Selective oxidation of hydrocarbons under air using recoverable silver ferrite-graphene (AgFeO2-G) nanocomposite: A good catalyst for green chemistry

Article abstract of DOI:10.1016/j.inoche.2016.03.011

The selective oxidation of hydrocarbons is a main academic and industrial research challenge. A lot of researches have been done about this issue, but till now relatively little attention has been paid to graphene-complex oxide nanocomposites. Herein, we report our studies on a new catalyst. Silver ferrite-graphene (AgFeO₂-G) as a separable nanocomposite from the reaction solution, was used as an effective oxidizing agent for the oxidation of various hydrocarbons (1- decene, cyclohexene, cis-cycloctene, cyclohexane, cyclooctane etc.) under mild conditions (55 °C, 8 h) with high conversion and selectivity using air, that is proper for 'green' chemistry. Metal or metal oxide nanoparticles assembled on graphene sheets revealed high electrocatalytic activity. Indeed, AgFeO₂ with graphene due to low band gap and graphene oxide with large amounts of oxygen-containing groups, provide facility catalytic activity of catalyst-supported system. We also found that, with this catalyst, selective oxidation could be achieved without the need for the addition of solvent, which is appropriate in particular for 'green' chemistry. The catalysts showed little deactivation and maintained their conversion and selectivity levels duration of the measurements.

Full text of DOI:10.1016/j.inoche.2016.03.011

Selective oxidation of hydrocarbons under air using recoverable silver
ferrite–graphene (AgFeO2–G) nanocomposite: A good catalyst for green
chemistry
Seyed Majid Hosseini, Hassan Hosseini Monfared, Vahideh Abbasi,
Mohammad Reza Khoshroo
PII:
DOI:
Reference:
S1387-7003(16)30072-7
doi: 10.1016/j.inoche.2016.03.011
INOCHE 6261
To appear in:
Inorganic Chemistry Communications
Received date:
Revised date:
Accepted date:
20 January 2016
9 March 2016
13 March 2016
Please cite this article as: Seyed Majid Hosseini, Hassan Hosseini Monfared, Vahideh Ab-
basi, Mohammad Reza Khoshroo, Selective oxidation of hydrocarbons under air using re-
coverable silver ferrite–graphene (AgFeO2–G) nanocomposite: A good catalyst for green
chemistry, Inorganic Chemistry Communications (2016), doi: 10.1016/j.inoche.2016.03.011
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ACCEPTED MANUSCRIPT
Selective oxidation of hydrocarbons under air using recoverable silver ferrite-graphene
(AgFeO2-G) nanocomposite: a good catalyst for green chemistry
*
⊥
Seyed Majid Hosseini , Hassan Hosseini Monfared, Vahideh Abbasi and Mohammad Reza Khoshroo
⊥
Department of Chemistry, Zanjan University, 45195-313 Zanjan, Iran
*
E-mail: hseidmajid@znu.ac.ir
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Abstract
The selective oxidation of hydrocarbons is a main academic and industrial research challenge. A lot of researches
have been done about this issue, but till now relatively little attention has been paid to graphene-complex oxide
nanocomposites. Herein, we report our studies on a new catalyst. Silver ferrite-graphene (AgFeO2-G) as a separable
nanocomposite from the reaction solution, was used as an effective oxidizing agent for the oxidation of various
hydrocarbons (1- decene, cyclohexene, cis-cycloctene, cyclohexane, cyclooctane etc.) under mild conditions (55 ০C,
8h) with high conversion and selectivity using air, that is proper for ‘green’ chemistry. Metal or metal oxide
nanoparticles assembled on graphene sheets revealed high electrocatalytic activity. Indeed, AgFeO2 with graphene
due to low band gap and graphene oxide with large amounts of oxygen-containing groups, provide facility catalytic
activity of catalyst-supported system. We also found that, with this catalyst, selective oxidation could be achieved
without the need for the addition of solvent, which is appropriate in partcular for ‘green’ chemistry. The catalysts
showed little deactivation and maintained their conversion and selectivity levels duration of the measurements.
Keywords: Oxidation, Silver, Selective, Nanocomposite, Graphene
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1. INTRODUCTION
Oxidation is an important method for the synthesis of fine chemicals and chemical intermediates in the
manufacture of high-tonnage goods, pharmaceuticals and agrochemicals [1, 2]. For example, propylene oxide (PO)
is a major chemical intermediate with a universal estimated production of 6.7 million tons in 2003 [3], and by
volume it is among the top 50 chemicals produced around the world [4]. Nevertheless, the selective oxidation of
hydrocarbons is a main academic and industrial investigation challenge and oxidations are often useless [5]. The
present of catalytic systems using oxygen from air is preferred for ‘green’ chemistry [6]. Among the metal-based
nanocomposites, nanogold and nanosilver play an important role in catalysis, which have been widely explored in
many reactions. Gold catalysis is now displaying potential in selective oxidation processes [7-10]. But, gold-based
catalysts are usually costly. Among many metal catalysts, silver is an extremely effective noble metal and has some
prominent characteristics such as antimicrobial activity and environmental friendliness [11]. More notably, silver is
exclusively appropriate for industrial catalysis and heterogeneous catalysis because of its relatively low prices, for
example, less than 1/50 of the price of gold or platinum and about 1/25 of the price of palladium [12,13]. So, silver
compounds have been used in different reations such as isomerization [14], substitution [15], oxidation [16-20],
antimicrobial agents [21,22], synthesis [23,24], catalytic [25], photocatalytic [26-28], hydrogenation [29], optical
[30], biological [31], reduction [32], adsorption [33,34], metathesis [35], polymerization [36], formylation [37],
ammonia oxidation [38,39], electron microscopy and EXAFS studies [40], and as sensor [41]. Even though ethene is
epoxidized efficiently using molecular oxygen with silver catalysts in a high-scale industrial process [42], but for
higher alkenes can only be effectively epoxidized using hydroperoxides [43], hydrogen peroxide [44,45], or
stoichiometric oxygen donors. The use of silver alone does not have economically advantageous. On the other hand,
the utilize of silver compounds not only increase the efficiency of the reaction, but also work in terms of industrial.
Metal and traditional semiconductor nanoparticles are considered as a suitable factor for nanocatalysts (or catalysts
support) and have received notable attention in photoreduced oxidation, hydrocarbon selective oxidation, solar water
splitting and so on [46,47]. It is well-known that the support plays a vital role in the catalytic performance of a
heterogeneous catalyst [48]. In recent years, there has been an increasing attention in the use of nanostructure carbon
materials as catalyst supports [49, 50]. Graphene has attracted worldwide interest since it is an appealing support due
to its outstanding properties, such as superb mechanical strength, high adsorption capability, easiness of
modification large, specific surface area and remarkable electrical conductivity with a single layer of sp2-bonded
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carbon atoms tightly packed into a two-dimensional (2D) honeycomb structure [51, 52]. Also it is well-known that a
single graphene layer has a zero-gap semiconductor with a linear Dirac-like spectrum around the Fermi energy. To
cut a long story short, graphene has awarded both the Nobel Prize in Chemistry to Robert Curel et al. in 1996 and
Physics to Andre Geim et al. in 2010, which illustrate graphene is an exceptional material. Hence, graphene has
received late consideration as an ideal catalyst support [53, 54]. Besides, graphene oxide (GO) compared with other
supports such as mesoporous silicates (MCM-41 and SBA-15), has unique nanostructure (monolayer), abundant
oxygen carrying functionalities on its basal planes and at its edges (hydroxyl, epoxide, and carboxylic groups),
excellent mechanical strength and hydrothermal stability, and the viewpoint of various applications such as
composite materials, catalysis, optoelectronics, supercapacitors, memory devices, etc [55, 56].
However, based on our knowledge up to now, relatively little attention has been paid to nanocomposites [57, 58],
or graphene-complex oxide nanocomposites for oxidation. Of course, a few studies have been conducted on the
photocatalyst [59, 60]. It is of great appetite to study the facility of graphene complex oxide nanocomposites, such as
AgFeO2-G systems. If that can be accomplished, then it may be feasible to gain some specific properties as a
outcome of the interaction of complex oxide nanoparticles and support as well as the good consequence.
Nanocomposite not only has a low band gap [61], due to the AgFeO2, but also large amounts of oxygen-containing
groups, because of the graphene oxide, which cause oxygen easily be transferred to the substrate. Magnetically
recoverable nanocatalysts have been used in organic synthesis for a wide range of catalytic processes [62, 63]. For
the reason that AgFeO2 is a magnetic semiconductor substance, thus AgFeO2-based catalysts can be magnetically
separable in a suspension system by virtue of their own magnetic properties without other magnetic materials, which
makes we can reuse and recovery catalysts after process. Hence, we for the first time report our work on AgFeO2-G
as an inimitable semiconductor nanoparticles for oxidation of various hydrocarbons. Here we show that AgFeO2-G
nanocomposites can perform a good activity for the oxidation of hydrocarbons using air, with excellent selectivity to
oxidation products and substantial conversions. Moreover, our catalyst does not need to initiator in contrast to the
way in which initiator is required in previous studies for hydrocarbons oxidation [64].
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2. EXPERIMENTAL
2.1. Materials
Graphite powder, potassium permanganate, Fe(NO3)3.9H2O, H2SO4 (98 wt%), H2O2 (30%), HCl (37 wt%), silver
nitrate, formaldehyde, and ethylene glycol were purchased from Merck. Cyclohexene (99%, Fluka), Cyclohexane
(99%, Fluka), 1-methyl-1-cyclohexene (97%, Sigma-Aldrich), alpha-methyl styrene (>99%, Merck), styrene (>99%,
Merck), cis-stilbene (>95%, Merck), trans-stilbene (96%,Sigma), 1,2,3,4-tetrahydronaphthalene (>98%, Merck), 1-
decene and other reagents were obtained from commercial sources and were used as received without further
purification. The deionized water used throughout experiments. For obtaining graphene oxide (GO), graphite
powder was oxidized using reported procedures Hummers’ method [65].
2.2. Characterization
Fourier transform infrared (FT-IR) spectra were recorded using a Perkin-Elmer 597 spectrophotometer in the
range of 400-4000 cm−1 as KBr disks. 1H NMR spectra of a reaction mixture (without purification) were recorded on
a Bruker 250 MHz spectrometer. UV-Vis spectra of solutions were recorded with a Shimadzu 160
spectrophotometer. Powder X-ray diffraction (XRD) data were recorded on a Bruker D8ADVANCED
diffractometer with a wavelength of 1.5406 Å (Cu Kα ), a voltage of 40 kV, and a current of 40 mA. Field-emission
scanning electron microscopy (FESEM) was performed with a Hitachi F4160 microscope at an accelerating voltage
of 15 kV. The resulted suspensions were deposited on a holey carbon film supported by a copper grid. The Brunauer
−Emmett−Teller surface area of as-synthesized samples was measured using an ASAP2010C surface aperture
adsorption instrument (Micromeritics Instrument Corporation, USA) by N2 physisorption at 77 K. Raman spectra of
graphene-based materials were recorded in the spectral range 200-3500 cm−1 on a BRUKER (SEN-TERRA 2009)
Raman spectrometer with laser power 50 mW and 785 nm. The reaction products of the oxidation were determined
and analyzed by using an HP Agilent 6890 gas chromatograph equipped with an HP-5 capillary column (phenyl
methyl siloxane 30 m × 320μ m × 0.25 μm) with a flame-ionization detector (FID). The magnetization measurement
was performed at room temperature using a vibrating sample magnetometer (VSM) device, in the Development
Center of the University of Kashan (Kashan, Iran).
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2.3. Synthesis of magnetic AgFeO2-graphene nanocomposite
A typical condition for the synthesis of AgFeO2-graphene nanocomposite, is as follows: 50 mg of GO was added
into 50 ml ethylene glycol (EG) with ultrasonication for 1 h to form a steady GO colloid. Afterward, 0.808 g of
Fe(NO3).9H2O and 0.340 g of AgNO3 were added in 10 ml EG and added slowly into the above colloid with
magnetic stirring for 1 h. Then, formaldehyde was added as reducing agent into the mixture followed by stirring for
another 20 min, yielding a stable bottle-green homogeneous emulsion. The resulting mixture was then transferred to
°
a 100 ml teflon-lined stainless steel autoclave and heated in an oven at 200 C for 14 h, and cooled to room
temperature. The resulting product were separated by filtration and washed with absolute ethanol and deionized
water, then dried at 55 °C for 10 h. The product was labeled as AgFeO2-G. The formation of AgFeO2-G composite is
schematically illustrated in Fig. 1.
2.4. Catalytic aerobic oxidation with AgFeO2-graphene
The oxidation processes were performed in a glass inlay of a 32 ml steel autoclave. The autoclave was
conditioned by discharge and replenish with dioxygen. All autoclave loading was carried out under air and heated to
the required temperature (55 °C) in an oil bath. In a generic test, 2.0 mmol of substrate was added to the reactor with
0.01 g AgFeO2-G, 3.0 mmol isobutyraldehyde as a co-oxidant. After purgation with O2, the reactor was pressurized
to 1.5 bar. The stirring rate was 350 rpm. At the end of 8 h the reactor was depressurized, the catalyst deleted via an
1
external magnet (1.2 T) and the product mixture was analyzed by gas chromatography and H NMR. The products
1
were identified with authentic samples and H NMR. Conversions and yields were computed about the starting
substrate. The reaction products were measured by gas chromatography and recognized by comparison with the
retention time and spectral data to those of an authentic sample. To ensure reproducibility, each catalytic reaction
was performed at least three times. For recycling experiments, after finishing the process, the nanocomposite was
recollected using a magnet, washed with acetonitrile, dried and reused. GC circumstances with column Hp-5: carrier
gas N2 flow = 0.7 ml min−1, inlet temp 250 °C, initial column temp 90 °C, final column temp 190 °C, sleep 10 °C
min−1.
3. Results and discussions
3.1. Characterization of composite
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Fig. 2, shows FT-IR spectra of GO and AgFeO2-G. For GO, the stretching vibrations of carbonyl functional group
was indicated clearly at round 1730 cm−1 and ether/epoxide functional groups were at 1232 cm−1 [66]. The carbonyl
and ether/epoxide groups demonstrate that the original extended conjugated π-orbital system of the natural graphite
was destroyed and oxygen-containing groups were inserted into carbon skeleton during the oxidation of graphite
powder [67]. Also there is a C-O peak at 1420 cm−1 which is ascribed of carboxy groups in these structures [68].
The spectra of graphene oxides also show a C=C peak at 1622 cm−1 and a C-O peak at 1060 cm−1 corresponding to
the remaining sp2 character and alkoxy group, respectively [69]. The peaks at 2923 and 2853 cm−1 can be assigned
to a methylene stretch and represents the existence of CH2 or CH groups [70]. Furthermore, O-H groups are seen for
graphene oxides about 3600 cm−1 as shoulder. The obvious peak at 3433 cm−1 assigned to the stretching vibration of
hydroxy group indicates that both graphite and graphene oxide had a certain amount of adsorbed water. As can be
seen, all the characteristic peaks of GO vanished after the hydrothermal process. For AgFeO2-G, the adsorption peak
around 1530 cm-1 may be assigned to the stretching vibrations of the unoxidized carbon backbone [71] and the two
strong absorption peaks at lower frequency (around 475 and 553 cm-1) can be assigned to the stretching vibrations of
the Ag-O bonds in tetrahedral positions and the Fe-O bonds, respectively [72]. This indicates that there is reduced
GO in the AgFeO2-G composite.
Fig. 3A gives the nitrogen adsorption-desorption isotherms (inset) and pore size distribution plots for AgFeO2-G.
The N2 isotherm of the AgFeO2-G composite is close to Type IV, revealing the existence of mesopores. It is well-
known that the mesoporous structure is a more efficient photocatalyst structure for degrading organic pollutants in
water. The specific surface area of the AgFeO2-G sample was determined to be 252.35 m2.g-1, with the
Brunauer−Emmett−Teller (BET, nitrogen, 77 K) method. The Barrett−Joyner−Halenda (BJH) desorption average
pore diameter was 1.95 nm with a very narrow pore size distribution, and the pore volume was 0.23 m2.g-1.
Raman spectroscopy gives useful information related to the electronic and structural properties of graphene. Fig.
3B, displays Raman spectra of GO and AgFeO2-graphene. The D band (~1363 cm-1) is related to the defect induced
breathing mode of A1g symmetry and the G band (~1605 cm-1) is of E2g symmetry, representing the relative degree
of graphitization [73]. Both GO and AgFeO2-G exhibit two bands at about 1363 and 1605 cm-1, which are associated
with the D and G bands of carbon-based materials, respectively. Also, compared with GO (curve a), AgFeO2-G
(curve b) shows relative higher intensity of D to G band. These observations offer a decline in the average size of
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the sp2 domains from AgFeO2-G and further affirm the formation of new graphitic domains after the reduction [74].
Furthermore, an increase in D/G intensity ratio (ID/IG = 1.24) of AgFeO2-G illustrated increased defects in
graphene sheets after reduction, which is likely because smaller but more numerous graphitic sp2 domains were
manufactured compared with the ones previously present in graphite oxide [75].
The XRD diffraction patterns of the as-prepared AgFeO2-graphene nanocomposite and graphene oxide (GO) are
shown in Fig. 4A, It can be seen that nearly all the diffraction peaks of AgFeO2-graphene may be pertained to
spinel-type AgFeO2 (JCPDS 21-1081) [76]. The peaks at 2θ values of 12.3 , 25.1 , 27.3 , 31.4 , 34.2 , 42.8, 48.5,
56.3, 60.1, 63.2 and 77.1 can be indexed to (003), (006), (101), (102), (104), (009), (108), (0012), (110), (116), and
(202) crystal planes of spinel AgFeO2, respectively. The average diameter of the AgFeO2 nanoparticles was
surveyed by the Scherrer equation, which is about 45.78 nm. No typical diffraction peak of graphene (002) or GO
(001) is observable in the XRD pattern for AgFeO2-graphene, due to the fact that GO can be destroyed by the
presence of AgFeO2 among the interlayers during the hydrothermal process, leading to the exfoliation of GO. On the
other hand, and the reduced GO sheets show no visible sign of the (002) peak [77].
UV-vis spectroscopy is an instructive and important method to recognize the change in the absorption of the
semiconductors. As seen in Fig. 4B, the UV−vis absorbance spectra of GO shows an distinct characteristic
absorption peak at about 230 nm that pertain to the π-π* transition of aromatic C=C bonds. For AgFeO2-G, the
absorption peak of GO at 230 nm vanishes and the absorption is much stronger than that of the pure AgFeO2
particles coating the entire visible region because of the presence of graphene.
3.2. Structure and morphology of AgFeO2-graphene nanocomposite
The size, shape and size distribution of the nanoparticles of AgFeO2 and GO were examined by field-emission
scanning electron microscopy (FESEM). The as-synthesized AgFeO2 nanoparticles Fig. 5A have good spherical
shape and have a mean diameter of 50 nm. As can be seen in Fig. 5B, the approximately transparent graphene sheets
are totally exfoliated and decorated homogeneously with AgFeO2 nanocrystals having an average diameter of 50 nm
and a narrow particle size distribution.
3.3. Magnetic separation properties of AgFeO2-graphene nanocomposite
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The magnetic properties of the synthesized AgFeO2 and AgFeO2-G were analyzed by vibrating sample
magnetometry (VSM). Fig. 6A shows the room-temperature magnetization hysteresis loops of the AgFeO2-G
composite and pure AgFeO2 particles. The saturation magnetization of the AgFeO2-G composite is 50.5 emu/g,
which is lower than that of pure AgFeO2 particles (62.2 emu/g), chiefly attributing to the presence of graphene. The
hysteresis loops of the powdered material showed no magnetic hysteresis, with both the magnetization and
demagnetization curves passing through the origin, which clearly indicates the superparamagnetic nature of the
material. Moreover, the synthesized heterogeneous nanocomposite possess strong magnetic features due to a high
saturation magnetization value. As said in the introduction, the magnetic properties of AgFeO2 give it good
efficiency in magnetic separation for the AgFeO2-graphene nanocomposite. Also, we surveyed magnetic separation
properties of the AgFeO2-graphene nanocomposite. As shown in Fig. 6B, the catalyst can be easily separated from
the reaction mixture by a magnetic field after 30 seconds.
3.4. Catalytic activity of the catalyst
For select the optimum solvent, we examined the reaction using magnetite nanocomposite as catalysts into
oxidation of 1-decene in the presence of air under the optimized conditions (55 °C, 8h and isobutyraldehyde as co-
oxidant) for various solvents by a stirred non-pressurized glass reactor (Table 1). The highest conversion for 1-
decene (69%) was observed with acetonitrile (Table 1, entry 10). Also, highest selectivity (97%) was obtained in the
oxidations of 1-decene with DMSO (Table 1, entry 8). As you can see, under relatively mild conditions, the most
significant finding with these solvents is that the products distribution is dependent on the solvent. In a further set of
experiments, to confirm the general applicability of this oxidation catalyst, different hydrocarbons were used as
substrates, using acetonitrile as solvent and AgFeO2-graphene nanocomposite as catalyst, and a high selectivity for
the epoxide products were achieved (Table 2). The high selectivity for the epoxide, in particular for unsaturated
hydrocarbons (for example, cyclohexene), demonstrates that direct oxidation of the carbon = carbon double bond is
happening with this catalyst structure.
In a final set of experiments, we investigated the oxidation of 1-decene in the absence of solvents. We found that,
selective oxidation could be achieved without the need for the addition of solvent (Table 3), which is a main
principle of ‘green’ chemistry. Also we tested aerobic oxidation of 1-decene in the absence of support and AgFeO2.
As you can see, catalyst or support unaccompanied don’t have a proper act, whereas it is possible to improve the
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efficiency of AgFeO2 by coupling it with another semiconductor (graphene oxide), resulting in high catalytic
performance.
3.5. The possible oxidation mechanism
The proposed mechanism is presented in Fig. 7, in which the conversions of an olefin in the presence of AgFeO2-
graphene nanocomposite and isobutyraldehyde as a co-oxidation are plotted. The initiation starts with the conversion
of the O2 to the corresponding superoxide radical catalysted by the nanocomposite. (Fig. 7A) Afterward this radical
reacts with aldehyd producing an acyl radical (Fig. 7B), subsequently this radical reacts with O2 to that produces
acylperoxy radical (Fig. 7C) which is the intermediate, responsible for the convey of oxygen from its molecular
form in the gaseous phase to the products of olefin oxidation. This observation and the mechanism were similar to
those of graphitic carbon nitride (g-C3N4) [78], which were used as catalysts for the selective allylic oxidation. The
reaction then proceeds on the surface of nanocomposite by the attack of the acylperoxy radical on the coordinated
olefin (Fig. 7D), which consequences finally in the epoxide and isobutyric acid.
Although detailed considerations on the transition state are not yet clear, the mediation of the co-oxidant
(isobutyraldehyde) in the oxidation process could be via a interaction with the nanocomposite surface, particularly
influencing the ease of electron transfer from the nanocomposite to establish the active carrier. As matter of fact, as
mentioned in the introduction, nanocomposite properties are also vital in this process.
3.6. Catalyst recycling
The AgFeO2-G catalysts can be used repeatedly for the catalytic oxidation of hydrocarbons. The reusability of
AgFeO2-G catalysts for the oxidation of hydrocarbons using molecular oxygen was investigated under identical
conditions. After the required time, the catalyst was filtered and washed with methanol and acetonitrile and dried.
The recovered solid was used for another consecutive run without further treatment. Also, as shown in Fig. 8, the
catalytic activity of the AgFeO2-G nanocomposite does not show any clear loss after ten recycles for the oxidation
of 1-decene, illustrating the composite has fine stability.
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4. Conclusions
In a nutshell, to the best of our knowledge, this is the first report on graphene-complex oxide nanocomposites
aerobic oxidation by inexpensive and easily prepared magnetite nanoparticles and O2, allowing for general oxidation
of a relatively wide variety of hydrocarbons in good conversion and selectivity. Moreover, the synthesized
heterogeneous nanocatalysts bear strong magnetic features due to a high saturation magnetization value (∼60 emu
g−1). After completion of the reaction, the catalysts can be collected by magnet. In addition, the heterogeneous
nanocatalysts are stable and can be reused frequently. Also, the method represents a number of highly desirable
practical specifications: mild temperature reaction, oxygen can be used as the oxidant, ethyl acetate, a normal
organic solvent which is not as unsafe as halogenated compounds, is the reaction medium and all of the catalyst
components are almost low-cost, steady, and commercially on hand reagents. Above all, oxidation could be gained
without the need for the addition of solvent, which is a major tenet of ‘green’ chemistry. Eventually, if
nanostructured carbon materials are often considered as model supports, the real driving force for the fast
development of these materials in catalysis has been the increasing demand for new catalysts that should be more
affective, energy-saving, resource-saving and environment-friendly, together with an increasing request for
renewable and alternative energies needed for the sustainable development of our society.
Acknowledgment
We acknowledge the support of the University of Zanjan.
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Figures and tables captions:
Fig. 1. Schematic illustration of the synthesis procedure of the AgFeO2-graphene composite.
Fig. 2. Fourier transform infrared (FT-IR) spectra of (a) graphene oxide (GO), (b) AgFeO2-G.
Fig. 3. (A) Nitrogen Adsorption-Desorption isotherm (inset) and corresponding pore size distribution curves for
AgFeO2-G. (B) Raman spectra ofgraphene oxide (GO) and AgFeO2-G composite.
Fig. 4. (A) XRD pattern of (a) graphene oxide (GO) and (b) AgFeO2-G in the range of 5-80°. (B) UV-vis
absorbance spectra of graphene oxide (GO), AgFeO2-G and pure AgFeO2.
Fig. 5. SEM image of (A) AgFeO2, (B) AgFeO2-G and (C) AgFeO2-G after 10 cycles of reaction.
Fig. 6. (A) Room-temperature magnetization hysteresis loops of (a) AgFeO2-G composite, and (b) AgFeO2. (B)
Images of AgFeO2-G suspension with (a) and without (b) a magnetic field.
Table 1. 1-decene oxidation using G-AgFeO2 in different solvents
Table 1. oxidation of hydrocarbons using G-AgFeO2
Table 3. 1-decene oxidation with molecular oxygen in the absence of a solvent
Fig. 7. The possible mechanism for the oxidation of hydrocarbons by oxygen in the presence of AgFeO2-G and
isobutyraldehyde.
Fig. 8. Bar plot showing the oxidation of 1-decene in acetonitrile for 10 cycles using AgFeO2-G in the presence of
air.
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Fig. 1. Schematic illustration of the synthesis procedure of the AgFeO2-graphene composite.
Fig. 2. Fourier transform infrared (FT-IR) spectra of (a) graphene oxide (GO), (b) AgFeO2-G.
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Fig. 3. (A) Nitrogen Adsorption-Desorption isotherm (inset) and corresponding pore size distribution curves for
AgFeO2-G. (B) Raman spectra of graphene oxide (GO) and AgFeO2-G composite.
Fig. 4. (A) XRD pattern of (a) graphene oxide (GO) and (b) AgFeO2-G in the range of 5-80°. (B) UV-vis
absorbance spectra of graphene oxide (GO), AgFeO2-G and pure AgFeO2.
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Fig. 5. SEM image of (A) AgFeO2, (B) AgFeO2-G.
Fig. 6. (A) Room-temperature magnetization hysteresis loops of (a) AgFeO2-G composite, and (b) AgFeO2. (B)
Images of AgFeO2-G suspension with (a) and without (b) a magnetic field.
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Table 1
1-decene oxidation using G-AgFeO2 in different solvents
Conv.a (%)
Product Selectivity (%)
Entry
Solvent
O
O
O
HO
1
2
3
4
5
6
7
8
9
10
1,4-dioxane
Methanol
THF
8
14
(100)
(24)
(0)
(0)
(19)
(0)
(4)
(0)
(0)
(0)
(0)
(0)
(0)
(0)
(22)
(0)
(5)
(0)
(35)
(0)
Trace
61
Ethylacetate
Chlorobenzene
DMF
(75)
(66)
(95)
(97)
(100)
(0)
(16)
(0)
60
(34)
(5)
(3)
8
(0)
Chloroform
DMSO
46
(0)
3
(0)
(0)
Mesitylene
Acetonitrile
Trace
69b
(0)
(0)
(0)
(100)
(0)
Reaction conditions: 0.01 g catalyst, 0.002 mol hydrocarbon, 55 °C, 8 h, solvent (3 ml), isobutyraldehyde (0.003 mol).
aConversions were determined by GC. bEvaluated from 1H-NMR.
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Table 2
oxidation of hydrocarbons using G-AgFeO2 in CH3CN as solvent
Hydrocarbon Conv.a (%)
Entry
Products Selectivity (%)
O
OH
O
O
O
1
2
3
96
97
23
(98)
(80)
(73)
(1)
(1)
(0)
OH
O
O
O
O
(8)
(4)
(5)
O
OH
O
(0)
(0)
(27)
O
O
O
OH
O
4
5
100
66
(100)
(78)
(0)
(0)
(0)
O
HO
(8)
O
O
(5)
(9)
O
O
HO
O
O
O
O
6
7
10
99
(0)
(0)
(0)
(0)
HO
(18)
(57)
(20)
(25)
(00)
O
O
O
8
87
(50)
(15)
(15)
Ph
Ph
O
O
O
O
HO
9
69
27
(78)
(13)
(4)
(3)
(0)
O
O
OH
O
10
11
(0)
(100)
(0)
O
O
S
S
S
S
58
(88)
(3)
(9)
(0)
S
OH
O
O
O
Reaction conditions: 0.001g catalyst, 0.002 mol hydrocarbon, 55 °C, 8 h, solvent (3 ml), isobutyraldehyde (0.003 mol). aConversions were
determined by GC and are an average of at least three runs
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Table 3
1-decene oxidation with molecular oxygen in the absence of a solvent
Conv.a (%)
Catalyst
Selectivity (%)
O
O
O
HO
AgFeO2
GO
4
(70)
(70)
(19)
(0)
(0)
(0)
(30)
(30)
(81)
(0)
(0)
(0)
4
AgFeO2-G
8
Reaction conditions: 0.01 g catalyst, 0.002 mol hydrocarbon, , 55 °C, 8 h, solvent (3 ml), isobutyraldehyde (0.003 mol). aConversions
were determined by GC and are an average of at least three runs
18

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Fig. 7. The possible mechanism for the oxidation of hydrocarbons by oxygen in the presence of AgFeO2-G and
isobutyraldehyde.
19

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Fig. 8. Bar plot showing the oxidation of 1-decene in acetonitrile for 10 cycles using AgFeO2-G in the presence of
air. Reaction conditions: 0.01 g catalyst, 0.002 mol hydrocarbon, 55 °C, 8 h, solvent (3 ml), isobutyraldehyde (0.003
mol), Conversions were determined by GC and are an average of at least three runs
20

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Graphical Abstract
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Highlights
 Silver ferrite-graphene is a semiconductor with a relatively narrow bandgap which was applied for the
oxidation of hydrocarbons.
 Graphene oxide was used as a support for improvement of catalytic activity.
 High catalytic activity for the oxidation of various hydrocarbones (1- decene, cyclohexene, cis-cycloctene, etc.)
was under mild conditions (55 ০C, 8h) with high conversion and selectivity using air. We found that selective
oxidation could be achieved without the need for the addition of solvent, which is appropriate for ‘green’
chemistry.
24