Synthesis and characterization of magnetic perovskites La1-xSrxMnO3: Green catalyst for oxidation of olefins in aqueous medium

Article abstract of DOI:10.1016/j.inoche.2020.107892

The main goal of this work is the preparation of magnetic perovskites La_1-xSr_xMnO₃ (x = 0, 0.2 and 0.4) with a modified sol-gel process and the assessment of their catalytic activity in the oxidation of styrene in neat water (aqueous medium). The structural properties of LaMnO₃, La_0.8Sr_0.2MnO₃ and La_0.6Sr_0.4MnO₃ were characterized using the X-ray Diffraction and infrared techniques. Microstructural features of the catalyst were confirmed by the Scanning Electron Microscopy. The sample La_0.6Sr_0.4MnO₃ has proven a good catalytic activity in the oxidation of styrene after different optimization steps. The catalyst has shown a good recyclability after four cycles. The optimized parameters of the reaction procedure were applied successfully in the oxidation of other simple olefins.

Full text of DOI:10.1016/j.inoche.2020.107892

Journal Pre-proofs
Synthesis and characterization of magnetic perovskites La1-xSrxMnO3: Green
catalyst for oxidation of olefins in aqueous medium
Ali Hasnaoui, Lahcen Fkhar, Abdallah Nayad, Abdelfattah Mahmoud,
frederic Boschini, Omar Mounkachi, Mohamed Hamedoun, Abdelilah
Benyoussef, Larbi El firdoussi, Mustapha Ait Ali
PII:
S1387-7003(20)30220-3
DOI:
https://doi.org/10.1016/j.inoche.2020.107892
INOCHE 107892
Reference:
To appear in:
Inorganic Chemistry Communications
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Revised Date:
Accepted Date:
17 February 2020
10 March 2020
18 March 2020
Please cite this article as: A. Hasnaoui, L. Fkhar, A. Nayad, A. Mahmoud, f. Boschini, O. Mounkachi, M.
Hamedoun, A. Benyoussef, L. El firdoussi, M. Ait Ali, Synthesis and characterization of magnetic perovskites
La1-xSrxMnO3: Green catalyst for oxidation of olefins in aqueous medium, Inorganic Chemistry Communications
(2020), doi: https://doi.org/10.1016/j.inoche.2020.107892
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Synthesis and characterization of magnetic perovskites
La1-xSrxMnO3: Green catalyst for oxidation of olefins in
aqueous medium
Ali Hasnaoui(1), Lahcen Fkhar(1 ,2), Abdallah Nayad (1), Abdelfattah Mahmoud(3),
frederic Boschini(3), Omar Mounkachi(4), Mohamed Hamedoun(2), Abdelilah
Benyoussef(2.,4,5) , Larbi El firdoussi(1) and Mustapha Ait Ali(1)*
.
1Coordination Chemistry Laboratory, Cadi Ayyad University, Faculty of sciences Semlalia (UCA-
FSSM), B.P. 2390 - 40000 Marrakech, Morocco.
2Materials and Nanomaterials Center, MAScIR Foundation, B.P. 10100-Rabat, Morocco
3 GREENMAT, CESAM, Institute of Chemistry B6, University of Liege, 4000 Liège, Belgium
4 Laboratory of Condensed Matter and Interdisciplinary Sciences (LaMCScI) , B.P. 1014,
Faculty of science, Mohammed V University, Rabat, Morocco.
5Hassan II Academy of Science and Technology, Rabat, Morocco.
*Corresponding author. E-mail: aitali@uca.ac.ma,
Abstract
The main goal of this work is the preparation of magnetic perovskites La1-xSrxMnO3 (x= 0, 0.2
and 0.4) with a modified sol-gel process and the assessment of their catalytic activity in the
oxidation of styrene in neat water (aqueous medium). The structural properties of LaMnO3,
La0.8Sr0.2MnO3 and La0.6Sr0.4MnO3 were characterized using the X-ray Diffraction and infrared
techniques. Microstructural features of the catalyst were confirmed by the Scanning Electron
Microscopy. The sample La0.6Sr0.4MnO3 has proven a good catalytic activity in the oxidation
of styrene after different optimization steps. The catalyst has shown a good recyclability after
four cycles. The optimized parameters of the reaction procedure were applied successfully in
the oxidation of other simple olefins.
Keywords
Catalysis; Sol-gel; Oxidation; Water solvent; Olefins
1-Introduction
Oxidation of alkenes by C‒C cleavages is an important reaction providing carbonyl compounds.
These class of molecules are useful in perfumery, flavoring and pharmaceutical industry [1].

The most popular industrial oxidation is Wacker-Tsuji process which uses PdCl2, CuCl2 and
O2 in a DMF–H2O solvent system [2]. This process was then modified with others palladium
complexes and different oxidants [3,4]. However, the major disadvantages such as the cost of
catalysts preparation, the difficulty of the oxidation process, copper waste, olefin isomerization,
and the chlorinated by products are limitations of this reaction [5]. The exploration of other
alternative catalysts for the oxidation of alkenes is attracting the scientific community [6,7].
Among the carbonyl compounds, benzaldehyde is extensively used as an intermediate in fine
chemical perfumes, pharmaceutical, agri-food and fragrance industries [8]. However, its
preparation is a costly process, not very selective and polluting. The classic preparation of
benzaldehyde based on the hydrolysis of benzyl chloride is a harmful process for the
environment due to the employment of organic solvents and may produce traces of chlorine [9].
The quest and development of novel heterogeneous catalysts environmentally benign and easily
recyclable are gaining a huge attention in view of their economic and ecological interest [10].
In the last decades, metallic materials are among the recyclable catalysts which attracted more
interest [11–15], and are highly active in a variety of organic synthesis such as hydrogenation,
carbon-carbon coupling and oxidation reactions [16]. Therefore, different metallic materials
were used for the synthesis of benzaldehyde via the oxidation of styrene as starting material
[17] and only few nanosized materials were successfully performed in the oxidation of natural
olefins [18]. Moreover, the realization of reactions under environmentally conditions is an
important criterion in green chemistry. Recently some groups have performed the styrene
oxidation under benign conditions i.e. solvent free conditions [19–21] and water as green
solvent [22]. In this view, our laboratory has recently worked in an eco-friendly oxidation of
olefins in order to synthesis effective products with new environmentally friendly catalysts
[23,24].
Perovskites with general formula ABO3 with (A=La and Sr, B=Mn) are a family of oxide
with different applications in science such us catalysis [25], hyperthermia [26], magnetocaloric
effect [27], electronic [28], optical and electrical properties [29] and biological applications
[30]. Perovskites manganites can be prepared by several techniques like coprecipetation [31],
sol- gel [32], hydrothermal method [33], and thermal decomposition [34]. The perovskites
manganites have a higher thermodynamic stability, so they are a promising material for catalytic
application under low and high temperatures. Their catalytic activity is highly depending on the
chemical elements and the percent of doping elements of rare earth. In addition to their
remarkable activity, non-noble metal oxide catalysts based on (Mn, Sr, Fe) are low cost in
contrary to noble metals such as (Pd, Pt, etc.) [35]. La1-xSrxMnO3 catalysts are easily

synthesizable and have a good chemical stability especially when they are mixed with organic
solvents.
The present work is based on the synthesis of perovskite manganites (LaMnO3: PM1,
La0.8Sr0.2MnO3: PM2 and La0.6Sr0.4MnO3: PM3) by using the sol-gel method with a good
reproducibility. The evaluation of these non-noble materials in the oxidation of styrene and
other simple olefins was performed. In our effort for a safer and sustainable protocol, this
reaction was performed under water as a very abundant solvent, cheap, non-toxic, and non-
flammable.
2. Experimental
2.1. Material
La(NO3)3, 6H2O (99.99 %) Sr(NO3)2 (99.99 %) and Mn(NO3)2, 4H2O (99.99 %), Polyethylene
glycol 6000, tert-Butyl hydroperoxide (tBHP) (70%), Styrene, Isophorone, 4-methylstyrene,
Alphamethylstyrene, Ethanol, Methanol, Acetone, Tetrahydrofurane (THF) and Acetonitrile
(MeCN) were all purchased from Sigma-Aldrich chemical reagent grade and used as received.
2.2. Catalyst preparation
La1-xSrxMnO3 (x=0, 0.2 and 0.4) were prepared with a modified sol-gel process using
La(NO3)3,6H2O, Sr(NO3)2 and Mn(NO3)2,4H2O as starting materials. A stoichiometric amount
of nitrates was dissolved separately in 20 mL of distilled water. The obtained solution was kept
at 80 °C for 30 min under regular magnetic stirring. 20 mL of citric acid (molar ratio of citric
acid to metal ions = 1:1) were added to the mixture in order to chelate metal ions. 0.5 g of PEG
was dissolved in 20 mL at room temperature and added to the mixture to avoid the
agglomeration of the materials. After six hours, the mixture has changed from a clear solution
to a viscous gel. This gel was dried in an oven at 100 °C over night to form a brown powder.
Then, the powder was calcined at 1000 °C for 2 hours. Finally, the obtained La1-xSrxMnO3
powders were subjected to several characterizations i.e. the X-ray Diffraction (XRD),
Thermogravimetric Analysis (TGA), infrared techniques (FT-IR), and Scanning Electron
Microscopy (MEB).
2.3. Instrumentation methods
The synthesized materials were characterized by X-ray powder diffraction (XRD) using D8
Discover Bruker (AXS) with CuKα radiation (λCu =1.5407 Å) model. Fourier Transform FT-
IR of compounds were recorded on a FT-IR Model ABB Bomem FTLA2000 in the range of
400–4000 cm-1 using KBr as a mulling agent. Thermogravimetric analysis (TGA) was gathered
using TA Instrument Q500 equipment. Microstructural characterization was performed using

Scanning Electron Microscope (SEM) (FEI, Quanta FEG 450) from BRUKER. Magnetic
properties were performed using Magnetic Properties Measurement System (MPMS-7XL), with a
Quantum Design XL-SQUID magnetometer. Conversion and selectivity were determined using
Trace GC Shimadzu gas chromatography with flame ionization detector using nitrogen as
carrier gas. The products from oxidation were confirmed by injecting the reaction mixture on
an ISQ LT single quadrupole mass spectrometer in positive EI mode using a mass scan range
of 50 to 400 Da.
2.4. Catalytic activity
The oxidation of styrene using tBHP was performed in 100 mL flask with continuous stirring.
The optimization of different parameters was studied: doping percents of 0≤x ≤0.4 in catalyst
(La1-xSrxMnO3); tBHP/styrene molar ratios from 1 to 3, amount of the catalyst (0.01–0.06 g),
aprotic and protic solvents, and reaction temperature ranging from room temperature (25°C) to
60 °C. The reaction mixture of different samples was taken at regular intervals and were
analyzed using a gas chromatography (GC) equipped with FID using Rtx®-5 capillary column.
3. Results and discussion
3.1. Structural characterization
The XRD patterns of PM1, PM2 and PM3 samples are shown in Figure 1. It was
observed that all samples have a perovskite structure and crystallize in a pure rhombohedral
phase with a space group of R-3c (167). No secondary phases were detected. The cells
parameters (a, c), the cells volume (V) and the crystallite size (G) were calculated from XRD
data using rietveld refinement created by the TOPAS software. The fixed parameters are
collected from the references JCPDS (01-089-2469), (01-089-0648), (01-070-2775) for PM1,
PM2 and PM3, respectively. The refined lattice parameters and calculated crystalline size of all
compounds are regrouped in Table 1. We noticed that the cells volume increase with the
increasing of Sr amounts, whereas the volume decreases when the percent of Sr exceeds 0.2 %.
This effect was already observed in the literature [36]. This is related to the double exchange
(DE) phenomena when a part of Mn3+ migrates to Mn4+ sites by insertion of Sr2+ in the structure
and affects the Mn-O and Mn-O-Mn length [37–40].

Figure 1: X-ray diffraction patterns of PM1, PM2 and PM3 samples.
Table 1 Lattice parameters and crystals size of PM1, PM2 and PM3.
Samples
LaMnO3
a (Å)
c (Å)
V (Å3)
XRD crystals
Size G (nm)
5.5100 ± (0.00016) 13.3243± (0.00067)
350.3432± (0.02988)
351.8248± (0.04534)
347.4072± (0.10549)
61± (2.1)
61± (3.8)
La0.8Sr0.2MnO3 5.5153± (0.00029)
La0.6Sr0.4MnO3 5.4847± (0.00071)
13.3550± (0.00096)
13.3348± (0.00204)
34.1± (2.4)
The FT-IR spectra of the three studied samples are given in Figure 2. For all samples,
we observed the presence of a bond at around 600 cm-1 attributed to the stretching vibration of
Mn-O [41]. This finding indicates that the prepared specimens mainly consist of metal–oxygen
linkages which cover the length’s changes in Mn–O–Mn bond. The symmetric vibration mode
(stretching) is associated to the change of Mn–O–Mn length while the asymmetric vibration
mode (bending) is related to the change of Mn–O–Mn bond angle. Additionally, a variation in
bond location is detected. It is clearly observed that the stretching vibration of Mn-O shifts to
lower frequencies with an increase of the Sr content. This may be due to the restriction of the
internal motion of Mn-O bond when Sr is incorporated in the perovskite crystal structure, which
induces the shift to lower wavenumbers.

PM1
PM2
PM3
Mn-O
610
Mn-O
607
Mn-O
601
2000
1500
1000
500
Wavenumber (cm-1)
Figure 2: FT-IR spectra of PM1, PM2 and PM3.
TGA curves of the uncalcinated samples are shown in Figure 3. The TGA measurements are
performed in the temperature range of 50 to 1000 °C under air. According to TGA results, three
essential weight losses are observed at temperatures 200 °C (loss of 5%), 400 °C (loss of 10 %)
and 800 °C (loss of 5 %), which are attributed respectively to nitrate depart, degradation of
organic compounds (citric acid and polyethylene glycol) and the starting crystallization of
magnetic perovskite. In addition, a small weight loss is observed at 120 °C which is related to
the elimination of water adsorbed on the samples [42]. After 900°C, no sign of more weight
loss is detected. According to this TGA results, we have selected 1000°C as temperature for the
calcination of the samples.

Figure 3: TGA analyses of uncalcinated samples (a) PM1, (b) PM2 and (c) PM3.
3.2. Micro-structural characterizations
The morphological properties of PM1, PM2 and PM3 were analyzed by SEM and the
corresponding micrographs are shown in Figure 4. For all catalysts the SEM images show
clearly that most of materials have spherical shape with an uniform distribution size in the range
of 140 - 160 nm. Moreover, the energy Dispersive X-ray Spectroscopy (EDS) analysis of the
three samples gave the chemical compositions and a homogeneous distribution of elements in
the particles. Only the elements corresponding to the composition of our samples are detected,
and the obtained percents of element are in good agreement with theoretical composition of
catalysts. These results are very similar to other published work concerning the perovskite
manganite prepared using the same method with another polymer (PVA) as organic additive
[41].

Figure 4: SEM micrographs and EDS analyses of (a) PM1, (b) PM2 and (c) PM3.
3.3. Magnetic characterization
In order to confirm the magnetic character of the prepared catalysts, we have performed the
M(H) curves at room temperature under a magnetic field up to 50000 Oe as shown in figure.
5. For the PM1 and PM2 at this temperature, both catalysts present a paramagnetic behavior,
which is characterized by a low increase of magnetization with the increase of the magnetic
field. However, PM3 presents a ferromagnetic behavior which is characterized by a quick
increase of magnetization at low values of the magnetic field and tends to saturation. The value
of magnetization saturation at room temperature is about 50 emu/g. This observation was
discussed for perovskites metals oxide materials [43].

Figure 5. Magnetization as function of magnetic field.
3.4. Catalytic activity study
The prepared perovskite manganites (LaMnO3:PM1, La0.8Sr0.2MnO3: PM2 and La0.6Sr0.4MnO3:
PM3) were evaluated as catalysts in the oxidation of styrene and other simple olefins in water
as solvent. Then, we investigated the catalytic oxidation of styrene by screening different
parameters in order to find the optimum conversion and selectivity towards benzaldehyde
(Scheme 1).
OH
O
O
O
H
LaSrMnO3
TBHP/Water
1
2
4
3
Scheme 1: Styrene oxidation
The oxidation of styrene in the presence of PM1 has shown a lower activity rather than
PM2 and PM3 (Table 2, entries 2-4). Moreover, the selectivity with PM3 gave the higher result.
Thus, in this study, we have chosen the PM3 catalyst in order to show the effect of catalyst
amount in the oxidation of styrene. Different quantities of the PM3 catalyst have been
investigated and the results are shown in Table 2. The results show that the catalyst substrate
ratio of 30 (0.02 g) allowed a good return of benzaldehyde (65 %) (Table 2, entry 2).
Table 2 Effect of the catalyst amount.
Selectivity* (%)

Entry
Catalyst Amount of Catalyst (g) Conversion* (%)
2
3
1
2
3
4
5
6
7
8
Without
PM3
PM2
PM1
PM3
PM3
PM3
PM3
0
20
87
89
58
98
87
85
74
12
65
50
42
41
46
53
55
8
0.02
0.02
0.02
0.06
0.03
0.015
0.01
22
39
16
55
50
32
18
Reaction conditions: tBHP/styrene; temperature 40 °C; solvent water (8 mL); reaction time 12
h. (*) determined by GC.
The selectivity of the oxidation of styrene catalyzed by the PM3 in water was also carried
out in the temperature range from 25 °C to 60 °C (Table 3) with a molar ration of tBHP/styrene
of 3:1. The reaction performed at RT shows a good conversion of 73 % and a selectivity of 55
% for benzaldehyde. Increasing the temperature of the reaction up to 40 °C gives a better
selectivity of (65 %) of benzaldehyde (Table 3, entry 2). However, at 50 and 60 °C, the
formation of benzaldehyde decreases in competition with benzoic acid (Table 3, entry 3 and
4).
The polarity of solvents is an important factor, and it was found recently that the
oxidation of styrene to benzaldehyde is more optimal in aprotic solvents [23]. In our case, the
reaction was conducted in several solvents with different polarities such as water, methanol,
acetonitrile, acetone, tetrahydrofurane (THF), and ethanol (Table 3). The results indicated that
protic solvents give better performance than aprotic solvents in the catalytic activity. The best
result (65 % of the desired product) was obtained in water as a green solvent (Table 3, entry
2).
The effect of oxidant agent (tBHP) in the oxidation reaction was next investigated by
testing different molar ratio tBHP/styrene and the obtained results are listed in Table 3. The
results show that increasing the molar ratio tBHP/styrene from 1 to 3 induces an increase of the
selectivity to the desired product from 33 % to 65 % (Table 3, entries 2, 5-8).
Table 3 Effect of styrene, tBHP molar ratio, temperature (T) and solvent.
Selectivity*(%)
Entry
T (°C)
tBHP/Styrene
Solvent
Conversion (%)
2
3
4
1
2
3
4
5
6
25
40
50
60
40
40
3
3
3
3
2.5
2
Water
Water
Water
water
Water
Water
73
87
100
100
88
55
65
10
3
55
53
18
22
6
2
33
20
None
None
68
75
None
None
77

7
8
9
10
11
12
13
40
40
40
40
40
40
40
1.5
1
3
3
3
Water
Water
71
50
87
5
28
40
11
47
33
52
3
22
29
7
22
17
5
2
6
None
None
24
None
None
4
Methanol
Ethanol
Acetone
MeCN
THF
3
3
7
4
None
Reaction conditions: PM3 catalyst (0.02g); solvent volume 8 mL; Reaction time, 12h. (*) determined by
GC.
The kinetic of the reaction was also studied. Different oxidation durations of styrene
were examined in this investigation. As shown in Table 4, the selectivity towards benzaldehyde
increases when the reaction time is extended. Thus, the appropriate time of the catalytic
oxidation of styrene was found to be 12h.
In order to obtain a better selectivity in benzaldehyde, the effect of dilution factor was
investigated by checking the impact of solvent volume on the catalytic reaction with three
different quantities of water: 6, 8, 16, and 24 mL. As illustrated in Table 4, when the quantity
of solvent was increased, the selectivity of benzaldehyde decreases. We can conclude that 8 mL
is the best dilution factor to get a good selectivity in benzaldehyde.
Table 4 Effect of the reaction time and dilution factor.
Selectivity* (%)
Dilution factor
(mL)
Conversion
(%)
Entry
Time (h)
2
3
4
1
2
3
4
5
6
7
8
9
3
8
8
18
35
79
87
100
92
87
71
28
13
23
45
65
60
48
65
57
23
5
None
None
None
None
20
6
11
21
22
18
16
22
14
5
9
8
12
16
12
12
12
12
8
8
6
15
8
None
None
None
16
24
Reaction conditions: PM3 catalyst (0.02 g); tBHP/styrene 3eq; temperature 40 °C; solvent
Water. (*) determined by GC.
3.5. Recycling of catalyst

The reusability of PM3 was investigated in order to evaluate its catalytic activity. The catalyst
was used for five cycles (Figure 6). Before reusing, PM3 was separated from the reaction
mixture by magnetic decantation, washed by water and dried at 100 °C over the night. As shown
in the Figure 6, PM3 presents a good catalytic activity in the first four reusing cycles. However,
in the fifth recycling, the selectivity of the catalyst decreased by 15 %. In order to determine
the causes of this decreasing, XRD and SEM characterizations of PM3 after five uses were
realized.
XRD pattern of the catalyst after five uses (Figure 7) shows the existence of two phases. One
corresponds to the rhombohedral of La1-xSrxMnO3 perovskite and the second phase was
attributed to the tetragonal Strontium Lanthanum Manganese Oxide Sr1-xLaxMnO4 which can
be formed by the oxidation of La1-xSrxMnO3 with tBHP and water.
SEM image of PM3 before and after five cycles has been studied. Before the catalytic test,
the SEM image shows some relatively agglomerated particles (Figure 8a). However, the SEM
morphology of the catalyst after five cycles of oxidation showed dispersed particles with the
presence of smaller single particles (Figure 8b). The matrice decomposition of catalyst during
reaction leads to a smaller change in wt % of Sr, La and Mn which is confirmed by EDS analysis
in table 5.
ConversionConversion Conversion Conversion
%, Cycle1, %, Cycle2, %, Cycle3, %, Cycle4,
87, 1, 20% 89, 2, 21% 88, 3, 21% 87, 4, 21%
Conversion
%, Cycle5,
71, 5, 17%
Benzaldehy
de, Cycle1,
57, 1, 21%
Benzaldehy
de, Cycle2,
56, 2, 21%
Benzaldehy
Benzaldehy
de, Cycle3,
53, 3, 20%
de, Cycle4,
54, 4, 20%
Benzaldehy
de, Cycle5,
47, 5, 18%
Conversion %
Benzaldehyde
AcetophenoAcetopheno
ne, Cycle3, ne, Cycle4,
24, 3, 21% 24, 4, 21%
Acetopheno
ne, Cycle2,
23, 2, 20%
Acetopheno
ne, Cycle5,
22, 5, 20%
Acetophenone
Acetopheno
ne, Cycle1,
20, 1, 18%
Figure 6: Reusability of the catalyst in oxidation of styrene. Reaction conditions: PM3
catalyst (0.02 g); tBHP/styrene, 3eq, temperature, 40 °C; solvent, water; reaction time, 12 h.
The selectivity was determined by GC.

(2 0 0)
-----
La1-xSrxMnO3
La1-xSrxMnO4
*
(2 3 0)
(2 4 0)
(0 4 0)
(2 2 0)
(0 2 0)
(1 6 1)
(1 4 1)
*
*
*
*
*
20
30
40
50
60
70
80
2 (degree)
Figure 7: X-ray diffraction pattern of PM3 after five uses.
(a)
(b)
Figure 8: SEM image of PM3 (a) before and (b) after five cycles.
Table 5 EDS analysis of PM3 before using and at the 1st and 5th cycles.
Elements
O K
SrL
LaL
MnK
Wt.%
18.27
13.66
42.98
25.09
Atomic %
55.33
7.55
14.99
22.13
As-prepared catalyst
5th cycle
O K
SrL
17.05
11.18
53.21
6.37

LaL
MnK
45.14
26.62
16.22
24.19
3.6. Comparison of catalytic activity of La1-xSrxMnO3 towards the selective oxidation of
styrene
The Table 6 shows a comparison results in the catalytic oxidation of styrene to benzaldehyde
with others catalysts reported in the literature [ 36–38]. Contrary to TiO2/GO and BaFe2O3, the
oxidation catalyzed by CexCoFe2O4 and Zn1-xAgxCoyO have given better results than our work.
However, they were conducted in organic solvents and in a high temperature. The advantages
of our work are the mild reaction conditions and the use of water as a green solvent.
Table 6 Comparison of catalytic activity of La1-xSrxMnO3.
Entry
Catalyst
Amount of
Solvent
Time Temperature Selectivity
Ref.
catalyst (mg)
(h)
8
9
18
24
12
(°C)
70
70
50
80
40
(%)
57
88
39
77
65
1
2
3
4
5
TiO2/GO
CexCoFe2O4
BaFe2O3
Zn1-xAgxCoyO
La1-xSrxMnO3
20
15
100
20
MeCN
1,4-dioxane
Acetone
MeCN
[48]
[49]
[50]
[23]
20
Water
This work
3.7. Application to others olefins
After getting the optimized parameters on the oxidation of styrene, we have investigated the
oxidation of others olefins, such as alphamethyl styrene (5) and 4-methylstyrene (6) in the same
conditions and the results were regrouped in (Table 7). The selectivity of the products was
monitored by (GC) equipped with FID using Rtx-5 capillary column. The reaction applied to
the olefin 5 afforded to acetophenone with an excellent yield (91 %). Finally, with the styrene
derivative bearing a methyl group in para (olefin 6), two products were obtained, the 4-
methylbenzaldehyde and the 4-methylbenzoic acid with selectivities of 58 % and 34 %,
respectively.
Table 7 Oxidation of other olefins with PM3 catalyst

Conversion (%)
Entry
Olefins
Products
O
81
1
81 %
5
H
O
HO
O
2
94
34 %
58 %
6
Conclusion
In summary, this work is focused on the synthesis and characterization of La1-xSrxMnO3 with
(x = 0, 0.2 and 0.4) using sol-gel as an easy and efficient method to obtain materials with high
homogeneity. The XRD proved that our samples crystallize in a pure rhombohedral phase. The
morphological characterizations showed that the particles have spherical shapes with an
uniform distribution size in the range of 140 - 160 nm. La1-xSrxMnO3 powders have been used
as green catalyst for styrene oxidation in water and promising results were found. Among all
the examined catalysts, the PM3 material exhibits the best activity and provided 65 % yield of
benzaldehyde in the presence of tBHP as an oxidant after 12 hours. The optimum reaction
conditions were: water as solvent, temperature reaction of 40 °C, tBHP/styrene molar ratio
equal to 3 and a catalyst amount of 0.02 g.
Acknowledgment:
This work was supported by the MESRSFC (Ministère de l'Enseignement Supérieur, de la
Recherche Scientifique et de la Formation des Cadres) in the Framework of the national

program PPR under contract no. PPR/2015/57. A. Mahmoud is grateful to the Walloon region
for a Beware Fellowship Academia 2015-1, RESIBAT n° 1510399.
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Graphic Abstract

Highlight
-
-
La1-xSrxMnO3 were prepared by a sol-gel method and fully characterized.
The catalytic activity of magnetic La1-xSrxMnO3 was examined in styrene oxidation in
aqueous medium.
-
-
La0.6Sr0.4MnO3 (PL6) showed a good recyclability in the oxidation of styrene in mind
condition.
The application of optimized conditions towards the oxidation of styrene derivatives
was successfully performed.

AUTHOR STATEMENT
Manuscript ID: INOCHE_2020_189
Manuscript title: Synthesis and characterization of magnetic perovskites La1-xSrxMnO3: Green
catalyst for oxidation of olefins in aqueous medium
Ali Hasnaoui(1), Lahcen Fkhar(1 ,2), Abdallah Nayad (1), Abdelfattah Mahmoud(3), frederic
Boschini(3), Omar Mounkachi(4), Mohamed Hamedoun(2), Abdelilah Benyoussef(2.,4,5)
Larbi El firdoussi(1) and Mustapha Ait Ali(1)*
,
.
1Coordination Chemistry Laboratory, Cadi Ayyad University, Faculty of sciences Semlalia (UCA-
FSSM), B.P. 2390 - 40000 Marrakech, Morocco.
2Materials and Nanomaterials Center, MAScIR Foundation, B.P. 10100-Rabat, Morocco
3 GREENMAT, CESAM, Institute of Chemistry B6, University of Liege, 4000 Liège, Belgium
4 Laboratory of Condensed Matter and Interdisciplinary Sciences (LaMCScI) , B.P. 1014,
Faculty of science, Mohammed V University, Rabat, Morocco.
5Hassan II Academy of Science and Technology, Rabat, Morocco.
*Corresponding author. E-mail: aitali@uca.ac.ma,
All persons who meet authorship criteria are listed as authors, and all authors certify that they have
participated sufficiently in the work to take public responsibility for the content, including participation
in the concept, design, analysis, writing, or revision of the manuscript. Furthermore, each author certifies
that this material or similar material has not been and will not be submitted to or published in any other
publication before its appearance in the Inorganic Chemistry Communications

Declaration of interests
The authors declare that they have no known competing financial interests or personal relationships
that could have appeared to influence the work reported in this paper.
☐The authors declare the following financial interests/personal relationships which may be
considered as potential competing interests: