Cetyl alcohol mediated synthesis of CuCr2O4 spinel nanoparticles: A green catalyst for selective oxidation of aromatic C-H bonds with hydrogen peroxide

Article abstract of DOI:10.1039/c4ra12652a

We report here cetyl alcohol-promoted synthesis of spherical CuCr₂O₄ spinel nanoparticles with almost uniform morphology, prepared hydrothermally. Detailed characterization of the material was carried out by XRD, XPS, ICP-AES, SEM, TEM, and TGA. XRD revealed the exclusive formation of the CuCr₂O₄ spinel phase and TEM showed the formation of a 20-40 nm particle size. The catalyst was highly active for selective oxidation of benzene to phenol with H₂O₂. The influence of reaction parameters was investigated in detail. The catalyst was found to be selective for hydroxylation of other aromatic alkanes as well. The reusability of the catalyst was tested by conducting the same experiments with the spent catalyst and it was found that the catalyst does not show any significant activity loss even after 5 reuses. The benzene conversion of 67% with 94% phenol selectivity was achieved at 75°C temperature.

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Cetyl Alcohol Mediated Synthesis of CuCr O Spinel
2
4
Nanoparticles: A Green Catalyst for Selective
Oxidation of Aromatic C-H Bonds with Hydrogen
Peroxide
Cite this: DOI: 10.1039/x0xx00000x
Received 00th January 2012,
Accepted 00th January 2012
DOI: 10.1039/x0xx00000x
www.rsc.org/
a
a
a
a
Shankha S. Acharyya, Shilpi Ghosh, Nazia Siddiqui, L.N. Sivakumar Konathala,
and Rajaram Bal
*
a
We report here cetyl alcohol-promoted synthesis of spherical Among these oxygenates, phenol is the most desirable and valueꢀ
added product due to its widespread use in the fields of resin,
CuCr O
spinel nanoparticles with almost uniform
2
4
plastics, pharmaceuticals, agrochemicals, etc. It is mainly used for
the production of a large number of intermediates such as bisphenol,
caprolactum, aniline, alkylphenol, chlorophenol, salicylic acid, etc.,
which are then further used to produce epoxy resin for paints,
morphology, prepared hydrothermally. Detailed
characterization of the material was carried out by XRD,
XPS, ICP-AES, SEM, TEM, and TGA. XRD revealed the
exclusive formation of CuCr O spinel phase and TEM polycarbonate plastics for CDs and domestic appliances, nylon,
2
4
showed the formation of 20-40 nm particle size. The catalyst polyamides, antioxidants, surfactants, detergents, anticeptics,
3
medicines etc. Industrially, phenol is produced by cumene process.
was highly active for selective oxidation of benzene to phenol
The cumene process is performed by first the reaction of benzene
with propene on acid catalysts such as MCMꢀ22, second autoꢀ
oxidation of the obtained cumene to form explosive cumene
with H O . The influence of reaction parameters were
investigated in detail. The catalyst was found to be selective
for hydroxylation other aromatic alkanes as well. The
2
2
hydroperoxide, and finally the decomposition of cumene
4
reusability of the catalyst was tested by conducting same hydroperoxide to phenol and acetone in sulfuric acid. Apart from
experiments with the spent catalyst and it was found that the multistep nature, this process suffers from low yield (~5% based on
the amount of benzene initially used) and produces explosive
intermediate, cumene hydroperoxide and byꢀproducts. So, the oneꢀ
step process for the direct conversion of benzene to phenol is an area
of great potential interest. Although there have been several reports
catalyst does not show any significant activity loss even after
reuses. The benzene conversion of 67% with 94% phenol
selectivity was achieved at 75 ºC temperature.
5
5
6
7
using different oxidizing agents like N O, H O , NH + O ,
2
2
2
3
2
Direct functionalization of CꢀH bonds has been developed as a
8
1
air+CO etc. however, the selectivity of phenol is rather poor, since
phenol is more reactive towards oxidation than benzene itself and
substantial formation of overꢀoxygenated byꢀproducts (catechol,
powerful strategy to form new chemical bonds. Among them,
transitionꢀmetalꢀcatalyzed hydroxylation of CꢀH bond has drawn
considerable attention because of the industrially important alcohol
or phenol products. Inspite of the significant development in the past
decades, catalytic hydroxylation of Csp2ꢀH bonds still remains a very
9
hydroquinone, benzoquinones and tars) also occurs, and rapid
deactivation of the catalyst by coke deposition during gas phase
10
reaction. The use of H O2 as oxidizing agent in liquid phase
2
challenging task. Selective oxidation of inactive hydrocarbons to2
hydroxylation of benzene is of great advantage from both
environmental and industrial viewpoint and thus recognized as
industrially important intermediates still remains a major challenge.
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DOI: 10.103
R
9/
S
C
C
4R
A
A
d
12
v
6
a
5
n
2
c
A
es
1
1
“
green oxidant”. Bianchi et al. have developed a waterꢀacetonitrile procedure. By using the Scherrer equation, the average crystallite
biphasic reaction method in which FeSO , soluble in the aqueous
4
size (based on 35.16°) was found 28 nm. XRD diffractogram also
predicts that, the catalyst retains its spinel phase even after 5
recycles. The surface composition of the catalyst was detected from
XPS analysis (Fig. S1ꢀS3, ESI†) which stated that copper is in the
1
2
medium, was used as catalyst and H O as oxidant. By employing
2
2
this method, a significant selectivity to phenol (97%) was observed,
although the benzene conversion was 8.6%. Zhang et al. reported a
benzene conversion of 34.5 % with a selectivity of 100% towards the
phenol using H O as oxidant in a mixture of glacial acetic acid and
+2 oxidation state and chromium is in the +3 oxidation state which
2
2
matched with the CuCr O4 individual element’s oxidation states.
acetonitrile, over Kegginꢀtype molybdovanadophosphoric heteropoly
2
13
acids. Recently, Borah et. al reported a benzene conversion of 27% SEM images of the catalyst (Fig. 2aꢀc) showed the formation of
and a phenol selectivity of 100% over vanadylꢀcomplex grafted on almost homogeneously distributed uniform particles, whereas, that
1
4
periodic mesoporous organosilica. So far it is concern, apart from of commercial catalyst (Fig. S4) and prepared CuꢀCr catalyst without
high yield of phenol, recyclability of the catalysts, product
separation and maintaining efficiency of H O are major issues in
using cetyl alcohol (Fig. S5) showed formation of agglomerates and
nonꢀuniform particles. These results indicated the fact that, cetylꢀ
alcohol plays an important role in orchestrating the CuCr O spinel
nanoparticles size. During synthesisꢀprocedure, addition of cetyl
alcohol probably formed micelle under alkaline medium and binded
Cu and Cr ions and segregated in a spherical manner. Thus, after
2
2
liquid phase benzene hydroxylation; therefore, production of phenol
by direct hydroxylation of benzene in liquid phase with both high
activity and selectivity using heterogeneous catalyst(s) that contain
nonꢀleachable species is of current interest. Thus, the direct and
selective introduction of the hydroxyl group into the aromatic
2
4
compounds, especially conversion of benzene to phenol, is one of calcination, almost spherical CuCr
O spinel nanoparticles (with
4
2
the most challenging fields in oxidation chemistry today and uniform morphology) were formed (confirmed from SEM). The
2e,15
therefore, regarded as one of the ten most challenges of catalysis.
attachment of cetyl alcohol on Cu and Cr surface was further
Copper chromium mixed oxides with a spinel structure had been confirmed from the TGA analysis of the uncalcined sample (Fig.
recognized as an important class of biꢀmetallic oxides that act as a S6).The TGA diagram showed that the weight loss occurs in three
16
versatile catalyst. Apart from its usage in chemical industries, stages, first being the loss of water followed by the decomposition of
copper chromite finds its major application as a burn rate modifier in reactants to form NO and organic phases at 150 to 250 °C and
x
17
solid propellant processing for space launch vehicles globally. The finally the combustion of cetyl alcohol between 250°–400 °C. A
higher activity of copper chromite is attributed to the tetragonally further small mass loss is noticed between 400°–550 °C due to the
distorted normal spinel structure with c/a < 1(where a and c are elimination of remaining carbon and organic compounds. No weight
lattice constants in a unit cell along x and z axes respectively) and loss was observed when the temperature was further increased from
1
8
the arrangement of copper in its structure. Although, a variety of 550° to 1000° C, indicating the stability of the catalyst (spinel phase)
synthetic methods have been employed in the preparation of CuꢀCr upto 1000° C. Total mass reduction of 34.4% confirmed the
catalysts, yet controlled syntheses at large scale, with tunable complete the removal of the template. The EDX analysis confirmed
morphology and its fruitful application in catalytic oxidation still that the synthesized product was composed of Cu, Cr and O only
remain a challenging task in the field of catalysis.
(Fig. 2d), which indicated that, the template has been completely
Herein, we report cationic surfactant cetyl alcoholꢀpromoted removed upon calcinations; furthermore, it also confirmed the purity
synthesis of the preparation of CuCr O nanoparticles spinel catalyst of the synthetic procedure. Elemental mapping obtained from EDX
2
4
with 20ꢀ40 nm particle size. Although cetyl alcohol has been used in analysis (based on Fig.2b) showed the coordinateꢀlocations of Cu, Cr
19
different purposes, so far, there is no report of using cetyl alcohol and O respectively (Fig. S7 bꢀd). A representative TEM image of the
as template for the preparation of spinel nanparticles, to the best of catalyst has been shown in Fig 3. The sizes of the particles estimated
our knowledge. Here, we also report direct hydroxylation of benzene from TEM were in good agreement with those obtained from XRD.
to phenol using the so prepared CuCr O4 nanoparticles spinel In the HRTEM image, distinct lattice fringes were clearly seen with
2
catalyst and H O as oxidant. A benzene conversion of 67% and a dꢀspacing of 0.30 nm corresponding to [220] plane of CuCr O
2
2
2
4
17a
phenol selectivity of 94% was achieved over this catalyst.
The CuCr O nanoparticles spinel catalyst was prepared spent catalyst (after 5 recycle) (Fig. 3d) revealed that the particle size
spinel with diffraction angle (2θ) of 29.6°. The TEM image of the
2
4
modifying our own synthetic method using nitrate precursors of of the CuCr O spinel was almost unchanged during the catalysis.
2
4
20
copper and chromium and substituting CTAB by cetyl alcohol.
Although the mechanism for the formation of CuCr O4 spinel oxidation systems, the CꢀH bond(s) adjacent to a πꢀsystem is
It is a known fact that, in most transition metalꢀcatalyzed
2
11
nanoparticles promoted by cetyl alcohol is not very clear, we believe hydroxylated selectively and we explored benzene hydroxylation
that this material served as modifier, that played an important role in reaction in liquid phase using different catalysts of transition metals.
the orchestrating the particle size. The catalyst was characterized by In our previous report, we showed synthesis of cationic surfactant
XRD, XPS, ICPꢀAES, SEM, TEM, TGA. The crystalline phase, CTAB mediated synthesis of Cu (II) nanoclusters supported on
degree of crystallinity and phase purity were determined by Xꢀray nanocrystalline Cr O3 catalyst, which effectively catalyzed the
2
diffraction (XRD). The XRD patterns of the CuꢀCr catalysts are oxidation of cyclohexane at room temperature by activating CꢀH
3
20
presented in Fig 1. showed the typical diffraction lines of the bulk, bond (sp C atom) effectively. We employed this catalyst in
single phased tetragonal CuCr O spinel [space group I4 /amd, with benzene hydroxylation reaction in liquid phase taking H O as
2
4
1
2
2
lattice parameters : a (Å)= 6.03277(1); b (Å) = 6.03277(1); c (Å) = oxidant. Although the catalyst showed efficiency towards phenol
21
7
.78128(1)] exclusively with the maximum intensity peak at 2θ selectivity (Table 1, entry 7), but it suffered severe leaching, waning
value of 35.16° (JCPDS. 05ꢀ0657; 21ꢀ874); no impurity phase was the catalytic system. We therefore modified Cu: Cr molar ratio
found such as CuCrO and not even other phases of CuCr O like (taking 1:2) and prepared CuCr O4 spinel nanoparticles catalyst,
2
2
4
2
cubic or monoclinic, which reflected the high purity of our synthetic which is devoid of leaching properties.
2
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DOI: 10.1039/C4RA12652A
NP
The activities of CuCr O spinel nanoparticles (CuꢀCr ) catalyst spinel nanoparticles catalyst possess comparatively high specific
2
4
2
in the direct hydroxylation of benzene to phenol in liquid phase by surface area (65 m /g) which corresponds to higher dispersion of the
using H O as oxidant have been summarized in Table 1. Complete catalyst that leads to the availability of more exposed surface active
2
2
analyses showed that detected major product in the reaction mixture sites, where the catalytic reaction takes place in comparison to the
2
was phenol, with some catechol and 1, 4 benzoquinone as byꢀ commercial CuCr O (with surface area 5 m /g). Inevitably, a higher
2
4
products. While optimizing the reaction conditions, we noticed that reaction rate was observed in case of the CuCr O spinel
2
4
the yield of the desired product (i.e. phenol) increased by increasing nanoparticles catalyst.
the amount of H O (Fig. S8, ESI†). However, the use of excess of
2
2
oxidant (H O ) did not meet the economy of chemical reactions at
2
2
Conventional catalyst prepared by impregnation method also showed
negligible activity (Table 1, entry 5). The concentrations of both
components as found with ICPꢀAES were low and a hot filtered
solution did not continue even when either Cu(NO ) , Cr(NO ) or
even the mixture of both were added in the reaction medium in
absence of the catalyst.The corroboration of all these detailed to the
this temperature, due to the formation of overꢀoxidized products.
Blank experiment was performed in absence of catalyst; conversion
of benzene was too poor to be detected by GC analysis (Table 1,
entry 10); this result reflected the necessity of the catalyst.
Maintaining all the optimum conditions, when the reaction was
allowed to run for hours, conversion of benzene with significant
decrease in phenol selectivity was noticed (Fig. S9, ESI†). A
decreasing trend for the H O efficiency on increase in reaction time
3
2
3 3
conclusion that, nanoparticles of CuCr O4 spinel, as well as
2
acetonitrile medium is necessary for the benzene hydroxylation
reaction. When nꢀoctane and dimethylformamide (DMF) were used
as solvents, the catalyst showed very poor activity. Although high
phenol selectivity was achieved in these solvents, but the conversion
of benzene was very less. This can be attributed to the fact that, nꢀ
octane is highly hydrophobic and DMF is highly hydrophilic in
2
2
was also speculated, presumably because of selfꢀdecomposition
nature of H O . Furthermore, polymerized phenol was also noticed
2
2
in the reaction mixture after 24 hours. This may be a possible reason
for the deactivation of the catalyst.
It is worth mentioning that, small amount of biphenyl was also
discovered in the reaction mixture when excess amount of H O was
12
nature.
2
2
used. This phenomenon indicates the probable involvement of freeꢀ
radical mechanism. The hypothesis was confirmed, when we used
The reusability test of the catalyst has been displayed in Table 2.
After each run, a used catalyst was used several times by acetone
and ethanol and kept at oven (120 °C) for 2 h and employed for the
next run. We observed that the catalyst showed negligible change in
its activity. After the catalyst had been used in 5 runs, significant
change in the activity of the catalyst was hardly observed (Table 1,
entry). XRD diffractogram of the used catalyst showed that the
spinel phase was retained even after 5 reuses. The amount of Cu and
Cr present in CuCr O catalyst after 5 reuses was almost same as that
in the fresh catalyst (estimated by ICPꢀAES) confirming the true
heterogeneity of the catalyst.
In view of the above results, the catalytic system that renders the
best yield in oxidation of benzene to phenol was applied in the
subsequent studies. Various substituted benzenes were tested under
this reaction conditions and the results are summarized in Table 3.
2
,6ꢀdiꢀtertꢀbutylꢀ4ꢀmethyl phenol as a radical scavenger with
benzene (10 wt% wrt benzene) was taken. No phenol was detected
till 12h. We also observed that, the catalyst was active only in
2
+
acetonitrile solvent. We believe that, Cu in the catalyst framework
interacts with the πꢀelectron cloud of benzene and probably, the
flexibility property of the Cu (II)ꢀframework renders the catalytic
system suitable for lowering the activation energy of the oxidation
2
4
22
reaction. Cr (III) is not involved in this reaction, but stabilizes Cu
2
3
(
II) ions against aggregation during reaction. Probably, the high
OSPE (octahedral site preference energy) for Cr (III) inhibits it to
2
4
take part in the reaction, thus the stable spinel framework remains
uninterrupted and the oxidation reaction follows the “single site
2
2
3+
heterogeneous catalysis” path. Cr is not involved in the reaction
but stabilizes the copper ion(s) against aggregation during the
Electron donor groups (ꢀCH ) favour the hydroxylation (Table 3,
3
23
reaction condition. H O does not interact with benzene at normal
2
2
entry 1ꢀ3) in the phenyl ring. This may be attributed to the fact that,
electron donor groups enhances electron density in the phenyl ring
and welcome hydroxyl radicals (serve as electrophiles) to attack CꢀH
bonds of phenyl ring to facilitate hydroxylation in the aromatic CꢀH
bonds. In contrast, strongly electron withdrawing group (ꢀCl, ꢀNO2)
prohibit the attack of hydroxyl radicals in the phenyl ring (Table 3,
entry 4ꢀ6). Consequently, phenyl ring with strong electronꢀ
withdrawing groups showed very poor yield. Furthermore, pꢀ
hydroxy product was found as the main product in most of the cases,
indicating the selective nature of the catalyst. We also noticed that,
with the increment of branching of alkyl groups in the phenyl ring,
oxidation in the side chain is favoured rather than hydroxylation in
the phenyl ring; this may be attributed to well interaction of the
exposed side chain with the catalyst.
condition. H O dissociation is believed to occur homogeneously
2
2
over the CuCr O catalyst and follows the mechanism, suggested by
2
4
2
5
Kazarnovsky. Dissociation of H O over CuCr O generates the
2
2
2
4
•
active species OH (free hydroxy radical).These hydroxy radicals
2
6
participate as an electrophile in this reaction which attacks the
phenyl carbon atom by means of homolytic C–H bond cleavage
mechanism, thereby produces phenol moiety on the surface of the
catalyst. Use of excess H O increases the dissociation rate, causing
2
2
7
2
•
an increase of local pH;
consequently, generated excess OH
radicals attack concomitantly the phenyl radical to produce biphenyl
moiety, and thereby explains the presence of biphenyl in the reaction
medium.
Notably, commercial Cr O , CuO, Cu O and CuCr O catalyst did
2
3
2
2
4
not show any good activity for phenol yield (Table 1, entry 1ꢀ4).
Commercial CuCr O catalyst did not show any activity. The reason
2
4
can be attributed to the small size as well as extreme stable spinel
phase, containing nonꢀleachable species of the CuCr O spinel
Conclusions
2
4
nanoparticles catalyst. The comparatively smaller size of CuCr O4
2
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In summary, we have reported cetyl alcoholꢀpromoted simple
7
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preparation method to prepare 20ꢀ40 nm CuCr O4 spinel
2
nanoparticles having high thermal stability and good catalytic
activity for the single step conversion of benzene to phenol using
H O , exhibiting 67% benzene conversion and 94% selectivity
2
2
8
9
1
M. Tani, T. Sakamoto, S. Mita, S. Sakaguch and Y. Ishii, Angew.
Chem., 2005, 44, 2586.
towards phenol at 75 °C. The catalyst can be reused several times
without any activity loss. The experimental findings form new basis
for the structureꢀactivity relationships of the copperꢀchromium
catalysts in benzene to phenol hydroxylation chemistry, which
reflects the prerequisites for a knowledgeꢀbased design of improved
catalytic materials.The proposed method is also advantageous from
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Acknowledgement
S.S.A. thanks CSIR and S.G. thanks UGC, New Delhi, India,
for their respective fellowships. R.B. thanks CSIR, New Delhi, for
financial support in the form of the 12 FYP Project (CSCꢀ0125,
CSCꢀ0117). The Director of CSIRꢀIIP is acknowledged for his help
and encouragement. The authors thank the Analytical Section
Division, IIP, for the analytical services.
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†
Electronic Supplementary Information (ESI) available: detailed
experimental procedure, detailed characterization techniques, XPS data,
effect of different parameters on benzene hydroxylation reaction etc. See
DOI: 10.1039/c000000x/
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(a) C. Walling, Acc. Chem. Res., 1975, 8, 125; (b) P. T. Tanev, M.
Chibwe and T. J. Pinnavaia, Nature, 1994, 368, 321 (c) L. Balducci, D.
Bianchi, R. Bortolo, R. D'Aloisio, M. Ricci, R. Tassinari and R.
Ungarelli, Angew. Chem., 2003, 115, 5087.
9
2.
2
2
5
6
I. A. Kazarnovsky, Dokl. AN SSSR. 1975, Vol. 221, S353 (in Russian).
A. Dubey, V. Rives and S. Kannan, J. Mol. Catal. A: Chem., 2002, 181,
1
51.
4
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DOI: 10.1039/C4RA12652A
2
7
R. Araminaite, R. Garjonyt and A. Malinauskas, Cent. Eur. J. Chem.
008, 6, 175.
2
a
c
35
b
30
25
20
15
10
5
0
(
a)
20
25
30
35
40
45
50
Particle size/nm
30 nm
(
b)
2
0
30
40
50
60
70
80
d
2
Theta/degree
0
[
.3 nm
220]
2 4
CuCr O
Fig. 1 XRD diffractogram of (a) fresh and (b) spent (after 5 reuses)
of the CuCr O nanoparticles catalyst.
2
4
1nm
20 nm
a
b
Fig. 3 (a) TEM image, (b) particle size distribution (histogram), (c)
HRTEM of fresh and (d) TEM image of spent (after 5 recycles)
CuCr O nanoparticles catalyst.
2
4
a)
Table 1. Reaction Conditions of Catalytic Oxidation of Benzene
3
µm
2µm
b)
c)
d)
e)
Entry
Catalyst
CB
(
SP
YP
%)
Eo
%)
(%)
(
(%)
COM
c
d
1
2
3
4
5
CuO
5.5
6.8
7.5
13.5
12
5.5
0.3
0.5
0.1
2
0.06
COM
Cu O
8.0
2.0
15.0
15
75
94
92
ꢀ
0.1
0.03
0.4
0.4
4.2
12.6
11.7
ꢀ
2
COM
Cr O3
2
COM
CuCr O4
2
2
00 nm
IMP
CuOꢀCr
O
3
1.8
21
62.9
58.7
ꢀ
2
f)
6
CuOꢀCr O3
28
Fig. 2 SEM images (aꢀc) and (d) the SEMꢀEDAX image of the
CuCr O nanoparticles catalyst.
2
2
4
g)
NP
7
CuCr O4
67
2
h)
NP
8
CuCr O4
63.8
ꢀ
2
i)
NP
9
CuCr O4
2
1
0
No Catalyst
ꢀ
ꢀ
ꢀ
ꢀ
a)
Typical reaction conditions: solvent (MeCN) = 10ml, substrate
benzene) = 1g, catalyst= 0.05g, benzene: H O (molar ratio) = 1:5,
(
2
2
b
reaction temperature = 75 °C; time = 12 h. C = Conversion of
B
benzene based upon the FIDꢀGC using anisole as external standard =
c
[
Moles of benzene reacted/initial moles of benzene used] x 100. S
P
=
Selectivity to phenol = [Moles of products produced/ moles of
d
e)
benzene reacted] x 100. Y = Yield of phenol= C × S /100 Eo =
P
B
P
.
H O efficiency = [Moles of phenol formed/total moles of H O
2
2
2
2
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f)
g)
NO2
NO2
added]× 100.
Cuꢀnanoclusters supported on Cr O . Prepared
5
2
3
h)
i)
CuCr O spinel nanoparticles and catalyst after 5 reuse. Using
2
4
0.2
>99
0.2
2
,6ꢀdiꢀtertꢀbutylꢀ4ꢀmethyl phenol as radical scavanger. COM:
commercial; IMP: impregnation method; CPM: coꢀprecipitation
method; NP: nanoparticles.
OH
Table 2. Recyclability Tests of CuCr O Spinel Nanoparticles
Catalyst for the Hydroxylation of Benzene to Phenol.
2
4
a)
NO2
ꢀ
b)
c)
d)
6
7
ꢀ
ꢀ
ꢀ
Recycling
No.
CB
SP
YP
NO2
(%)
(%)
(%)
1
2
3
4
5
6
67
94
94
93.5
93
92.5
92
62.9
62.5
61.2
60.9
59.2
58.7
66.5
65.5
65.5
64
CH CH3
CH CH3
2
2
7
5.0 68.0 51.0
63.8
OH
a)
Reaction Condition: solvent (MeCN) = 10 ml; benzene =1g;
catalyst= 0.05g; benzene: H O mole ratio =1:5.; temperature =
2
2
b)
c)
7
5°C; time =12 h. C = Conversion of benzene; SP = Selectivity
B
(CH ) CH
COCH CH
2 3
8
9
2
2
3
82.0 57.0 46.8
d)
to phenol. Y =Yield of phenol.
P
Table 3. Activity of the CuCr O Spinel nanoparticles catalysts over
2
4
a)
different substituted benzenes in liquid phase oxidation
b)
c)
d)
(CH ) -CH
CO(CH ) -CH
2 5 3
Entry
1
Substrate
Main Product
CS
SP
YP
(%)
2
6
3
78
65.5 51.1
(
%)
(%)
CH3
CH3
6
5
5.0 75.0 48.8
1
0
HO
OH 55
70
38.5
OH
a)
2
3
Reaction Condition: solvent (MeCN) = 10 ml; substrate =1g;
catalyst= 0.05g; benzene: H O mole ratio =1:5; temperature = 75°C;
time =12 h. C = Conversion of substrate.
product. Y =Yield of product.
CH3
OH
2
2
CH3
b)
c)
SP = Selectivity to
S
d)
5.0 90.0 49.5
P
CH3
CH3
CH3
CH3
HO
OH
H C
CH3
57.0 97.0 55.3
3
H C
CH3
3
OH
Cl
Cl
4
1
.0
>99
1
OH
6
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