Comparison of selective oxidation of aromatic alcohols using copper(II) chromite-titanium dioxide nanocomposite at reflux, light irradiation, and microwave conditions

Article abstract of DOI:10.1080/24701556.2017.1284093

CuCr₂O₄/TiO₂ nanocomposites with different TiO₂ contents were synthesized by using sol-gel method. Products were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Results demonstrated a cubic normal spinel structure for copper (2+) chromite, with the particle sizes of about 25–40 nm. Activities of CuCr₂O₄ nanopowders and CuCr₂O₄/TiO₂ nanocomposite were tested for oxidation of benzylic alcohols to aldehydes at reflux, light irradiation, and microwave conditions. The influence of some parameters on the oxidation of alcohol, such as optimum molar ratio of chromite to titanium dioxide, catalyst dosage, and type and amount of oxidant and solvents (dichloromethane, acetonitrile, and ethanol) was studied to determine the optimal operating conditions for alcohol oxidation in reflux, light irradiation, and microwave conditions.

Full text of DOI:10.1080/24701556.2017.1284093

Inorganic and Nano-Metal Chemistry
ISSN: 2470-1556 (Print) 2470-1564 (Online) Journal homepage: http://www.tandfonline.com/loi/lsrt21
Comparison of selective oxidation of aromatic
alcohols using copper(II) chromite-titanium
dioxide nanocomposite at reflux, light irradiation
and microwave conditions
Abdollah Fallah Shojaei, Farhad Shirini & Elaheh Hedayati
To cite this article: Abdollah Fallah Shojaei, Farhad Shirini & Elaheh Hedayati (2017):
Comparison of selective oxidation of aromatic alcohols using copper(II) chromite-titanium dioxide
nanocomposite at reflux, light irradiation and microwave conditions, Inorganic and Nano-Metal
Chemistry, DOI: 10.1080/24701556.2017.1284093
To link to this article: http://dx.doi.org/10.1080/24701556.2017.1284093
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ACCEPTED MANUSCRIPT
Comparison of selective oxidation of aromatic alcohols using copper(II) chromite-titanium
dioxide nanocomposite at reflux, light irradiation and microwave conditions
Abdollah Fallah Shojaei*, Farhad Shirini, Elaheh Hedayati
Department of Chemistry, Faculty of Science, University of Guilan, P.O.Box 1914, Rasht, Iran
*Corresponding author. E-mail: shoja47@gmail.com, a.f.shojaie@guilan.ac.ir
Key words
Copper chromite; nanocomposite; alcohols oxidation; TiO2, microwave
Abstract
CuCr2O4/TiO2 nanocomposites with different TiO2 contents were synthesized by using sol–gel
method. Products were characterized by X-ray diffraction (XRD), scanning electron microscopy
(SEM) and transmission electron microscopy (TEM). Results demonstrated a cubic normal
spinel structure for copper (2+) chromite, with the particle sizes of about 25-40 nm. Activity of
synthesized nano powders CuCr2O4 and CuCr2O4/TiO2 nanocomposite were tested for oxidation
of benzylic alcohols to aldehydes at reflux, light irradiation and microwave condition. The
influence of some parameters on the oxidation of alcohol, such as optimum molar ratio of
chromite to titanium dioxide, catalyst dosage, type and amount of oxidant and solvents
(dichloromethane, acetonitrile and ethanol) were studied to determine the optimal operating
conditions for alcohol oxidation in reflux, light irradiation and microwave conditions.
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1. Introduction
Carbonyls are one of the important classes of the compounds and intermediates in chemical
industries and laboratories. Since alcohol oxidation to the corresponding aldehyde and ketone is
of importance because of the extensive usage of these compounds in the synthesis of various
chemicals, vitamins, drugs, and fragrances [1-3], numerous methods have been developed using
a variety of reagents for this purpose. In spite of the formation of toxic byproducts and large
amount of heavy metal wastes, these oxidation reactions have been performed mainly in non-
catalytic systems with stoichiometric amount of undesirable environmentally and economically
oxidants. Recent demand for eco-friendly chemical processes has encouraged the further
development of high yielding, efficient, chemoselective, clean and economical methods for the
oxidation of alcohols [4-7]. The copper chromite (CuCr2O4) with the spinel structure is one of the
most efficient materials, has wide commercial application as catalysts being used in the unit
processes of organic synthesis, such as C–O hydrogenolysis [8], conversion [9, 10]
hydrogenation [11], dehydrogenation [12], oxidation [13], alkylation [14], cyclization [15], with
several preparation methods have been established, for instance solid state reaction, co-
precipitation, ceramic and sol–gel [16-18]. Three of the most important parameters determining
the catalytic activity of the product; crystallinity, surface properties, and specific surface area, are
highly dependent on the preparation routes. Citric acid (CA)-assisted sol–gel method (namely
Pechini approach) is a facile method for producing homogeneous nanocomposites, in which the
intimate mixing of components ensures homogeneity of the final product [19]. Photocatalysis is
generally thought of as the catalysis of a photochemical reaction at a solid surface, usually a
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semiconductor [20]. The nanosized TiO2 has continued to attract interests in industries and
academia due to unique properties that has led to its applications as photocatalysis, solar energy
converters, interface in biomaterials, and sensors [21]. Yan and co-workers reported synthesis of
CuCr2O4/TiO2 heterojunction for hydrogen evolution under simulated sunlight irradiation [19].
Bajaj prepared BiVO4/CuCr2O4 for the degradation of methylene blue dye [22]. In addition,
Au/CuxCryOz mixed oxide and CuCr2O4 nanoparticle were applied for oxidation of glycerol and
aniline, respectively [23-24]. In our previously published research works [25-31], some catalytic
systems were synthesized and activities were described in relation to different reactions. In
addition, we synthesized CoCr2O4/TiO2 nanocomposite via sol–gel method for photodegradation
of methylene blue and methyl orange [32]. Herein, we wish to report the preparation of CuCr2O4
and CuCr2O4/TiO2 catalysts for oxidation of aromatic alcohols into corresponding aldehyde and
ketone in good to high yields under reflux, light irradiation and microwave condition. Products
were characterized by XRD, SEM and TEM techniques. The effect of some parameters on the
oxidation of alcohol, such as optimum molar ratio of Chromite to titanium dioxide, catalyst
dosage, type and amount of oxidant and solvents were studied.
2. Experimental
2.1. Material
All the chemicals used in the experiments were of analytical grade (Merck) and were utilized as
received without further purification.
2.2. Preparation of catalysts
Briefly, 5mmol Cu(NO3)2 and 10mmol Cr(NO3)3 were dissolved together in 50 ml deionized
water to get a mixed solution. Subsequently, the mixed solution was added into 100 ml 0.3 M
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citric acid (CA) solution under stirring, and produced a transparent mixed sol. The temperature
was controlled at around 50 oC by using a water bath during this mixing procedure. After that the
temperature was further kept at 80 °C until a transparent and viscous gel was obtained. The as-
obtained gel was subsequently transferred into an oven and kept at 130 °C for 3 h. The as-
prepared precursor was then calcined at 600 º C for 3 h with a heating rate of 6 ºC/min.
CuCr2O4/TiO2 heterojunction was synthesized via the same route by adding a certain amount of
fully anatase phase of TiO2 in the raw materials preparation when the transparent mixed sol had
been obtained.
2.3. Characterization and reactor set up
The crystal phase of the catalysts was identified in a Philips pw1840, X-ray diffractometer using
Cu Kα radiation (λ = 1.54 Å). The patterns were collected in the range of (2θ=10-70), and
continuous scan mode. A Varian Model Spectra AA 220 flame atomic absorption spectrometer
was used for the analysis of metals in the catalysts. Scanning electron microscopy (SEM) images
were obtained on Philips XL30 equipped with an energy dispersive X-ray spectroscopy. The
grain size and morphology of the catalysts were characterized with a Philips CM10 transmission
electron microscope (TEM) operated at 100 kV. The light was provided by a 400 W high
pressure Hg lamp without a filter which was placed vertically in the reactor. The temperature of
the photo reactor set up was adjusted using a water bath in which heating or cooling water
circulated through the jacket of the beaker.
2.4. Catalytic activity testing
The catalytic activity of the prepared catalysts was evaluated by oxidation of aromatic alcohols
under reflux, light irradiation and microwave condition at atmospheric pressure. Typically, 0.03
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g of prepared catalyst was placed in two necked flasks with (1-3) mmol of alcohols and 10 mL of
solvent (acetonitrile, dichloromethane and ethanol) and t-BHP 70%, (0.3-0.5 mL) or hydrogen
peroxide 30% (0.3 mL) used as oxidant. The reaction mixture was stirred continuously with a
magnetic stirrer and the progress of the reaction was followed using thin layer chromatography.
After the reaction was run for the desired time, the products were filtered out of the catalyst and
then oxidation products were analyzed using a gas chromatograph with a GC capillary column
HP 6890 and a FID detector.
3. Results and Discussion
3.1. Characterization
Fig. 1 (a) describes the XRD patterns of the as-prepared catalysts indicating good crystallinity
and small particle size since diffraction peaks of these samples are strong and broad. These
diffractions can be indexed to the spinel-type CuCr2O4 (JCPDS 87-0432) and showed tetragonal
structure; these findings are in agreement with the literature reports [9]. The presence of the
diffraction peaks of TiO2 (the patterns of anatase structures shown with A) and CuCr2O4 in the
CuCr2O4/TiO2 nanocomposite indicates TiO2 and CuCr2O4 crystallite phases separate from each
other which showed in Fig. 1 (b). The crystallite sizes for CuCr2O4 and CuCr2O4/TiO2
nanocomposite are calculated from Debye Scherrer formula applied to the major intense peak
and are found to be about 27 and 24 nm, respectively. The amounts of total copper, chromium
and titanium of catalysts were determined by atomic absorption spectroscopy of acid digested
samples (Cu, 17.78%, Cr, 32.83%, Ti, 18.98%). SEM results from CuCr2O4 and CuCr2O4/TiO2
samples show presence of strong agglomeration with spherical shapes as exhibited in Fig.2 (a)
and (b). It can be seen that, CuCr2O4/ TiO2 (nCuCr2O4:nTiO2 = 0.7) nanocomposite have smaller
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size than pure CuCr2O4. Fig.3 shows TEM images of CuCr2O4 and CuCr2O4/TiO2 nanocomposite
(nCuCr2O4:nTiO2 = 0.7) indicating morphology and size of these catalysts calcined at 600 °C. It
can be concluded that the particles have minor agglomeration with a relatively narrow particle
size distribution. The average particle size of catalysts is about 30 nm. Also, it can be seen that
the CuCr2O4 and TiO2 crystallite particles in the nanocomposite are homogeneously dispersed.
3.2. Activity of the catalytic systems
We studied the oxidation of different types of primary and secondary benzylic alcohols to
aldehydes and ketones with CuCr2O4 and CuCr2O4/TiO2 nanocomposite as the catalyst and t-
BHP as the oxidant. As expect, both of catalysts are able to oxidize alcohol in good conversion
and yield. The catalytic oxidation reaction was carried out at reflux, light irradiation and
microwave systems. Results are shown in Table one to three, respectively. Generally, it reveals
that the selective oxidation of benzylic alcohols to aldehyde with CuCr2O4/TiO2 nanocomposite
is efficiently higher than CuCr2O4 in the presence of TBHP. Indeed, 90 and 95 percent
conversion of oxidation reaction was achieved for 4-chlorobenzyl alcohol (Tables 1, Entry 2)
oxidized by CuCr2O4 and CuCr2O4/TiO2 respectively. Halogens are deactivating group which
share their free electron pairs in benzylic resonance that dominates on their electron drawing
affect and oxidize alcohol in high yield (Tables 1 Entries 2, 3). Among them, accession of
halogen groups to hydroxyl is a negative effect (Tables 1 Entry 3). Benzylic alcohol with
electron donor groups such as –R, –OR (Tables 1 Entries 4-6) successfully converted to their
corresponding aldehyde in good yields. Secondary alcohol has oxidized to ketones in good yield
(Tables 1 Entries 7, 8). Benzhydrol with two benzylic rings which participate in hydroxyl
electron resonance, oxidize to ketone in short time (Entry 7). The electron drawing groups like -
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NO2, -COR decrease conversion of alcohol to aldehyde and when these groups get closer to
hydroxyl, decrease on conversion of alcohol is more (Tables 1 entry 9-11). The distance between
hydroxyl group and benzylic ring (Entry 12) also can effect on conversion value. Tables 2 shows
oxidation of alcohols catalyzed by CuCr2O4 and CuCr2O4/TiO2 (0.7) under light irradiation set
up. The results show that the catalytic activity of both catalysts at light irradiation condition, are
much lower than that of reflux system reaction. However, traditional heating is not used in light
irradiation system. All parameters such as halogen effect, electron donor groups and electron
drawing groups are able to effect on conversion and subsequently on yield of oxidation reaction
like as reflux condition (Tables 2). Microwave method has shown the best results in shorter time.
As shown in Tables 3 compared to reflux procedure, in microwave reaction, benzylic alcohol and
its derivatives was successfully converted to their corresponding aldehydes and ketones at very
short time. Results showed that good conversions of starting material (90 %) were obtained after
1-3 minute of reaction. The use of microwave reduced times of reaction as well as the conversion
of starting material in the oxidation under relatively similar reaction conditions. This
demonstrates that the microwave irradiated synthesis is superior to that of conventional methods
in terms of reaction time and energy consumption.
3.2.1 Effect of nCuCr2O4:nTiO2
Access to the best molar ratio of nanocomposite was achieved by using 0.03 g of all catalysts for
conversion. Table 4 indicates that the highest conversion was found on the nanocomposite with a
CuCr2O4/TiO2 molar ratio of 0.7. According to this result, we decided to use (nCuCr2O4:nTiO2 =
0.7) molar ratio for the rest of alcohols in oxidation process.
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3.2.2. Effect of catalyst dosage
Whereas catalyst dosage in catalytic processes is an important factor that can strongly influence
in this process, different concentration of CuCr2O4 and CuCr2O4/TiO2 (0.7) nanopowders have
been tested and showed that the oxidation of benzyl alcohol efficiency increased with an increase
in nanopowders concentration up to 0.03 g and then no great change have seen in conversion as
showed in Table 5. A small but significant increase in the rate of the catalytic oxidation observed
with an increase in the catalyst weight from 0.01 to 0.04 g. On the other hand, the conversion
increased from 60% to 82% by increasing the catalyst amount from 0.01 to 0.04 g. In the higher
amount of the catalyst, the better the chances for the reactants (benzyl alcohol and TBHP) to
react before diffusing out of the catalysts surface. Consequently, the extent of oxidation of
benzyl alcohol increases on increasing the catalyst amount and suitable efficiency (80%, after 15
min) of benzyl alcohol was obtained at catalyst dosage of 0.03 g.
3.2.3 Effect of oxidant
The utilizing of oxidants plays a crucial role in the oxidation process. Furthermore, the catalytic
efficiency of CuCr2O4 and CuCr2O4/TiO2 (0.7) was examined for the alcohol oxidations using t-
BHP and H2O2 as oxidant. As showed in Table 6, the result of selective oxidation of benzylic
alcohols to aldehyde with CuCr2O4 and CuCr2O4/TiO2 (0.7) is more efficient in the presence of t-
BHP. Maximum conversion and good reaction time was obtained by t-BHP while H2O2 is not
found to be effective for the oxidation of alcohols. This observation can be explained in terms of
decomposition of H2O2 into molecular oxygen, and shows its effect on the times of their action
which were quite high. Also, in the absence of oxidant, no alcohol oxidation was observed. In
addition, concentration of oxidant has been tested and the results revealed that by increasing
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concentration of t-BHP from 0.2 to 0.5 ml no great changes in conversion has been occurred
(Table 7).
3.2.4 Effect of the nature of solvent
To investigate the solvents effect in the catalytic activity of the CuCr2O4/TiO2 (0.7), oxidation of
the benzhydrol and benzyl alcohol was studied in various other solvents e.g. acetonitrile, ethanol
and dichloromethane (Table 8). It can be seen that, acetonitrile is suitable solvent for the
oxidation reaction. As shown in Table 8, the best results were obtained when acetonitrile was
used as the solvent. However, in the presence of acetonitrile 90% and 80% conversion were
achieved for benzhydrol and benzyl alcohol. Ethanol and dichloromethane were also used as the
solvent where 80% and 45% of conversion was observed for benzhydrol in 15 min. It can be
concluded that the polarity index of acetonitrile (acetonitrile: 5.8, ethanol: 5.2 and
dichloromethane: 3.1) is higher than other solvents and strong polarity of solvent may be useful
for the oxidation of alcohols.
4. Conclusions
In this work, CuCr2O4 and CuCr2O4/ TiO2 nanocomposites with normal spinel structure were
synthesized by the sol-gel method and their structure and catalytic properties in alcohol oxidation
was studied. The result showed that alcohol was not oxidized in the absence of catalysts or
oxidant and also the catalytic activity of catalysis at reflux condition is much higher than that of
under light irradiation reaction. Pure CuCr2O4 or TiO2 displayed poor catalytic activity for
alcohol oxidation, whereas, after coupling of CuCr2O4/TiO2 heterojunction catalytic activity
were improved, because CuCr2O4 is a semiconductor with a small band gap and TiO2 has a large
band gap, therefore coupling of TiO2 with CuCr2O4 improve electron-hole separation.
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Acknowledgements
The authors are grateful to the Research Council of University of Guilan for the financial
assistance of this study.
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References
[1] X. Tang, L. Fang, F. Huang, Recent Advance in Green Catalytic Oxidation of Alcohols to
Aldehydes and Ketones with Hydrogen Peroxide as Oxidant, Advanced Materials Research
1049-1050 (2014) 158-166.
[2] K. Kawamura, T. Yasuda, T. Hatanaka, K. Hamahiga, N. Matsuda, M. Ueshima, K. Nakai
Oxidation of aliphatic alcohols and benzyl alcohol by H2O2 under the hydrothermal conditions in
the presence of solid-state catalysts using batch and flow reactors, Chemical Engineering
Journal, 285 (2016) 49–56.
[3] A.R. Hajipour, H. Karimi, Selective oxidation of alcohols over copper zirconium phosphate,
Chinese Journal of Catalysis, 35 (2014) 1529-1533.
[4] Y. Guo, J. Zhao, J. Xu, W. Wang, F. Tian, G. Yang, M. Song, Aerobic Oxidation of Benzyl
Alcohol Catalyzed by Cu-Mn Mixed Oxides and 2,2,6,6-Tetramethyl-piperidyl-l-oxyl, Journal of
Natural Gas Chemistry, 16 (2007) 210-212.
[5] R. R. Gowda, D. Chakraborty, La2O3 Catalyzed Oxidation of Alcohols International, Journal
of Organic Chemistry 1 (2011) 41-46.
[6] A. Yoshida, Y. Takahashi, T. Ikeda, K. Azemoto, S. Naito, Catalytic oxidation of aromatic
alcohols and alkylarenes with molecular oxygen over Ir/TiO2, Catalysis Today 164 (2011) 332-
335.
11
ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
[7] S. Higashimoto, N. Suetsugu, M. Azuma, H. Ohue, Y. Sakata, Efficient and selective
oxidation of benzylic alcohol by O2 into corresponding aldehydes on a TiO2 photocatalyst under
visible light irradiation: Effect of phenyl-ring substitution on the photocatalytic activity
Journal of Catalyst 274 (2010) 76-83.
[8] K. L. Deutsch, B. H. Shanks, Active species of copper chromite catalyst in C–O
hydrogenolysis of 5-methylfurfuryl alcohol, Journal of Catalysis 285 (2012) 235–241.
[9] S.A. Hosseini, M.C. Alvarez-Galvan, J.L.G. Fierro, A.Niaei, D.Salari, MCr2O4 (M=Co,
Cu,andZn) nanospinels for 2-propanol combustion: Correlation of structural properties with
catalytic performance and stability, Ceramics International 39 (2013) 9253–9261.
[10] Z. Ma, Z. Xiao, J.A.V. Bokhoven, C. Liang, A non-alkoxide sol–gel route to highly active
and selective Cu–Cr catalysts for glycerol conversion, Journal of Material Chemistry 20 (2010)
755-760.
[11] R. Rao, A. Dandekar, R.T.K. Baker, M.A. Vannice, Properties of Copper Chromite
Catalysts in Hydrogenation Reactions, Journal of Catalyst 171 (1997) 406-419.
[12] R. Prasad, Highly active copper chromite catalyst produced by thermal decomposition of
ammoniac copper oxalate chromate, Materials Letters 59 (2005) 3945-3949.
[13] K. George, S. Sugunan, Nickel substituted copper chromite spinels: Preparation,
characterization and catalytic activity in the oxidation reaction of ethylbenzene, Catalysis
Communication 9 (2008) 2149-2152.
[14] S. Barman, N.C. Pradhan, A. Acharya, P. Pramanik, Kinetics of Reductive Isopropylation of
Benzene with Acetone over Nano-Copper Chromite-Loaded H-Mordenite, Industrial &
Engineering Chemical Research 45 (2006) 3481-3487.
12
ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
[15] H. Wang, L. Chen, D. Luan, Y. Li, Z. Yan, Y. Zhang,J. Xing , A continuous process for the
synthesis of homopiperazine catalyzed by Cu-based catalysts, React. Kinetic Catalyst Letters 89
(2006) 201-208.
[16] P.S. Sathiskumar, C. R. Thomas, G. Madres, Solution Combustion Synthesis of Nanosized
Copper Chromite and Its Use as a Burn Rate Modifier in Solid Propellants, Industrial &
Engineering Chemistry Research 51 (2012) 10108-10116.
[17] A. Kaddouri, N. Dupont, P. Ge´lin, P. Deliche`re, Methane Combustion Over Copper
Chromites Catalysts Prepared by the Sol–Gel Process, Catalyst Letters 141 (2011) 1581–1589.
[18] W. Li, H. Cheng, Synthesis and characterization of Cu-Cr-O nanocomposites, Journal of
Central South University Technology 14 (2007) 291-295.
[19] J. Yan, L. Zhang, H. Yang, Y. Tang, Z. Lu, S. Guo, Y. Dai, Y. Han, M. Yao,
CuCr2O4/TiO2 heterojunction for photocatalytic H2 evolution under simulated sunlight
irradiation Solar Energy 83 (2009) 1534-1539.
[20] A. Fujishima, X. Zhang, D.A. Tryk, TiO2 photocatalysis and related surface phenomena,
Surface Science Reports 63 (2008) 515-582.
[21] K. Olurode, G.M. Neelgund, A. Oki, Z. Luo, A facile hydrothermal approach for
construction of carbon coating on TiO2 nanoparticles, Spectrochimica Acta Part A: Molecular
and Biomolecular Spectroscopy 89 (2012) 333-336.
[22] R. Bajaj, M. Sharma, D. Bahadur, Visible light-driven novel nanocomposite
(BiVO4/CuCr2O4) for efficient degradation of organic dye, Dalton Transactions 42 (2013) 6736-
6744.
13
ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
[23] I. Sobczak, K. Szrama, R. Wojcieszak, E.M. Gaigneaux, M. Ziolek, CuxCryOz mixed oxide
as a promising support for gold – The effect of Au loading method on the effectiveness in
oxidation reactions, Catalysis Today 187 (2012) 48-55.
[24] S.S. Acharyya, S. Ghosh, R. Bal, Catalytic Oxidation of Aniline to Azoxybenzene Over
CuCr2O4 Spinel Nanoparticle Catalyst, ACS Sustainable Chemical Engineering 2 (2014) 584 –
589.
[25] H.F. Moafi, M.A. Zanjanchi, A.F. Shojaie, Tungsten-doped ZnO nanocomposite: Synthesis,
characterization, and highly active photocatalyst toward dye photodegradation, Materials
Chemistry and Physics 139 (2013) 856- 864.
[26] M.H. Loghmani, A.F. Shojaei, Synthesis and characterization of Co–La–Zr–B quaternary
amorphous nano alloy: Kinetic study for hydrogen generation from hydrolysis of sodium
borohydride, Journal of Alloys and Compounds 580 (2013) 61-66.
[27] M.A. Rezvani, A.F. Shojaie, M.H. Loghmani, Synthesis and characterization of novel
nanocomposite, anatase sandwich type polyoxometalate, as a reusable and green nano catalyst in
oxidation desulfurization of simulated gas oil, Catalysis Communication 25 (2012) 36-40.
[28] A.F. Shojaei, M.D. Rafie, M.H. Loghmani, High Selective Oxidation of Alcohols Based on
Trivalent Ion (Cr3+ and Co3+) Complexes Anchored on MCM-41 as Heterogeneous Catalysts,
Bulletin of the Korean Chemical Society 33 (2012) 2748-2752.
[29] M.H. Loghmani, A.F. Shojaei, Effect of Microwave Irradiation on Morphology and Size of
Anatase Nano Powder: Efficient Photodegradation of 4-Nitrophenol by W-doped Titania,
Bulletin Korean Chemical Society 33 (2012) 3981-3986.
14
ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
[30] H.F. Moafi, A.F. Shojaie, M.A. Zanjanchi, Titania and titania nanocomposites on cellulosic
fibers: Synthesis, characterization and comparative study of photocatalytic activity, Chemical
Engineering Journal 166 (2011) 413- 419.
[31] A.F. Shojaei, M.H. Loghmani, La3+ and Zr4+ co-doped anatase nano TiO2 by sol-microwave
method, Chemical Engineering Journal 157 (2010) 263- 269.
[32] A.F. Shojaei, A.R. Tabari, M.H. Loghmani, Normal spinel CoCr2O4 and
CoCr2O4/TiO2 nanocomposite as novel photocatalysts, for degradation of dyes, Micro and Nano
letters 8 (2013) 426- 431.
15
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Table 1. Oxidation of alcohols catalyzed by CuCr2O4 and CuCr2O4/TiO2 under reflux conditiona.
CuCr2O4
Tim
CuCr2O4/TiO2
Tim
Yiel
d
%
Yiel
d
%
Entr
y
Conversi
e
e
Conversi
Substrate
Product
on %
(mi
n)
(mi
n)
on %
b
b
1
2
3
70
87
70
80
90
85
45
30
45
C6H5CH2OH
4-ClC6H5CH2OH
2-BrC6H5CH2OH
4-
C6H5CHO
4-ClC6H5CHO
2-BrC6H5CHO
4-
15
15
30
80
95
85
75
92
80
4
80
90
90 (CH3)2CHC6H5CH (CH3)2CHC6H5C 60
2OH HO
90
80
5
6
7
8
80
70
85
85
90
85
90
90
90 2-CH3C6H5CH2OH 2-CH3C6H5CHO 60
CH3(O)C6H5CH2O CH3(O)C6H5CH
95
85
90
90
92
80
84
84
60
45
60
30
15
H
O
C6H5CHOHC6H5
C6H5COC6H5
C6H5CHOHCH2C
C6H5COCH2CH3 30
2-NO2C6H5CHO 60
4-NO2C6H5CHO 60
H3
2-
9
34
40
40
50
90
90
40
50
35
40
NO2C6H5CH2OH
4-
10
NO2C6H5CH2OH
C6H5(O)C6H5CH2 C6H5(O)C6H5CH
11
12
45
43
50
50
30
60
15
C6H5(CH2)2CHO 30
50
50
45
40
OH
O
C6H5(CH2)3OH
aReactions were performed using 0.03 g of catalyst, 0.2 mL TBHP and 3 mL acetonitrile.
bGC yield.
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Table 2. Oxidation of alcohols catalyzed by CuCr2O4 and CuCr2O4/TiO2 under UV irradiation
systema.
CuCr2O4
Entr Yiel Conversi Tim
CuCr2O4/TiO2
Tim Conversi Yiel
Substrate
Product
y
d % on %
e
e
on %
d %
(mi
n)
(mi
n)
1
2
3
4
75
92
75
80
80
90
90
90
90
C6H5CH2OH
4-ClC6H5CH2OH
2-BrC6H5CH2OH
4-
C6H5CHO
4-ClC6H5CHO
2-BrC6H5CHO
4-
60
60
90
90
80
75
90
85
90
95
85
85
95
90
95
(CH3)2CHC6H5CH (CH3)2CHC6H5C
2OH HO
90 2-CH3C6H5CH2OH 2-CH3C6H5CHO 90
5
6
70
70
80
80
85
80
80
75
90 CH3(O)C6H5CH2O CH3(O)C6H5CH
60
H
O
7
8
80
70
85
80
90
C6H5CHOHC6H5
C6H5COC6H5
60
90
90
82
80
120 C6H5CHOHCH2C C6H5COCH2CH3 90
H3
9
28
30
36
35
30
40
40
40
120
2-
2-NO2C6H5CHO 90
30
40
40
40
28
36
30
30
NO2C6H5CH2OH
4-
NO2C6H5CH2OH
10
11
12
120
4-NO2C6H5CHO 60
120 C6H5(O)C6H5CH2 C6H5(O)C6H5CH 90
OH
O
120
C6H5(CH2)3OH
C6H5(CH2)2CHO 90
aReactions were performed using 0.03 g of catalyst, 0.2 mL TBHP and 3 mL acetonitrile.
bGC yield.
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Table 3. Oxidation of alcohols catalyzed by CuCr2O4 and CuCr2O4/TiO2 under microwave
irradiationa.
CuCr2O4
Entr Yiel Conversi Tim
CuCr2O4/TiO2
Tim Conversi Yiel
Substrate
Product
y
d
%
on %
e
e
on %
d
%
b
b
(mi
n)
4
(mi
n)
3.5
1
2.5
1
1
2
3
4
80
92
82
78
90
C6H5CH2OH
4-ClC6H5CH2OH
2-BrC6H5CH2OH
4-
C6H5CHO
4-ClC6H5CHO
2-BrC6H5CHO
4-
90
80
87
80
86
90
85
80
2
3
2
90
90
90
(CH3)2CHC6H5CH (CH3)2CHC6H5C
2OH HO
2-CH3C6H5CH2OH 2-CH3C6H5CHO 2.5
5
6
80
64
90
70
3
90
70
80
67
2.5 CH3(O)C6H5CH2O CH3(O)C6H5CH 1.5
H
O
7
8
90
85
95
90
4
2
C6H5CHOHC6H5
C6H5CHOHCH2C C6H5COCH2CH3 1.5
H3
C6H5COC6H5
3.5
90
90
85
85
9
30
35
40
30
40
40
50
40
3
2
2-
2-NO2C6H5CHO
2
40
50
50
50
35
40
40
43
NO2C6H5CH2OH
10
11
12
4-
4-NO2C6H5CHO 1.5
NO2C6H5CH2OH
C6H5(O)C6H5CH2 C6H5(O)C6H5CH 1.5
2
OH
O
2.5
C6H5(CH2)3OH
C6H5(CH2)2CHO
2
aReactions were performed using 0.03 g of catalyst, 0.2 mL TBHP and 3 mL acetonitrile.
bGC yield.
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Table 4. Effect of molar ratio (nCuCr2O4/nTiO2)
Catalyst molar ratio
Conversion(%)
0.3
70
0.5
75
0.7
80
1
83
Reactions were performed using 0.03 g of catalyst, 0.2 mL TBHP and 3 mL acetonitrile
compared in 15 min.
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Table 5. Effect of different concentration of CuCr2O4/TiO2(7:10) in acetonitrile
Catalyst dosage(mg)
Conversion(%)
10
60
20
75
30
80
40
82
Reactions were performed using 0.01, 0.02, 0.03,0.04 g catalysts, 0.2 mL TBHP and 3 mL
acetonitrile compared in 15 min.
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Table 6. Nature of the oxidant over CuCr2O4/TiO2(7:10) in acetonitrile under reflux condition
Oxidant
t-BHP
H2O2
No oxidant
Alcohol
Time Conversion(%) Time Conversion(%) Time Conversion(%)
Benzyl alcohol
Benzhydrol
aNo Reaction
15
15
80
90
30
30
30
40
-
-
NRa
NR
Reactions were performed using 0.03 g of catalyst, 0.2 mL oxidant, and 3 mL acetonitrile.
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Table 7. Effect of TBHP concentration on oxidation of benzyl alcohol by CuCr2O4/TiO2 (7:10)
TBHP concentration(ml)
Conversion(%)
0.1
70
0.2
80
0.3
80
0.4
80
0.5
85
Reactions were performed using 0.03 g of catalyst, 0.1, 0.2, 0.3, 0.4 and 0.5 mL TBHP and 3 mL
acetonitrile compared in 15 min.
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Table 8. Effect of solvent in the oxidation reaction over CuCr2O4/TiO2 (7:10) under reflux
condition
solvent
acetonitrile
dichloromethane
ethanol
Alcohol
Conversion(%)a
Conversion(%)
Conversion(%)
Benzyl alcohol
80
40
45
70
80
Benzhydrol
90
a Time (min) needed to 100% conversion
Reactions were performed using 0.03 g of catalyst, 0.2 mL TBHP and 3 mL solvent.
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Figure 1 XRD patterns of (a) CuCr2O4 (b) CuCr2O4/TiO2 composite (nCuCr2O4:nTiO2 = 0.7)
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Figure 2 SEM images of (a) pure CuCr2O4 (b) CuCr2O4/TiO2 composite (nCuCr2O4:nTiO2 =
0.7)
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Figure 3 TEM images of (a) pure CuCr2O4 (b) CuCr2O4/TiO2 composite (nCuCr2O4:nTiO2 = 0.7)
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