Synthesis, characterization and application of γ-MnO2/graphene oxide for the selective aerobic oxidation of benzyl alcohols to corresponding carbonyl compounds

Article abstract of DOI:10.1039/c5nj03140k

A facile low temperature approach was used to synthesize γ-MnO₂ on the surface of graphene oxide (GO) through a simple wet precipitation method using MnSO₄ as a precursor. X-ray diffraction analysis and Raman spectroscopy confirmed the formation of γ-phase MnO₂ in the MnO₂/GO nanocomposites. Transmission electron microscopy studies showed that γ-MnO₂ exists as flower and needle structures in GO with an average size of approximately 15 nm. Inductively coupled plasma atomic emission spectroscopy studies confirmed a 62.5 wt% loading of γ-MnO₂ in the GO nanocomposites. The γ-MnO₂/GO catalyst shows good activity for the selective aerobic oxidation of benzyl alcohols to corresponding carbonyl compounds even when present in sub-stoichiometric amounts giving 91% yield over 3 h under mild reaction conditions. The catalyst showed high activity even after three cycles indicating good recyclability.

Full text of DOI:10.1039/c5nj03140k

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Page 1 of 23
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Synthesis, Characterization and Application of γꢀMnO /Graphene Oxide for Selective
2
Aerobic Oxidation of Benzyl Alcohols to Corresponding Carbonyl Compounds
1
1
1,2
1
1, 3,
Kadam, Mahesh M. , Dhopte, Kiran B. , Jha, Neetu , Gaikar, Vilas G. , Nemade, Parag R.
*
1
Department of Chemical Engineering, Institute of Chemical Technology, Nathalal Parekh
Marg, Matunga, Mumbai Maharashtra, 400019, India.
2
Department of Physics, Institute of Chemical Technology, Nathalal Parekh Marg, Mumbai,
Maharashtra, 400 019, India.
3
Department of Oils, Oleochemicals and Surfactant Technology, Institute of Chemical
Technology, Nathalal Parekh Marg, Mumbai, Maharashtra, 400 019, India.
*
Corresponding Author
Tel.: + 91ꢀ 22 3361 2027;
Fax: +91ꢀ 22 3361 1020.
Eꢀmail address: pr.nemade@ictmumbai.edu.in.
1

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Abstract
Facile low temperature approach was used to synthesize γꢀMnO on the surface of graphene
2
oxide (GO) through simple wet precipitation method using MnSO as precursor. Xꢀray
4
diffraction analysis and Raman spectroscopy confirmed the formation of γꢀphase MnO in
2
MnO /GO nanocomposites. Transmission electron microscopy studies showed γꢀMnO exists as
2
2
flower and needle structures in GO with an average size of approximately 15 nm. Inductive
coupled plasma atomic emission spectroscopy studies confirm a 62.5 wt. % loading of γꢀMnO in
2
GO nanocomposites. γꢀMnO /GO catalyst shows good activity for the selective aerobic oxidation
2
of benzyl alcohols to corresponding carbonyl compounds even when present in subꢀ
stoichiometric amounts giving 91% yield over 3 h under mild reaction conditions. The catalyst
showed high activity even after three cycles indicating good recyclability.
Keywords : heterogeneous catalyst, GO, γꢀMnO /GO, flower shaped, benzyl alcohol,
2
benzaldehyde
2

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Introduction
Manganese dioxide (MnO ) is reported to be one of the most stable oxides with high catalytic
2
activity and low cost. MnO exists in α, β, and γ forms depending on the arrangement of the
2
1
,3
basic [MnO ] octahedral unit. Polymorphism had opened broad range of applications in
6
1
ꢀ3
catalysis, biosensors, energy storage. Several efforts have been directed towards the synthesis
3
ꢀ6
of polymorphs of MnO with different morphology. However, only few reports have focused
2
7
,8
on the synthesis of MnO hierarchical architecture. Among MnO phases, γꢀphase MnO is
2
2
2
more active catalytically in comparison to α and βꢀphases.
MnO is commonly used as catalyst for selective oxidation of aromatic alcohols to carbonyl
2
compounds. However, it is used in in greater than stoichiometric amounts, thereby generating
large amount of waste. Owing to its high activity, γꢀMnO when used in greater than
2
stoichiometric amounts for catalyzing the oxidation gives large amount of undesirable overꢀ
oxidation products such acids and esters. Therefore, αꢀMnO is commonly employed for
2
industrial oxidations. Several noble metal and nanoꢀcatalysts have been reported for this
industrially important oxidation. Over 98 % conversion has been reported using metallic and
1
0
11
bimetallic catalysts such as goldꢀcopper on silica, palladium nanoclusters. Gold nanoparticles
1
2
13
in presence of trace amount of metal carbonates, Ru supported on Al O have showed almost
2
3
99% selectivity. Kamimura and coꢀworkers reported use of subꢀstoichiometric amount (28 %
mol) of Co activated birnessite MnO for oxidation of benzyl alcohols to corresponding carbonyl
2
9
compounds at 110 °C and oxygen atmosphere obtaining 84 % yield in 24 h. However,
performance of the catalyst under aerobic conditions was much lower. Use of pure oxygen for
oxidations is typically not feasible, and loss of noble metalꢀbased catalysts during processing is
also a concern.
2

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Performance of inorganic nanostructures can be enhanced by tethering it with carbonaceous
materials like highly ordered pyrolytic graphite, graphene, graphene oxide (GO), etc. GO, in
particular, has been shown to enhance catalytic activity by synergistic charge delocalization,
oxidizing properties, etc. Additionally, GO due to its large surface area and good thermal
1
4,15
stability is ideal as catalytic support.
Oxygenated functional groups such as epoxy, carboxyl
and hydroxyl, attached on GO sheet act as anchor sites for growth of inorganic nanostructures,
1
6
complexation of ions, etc. Recently, transition metal free oxidation pathway using graphene
17,18
oxide (GO) as ‘carbocatalyst’ has been reported for oxidation of benzyl alcohols.
However,
the methodology involved long reaction times even under sonicating conditions as well as the
large catalytic loading. During oxidation of benzyl alcohols to carbonyl compounds, the
elimination of hydrogen from the hydroxyl groups is considered to be the rate determining step,
and an alkali is added to accelerate the rate of elimination. GO can complex with ions such as
potassium, and the acceleration of elimination can be achieved using a mild base such as K CO .
2
3
Further tethering MnO on GO, we can exploit the synergistic charge transfer effects stabilizing
2
carbanion formed during the reaction, thereby enhancing the catalytic activity of MnO . Thus, γꢀ
2
MnO /GO composite is expected to be an excellent catalyst, and when used in subꢀstoichiometric
2
amounts, formation of most overꢀoxidation products could also be prevented.
Here, we report methodology for low temperature synthesis of 3D nanostructures of γꢀMnO2
supported on GO nanocomposites combining high catalytic ability of γꢀMnO with high surface
2
area and thermal stability of GO. γꢀMnO /GO nanocomposites were characterized using Xꢀray
2
diffraction, Raman spectroscopy, inductively coupled plasmaꢀatomic emission spectroscopy,
thermogravimetric analysis and high resolution transmission electron microscopy. Catalytic
activity of γꢀMnO /GO nanocomposites was studied for selective aerobic oxidation of benzyl
2
3

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alcohols to benzaldehyde. αꢀMnO nanorods supported on GO have been previously reported as
2
1
9
an active catalyst for amide synthesis in aqueous media. However, the significance of crystal
phase and precursor for MnO synthesis was not explicated. Further, the reaction was carried out
2
under 3 MPa pure oxygen pressure while our methodology pursues oxidation of benzyl alcohol
under aerobic conditions at atmospheric pressure, and at much lower catalyst loading. The effect
of temperature, loading of base and recycle of catalyst on yield was also studied.
Experimental
Materials
Manganese sulfate (MnSO ), potassium permanganate (KMnO ), 2ꢀpropanol (AR grade)
4
4
were purchased from S. D. Fine Chemicals Ltd., Mumbai. Deꢀionized water was used for the all
the experiments.
Synthesis of γꢀMnO /GO nanocomposites
2
Graphene oxide (GO) was prepared from natural graphite powder by modified Hummer
2
0
method. γꢀMnO /GO nanocomposites were synthesized by simple chemical precipitation
2
3
method. Graphene oxide (0.60 g) was dispersed in deꢀionized water (50 cm ) by sonicating for
3
3
0 min, followed by addition of MnSO (1.80 g) and 2ꢀpropanol (50 cm ) under continuous
4
stirring. Reaction mixture was heated to 80 °C for 15 min under vigorous stirring. Aqueous
3
solution of KMnO (0.6 g/5 cm ) was added dropꢀwise to the above refluxing solution. After 30
4
min, the reaction mixture was cooled and centrifuged. The residue obtained was further washed
with DI water, followed by 2ꢀ propanol for removal of any inorganic salts formed in reaction and
1
was then dried at 30 °C for 24 h.
Characterization of γꢀMnO /GO nanocomposites
2
4

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Crystal structure of the γꢀMnO /GO nanocomposites was studied using Xꢀray diffraction (2θ
2
=
5° to 80°, Bruker Xꢀ ray Diffractometer, D8ꢀAdvance) with a data scanning rate of 0.016
sec/step, using monochromatized Cu Kα radiation (1.5406 Å). Raman spectra were analyzed by
HRꢀ800 (Horiba Scientific) by using an excitation at 632 nm. Size of γꢀMnO /GO
2
nanocomposites was determined using high resolution transmission microscopy (HRꢀTEM,
JEOL, 2100). Images were collected with an operating voltage of 200 kV. Fourier transform
infrared spectra (FTIR) were recorded on BrukerꢀVERTEX 80V instrument aligned with Ultraꢀ
ꢀ1
Scan interferometer with a resolution of 1 cm wave number. MnO loading on GO surface was
2
calculated by using inductive coupled plasma (ICPꢀAES, Element XR, Thermo Fisher Scientific,
Germany). This was further supported by Thermogravimetric analysis (TGA) carried out from
ꢀ1
3
0 to 700 °C with Thermax 700 TGA at a heating rate of 20 °C min in air flow.
Catalytic oxidation of benzyl alcohols
3
Alcohol (1.0 mmol), γꢀMnO /GO (0ꢀ10% mole basis), K CO (0ꢀ1.0 mmol) and 3 cm
2
2
3
3
toluene were stirred for appropriate time in a 10 cm reactor at 80°C under aerobic conditions.
Reaction was monitored using thinꢀlayer chromatography (TLC). After completion of reaction,
the reaction mass was cooled to 30 °C, followed by filtration to recover the catalyst. Reaction
3
mass was washed with DI water (2 × 5 cm ). The organic layer was concentrated under vacuum
and further purified by column chromatography (silica gel 100ꢀ200 mesh, hexane/ethyl acetate)
to obtain corresponding products.
Catalyst recycle
Catalyst was recovered by filtering it from reaction mixture cooled to 30 °C. Filtered
catalyst was washed with DI water until neutral pH was obtained. It was then washed with 2ꢀ
5

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propanol. The residue was further dried at 30 °C for 12 h followed by 4 h drying at 50 °C and
was then used for the oxidation of alcohol.
Results and Discussion
γꢀMnO /GO nanocomposites were synthesized by wet impregnation by oxidation MnSO4
2
precursor. The nanocomposites were characterized and evaluated for selectively catalyzing
aerobic oxidation of benzyl alcohols to benzaldehyde. γꢀphase of the MnO was confirmed by Xꢀ
2
ray diffraction and Raman analysis. MnO loading was confirmed by inductive coupled plasma
2
(
ICPꢀAES) and thermal stability was studied using thermogravimetric analysis (TGA) analysis.
High resolution transmission microscopy (HRꢀTEM) was used to determine the morphology of
MnO nanoparticles.
2
GO
GO/γꢀMnO2
(001)
(131)
(120)
(300)
(160)
0
10
20
30
40
50
60
70
80
2θ
Figure 1. XRD pattern of GO and γꢀMnO /GO nanocomposites.
2
6

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Powder XRD pattern of GO shows an intense and sharp diffraction peak of GO at 2θ =
10.34° corresponds to (001) reflection giving an interlayer dꢀspacing of 0.85 nm (Figure 1). This
value of dꢀspacing is higher than in pristine graphite (0.34 nm) due to the localization of several
20
oxygenated functional groups on the graphite sheet. In γꢀMnO /GO nanocomposites, (001)
2
diffraction peak of GO disappeared. Diffraction peaks of γꢀMnO /GO nanocomposites at 2θ
2
values of 22.11°, 37.76°, 43.07° and 55.84° correspond to (120), (131), (300) and (160) lattice
planes respectively, indicating formation of closely packed hexagonal crystal structure of γꢀ
Figure 2. Raman spectra of GO and γꢀMnO /GO nanocomposites
2
7

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2
1
MnO (ICDDꢀJCPDS No. 14ꢀ0644). Average size of γꢀMnO nanocrystals estimated using
2
2
Scherrer equation is 19.5 nm. On the other hand, the (001) diffraction peak of layered GO in the
γꢀMnO /GO nanocomposite disappeared (Figure 1). This is due to the incorporation of MnO2
2
nanocrystals within the GO sheets, resulting in exfoliation and disturbance of regular stacking of
GO sheets.
Structural and electronic changes due to the growth of MnO crystals on GO sheets were
2
ꢀ1
studied by Raman spectroscopy. Figure 2. shows a sharp peak at 648 cm in γꢀMnO /GO
2
2
1
nanocomposites spectrum, which can be attributed to γꢀphase of MnO . Raman spectra of γꢀ
2
ꢀ1
ꢀ1
MnO /GO nanocomposites show red shift of characteristic G (1583 cm to 1603 cm ) and D
2
ꢀ1
ꢀ1
(
1331 cm to 1356 cm ) peaks as compared to GO which is an important evidence of the strong
2
2
coupling and charge transfer between the γꢀMnO and GO sheet. Interaction of γꢀMnO with
2
2
GO was also investigated using FTIR spectroscopy (Figure 3). In GO, the stretching frequencies
ꢀ
1
ꢀ1
of carbonyl group (υC=O) and alkoxy group (υCꢀO) are observed at 1742 cm and 1050 cm
1
0
0
0
0
0
0
.00
.95
.90
.85
.80
.75
.70
GO
γ
ꢀ MnO /GO
2
CꢀO
C=O
MnꢀO
00
OꢀH
3500
5
1000
1500
2000
2500
3000
ꢀ
1
Wavenumber (cm )
Figure 3. FTIR spectra of GO oxide and γꢀMnO /GO
2
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ꢀ1
respectively. Broad peak at 3418 cm is due to stretching of hydroxyl groups (υOꢀH) present on
ꢀ1
surface of GO. Peak at 1638 cm indicates skeletal vibrations from unoxidized graphitic carbon
23,24
−1
−1
(υC=C).
In γꢀMnO /GO nanocomposites, bands located at 466 cm and 524 cm can be
2
25,26
ascribed to MnꢀO vibrations in MnO2.
Frequencies of vibration of carbonyl (υC=O) group
ꢀ1
significantly shift towards lower wavenumber viz. 1729 cm , which indicate interaction of γꢀ
MnO with GO sheets.
2
Morphology of γꢀMnO and manganese loading was determined by HRꢀTEM and ICPꢀAES
2
analyses, respectively. Figure. 4 (a) displays TEM image of pure GO which possesses a thin
sheet like silky transparent morphology, whereas γꢀMnO /GO nanocomposites (Figure. 4 (b) and
2
4
(c)) exhibit a dispersion of flower and needle shaped MnO nanocrystals on the surface as well
2
a
b
d
c
5
0 nm
Figure 4. HRꢀTEM images of (a) GO, (b) γꢀMnO /GO, (c) γꢀMnO /GO at higher
2
2
magnification and (d) γꢀMnO /GO after 2 recycles
2
9

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as on the edge of GO sheets. GO sheets in γꢀMnO /GO appear slightly crumpled due to
2
attachment of γꢀMnO with oxygenated functional groups on the GO surface, as compared to
2
pure GO sheets. The few nanocrystals appears dark while others appear bright, which indicates
that MnO nanocrystals are attached to both sides of GO sheets. The size of the synthesized
2
MnO nanocrystals, were found to be range of 15ꢀ30 nm. TEM image of catalyst obtained after
2
two recycles is shown in Figure 4 (d), shows slight aggregation of MnO crystal. Inꢀsitu bonding
2
2
+
of divalent Mn (formed by the dissociation of MnSO .2H O in aqueous 2ꢀpropanol) to the
4
2
negatively charged oxygenated functional groups present on plane and on edges of GO sheets.
On addition of KMnO solution at 80 °C, several nuclei are generated in a short duration from
4
2
+
7+
the redox reaction occurring between Mn and Mn , which further leads to formation of MnO .
2
1
MnO crystalline pattern and morphologies is related to arrangement of basic MnO octahedron
2
6
27
units. Mn atoms of the MnO octahedron may link with O atoms of GO functional groups via
6
an intermolecular hydrogen bond or a covalent coordination bond. These O atoms on GO act as
anchor sites for the growth of MnO crystals and hence the regular layer stacking of GO sheets
2
gets disturbed. The flower and needle shaped MnO nanocrystals in the γꢀMnO /GO
2
2
nanocomposites were formed in H O/2ꢀpropanol mixture. Further, confinement for growth of
2
crystals between GO sheets probably leads to formation of flower and needle shaped structures
on the planes of GO sheets.
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0

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nd
Figure 5. Thermogravimetric analysis of pure γꢀMnO and γꢀMnO /GO after 2 recycle.
2
2
ICPꢀAES analysis indicates 39.5% (w/w) of Mn present in the γꢀMnO /GO
2
nanocomposites, giving about 62.5 wt.% of MnO in nanocomposites. Thermogravimetric
2
analyses (TGA) was carried out to determine the stability of γꢀMnO /GO (Figure 5). Due to
2
1,29,30
heating in air, GO sheets get oxidized while MnO gets converted into Mn O
GO showed
2% weight loss between 100 to 200 °C, which is attributed to the loss of free and bound
2
2
3.
2
moisture. Further, significant weight loss, observed between 200ꢀ700 °C, can be attributed to the
loss of chemical functionality and oxidation of GO sheets. Total weight loss of γꢀMnO /GO
2
nanocomposites was found to be 38.5%, this may be due to degradation of GO and loss of
oxygen during conversion of MnO to Mn O .
2
2
3
Catalytic activity of γꢀMnO /GO nanocomposite was studied for selective oxidation of
2
benzyl alcohol to benzaldehyde with air as the oxidant at different temperatures, 50 °C and 80
°
C; catalyst loading, 5ꢀ20 % mol; and in presence and absence of base, K CO (Table 1). The
2 3
yield of benzaldehyde obtained after 5 h was found to be only 3 % and 6 % in the presence of
1
1

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a
Table 1 Reaction for oxidation of benzyl alcohol to benzaldehyde
Entry
Catalyst
Base (K CO ) Catalyst
Temp.
(°C)
Yield
2
3
(mmol)
(% mol)
(%)
1
2
GO
ꢀ
ꢀ
10
10
50
80
3
6
GO
3
γꢀMnO /GO
ꢀ
10
80
35
2
4
5
GO
GO
1.0
1.0
10
10
50
80
10
15
6
7
8
9
γꢀMnO /GO
1.0
1.0
1.0
1.0
0.5
10
5
50
50
50
50
80
91
42
75
72
2
γꢀMnO /GO
2
γꢀMnO /GO
15
20
10
2
γꢀMnO /GO
2
b
10
γꢀMnO /GO
91
2
a
Reaction conditions: Substrate: benzyl alcohol (1 mmol), catalyst (5, 10, 15 and 20% mmol),
solvent (3 mL), base (1.0 mmol), time 5 h
b
time: 3 h
GO without K CO at 50 °C and 80 °C respectively. Addition of 1 mmol of K CO with
2
3
2
3
GO showed an increase in the yield, however overall yield being only 10% and 15% at 50 °C
and 80 °C respectively. Use of γꢀMnO /GO nanocomposites led to almost 9 fold increment in
2
reaction yield as compared to pure GO both in presence and in absence of base at 50 °C. As the
catalyst loading decreased from 10 to 5 % mol, yield was found to be decrease from 91% to
42%, respectively. However, an increase in catalyst loading to 20 % mol also decreased the yield
due to overꢀoxidation to benzoic acid and benzyl benzoate. Also, yield obtained in absence of
1
2

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base was low. Yield obtained for optimum reaction parameters at 50 °C was compared to that
obtained at 80 °C. At higher temperature, the same yield was obtained in only 3h and in presence
of lower amount of base.
The effect of electron withdrawing and electron donating functional groups of the reactant
on the catalytic activity was studied and is discussed (Table 2). Aromatic alcohols bearing
electron donating groups at paraꢀposition (1a, 1b) showed slightly better yield than those with
the electron donating group (1c, 1d) at orthoꢀposition possibly due presence of steric hindrance
in the latter. Presence of halogen (F, Cl or Br) substituent results in lowered yield (79ꢀ84%).
However, the yield of the aldehyde is not significantly affected by the position of the halogen
substituent. The substitution of electron withdrawing –NO group (1i) at ortho position retards
2
the reaction, resulting in longer reaction time with only 62% aldehyde formation.
The recovery efficiency and reuse potential of γꢀMnO /GO nanocomposites (catalyst) was
2
studied for 4ꢀmethoxy benzyl alcohol as the model substrate (1a). The catalytic activity of the
st
nd
recycled catalyst resulted in slightly lower yield (91% after 1 recycle and 88% after 2 recycle)
with negligible loss after as compared to the freshly prepared catalyst (Table 3). Recycled γꢀ
MnO /GO was further characterized by ICPꢀAES, TGA and TEM analysis. ICPꢀAES analysis of
2
recycled catalyst confirmed presence of 59 wt. % of MnO . Further, Mn was not detected during
2
ICPꢀAES analysis of the reaction mass and therefore, leaching of γꢀMnO was in reaction mass
2
was negligible. TGA analysis of recycled catalyst showed weightꢀloss trends similar to the
pristine catalyst. TEM images of γꢀMnO /GO nanocomposites (catalyst) after second recycle
2
showed slight aggregation and wrinkling of GO sheets (Figure 4d). This agglomeration may be
the cause of marginal decrease in the catalytic activity of recycled catalyst.
1
3

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a
Table 2. γꢀMnO /GO catalyzed oxidation of alcohols to carbonyl compounds.
2
Entry
Substrate
Product
Yield (%)
1
OH
93
MeO
Me
1
a
CHO
2
3
4
OH
90
85
82
Me
1
b
2
b
CHO
OH
OMe
OMe
CHO
Me
1
c
2c
OH
OH
Me
1
d
2d
CHO
c
5
6
91
1
e
2e
CHO
OH
84
Br
Br
1
f
2f
CHO
7
8
9
OH
79
81
62
F
F
1
g
2g
a
Reaction conditions: Substrate (1 mmol), solvent: toluene (3 mL), catalyst (10 % mol),
K CO (0.5 mmol), temperature: 80 ℃, time: 5 h
2
3
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Table 3. Catalyst activity upon reuse of the catalyst
Catalyst
Fresh
First
Second
Yield (%)
93
91
88
a
Reaction conditions: Substrate: 4ꢀmethoxy benzyl alcohol (1 mmol), solvent: toluene (3 mL),
catalyst (10 % mol), K CO (0.5 mmol), temperature: 80 ℃, time: 5 h
2
3
We propose that γꢀMnO /GO catalyzes the oxidation synergistically (Figure 6). Oxygen
2
atoms in benzyl alcohol initially adsorb on MnO . K CO undergoes dissociation in presence of
2
2
3
+
2ꢀ
31
GO. K ions formed are coordinated to GO leaving free CO3 ions, which increase the rate
hydrogen elimination, the rate determining step, from the transition complex formed between
MnO and benzyl alcohol, producing carbanion. This carbanion undergoes charge transfer giving
2
benzaldehyde. During the reaction, Mn (IV) undergoes reduction to Mn (II), which gets
converted back to Mn (IV) by oxygen. Increased reactivity of the catalyst can be attributed to the
complexation of potassium ions with functional groups in GO, which ultimately accelerates the
rates of oxidation. In this reaction, GO acts both as a catalyst support and as a surface initiator
for the base dissociation, while MnO mediates the oxidation.
2
Conclusion
We have developed methodology for the synthesis of γꢀMnO /GO nanocomposites by a
2
simple nonꢀhydrothermal, wet precipitation method without the use of any external stabilizer or
surfactant. We used a mixture 2ꢀ propanol/water as solvent which restricts the structure and
orientation of crystals during MnO growth on GO sheets. This γꢀMnO /GO nanocomposite acts
2
2
as an efficient and easily recyclable heterogeneous catalyst for the selective aerobic oxidation of
benzyl alcohols into corresponding aldehydes in presence of a mild base. The resulting process is
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Figure 6. Proposed mechanism for oxidation of benzyl alcohol by using γꢀMnO /GO as
2
catalyst
very selective giving only benzaldehyde using lower amount of base and atmospheric oxygen as
oxidant.
Acknowledgement
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The authors are greatly thankful to the University Grants Commission’s (UGC) of India for
financial assistance under Special Assistant Program (SAP). Authors would also like to thank the
funding provided by Department of Science and Technology (DST), India for support under
FIST program.
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Graphical Abstract
Synthesis, Characterization and Application of γꢀMnO
2
/Graphene Oxide for Selective
Aerobic Oxidation of Benzyl Alcohols to Corresponding Carbonyl Compounds
1
1
1
1
1, 2,
Kadam, Mahesh M. , Dhopte, Kiran B. , Jha, Neetu , Gaikar, Vilas G. , Nemade, Parag R.
*
1
Department of Chemical Engineering, Institute of Chemical Technology, Nathalal Parekh
Marg, Matunga, Mumbai Maharashtra, 400019, India.
2
Department of Oils, Oleochemicals and Surfactant Technology, Institute of Chemical
Technology, Nathalal Parekh Marg, Mumbai, Maharashtra, 400 019, India.
*
Corresponding Author
Tel.: + 91ꢀ 22 3361 2027;
Fax: +91ꢀ 22 3361 1020.
Eꢀmail address: pr.nemade@ictmumbai.edu.in.
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Table of Contents
Sr. No. Contents
Page No.
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Graphic
Text
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Text
Selective aerobic oxidation of benzyl alcohols to corresponding aldehydes catalyzed by subꢀ
stoichiometric amount of novel γꢀMnO /GO nanocomposites giving over 90 % yield.
2
4