A Janus-type Heterogeneous Surfactant for Adipic Acid Synthesis

Article abstract of DOI:10.1002/cctc.202000140

A highly water-dispersible heterogeneous Br?nsted acid surfactant was prepared by synthesis of a bi-functional anisotropic Janus-type material. The catalyst comprises ionic functionalities on one side and propyl-SO₃H groups on the other. The novel material was investigated as a green substitute of a homogeneous acidic phase transfer catalyst (PTC). The activity of the catalyst was investigated for the aqueous-phase oxidation of cyclohexene to adipic acid with 30 % hydrogen peroxide even in a decagram-scale. It can also be used for the synthesis of some other carboxylic acid derivatives as well as diethyl phthalate.

Full text of DOI:10.1002/cctc.202000140

Accepted Article
Title: A Janus-type Heterogeneous Surfactant for Adipic Acid Synthesis
Authors: Majid Vafaeezadeh, Christian Wilhelm, Paul Breuninger,
Stefan Ernst, Sergiy Antonyuk, and Werner R. Thiel
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10.1002/cctc.202000140
ChemCatChem
COMMUNICATION
A Janus-type Heterogeneous Surfactant for Adipic Acid
Synthesis
Majid Vafaeezadeh,*[a] Christian Wilhelm,[b] Paul Breuninger,[c] Stefan Ernst+,[b] Sergiy Antonyuk,[c] and
Werner R. Thiel*[a]
Abstract: A highly water dispersible heterogeneous Brønsted acid
surfactant was prepared by synthesis of a bi-functional anisotropic
Janus-type material. The catalyst comprises ionic functionalities on
one side and propyl-SO3H groups on the other. The novel material
was investigated as a green substitute of a homogeneous acidic
phase transfer catalyst (PTC). The activity of the catalyst was
investigated for the aqueous-phase oxidation of cyclohexene to adipic
acid with 30% hydrogen peroxide even in a decagram-scale. It can
also be used for the synthesis of some other carboxylic acid
derivatives as well as diethyl phthalate.
significant advantages of this reaction are the formation of water
as the sole by-product, the relatively mild reaction conditions and
the high selectivity. However, in order to obtain sufficient miscibi-
lity between the aqueous oxidizing agent and the organic sub-
–
strate, the phase transfer catalyst (CH3(n-C8H17)3N+HSO4 ) has to
be used. It was shown that this PTC also promotes the activity of
H2O2 for the oxidation. However, the quaternary ammonium salt
is expensive and not a safe reagent in terms of its environmental
impact.
Based on the strategy implemented by Noyori, several other
homogeneous and heterogeneous catalysts were developed for
the oxidative cleavage of cyclohexene to adipic acid during the
last years.[ 4 ] Although some valuable achievements could be
realized, the reaction still requires further improvements
especially in an environmental point of view. In particular, the
removal of the PTC from the reaction mixture and its reuse has
not been realized in a satisfying manner up to now. In contrast, a
heterogeneous version in the form of a PTC or a surfactant is less
corrosive, can be simply handled, stored and separated from the
reaction mixture. The Janus strategy for the synthesis of aniso-
tropic materials gives novel opportunities for the synthesis of a
new generation of heterogeneous catalysts with comparable
miscibility to homogeneous catalysis.
Since adipic acid is one of the building blocks for the production
of nylon-6,6 by polycondensation with hexamethylene diamine, it
is the industrially most important dicarboxylic acid.[1] In commer-
cial processes adipic acid is mainly synthesized by the nitric acid
oxidation of a mixture of cyclohexanol and cyclohexanone (so-
called KA oil) with copper(II) and ammonium metavanadate as the
catalysts.[1] The emission of stoichiometric amounts of nitrous
oxide (N2O) as the by-product is surely a serious environmental
disadvantage of this process. N2O is a greenhouse gas with a very
long atmospheric lifetime and a powerful heat trapping efficiency.
Further negative environmental effects of N2O are related to its
capability to destroy ozone in the atmosphere and its contribution
to the acidification of rain.
Janus-type materials are defined as solids possessing a chemic-
ally anisotropic surface. During the last years, they have attracted
[5]
attention for their synthesis and applications in different fields
Due to this, there is interest in using alternative, cheap and
greener oxidizing reagents such as hydrogen peroxide. Due to
new technologies for a safer and more efficient use of hydrogen
peroxide in industry, the production of H2O2 was increased while
its price had decreased during the last decades.[2] The aqueous-
phase oxidation of cyclohexene with hydrogen peroxide as the
oxidizing agent and tungstate as the catalyst was introduced by
Noyori and co-workers.[3] It opens up an economically and ecolo-
gically interesting alternative access to adipic acid. Further
especially in catalysis.[6] A novel sub-group of these materials are
anisotropically functionalized catalysts so-called Janus
interphase catalysts. Very recently, we published a simple and
practical procedure for the preparation of such Janus interphase
catalysts.[7] In the present manuscript we report the synthesis of
the first amphiphilic and water dispersible Janus interphase
Brønsted acid catalyst and its application as a heterogeneous
analogue of
a PTC for the aqueous-phase oxidation of
cyclohexene to adipic acid. The functionalization of the material’s
surface is highly compatible with both the aqueous oxidant and
the organic substrate. In other words, the catalyst provides an
optimal balance of hydrophobicity/hydrophilicity for an efficient
emulsification of organic and aqueous phases. Consequently, the
surfactant-like material can be used as a substitute for the
established homogeneous acidic PTC. A schematic illustration of
the material’s preparation is shown in Scheme 1.
[a]
Dr. M. Vafaeezadeh, Prof. Dr. W. R. Thiel
Fachbereich Chemie, Anorganische Chemie
Technische Universität Kaiserslautern
Erwin-Schrödinger-Str. 54, 67663 Kaiserslautern (Germany)
E-mail: majidvafaeezadeh@yahoo.com
thiel@chemie.uni-kl.de
[b]
[c]
Dr. C. Wilhelm, Prof. Dr. S. Ernst
Fachbereich Chemie, Technische Chemie
Technische Universität Kaiserslautern
Erwin-Schrödinger-Str. 54, 67663 Kaiserslautern (Germany)
P. Breuninger, Prof. Dr. S. Antonyuk
Fachbereich Maschinenbau und Verfahrenstechnik
Mechanische Verfahrenstechnik
Technische Universität Kaiserslautern
Gottlieb-Daimler-Str. 44, 67663 Kaiserslautern (Germany)
+ Prof. Ernst passed away on Jan. 28, 2019.
Supporting information for this article is given via a link at the end of
the document.
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10.1002/cctc.202000140
ChemCatChem
COMMUNICATION
Scheme 1. Schematic synthesis of the water dispersible Janus surfactant.
In the first step, porous hollow silica particles 1 bearing immobil-
ized 3-mercaptopropyl groups on the inner surface were synthe-
sized by applying a modified method for the preparation of Stöber
silica particles.[8] After removing the surfactant (material 2), zwit-
terionic groups were grafted on the outer surface of the hollow
silica particles giving material 3. Finally, the hollow spheres were
crushed and the thiol groups were oxidized using 30% H2O2.[9]
Details for the synthesis of catalyst 4 are described in the Sup-
porting Information.
Figure 1. SEM images of a) the hollow structures of 3. The yellow arrows assign
some deformations on the surface of the hollow silica spheres. A demonstration
of the uniform wall thickness and the size of a hallow sphere is assigned by the
red arrow. b) The curved/nanosheet structures of the final, crushed catalyst 4.
The decrease of the specific surface area and of the pore volume
from the freshly synthesized hollow silica spheres 2 to the final
crushed catalyst 4 provides evidence for the successful function-
alization of the surface. The specific surface area of the catalyst
after two steps of functionalization is comparable to some other
established mesoporous silica-based catalysts.[10]
Elemental analysis (CHNS) of material 2 revealed that the loading
of thiol groups is 0.65 mmol·g–1, while the loading of ionic func-
tionalities in 3 was found to be 0.54 mmol·g–1. The morphology of
the material before and after the crushing was explored by means
of scanning electron microscopy (SEM, Figure 1). SEM images
show sphere-like geometries for 3 with a rather uniform size of
approx. 1 µm and some surface deformations (yellow arrows)
coming from the intrinsic hollow structure. Moreover, a uniform
wall thickness of the particles is clearly observable from a broken
species (red arrow). The N2 adsorption-desorption isotherms of
materials 2 and 4 (Figure 1S, Supporting Information) show a
type-IV profile, which is typical for mesoporous compounds. The
calculated BET surface areas, the pore size distributions (BJH
method) and the pore diameters for the as-synthesized material 2
are 1021 m2/g, 2.24 nm and 0.57 mL/g while the according values
for the final catalyst 4 are 530 m2/g, 2.6 nm and 0.34 mL/g, re-
spectively.
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All peaks in the 13C CP-MAS NMR spectra (Figure 2) of material
4 can be assigned to the carbon atoms of the introduced func-
tional groups. Carbon atoms C1 and C12 are directly connected
to silicon atoms and thus are highly shielded leading to a broad
resonance at around 9.7 ppm. Carbon atoms C10 and C13 can
be identified as separated signals while carbon atoms C2 and C7
have rather identical chemical shifts and are observed as a shoul-
der at around 19.8 pm. In addition, carbon atoms C3-C6 have
almost identical chemical shifts and therefore are observed as
one broad signal. The chemical shift of carbon atoms C8 and C14
diameters of up to 30 µm. These agglomerated structures were
proposed as the catalytically active regions in the emulsion. In the
present case however, a bimodal particle distribution with a major
population having a particle size at around 240 nm and a minor
population having a size around 1.8 µm (approx. the double size
of the hollow spheres of material 3) were observed. This results
suggests that unlike our previous report, most of the crushed
particles of material 4 are completely dispersed in the aqueous
medium without the formation of
agglomerations.
a significant amount of
–
that are directly connected to the -SO3H resp. -SO3 groups is
52.5 ppm, the resonance of the α-carbon atoms of some residual
ethoxy groups coming from the grafted ionic precursor is
observed at 58.1 ppm. The resonance of the unique sp2 hybrid-
ized carbon atom C11 is observed at 157.6 ppm.
Figure 3. Laser diffraction particle size analysis summarized over six measure-
ments of material 4 dispersed in water.
The activity of the surfactant-like material 4 was investigated for
the oxidative cleavage of cyclohexene to adipic acid. Scheme 2
presents the mechanism for this reaction as proposed by Noyori
et al..[3] An in-situ generated peroxotungstate species converts
cyclohexene to epoxycyclohexane, followed by a proton catal-
yzed the ring opening of this intermediate to trans-1,2-cyclohex-
anediol in the acidic aqueous medium. The oxidation of one of the
hydroxyl groups gives the corresponding α-hydroxyketone, which
is the substrate for a Baeyer–Villiger oxidation leading to a
hydroxylactone. Finally, the remaining hydroxyl group is oxidized
to produce adipic anhydride, which is rapidly hydrolyzed in the
presence of the acidic Janus-type catalyst 4.
Figure 2. Solid-state 13C CP-MAS NMR spectra of
4.
The 29Si CP-MAS NMR spectrum of material 4 (see Figure 2S,
Supporting Information) exhibits two dominant resonances at
around -110 and -120 ppm, being attributed to Q3 [Si(OSi)3OH]
resp. Q4 [Si(OSi)4] species in the framework of the materials. Two
further resonances in this spectrum at around -68 and -75 ppm
can be assigned to T2 [RSi(OSi)2(OH)] and T3 [RSi(OSi)3] units
and thus provide further evidence for the successful covalent im-
mobilization of the triethoxysilane precursors on the surface of the
materials.
To study the particle size distribution as well as particle dispersibi-
lity of catalyst 4 in water, laser diffraction analysis was employed
(Figure 3). The analyses were repeated six times and the results
indicate an excellent reproducibility of the measured data. In our
previous report,[7] we investigated two different hydrophobic/hydr-
ophilic catalysts by means of this analytic method. In these cases,
the formation of some temporary agglomerations of Janus-type
nanosheets in the solution was found, leading to particles with
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Scheme 2. Stepwise oxidation of cyclohexene to adipic acid. The inset shows
the action and regeneration of the catalyst.
An image of the initial reaction mixture containing the catalyst,
cyclohexene and aqueous H2O2 is shown in Figure 4a. After
shaking the suspension for 5 minutes, the color of the mixture
turned to red in the presence methyl orange as pH indicator.
Moreover, the phase boundary had disappeared and a uniform
suspension had formed, which turned out to be stabile for up to
one hour under static conditions. This proves the excellent mis-
cibility of organic and aqueous phases in the presence of the
heterogeneous surfactant 4. It is worth to be mentioned at this
point that the homogeneity of the reaction mixture increased
shortly after the reaction was started, which can be explained by
the formation of more polar intermediates from the initially present,
non-polar cyclohexene.
Figure 4. a) Images of the reaction mixture for the oxidation of cyclohexene at
different times (0 to 60 min) in the presence of two drops of an aqueous 0.1%
molar methyl orange solution as a colour and pH indicator and an image of the
final mixture in the absence of the indicator (right). Composition of the initial
mixtures: 75 mg of catalyst 4, 5 mmol (0.5 ml) of cyclohexene, 22 mmol (2.25
mL) of 30% H2O2 and 17 mg (0.05 mmol) of Na2WO4·2H2O. b) SEM image of
the labelled material before the oxidation step of the thiol (–SH) groups
decorated with citrate@Fe3O4 nanoparticles. The outer ionic liquid face is
labelled with citrate@Fe3O4 nanoparticle and the inner –SH face shows almost
no interaction.
At the end of reaction, a completely uniform suspension was
observed due to the interaction of the polar product with the
anisotropic functionalities of the catalyst’s faces (Figure 4a, right).
To provide additional evidence for the selective functionalization
of the material, negatively charged citrate-capped Fe3O4
nanoparticles (citrate@Fe3O4) were used according to a recently
published process to label the ionic liquid face of catalyst.[Fehler!
Textmarke nicht definiert.l] To do this, material 3 was partially crushed to
form large particles which are more suitable for the analysis by
SEM than smaller ones. Then the material was labelled by mixing
with citrate@Fe3O4 before the oxidation of the –SH groups and
the resulting solid was analyzed by SEM. The resulting image
(Figure 4b) shows the high affinity of the outer (ionic liquid) face
to the citrate@Fe3O4 particles, while the inner –SH face almost
remains untouched by the citrate@Fe3O4 particles. This indicates
that the two different groups are selectively bound to the inner
resp. outer surface of the support.
According to Scheme 2, the reaction requires four equiv. of H2O2.
To guarantee an almost complete conversion of cyclohexene, 4.4
equivalents of the oxidant were used.[3] It turned out to have a
positive impact on the outcome of the reaction,[11] to heat the
mixture first to 71 ᵒC (near to the boiling point of the initial reaction
mixture) for 3 h. At the end of this step, cyclohexene was
completely converted to cyclohexene oxide which has higher
boiling point. Then, the temperature was raised to 87 ᵒC for 16 h.
The dependence of the yield from the amount of material 4 in the
mixture is depicted in Figure 5. Moderate yields of adipic acid are
obtained with 25 and 50 mg of the 4. However, in the presence of
75 mg of 4 overall 78% of pure adipic acid (after recrystallization)
were formed. By further increasing the amount of surfactant 4 to
100 mg, the yield of adipic acid reached 62%. Such a decrease
of yield can be explained by the increase of the ionic strength in
the suspension in the presence of large amounts of the catalyst.
This will slow down the diffusion of an organic substrate.
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material 4 was tested for the ring opening of the phthalic anhy-
dride in water (entry 7) since an acid-catalyzed ring opening was
postulated to occur during the formation of adipic acid. Here,
excellent yields of phthalic acid demonstrate that the ring-opening
step in the depicted mechanism (Scheme 2) is indeed a rapid
reaction. The acidity of the catalyst was further investigated for
the synthesis diethyl phthalate being an important plasticizer used
in industries. The reaction proceeded well with up to 85% yield of
diethyl phthalate (entry 8).
To understand the mode of action of surfactant 4, it helps to recall
the mechanistic discussions on this reaction that have been
published in the past. It is not yet completely clear, which step of
the described reaction sequence in Scheme 2 is the rate-deter-
mining one. The olefin epoxidation should be rapid with the given
tungsten catalyst. The same is true for the ring-opening of the
epoxide in the presence of the Brønsted acidic material 4 as
shown above Thomas et al. found that in the following step the
trans-diol isomer reacts significantly slower than the cis-diol.[12]
Therefore, improvement of the trans-diol oxidation step is expec-
ted to affect the overall reaction rate. However, when we used the
trans-diol instead of the cyclohexene as starting material, no
noticeable changes in the yield of adipic acid was found. This
observation explains the independence of the reaction rate from
the epoxidation of cyclohexene. In the synthesis of adipic acid by
oxidation of cyclohexanol and cyclohexanone, Sato et al.
proposed that the Baeyer-Villiger oxidation might be the rate-
determining step of the reaction.[13] A low reaction rate of the
Baeyer-Villiger oxidation of α-hydroxyketones was also proposed
by Noyori et al..[3a]
Figure 5. The influence of the amount of catalyst 4 on the outcome of the
oxidation of cyclohexene to adipic acid. Reaction conditions: 5 mmol (0.5 ml) of
cyclohexene, 22 mmol (2.25 mL) of 30% aqueous H2O2 and 17 mg (0.05 mmol)
of Na2WO4·(H2O)2, 71 °C (3 h) then 87 °C (16 h). Yields refer to isolated, pure
adipic acid after recrystallization from ethyl acetate.
It was found that in the absence of catalyst, the oxidation of cyclo-
hexene led to the formation of small amounts of adipic acid under
the optimized conditions (less than 5%). Moreover, the yield of
adipic acid reached only 8% when material 2 (75 mg) was used
as the catalyst and the catalyst showed just a weak emulsifying
character. Although material
3 showed better emulsifying
properties compared to 2, the yield of adipic acid did not exceed
over 15%. We found that when the acidic site of catalyst 4 was
neutralized with a 1% solution of sodium bicarbonate, the
resulting material had a very good emulsifying performance.
However, the oxidation of cyclohexene with this catalyst afforded
just 10% of adipic acid. These observations suggest that the
presence of acidic groups accompanied by amphiphilic nature of
the material is crucial for achieving high catalytic activity.
To find evidence for these suggestions, we set up two experi-
ments considering the oxidation of cyclohexanone and cyclohex-
anol according to the conditions employed in entries 3 and 4 of
Table 1. The reactions were quenched after 8 h, then the mixtures
were analyzed by means of gas chromatography. In case cyclo-
hexanone was used as the starting material the conversion was
not quantitative, some cyclohexanone was still present in the mix-
ture. On the other hand, in the same reaction time, the oxidation
of cyclohexanol led to complete conversion of the starting material.
However, again the presence of some cyclohexanone (from the
oxidation of cyclohexanol) was observed. These findings make
plausible that the Baeyer-Villiger oxidation of the ketone is the
rate-determining step.
In each reaction, the catalyst was simply separated by filtration or
centrifugation from the reaction mixture. Regeneration of catalyst
4 is possible by drying the filtered solid under vacuum. The
catalyst recovered this way was tested in two further batch
reactions under the conditions shown in the caption of Figure 5
and afforded 76% resp. 70% of adipic acid for the second resp.
the third run. Including the fact that there is some loss of solid
material during the filtration process, surfactant 4 has preserved
it’s activity over three runs.
Encouraged by the results obtained from the oxidation of cyclo-
hexene to adipic acid, we investigated the application of material
4 for further oxidation reactions in the following (Table 1). The
oxidation of trans-1,2-cyclohexanediol furnished with an almost
identical yield of adipic acid as the oxidation of cyclohexene (entry
2). Cyclohexanone and cyclohexanol can also be converted to
adipic acid with high yield (entries 3 and 4) which is in general
fitting to the mechanistic image given in Scheme 2. Aside to adipic
acid, glutaric acid is another important building block for polymer
synthesis. By using material 4 and sodium tungstate, glutaric acid
can be prepared by the oxidation of cyclopentene. Due to the low
boiling point of this substrate (44-46 ᵒC), the mixture was heated
only to 45 ᵒC in the first step (entry 5). When styrene was used as
the substrate, high yields of benzoic acid were obtained (entry 6).
The according C1 product generated by the cleavage of the C=C
double bond of styrene was not analyzed in detail. Moreover,
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COMMUNICATION
Table 1. Investigation of the catalytic activity of material 4.
entry
substrate(s)
time [h]/ temp. [ᵒ C]
3/ 71 then 16/ 87
16/ 87
H2O2 [equiv.]
product
isolated yield(%)a
1
2
3
4
5
6
7
8
a
cyclohexene
4.4
3.3
3.3
4.4
4.4
4.4
–
adipic acid
adipic acid
adipic acid
adipic acid
glutaric acid
benzoic acid
phthalic acid
diethyl phthalate
78
trans-1,2-cyclohexanediol
cyclohexanone
cyclohexanol
79
16/ 87
83
16/ 87
80
cyclopentene
3/ 45 then 16/ 87
16/ 87
76
styrene
84
phthalic anhydride
phthalic anhydride + ethanol
16/ 70
98b,c
85b,d
16/ 70
–
b
reaction conditions: 5 mmol of substrate, 75 mg of material 4, 17 mg of Na2WO4·(H2O)2, unless otherwise stated. The reactions were performed in the
absence of the oxidant and sodium tungstate. c 2 mL of H2O were used for the hydrolysis reaction. d 2 mL of ethanol were used.
As a working hypothesis to explain the high efficiency of material
4, we believe that the rapid epoxide formation and hydrolysis
generates large amounts of the intermediate 1,2-diol that can
strongly interfere with the functional groups on the surface of the
material. The same is true for all other intermediates, hydrogen
peroxide and tungsten species. It might be that highly polar water
is partially expelled from the surface,[14] which despite all polar
groups still has some organic character. This would in addition
oxidized such as cyclopentene, cyclohexanol, cyclohexanone and
trans-1,2-cyclohexanediol). A scale-up resulting in the formation
of almost 18 g of adipic acid was realized without further
optimization of the reaction conditions. Catalyst regeneration is
possible by simple filtration of 4. The catalyst was tested in three
consecutive batches without significant loss of reactivity. The
complete and simple recovery of a highly active solid surfactant is
a substantial step towards greener protocols and therefore of
increase the local concentrations of all other players at the surface. general importance for chemical synthesis and catalysis.
The final product adipic acid is the most polar organic compound
in the reaction sequence. It therefore should be better soluble in
the aqueous phase and leave the surface.
Experimental Section
Since adipic acid synthesis is an industrially important process,
the possibility for a process scale-up is of interest. Only a few
examples for applications of Janus-type materials in catalytic
large-scale syntheses have been reported so far.[15] Therefore a
protocol was worked out wherein the amounts of all reaction
partners were increased by a factor of 30 (e.g. 12.3 g resp. 150
mmol of cyclohexene). At the end of this reaction, the catalyst was
separated from the hot slurry by filtration. The flask containing the
filtrate was immersed into an ice bath for 30 min and the pre-
cipitated adipic acid was separated by filtration. After washing with
water to remove residual H2O2 and tungsten(VI) species and
drying at room temp. 17.8 g (81%) of pure adipic acid could be
obtained.
The details of experimental procedure for the synthesis of the catalyst and
oxidation of cyclohexene are provided in the electronic supporting
information.
Acknowledgements
The authors wish to thank the Alexander von Humboldt Found-
ation for a Georg Forster research fellowship to M. Vafaeezadeh
and the research unit NanoKat at the TU Kaiserslautern for
financial support.
To conclude, by mimicking the properties of a homogeneous
Brønsted acidic PTC, the heterogeneous surfactant 4 was pre-
pared. In combination with Na2WO4·(H2O)2 it turned out to give a
highly active mixture for the selective oxidation of cyclohexene to
adipic acid. In addition, some other substrates can efficiently be
Keywords: heterogeneous surfactant • Janus interphase
catalyst • miscibility • aqueous-phase oxidation • adipic acid
[3]
[4]
a) K. Sato, M. Aoki, R. Noyori, Science 1998, 281, 1646–1647; b) R.
Noyori, M. Aoki, K. Sato, Chem. Commun. 2003, 1977–1986.
References
[1]
a) R. A. Mayer in The 100 most important chemical compounds, 1st ed,
Greenwood Press, London, 2007, pp. 20–23; b) M. T. Musser in Ull-
mann's encyclopedia of industrial chemistry, Wiley-VCH, Weinheim,
2005; c) S. Van de Vyver and Y. Román-Leshkov, Catal. Sci. Technol.
2013, 3, 1465–1479.
a) W. Zhu, H. Li, X. He, Q. Zhang, H. Shu, Y. Yan, Catal. Commun. 2008,
9, 551–555; b) Y. Wen, X. Wang, H. Wei, B. Li, P. Jin, L. Li, Green Chem.
2012, 14, 2868–2875; c) M. Vafaeezadeh, M. M. Hashemi, RSC Adv.
2015, 5, 31298–31302; d) M. Vafaeezadeh, M. M. Hashemi, Chem. Eng.
J. 2013, 221, 254–257; e) Z. Saedi, S. Tangestaninejad, M. Moghadam,
V. Mirkhani, I. Mohammadpoor-Baltork, Catal. Commun. 2012, 17, 18–
22; f) M. N. Timofeeva, O. A. Kholdeeva, S. H. Jhung, J. -S. Chang, Appl.
[2]
F. Cavani J. H. Teles, ChemSusChem 2009, 2, 508–534.
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10.1002/cctc.202000140
ChemCatChem
COMMUNICATION
8057; g) M. Zhang, Z. Tang, W. Fu, W. Wang, R. Tan, D. Yin, Chem.
Commun. 2019, 55, 592–595; h) S. Cobo, J. Heidkamp, P. Jacques, J.
Fize, V. Fourmond, L. Guetaz, B. Jousselme, V. Ivanova, H. Dau, S.
Palacin, M. Fontecave, V. Artero, Nat. Mater. 2012, 11, 802–807; i) Z.
Xue, H. Su, Q. Yu, B. Zhang, H. Wang, X. Li, J. Chen, Adv. Energy Mater.
2017, 7, 1602355–1602361; j) X. Wang, B. Guan, Y. He, Y. Zhang, Y.
Cao, Y. Liu, Z. Qiao, Q. Huo, ChemNanoMat 2015, 1, 562–566; k) L. Xia,
H. Zhang, Z. Wei, Y. Jiang, L. Zhang, J. Zhao, J. Zhang, L. Dong, E. Li,
L. Ruhlmann, Q. Zhang, Chem. Eur. J. 2017, 23, 1920–1929; l) X. Ji, Q.
Zhang, X. Qu, Q. Wang, X. Song, F. Liang, Z. Yang, RSC Adv. 2015, 5,
21877–21880; m) S. Yan, H. Zou, S. Chen, N. Xue, H. Yang, Chem.
Commun. 2018, 54, 10455–10458; n) W. Gao, A. Pei, R. Dong, J. Wang,
J. Am. Chem. Soc. 2014, 136, 2276–2279; o) R. A. Pavlick, S. Sengupta,
T. McFadden, H. Zhang, A. Sen, Angew. Chem. Int. Ed. 2011, 50, 9374–
9377; Angew. Chem. 2011, 123, 9546–9549.
Catal. A 2008, 345, 195–200; g) G. Lapisardi, F. Chiker, F. Launay, J.-P.
Nogier, J.-L. Bonardet, Catal. Commun. 2004, 5, 277–281; h) Y. Deng,
Z. Ma, K. Wang, J. Chen, Green Chem. 1999, 1, 275–276; i) M.
Vafaeezadeh, M. M. Hashemi, M. Shakourian-Fard, Catal. Commun.
2012, 26, 54–57; j) M. Vafaeezadeh, M. M. Hashemi, Catal. Commun.
2014, 43, 169–172; k) M. Damm, B. Gutmann, C. O. Kappe,
ChemSusChem 2013, 6, 978–982; l) C.-Y. Cheng, K.-J. Lin, M. R.
Prasad, S.-J. Fu, S.-Y. Chang, S.-G. Shyu, H.-S. Sheu, C.-H. Chen, C.-
H. Chuang, M.-T. Lin, Catal. Commun. 2007, 8, 1060–1064; m) B. C.
Ranu, S. Bhadra, L. Adak, Tetrahedron Lett. 2008, 49, 2588–2591; n) Z.
Bohström, I. Rico-Lattes, K. Holmberg, Green Chem. 2010, 12, 1861–
1869.
[5]
a) A. Walther, A. H. E. Müller, Chem. Rev. 2013, 113, 5194–5261; b) M.
Lattuada, T. A. Hatton, Nano Today 2011, 6, 286–308; c) J. Hu, S. Zhou,
Y. Sun, X. Fang, L. Wu, Chem. Soc. Rev. 2012, 41, 4356–4378; d) Y.
Song, S. Chen, Chem. Asian J. 2014, 9, 418–430; e) A. Walther, A. H.
E. Müller, Soft Matter 2008, 4, 663–668; f) E. Poggi, J. -F. Gohy, Colloid
Polym. Sci. 2017, 295, 2083–2108; g) F. Liang, C. Zhang, Z. Yang, Adv.
Mater. 2014, 26, 6944–6949; h) F. Liang, B. Liu, Z. Cao, Z. Yang,
Langmuir 2018, 34, 4123−4131; i) Z. Teng, X. Su, Y. Zheng, J. Sun, G.
Chen, C. Tian, J. Wang, H. Li, Y. Zhao, G. Lu, Chem. Mater. 2013, 25,
98−105; j) Y. Chen, F. Liang, H. Yang, C. Zhang, Q. Wang, X. Qu, J. Li,
Y. Cai, D. Qiu, Z. Yang, Macromolecules 2012, 45, 1460−1467; k) F.
Liang, J. Liu, C. Zhang, X. Qu, J. Li, Z. Yang, Chem. Commun. 2011, 47,
1231–1233; l) X. Ji, Q. Zhang, F. Liang, Q. Chen, X. Qu, C. Zhang, Q.
Wang, J. Li, X. Song, Z. Yang, Chem. Commun. 2014, 50, 5706–5709;
m) F. Liang, K. Shen, X. Qu, C. Zhang, Q. Wang, J. Li, J. Liu, Z. Yang,
Angew. Chem. Int. Ed. 2011, 50, 2379–2382.
[7]
M. Vafaeezadeh, P. Breuninger, P. Lösch, C. Wilhelm, S. Ernst, S. An-
tonyuk, W. R. Thiel, ChemCatChem 2019, 11, 2304–2312.
[8]
[9]
W. Stöber, A. Fink, E. Bohn, J. Coll. Interf. Sci. 1968, 26, 62–69.
B. Schäfgen, O. D. Malter, E. Kaigarula, A. Schüßler, S. Ernst, W. R.
Thiel, Microporous Mesoporous Mater. 2017, 251, 122–128.
[10] a) L. Wang, A. Reis, A. Seifert, T. Philippi, S. Ernst, M. Jia, W. R. Thiel,
Dalton Trans. 2009, 3315–3320; b) L. Wang, S. Shylesh, D. Dehe, T.
Philippi, G. Dörr, A. Seifert, Z. Zhou, M. Hartmann, R. N. K. Taylor, M.
Jia, S. Ernst, W. R. Thiel, ChemCatChem 2012, 4, 395–400; c) S.
Farsadpour, L. T. Ghoochany, S. Shylesh, G. Dörr, A. Seifert, S. Ernst,
W. R. Thiel, ChemCatChem 2012, 4, 401–407.
[11] P. Jin, Z. Zhao, Z. Dai, D. Wei, M. Tang, X. Wang, Catal. Today 2011,
175, 619–624.
[12] S. Lee, R. Raja, K. D. M. Harris, J. M. Thomas, B. F. G. Johnson, G.
Sankar, Angew. Chem. Int. Ed. 2003, 42, 1520–1523.
[6]
a) Z. Wu, L. Li, T. Liao, X. Chen, W. Jiang, W. Luo, J. Yang, Z. Sun, Nano
Today 2018, 22, 62–82; b) D. J. Cole-Hamilton, Science 2010, 327, 41–
42; c) S. Crossley, J. Faria, M. Shen, D. E. Resasco, Science 2010, 327,
68–72; d) R. A. Pavlick, S. Sengupta, T, McFadden, H. Zhang, A. Sen,
Angew. Chem. Int. Ed. 2011, 50, 9374–9377; e) L. Xia, H. Zhang, Z. Wei,
Y. Jiang, L. Zhang, J. Zhao, J. Zhang, L. Dong, E. Li, L. Ruhlmann, Q.
Zhang, Chem. Eur. J. 2017, 23, 1920–1929; f) X. Kong, C. Wu, L. Feng,
J. Qu, P. Liu, X. Wang, X. Zhang, Chem. Commun. 2017, 53, 8054–
[13] Y. Usui, K. Sato, Green Chem. 2003, 5, 373–375.
[14] B. Karimi, M. Vafaeezadeh, RSC Adv. 2013, 3, 23207–23211.
[15] a) C, Tang, C. Zhang, J. Liu, X. Qu, J. Li, Z. Yang, Macromolecules 2010,
43, 5114–5120; b) C. Zhang, B. Liu, C. Tang, J. Liu, X. Qu, J. Li, Z. Yang,
Chem. Commun. 2010, 46, 4610–4612.
This article is protected by copyright. All rights reserved.

10.1002/cctc.202000140
ChemCatChem
COMMUNICATION
Entry for the Table of Contents
COMMUNICATION
A novel surfactant-like heterogeneous
Janus nano-catalyst is applied for the
decagram-scale synthesis of adipic
acid from the oxidation of cyclohexene
with hydrogen peroxide. The catalyst
was also used for the oxidation of
other compounds to carboxylic acid
derivatives as well as the synthesis of
diethyl phthalate by esterification of
phthalic anhydride with ethanol.
Majid Vafaeezadeh,* Christian Wilhelm,
Paul Breuninger, Stefan Ernst+, Sergiy
Antonyuk, and Werner R. Thiel*
Page No. – Page No.
A Janus-type Heterogeneous
Surfactant for Adipic Acid Synthesis
This article is protected by copyright. All rights reserved.