepting ability of the ligand, changing the electronic proper-
ties of the rhodium catalyst. It has previously been reported that
the ligands of the Danphos-family improved the catalyst activity
in the biphasic hydroformylation of vinyl acetate and allyl
cyanide.25
The catalyst performance using different sulfonated
ligands decreased when decreasing the number of sulfonate
groups; TPPTS > TPPDS > TPPMS (entries 1–3, Table 3 and
Fig. 6). As mentioned above, the trimethylammonium salt in
Fig. 5 Sulfonated ligands employed in the multiphasic hydroformylation of 1-octene.
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Table
3
Multiphasic hydroformylation of 1-octene with different Table 4 Recycling experiments of the multiphasic hydroformylation
ligandsa
of 1-octenea
TOF at 10%
TOF at 10%
Conversion (%) Chemosel. (%) l : b conv. (hꢀ1
Entry
Ligand
Conversion (%)
l : b
conv. (hꢀ1
)
Run Ligand
)
1
2
3
4
5
TPPTS
TPPDS
TPPMS
Danphos
Dan2phos
73
37
33
56
46
2.5
1.9
2.8
2.9
4.6
1600
732
652
1640
1050
1
2
3
4
1
2
3
4
TPPTS
73
74
67
74
97
95
93
88
98
97
96
91
2.5 1600
2.4 1700
2.4 1384
2.3 1400
2.9 1640
2.8 1532
2.7 1104
2.4 988
Danphos 56
50
44
44
a
[Rh(acac)(CO)2], 150 mmol 1-octene, 15 mmol n-dodecane as internal
standard, 700 mg of polymer [S] : [L] : [Rh] ¼ 40 000 : 20 : 1, 20 ml H2O.
80 ꢁC, 350 rpm, 100 bar CO : H2 (1 : 1), 22 h. Complete chemoselectivity
towards aldehydes was observed for all reactions.
a
Reaction conditions: 0.00375 mmol [Rh(acac)(CO)2], 0.075 mmol
ligand, 150 mmol 1-octene, [Rh] : [L] : [S] ¼ 1 : 20 : 40 000, 15 mmol n-
dodecane as standard, 700 mg of PTA, 20 ml H2O, 80 ꢁC, 350 rpm,
100 bar CO : H2 (1 : 1), 22 h.
Similar results were obtained for the recycling of the Dan-
phos system, but apart from the drop in regioselectivity, the rate
dropped more signicantly. With the Danphos ligand, the
amount of rhodium in the oil phase aer the rst reaction
determined by ICP-MS was 0.2 ppm, which represents 1.4% of
the initial rhodium amount.
Table
5
Multiphasic hydroformylation of different long chain 1-
alkenesa
TOF at 10%
In our previous work the separation of the organic product
phase and the catalyst containing aqueous phase was supported
by the use of diethylether for extraction.22 The particles showing
improved phase separation in this work, allowed to avoid
additional organic solvents. Further improvement of the phase
separation kinetics would make centrifugation obsolete and
only require simple decantation. Additionally, ultraltration
can be examined as a means to retain the catalyst-carrying
particles in future work.
Entry Substrate
Conversion (%) Chemosel. (%) l : b conv. (hꢀ1
)
1
2
3
4
1-Hexene
1-Octene
1-Decene
83
73
55
99
97
91
92
2.6 1873
2.5 1600
2.3 1024
2.3 744
1-Dodecene 36
a
Reaction conditions: 0.00375 mmol [Rh(acac)(CO)2], 0.075 mmol
TPPTS, 150 mmol of substrate, [Rh] : [L] : [S]
¼
1 : 20 : 40 000,
15 mmol of internal standard, 700 mg of PTA, 20 ml H2O, 80 ꢁC,
350 rpm, 100 bar CO : H2 (1 : 1), 22 h.
Aer the recycling experiments, it was possible to obtain
accumulated TONs of 115 000 with the TPPTS ligand and 77 000
for Danphos, indicating a high catalytic activity and good
recyclability.
The results applying the optimized conditions for 1-octene are
summarized in Table 5.
With all the substrates tested, conversion towards alde-
hydes were observed using the optimized conditions found for
1-octene (Table 5, entry 2), showing the versatility of the
polymer particles as phase transfer agents and catalyst
carriers. However, reaction rates decreased with increasing
chain length of the substrate. This is known in literature31 and
Different substrates
1-Alkenes of different chain lengths were converted by multi-
phasic hydroformylation using the polymer particles as phase
transfer agents in order to prove the versatility of the approach.
Fig. 6 Aldehyde yield vs. time in the multiphasic hydroformylation of Fig. 7 Aldehyde yield vs. time in the multiphasic hydroformylation of
1-octene with different sulfonated ligands, conditions see Table 3.
different 1-alkenes, conditions see Table 5.
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is caused by the lower concentration of double bonds in the
bigger volume of the long chain alkenes. In this case, the lower
solubility of the longer chain alkenes in the catalyst phase
might also attribute to the difference in rate. The regiose-
lectivity for the different substrates is similar in all cases, but
slightly decreases for the longer chains. This might be caused
by the increased number of double bond isomers formed in
competing isomerization reactions for the longer chain
alkenes, which can then lead to more branched aldehydes
(Fig. 7).
Preparation of the monomers and the polymer particles
The monomers and the polymer particles used as phase transfer
agents and catalyst carriers in multiphasic hydroformylation
reactions were synthesized according to the literature.22
Multiphasic hydroformylation reactions
1-Octene hydroformylation. [Rh(acac)(CO)2] and the phos-
phine ligands were introduced in the autoclave under argon,
together with the polymer particles suspended in 20 ml of water.
1-Octene (150 mmol) and n-dodecane (15 mmol) as internal
standard were introduced in a compensated-pressure addition
funnel connected to the autoclave. The system was then pres-
Conclusions
ꢁ
surized to 100 bar of syngas (1 : 1) and heated to 80 C at the
corresponding stirring rate. Aer 1 hour of catalyst preforma-
tion, the substrate and standard were added to the catalyst
aqueous phase and the gas consumption was recorded. Aer 22
hours, the temperature was lowered to 65 ꢁC and the autoclave
was slowly depressurized, aer which it was cooled to room
temperature. A drop of the organic phase was diluted with
diethyl ether and analyzed by GC to calculate the conversion
and the selectivity of the reaction. The TOF was calculated from
the gas uptake.
Recycling experiments. Aer the rst run, the reaction
mixture was transferred to a centrifuge tube, and the mixture
was centrifuged for 15 min at 3000 rpm. The aqueous phase was
then transferred to a Schlenk ask, purged with argon during
10 min, and reused as catalyst phase for the second run. The
process was repeated 3 times.
Other 1-alkenes hydroformylation. The same procedure as
for 1-octene was used for the rest of the 1-alkenes tested. Only
the internal standard was changed in order not to interfere
during the GC analysis. For the hydroformylation of 1-hexene, n-
dodecane was used as standard; toluene was used for 1-decene
hydroformylation and n-decane for the hydroformylation of 1-
dodecene.
Stable polymer particles suspended in water were successfully
applied as phase transfer agents in the multiphasic hydro-
formylation of long chain alkenes, catalyzed by water soluble
rhodium catalysts. For 1-octene, TOFs of 3000 hꢀ1 were ach-
ieved using a substrate to catalyst ratio of 80 000. However, the
chemoselectivity of the reaction towards aldehydes, and
particularly the regioselectivity towards the desired linear
aldehyde, were quite low. Therefor the [S] : [C] ratio of 40 000
was chosen as it yielded a good TOF of 2000 hꢀ1 as well as
a standard selectivity for monodentate phosphine ligand.
The optimization of the multiphasic hydroformylation of 1-
octene was carried out, focusing on the catalyst performance
and the phase separation aerwards. With the resulting system
recycling experiments of the aqueous catalyst phase were
carried out in four consecutive runs without signicant loss of
activity and achieving accumulated TONs of 115 000. Moreover,
ICP-MS measurements of the product phase indicated that the
organic phase contained less than 0.3 ppm of rhodium.
The effect of the sulfonated ligand on the catalyst perfor-
mance was also studied. While TPPTS gives the highest activity,
triuoromethylated phosphine sulfonates improved the regio-
selectivity of the system towards the desired linear aldehyde.
The polymer particles were also successfully applied as
phase transfer agents in the hydroformylation of other long
chain 1-alkenes. The rate and regioselectivity of the process
decreased with increasing chain length. However, these results
prove the versatility of the particles for other multiphasic cata-
lytic reactions.
Instruments and characterization methods
Gas chromatography (GC). The catalytic reactions were
analyzed using a Shimadzu GC-2010 instrument equipped with
a FID detector and an Ultra-19091B-102 capillary column
(25.0 m, 0.20 mm ID) from Agilent or an Agilent 7890A instru-
ment equipped with an Agilent 19091J-413 column (30 m,
0.25 mm ID). The following temperature program was used for
both instruments: 50 ꢁC (7 min); 20ꢁC minꢀ1 until 280 ꢁC;
Experimental section
ꢁ
280 C (3 min). Tinjector ¼ 280 ꢁC; Tdetector ¼ 305 ꢁC.
The commercial substrates used for the hydroformylation
Inductively coupled plasma mass spectrometry (ICP-MS).
experiments, 1-octene (Sigma Aldrich, 98%) 1-hexene (Alfa Samples were analysed by ICP-MS using an Agilent 7500ce (with
Aesar, 98%), 1-decene (Alfa Aesar, 96%) and 1-dodecene (Sigma octopole reaction system), employing an RF forward power of
Aldrich, 95%) were ltered through alumina and purged with Ar 1540 W and reected power of 1 W, with argon gas ows of 0.81
before use. [Rh(acac)(CO)2] (abcr, 99%), TPPTS (Sigma-Aldrich, L minꢀ1 and 0.19 L minꢀ1 for carrier and makeup ows,
$95), TPPMS (abcr, 95%), n-dodecane (Sigma-Aldrich, $99%), respectively. Sample solutions were taken up into the Micro
water (VWR, HPLC-grade) and n-decane (Sigma-Aldrich, >95%) mist nebuliser by peristaltic pump at a rate of approximately 1.2
were used as received from the commercial sources. Danphos,25 ml minꢀ1. Skimmer and sample cones were made of nickel. The
Dan2phos32 and TPPDS33 ligands were prepared according to instrument was operated in spectrum acquisition mode and
the literature.
three replicate runs per sample were employed. The mass
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¨
analysed for the metal was 103Rh. Each mass was analysed in 13 T. Pogrzeba, D. Muller, T. Hamerla, E. Esche, N. Paul,
¨
fully quant mode (three points per unit mass).
G. Wozny and R. Schomacker, Ind. Eng. Chem. Res., 2015,
54, 11953–11960.
¨
14 M. Illner, D. Muller, E. Esche, T. Pogrzeba, M. Schmidt,
Conflicts of interest
¨
R. Schomacker, G. Wozny and J. U. Repke, Ind. Eng. Chem.
Res., 2016, 55, 8616–8626.
15 E. Monier, G. Fremy, Y. Castanet and A. Mortreux, Angew.
Chem., Int. Ed. Engl., 1995, 34, 2269–2271.
There are no conicts to declare.
16 L. Leclercq, M. Sauthier, Y. Castanet, A. Mortreux, H. Bricout
and E. Monier, Adv. Synth. Catal., 2005, 347, 55–59.
17 M. Elard, J. Denis, M. Ferreira, H. Bricout, D. Landy, S. Tilloy
and E. Monier, Catal. Today, 2015, 247, 47–54.
18 E. Lobry, A. F. Cardozo, L. Barthe, J. Blanco, H. Delmas,
S. Chen, F. Gayet, X. Zhang, M. Lansalot, F. D. Agosto,
et al., J. Catal., 2016, 342, 164–172.
19 A. F. Cardozo, C. Julcour, L. Barthe, J. Blanco, S. Chen,
F. Gayet, E. Manoury, X. Zhang, M. Lansalot, B. Charleux,
et al., J. Catal., 2015, 324, 1–8.
Acknowledgements
We gratefully acknowledge the nancial support by the German
Science Foundation (DFG) (Project SFB/TR 63: “InPROMPT –
Integrated Chemical Processes in Multi-Phase Fluid Systems”,
Projects A2 EVF, B6). The authors would like to thank the Ein-
stein Foundation Berlin for the nancial support and express
our gratitude to Umicore AG & Co. KG for a generous loan of
noble metal compounds. We would also like to thank Maxi
Spiekermann, Jonas Diekmann who conducted experiments as
part of their bachelor and master thesis, respectively, Lorna
Eades for the ICP analysis and Thomas Seidensticker for cor-
recting the manuscript.
20 E. Maria Claesson, N. C. Mehendale, R. J. M. Klein Gebbink,
G. van Koten and A. P. Philipse, J. Magn. Magn. Mater., 2007,
311, 41–45.
21 B. G. P. van Ravensteijn, D.-J. Schild, W. K. Kegel and
R. J. M. Klein Gebbink, ChemCatChem, 2017, 9, 440–450.
22 D. Peral, D. Stehl, B. Bibouche, H. Yu, J. Mardoukh,
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