Rare earth Ce- and Nd-doped spinel nickel ferrites as effective heterogeneous catalysts in the (ep)oxidation of alkenes

Article abstract of DOI:10.1007/s13738-020-01983-2

Cerium (Ce)- and neodymium (Nd)-doped spinel nickel ferrites catalysts system were synthesized using a cost-effective sol–gel route. The as-prepared nickel ferrites and its doped Ce and Nd nanomaterials were characterized in terms of Fourier transform infrared spectrophotometry, X-ray diffraction, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, selected area diffraction pattern, zeta potential and magnetism techniques. Their catalytic potential was examined in the (ep)oxidation of 1,2-cyclooctene by using hydrogen peroxide (H₂O₂) or tert-butylhydroperoxide (t-BuOOH). Optimization of various parameters, including solvent, oxidant and catalyst type revealed that chloroform (CHCl₃) or 1,2-dichloroethane as a solvent and t-BuOOH as an oxidant were found to be the best choice for this catalytic system. The catalytic efficiency was found as Nd–NiFe₂O₄ > Ce–NiFe₂O₄ > NiFe₂O₄. Further, the applied nanocatalysts could be easily renovated and exhibited high catalytic reactivity for 5 times of recycling experiments with long-time durability. A reasonable discussion of the mechanism reaction reinforced the action of these spinel catalysts.

Full text of DOI:10.1007/s13738-020-01983-2

Journal of the Iranian Chemical Society
https://doi.org/10.1007/s13738-020-01983-2
ORIGINAL PAPER
Rare earth Ce‑ and Nd‑doped spinel nickel ferrites as efective
heterogeneous catalysts in the (ep)oxidation of alkenes
Mohamed Shaker S. Adam1,2 · Aly M. Hafez1 · Mai M. Khalaf1,2
Received: 3 April 2020 / Accepted: 16 June 2020
© Iranian Chemical Society 2020
Abstract
Cerium (Ce)- and neodymium (Nd)-doped spinel nickel ferrites catalysts system were synthesized using a cost-efective
sol–gel route. The as-prepared nickel ferrites and its doped Ce and Nd nanomaterials were characterized in terms of Fourier
transform infrared spectrophotometry, X-ray difraction, feld emission scanning electron microscopy, energy-dispersive
X-ray spectroscopy, transmission electron microscopy, selected area difraction pattern, zeta potential and magnetism tech-
niques. Their catalytic potential was examined in the (ep)oxidation of 1,2-cyclooctene by using hydrogen peroxide (H2O2)
or tert-butylhydroperoxide (t-BuOOH). Optimization of various parameters, including solvent, oxidant and catalyst type
revealed that chloroform (CHCl3) or 1,2-dichloroethane as a solvent and t-BuOOH as an oxidant were found to be the best
choice for this catalytic system. The catalytic efciency was found as Nd–NiFe2O4 >Ce–NiFe2O4 >NiFe2O4. Further, the
applied nanocatalysts could be easily renovated and exhibited high catalytic reactivity for 5 times of recycling experiments
with long-time durability. A reasonable discussion of the mechanism reaction reinforced the action of these spinel catalysts.
Keywords Nickel ferrite · Cerium- and neodymium-doped · Nanoparticles · Catalysis · (Ep)oxidation
Introduction
reagents [10–13], ferrofuids [14] and drug delivery systems
[15]. Moreover, spiral ferrites are used in medical proposes,
e.g., drug delivery, bio-molecules, bio-sensors and magnetic
separation of cells [16, 17].
A massive achievement in nanotechnology and nanoscience
felds induces the searching for advanced synthetic proce-
dures of various mixed metal oxides, as nanomaterials,
with crucial physicochemical characteristics in alternative
applicable proposes [1]. Among those uncountable mixed
metal oxides [2], the magnetic spinel nanostructured ferri-
tes, MFe2O4 (M=Co2+, Mn2+, Ni2+ and Cu2+), have gained
great regards of high chemical stability and marvelous
magnetic features [3, 4]. This meets the requirements for
wide applications, e.g., solar energy transformation [5, 6],
gas sensors [7], magnetic storage materials [8, 9], catalytic
The soft ferrites with interesting structural features have
an appropriate dielectric loss and low cost. The main advan-
tage of the spinel ferrites is the reduction of the particle size
in the nanoscales with observable magnetic losses and new
electromagnetic characteristics [18]. Spinel ferrites show
appreciable crystallinity of cubic structure, fne texture and
structure control [9]. The structural and chemical features
of spinel ferrites are extremely infuenced by the synthetic
pathway and their chemical compositions, which could pro-
mote their applicability. The spinel ferrites could be classi-
fed into three categories. The frst type is the normal spinel,
the second type is the inverse spinel, and the third type is the
intermediate spinel. Moreover, there are other two additional
categories; the inverse spinel, which are the most attractive
in research, resulted from their progressed saturated magnet-
ization [19]. In particular, nickel ferrite has an inverse spinel
structure, whereas the doped spinel ferrites with additional
cations provide various physical properties depending upon
their composition [20].
Electronic supplementary material The online version of this
article (https://doi.org/10.1007/s13738-020-01983-2) contains
supplementary material, which is available to authorized users.
* Mohamed Shaker S. Adam
madam@kfu.edu.sa; shakeradam61@yahoo.com
1
Department of Chemistry, College of Science, King Faisal
University, P.O. Box 380, Al Hofuf 31982, Al-Ahsa,
Saudi Arabia
2
Chemistry Department, Faculty of Science, Sohag
University, Sohag 82534, Egypt
Vol.:(0123456789)
1 3

Journal of the Iranian Chemical Society
As of great attention, magnetic spinel nanostructured
materials are considered as metal-based catalysts in the view
of their high dispersion, low oxidation potentials, ecological
protection, less toxicity, higher stability and proper catalyst
reprocessing. Accordingly, spinel ferrites and their reported
doped nanospecies were involved as sufcient catalysts for
many industrial applicable oxidative proposes [21]. The
oxidation of glucose a graphite paste electrode was accom-
plished by NiFe2O4 nanoparticles, which was reported by
Galindo et al. [22]. Furthermore, the catalytic properties of
nickel ferrites were examined recently in the oxidation of
glucose, β-nicotiamide adenine dinucleotide and methanol
by the same previous working group [23]. The chemoselec-
tive oxidation of thiols to disulfdes and sulfdes to sulfox-
ides using H2O2 and catalyzed by NiFe2O4-nanoparticles
was studied by Kulkarni et al. [24] with the suggestion of a
mechanistic pathway. The Aerobic oxidation of benzyl alco-
hol by air oxygen and catalyzed by NiFe2O4-nanoparticles
was reported recently [25]. The catalytic oxidation of aque-
ous sulfde to polysulfdes was studied by Cunha et al. [26]
in the presence of various metal ferrites (MFe2O4, M=Fe2+,
Cu2+ and Co2+), as heterogeneous catalysts. Nickel ferrite
nanoparticles were applied as highly durable catalysts for
catalytic transfer hydrogenation of bio-based aldehydes [27].
The retrievable modifed nickel ferrite nanoparticles were
used as efcient catalysts for the reduction of nitroarenes
and for the photo-oxidation of hazardous Dyes, which were
reported by Goyal et al. [28]. For the metal-doped spinel
nickel ferrites, some rare earth elements (La, Sm, Gd and
Dy)-doped spinel nickel ferrites were used as heterogeneous
catalysts for the wet hydrogen peroxide oxidation of Orange
II azo-dye [29]. Moreover, the ethyl acetate oxidation was
investigated catalytically by copper-doped nickel ferrites
catalyst [30].
templates, which are bounded to the metal ion, could be eas-
ily rearranged resulting in the cubic spinel ferrites structure
[40, 41]. Hence, the spinel structure of the metal-fed nickel
ferrites could be employed as heterogeneous catalysts for
selective catalytic oxidation processes due to the entrapment
of the reactant species on its surface [42]. Moreover, the
rare earth doping ferrites could strongly be imperative for
the high-performance catalytic processes, which was attrib-
uted to oxygen vacancies efect and the alteration of metal
valences.
The design of beneft catalysts (homogeneously or het-
erogeneously) in the control olefns (ep)oxidation has a
curial impact in the industrialized protocols of the dreamt
organic syntheses, economically and sustainably through
the diminution of the formation of unwelcomed harmful
wastes attracted many researchers’ interest [42–44]. Transi-
tion metal-chelating complexes were widely reported as the
most valuable catalysts for the alkenes (ep)oxidation to the
corresponding chemoselective epoxides, which were oper-
ated by various oxidizing agents, attractively, molecular oxy-
gen and hydrogen peroxide (H2O2), as the most eco-friendly
oxidants. The most efective metal-based catalysts, which
be utilized for the alkene (ep)oxidation, should gain fea-
tures with high Lewis acidity and high oxidation states, e.g.,
molybdenyl and vanadyl species in the homogeneous phase
[43]. Although the homogeneous metal-chelates exhibit
higher activity per unit mass of metal than the heterogeneous
catalysts, e.g., metal oxides [45], the heterogeneous catalysts
have additional advantages over the homogeneous ones, as
automatically removed and recovered from the process and
the plentiful reusability [42]. In another word, reusability
and extraction of the catalysts were the main difculties
in such homogeneous processes. Hence, recent researches
have shed light on the use of new heterogeneous catalysts
in the (ep)oxidation processes with recycling character and
easy extraction. Various types of heterogeneous catalysts
could be designed to be easily separated and recycled [46].
An early study was investigated using nickel spinel ferrites
with high magnetic features for the selective (ep)oxidation of
1,2-cyclooctene in the existence of tert-butyl hydroperoxide
(t-BuOOH), as an oxidant, in CCl4. The recyclability of such
catalysts was up to 4 times, losing only 13% of its potentials,
which was qualifed in chemical industry applications [46].
The strong demand of the Lewis acid character [47] of the
applicable catalyst in the oxidation protocols reinforced to
use the spinal ferrites doped by rare earth elements could
remarkably enhance their catalytic behavior and reusability
[48].
As a consequence, numerous date approaches like
mechanical milling [31], sol–gel [32], hydrothermal [33],
micro-emulsion [34], reverse micelle [35], co-precipitation
[36], polymer matrix-mediated synthesis and ultrasonic-
assisted hydrothermal processes [37] are widely proposed
to attain distinct nanostructured spinel ferrites.
The sol–gel method is considered as one of the most
promising eco-friendly methods, which utilized to prepare
alternative mixed metal oxides, nanomaterials and nanopo-
rous mixed metal oxides [38–41]. This method has abundant
advantages including forming of mixed sol of the precursors
and good homogeneous desired solid products. Addition-
ally, the sol–gel process is considered a cost-efective and
easy preparation procedure for the formation of nanoparti-
cles. It is noteworthy that the porous texture of the resulting
nanomaterials could be obtained by the hydrolysis of the
reacted species, forming prolonged networks with reduc-
ing of the synthetic temperature. In the sol–gel method, the
employed organic acids or polymers, as structure-directing
However, few previous works, which studied the (ep)oxi-
dation of alkenes catalyzed by such soft ferromagnetic spinel
ferrites, were reported [46, 48]. In this work, we investigate
the morphology and crystallinity of the introduced NiFe2O4,
Ce–NiFe2O4 and Nd–NiFe2O4 nanoparticles via FTIR,
1 3

Journal of the Iranian Chemical Society
FE-SEM, TEM, XRD, EDS, zeta potential and magnetism
(VSM) techniques. The catalytic efciency of NiFe2O4 and
its doped rare elements (Ce and Nd) as novel materials and
heterogeneous catalysts in the alkene (ep)oxidation processes
using aqueous H2O2 or t-BuOOH at diferent experimental
conditions.
Ce- and Nd-materials was examined using a Cary 630 FTIR
spectrophotometer, which recorded within a frequency range
from 400 to 4000 cm−1. The XRD patterns were conducted
with the help of a Burker D8 X-ray difractometer with Ni-
fltered Cu-Kα radiation and a graphite monochromator to
produce X-rays with a wavelength of 1.54060 Å at 35 kV
and 25 mA in a range of glancing—the angle from 10° to 80°
at scan steps of 0.02° with an accuracy≤0.001°. The surface
morphology study was also conducted by transmission elec-
tron microscopy (TEM) (model: Jeol TEM-1230) operating
at an acceleration voltage 120 kV and 20,000 magnifcations
and feld emission scanning electron microscopy (FE-SEM,
Model JEOL JSM 5410, Japan) with an accelerating voltage
of 20 kV. The materials composed morphology was stud-
ied by a JEOL model 5300 EDS with a playback voltage
of 5.0 kV. For further zeta potential calculation, Zetasizer
(model: Zetasizernano ZS 90 Malvern instruments, UK)
was applied. Magnetic features of NiFe2O4, Ce–NiFe2O4
and Nd–NiFe2O4 were evaluated by using vibration sample
magnetometer analysis under an external magnetic feld up
to 20 kOe.
Experimental
Materials
The materials were of analytical grade and used as obtained.
Iron nitrate nonahydrate Fe (NO3)3·9H2O (99.99%), nickel
nitrate hexahydrate Ni(NO3)2·6H2O (97.0%), cerium nitrate
hexahydrate Ce(NO3)3·6H2O (99.999%), neodymium nitrate
hexahydrate Nd(NO3)3·6H2O (99.99%), 1,2-cyclooctene
(C10H18) (95%), meso-tartaric acid monohydrate ≥ 97%,
PEG (H(OCH2CH2)nOH), average molecular weight
(M.wt) = 6500–7000 g/mol and all used solvents were
received from Sigma-Aldrich, Merck and Acros. The mate-
rials were used as obtained without further purifcations.
Preparation of NiFe2O4, Ce–NiFe2O4 and Nd–NiFe2O4
Catalytic procedures
NiFe2O4 was prepared by dissolving the stoichiometric
amounts of iron nitrate (0.01 M) and nickel nitrate hexa-
hydrate (0.01 M) in 30 mL deionized water with magnetic
stirring at room temperature. Then, 2.7 g of tartaric acid
was added to the reaction mixture with continuous stirring
for 30 min at room temperature. A specifed amount of PEG
(polyethylene glycol, 2.0 g) was added, as the structure-
directing template, with further stirring for 15 min at room
temperature. The obtained mixed sol was heated at 70 °C
for 2 h. The viscous gel was centrifuged with extraction and
then washed several times with ethanol and deionized water
to remove undesired contaminants. The resulted sample was
dried overnight at 100 °C in an oven and then ground to a
fne powder. The acquired sample was calcined at 450 °C
for 2 h with a rate of heating 10 °C min−1. The fnal sample
was coded as NiFe2O4.
The catalytic (ep)oxidation of 1,2-cyclooctene or other alk-
enes (1.0 mmol) was initiated by either 30% aqueous H2O2
(3.0 mmol) or 70% aqueous t-BuOOH (tert-butylhydrop-
eroxide, 1.5 mmol), as an internal oxidant, fed with 0.01,
0.02, 0.05 and 0.1 g of the spiral ferrite catalyst (NiFe2O4,
Ce–NiFe2O4 or Nd–NiFe2O4) in 10 mL of acetonitrile (or
other given solvent) at 85 °C in an oil bath with magnetic
stirring for 160 min under heterogeneous aerobic condi-
tions. The catalytic processes were controlled by withdraw-
ing samples (~1 mL) at diferent time intervals during the
catalytic process. The withdrawal samples were collected at
the desired time and treated with solid sodium thiosulfate
(~10 mg) to quench the unreacted excess an aqueous H2O2
or t-BuOOH in the reaction media under the same conditions
for each catalytic sample. The resulting slurry was fltered
on celite, and the fltrate was diluted by the given solvent (1:
3) mixed in a vortex. Then, 1 µL of the fltrated sample was
injected in the GC–MS.
For doped Ce–NiFe2O4 and Nd–NiFe2O4 preparation,
the same method was used as mentioned for NiFe2O4
preparation with a further addition of Ce(NO3)3·6H2O
and Nd(NO3)3·6H2O according to the composition of
CexNi1−xFe2O4 and NdxNi1−xFe2O4 (x = 0.05), and the
obtained were coded as Ce–NiFe2O4 and Nd–NiFe2O4,
respectively.
The catalytic products were examined by Shimadzu gas
chromatography mass spectrometer (GC–MS) of model
QP2010 SE furnished by a capillary column of Rxi-5 Sil MS
(30 m length× 0.25 mm ID× 025 um flm thickness. The
GC experimental conditions are 250 °C injector temperature,
40 °C initial oven temperature (held for 1 min), and then
the oven temperature was increased to 200 °C with a rate of
10 °C min−1. With the splitless mode, the inlet was operated.
The MS transfer line was held at 200 °C. High-purity helium
was the carrier gas with a fow rate of 1 mL min−1. The ana-
lytical data of the compounds’ percentages were determined
Characterization of NiFe2O4, Ce–NiFe2O4 and Nd–
NiFe2O4
Characterization of the chemical morphology and struc-
tural features of the as-prepared pure NiFe2O4 and its doped
1 3

Journal of the Iranian Chemical Society
and analyzed by LabSolution software. Peaks identifcation
was made by comparing the mass spectra of detected com-
pounds with NIST mass spectral library.
particles in the nickel ferrite. The tetrahedral and octahe-
dral modes of NiFe2O4 were assigned by the remarkable
stretching bands at 550 cm−1 and 448 cm−1, respectively.
These illustrious bands corresponded to the mutual substi-
tution among the spinel (Ni2+/Fe3+oxide) tetrahedral and
the octahedral (Fe3+–O) sites [51].
Result and discussion
XRD analysis of the prepared samples is presented in
Fig. 1b, and the patterns were in a good agreement of
the expected tetrahedral and octahedral spinal type of the
face-centered cubic nickel ferrite (Ref code 01-071-3850)
[52], confrming no impurities could be found. The crys-
talline planes were recorded at 30.2° (220), 35.3° (311),
38.5° (222), 43.2° (400), 53.6° (422), 57.2° (511), 63.2°
(440), 75.5° (533) and 76.3° (622). The similarity in the
XRD patterns of NiFe2O4 and its doped Ce and Nd species
without any further difraction observable peaks could be
mainly owed to the successful prevention of growth, which
caused a decrease in the crystallization intensity.
Synthesis of NiFe2O4, Ce–NiFe2O4 and Nd–NiFe2O4
Nickel ferrite and its Ce- and Nd-doped spinel nanomaterials
were prepared by using the sol–gel method forming nano-
powders. The appropriated amounts of polyethylene glycol
(non-ionic surfactant) and tartaric acid (dicarboxylic acid)
were mixed as structure-directing templates into control of
the shape and size of NiFe2O4 and its Ce- and Nd-doped
spinels. Moreover, the applied synthetic route could show
a signifcant infuence on the degree of ferrite-purity, size
distribution and crystallinity with less agglomeration. The
characterization analyses could be conducted for all samples,
which are shown below. The currently applied method for
nickel ferrite and its Ce- and Nd-doped spinel nanomateri-
als preparation was diferent from the previously used ones
[49, 50].
The crystallite size of NiFe2O4 and its doped nano-
materials was estimated by measuring the broadening
of the half-width of the full maxima (HWFM) of (311)
peak, which stipulated nanoscale of the prepared samples.
These data were confrmed with the calculated magnitudes
through Scherrer’s formula [53]:
Characterization
0.9ꢀ
D =
(1)
ꢁ cos ꢂ
Figure 1a shows the FTIR spectra of NiFe2O4, Ce–NiFe2O4
and Nd–NiFe2O4. A distinguished broad vibrational band
was observed at 2330 cm−1, which was assigned for the
adsorbed CO2. The adsorbed CO2 was due to the residual
species of the calcination process of the organic additives.
The organic additives were used already in the prepara-
tion of the spiral ferrites and helped to stabilize the doped
where λ is the wavelength of Cu Kα1 radiation (λ=1.54 Å),
β is the full width at half maximum of the difraction peak,
D is the crystallite size, 0.9 is a value of a shape constant,
and θ is the Bragg difraction angle. The crystallite sizes (D)
were found to be 8.5, 10 and 7 nm for NiFe2O4, Ce–NiFe2O4
and Nd–NiFe2O4, respectively.
Fig. 1 FTIR spectra of NiFe2O4 and doped Ce–NiFe2O4 and Nd–NiFe2O4 nanoparticles (a), XRD patterns (b)
1 3

Journal of the Iranian Chemical Society
Figure S1 presents the zeta potential distribution of the
NiFe2O4 nanoparticles, which was detected between − 25.4
and − 30.2 mV. The negative value of zeta potential could
be assigned for a negative surface charge on the NiFe2O4
nanoparticles. As a consequence, it aforded a compatible
description of the physiological stability and successful syn-
thetic process of the three spinel ferrite nanomaterials.
Figure 2a describes the FE-SEM morphology of the
Nd–NiFe2O4 material. From FE-SEM images, the agglom-
erated particles were investigated within the magnetic dipole
interaction between nanoparticles and interval sizes. The
estimated particle size was nearly to be 14.5–18.4 nm, which
is bigger than the resulted crystallite size by XRD. Such a
case could be accounted for the existence of particles as
polycrystalline. Figure 2b displays the EDS analysis of the
Nd–NiFe2O4 sample to confrm its elemental contents. The
EDS spectrum of Nd–NiFe2O4 showed characteristic peaks
corresponding to O, Fe and Ni, indicating the presence of
Nd atoms in NiFe2O4 in small scale, assigning the successful
synthetic process.
explored elsewhere for the Nd3+ substitution infuence in
the physical features of nanocrystalline nickel ferrites [55].
Therefore, in the current report, a slight decrease in particle
size of NiFe2O4 was obtained due to the incorporated Ce3+
or Nd3+ ions into its crystalline lattice at the inner borders.
Such a doping process could make some lattice strain, which
prevented the particle growth of NiFe2O4. Furthermore, the
energy was exerted in the insertion of Nd3+ into nickel fer-
rite lattice rather than particle size growth of NiFe2O4, as
observed for the impact of Dy3+-substituted nickel ferrite
[55]. On the other hand, SAED crystal difraction patterns
clarifed a bright spot surrounded by rings with diferent
d-spacing, as shown in Fig. 3e. Those results were matched
with the XRD studies and confrmed the crystalline nature
of the prepared nanonickel ferrites.
The vibrating sample magnetometer (VSM) analysis dis-
played the magnetic characteristics of NiFe2O4, Ce–NiFe2O4
and Nd–NiFe2O4, which presented as magnetization curves
in Fig. 4. The nonlinear and reversible behavior without any
hysteresis loop accomplished soft ferromagnetic properties
of the current nanomaterials, especially for Ce–NiFe2O4
and Nd–NiFe2O4. The magnetization magnitudes, which
are derived from Fig. 4, were obtained as 28.02, 17.98 and
16.00 emu g−1 for NiFe2O4, Ce–NiFe2O4 and Nd–NiFe2O4,
respectively. The observed dropping of the magnetization
for NiFe2O4 within its doped Ce and Nd species compared
to that of the free NiFe2O4 could be attributable to the incor-
porated nanoparticles of Ce and Nd in the nickel ferrite lat-
tice. The decline in the magnetization from 28.02 emu g−1
to 17.98 and 16.00 emu g−1 could be enough for any further
magnetic separation in the reusability of those catalysts in
the (ep)oxidation protocols.
From TEM micrographs, the nanoferrites were semi-
spherical in shape, as shown in Fig. 3a, b, c. The calcu-
lated particle sizes were so congruent with those evaluated
data by XRD for the three studied materials. The particle
size distributions were assigned to be 10, 11 and 8 nm for
NiFe2O4, Ce–NiFe2O4, and Nd–NiFe2O4, respectively. Fig-
ure 3d of HRTEM reveals the Millar indices of {311} with
the d-spacing of 0.25 nm among the adjacent planes exhib-
iting the growth tendency with the existence of each parti-
cle as a single crystal of NiFe2O4. The same behavior was
remarked by doping NiFe2O4 with the lanthanum element
(Ce or Nd). Coalescence of small particles (Ce or Nd) that
occurred within NiFe2O4 should logically confgure the large
size of NiFe2O4, as reported previously for the coalescence
of Ce-doped BiFeO3 nanofakes [54]. A typical trend was
From the above characteristic studies, the polymeric and
organic additives (tartaric acid) in the synthetic method
showed their critical role in the doped Ce and Nd in nickel
Fig. 2 FE-SEM micrograph of NiFe2O4 (a), EDS analysis of Nd–NiFe2O4 (b)
1 3

Journal of the Iranian Chemical Society
Fig. 3 TEM micrographs NiFe2O4 (a), Ce–NiFe2O4 (b), Nd–NiFe2O4 (c), HRTEM image (d) with its calculated histogram, and SAED patterns
(e) of NiFe2O4
1 3

Journal of the Iranian Chemical Society
stability of nickel ferrite sol performing as a well-dispersed
phase in PEG or the tartaric acid matrix.
Catalytic potential in (ep)oxidation of alkenes
The catalytic capacity of NiFe2O4, Ce–NiFe2O4 and
Nd–NiFe2O4 was probed in the (ep)oxidation of 1,2-cyclooc-
tene as the standard model substrate of alkenes by an aque-
ous H2O2 and t-BuOOH, as oxygen sources, in acetonitrile.
The optimized time for the catalytic processes was examined
at 85 °C with 0.10 g loaded of the heterogeneous catalyst,
and the results are recorded in Table 1. The percentages
of the most probable products of the catalytic (ep)oxida-
tion of 1,2-cyclooctene, which were detected by GC–MS,
are recorded in Table 1. The identifed products were listed
as epoxy-1,2-cyclooctane (as the main and chemoselective
product), 4-cyclooctene-1-one, cyclooctane, cyclooctane-
1,2-diol, 2-cyclooctene-1-one and 2-hydroxycyclooctaneone
[57]. The catalytic process of 1,2-cyclooctene (ep)oxidation
was not progressed in the absence of the studied catalysts
at 85 °C.
Fig. 4 Magnetic curves of NiFe2O4, Ce–NiFe2O4 and Nd–NiFe2O4
ferrite. The organic additives prevented the nanoparticle
growth of nickel ferrite obviously, resulting in the well-
defned and orderly formation of nickel ferrite nanoparticles
at a low calcination temperature of 450 °C. As well as, the
organic additives have a good action for improvement of the
Figures 5, 6 and 7 present the consumed time for the
(ep)oxidation of 1,2-cyclooctene catalyzed by NiFe2O4,
Table 1 Catalytic (ep)oxidation products conversion percentages of 1,2-cyclooctene oxidation using an aqueous H2O2 or TBHP catalyzed by
NdNiFe2O4, CeNiFe2O4 and NiFe2O4 at 85 °C for in acetonitrile
Catal.a
Time (min.) Conversion
(%)
Product selectivity (%)
1,2-Cyclooc- Epoxy-1,2-cy- 4-Cyclooc-
Cyclooc-
tanone
Cyclooctane- 2-Cyclooc-
2-Hydroxycy-
O
O
O
OH
OH
tene
O
OH
1,2-diol
clooctanoneO
clooctane
tene-1-one
tene-1-one
H2O2 TBHP H2O2 TBHP H2O2 TBHP H2O2 TBHP H2O2 TBHP H2O2 TBHP H2O2 TBHP
Nd–NiFe2O4 30
19.9 52.4
29.1 57.8
37.9 57.5
42.9 83.8
64.6 94.6
25.0 50.6
28.7 54.8
35.0 59.3
38.6 93.6
48.8 94.8
35.6 48.6
51.2 59.6
52.1 93.8
59.4 96.1
79.4 96.1
76.4 50.6
64.5 48.7
69.1 52.6
69.4 49.5
60.6 53.7
52.2 48.3
48.0 48.0
64.5 53.1
66.3 54.2
56.4 49.9
52.5 41.8
51.1 44.6
48.2 48.8
48.4 44.4
41.4 40.2
4.6
4.2
4.6
5.1
5.3
9.1
8.2
7.2
6.1
7.5
9.2
7.5
7.3
8.6
7.4
5.5
4.8
5.1
5.2
6.4
5.0
4.7
7.4
6.1
6.1
5.7
4.4
5.3
7.0
4.0
1.9
5.2
3.0
3.5
3.5
5.4
4.4
5.1
4.4
4.8
4.8
4.8
4.5
4.9
3.6
7.2
6.6
6.8
5.1
6.0
6.1
6.3
6.1
6.4
5.2
6.8
6.0
4.9
5.1
4.8
2.7 6.6
11.1 5.6
10.5 5.8
8.7 5.0
13.4 5.5
2.5 6.1
3.6 5.2
3.1 7.9
3.3 4.0
3.3 6.4
8.5 7.5
10.9 6.0
10.9 4.4
11.8 7.2
11.0 6.0
8.2 25.1
6.8 29.1
6.9 23.8
6.8 30.8
7.1 21.7
10.5 30.7
10.7 31.6
9.1 24.0
7.9 26.8
9.9 23.4
8.1 33.9
5.8 34.6
7.5 27.3
6.3 28.4
7.6 29.2
6.3
8.2
6.0
4.9
5.1
5.9
4.5
6.8
3.8
4.3
1.5
2.5
9.0
4.3
4.5
9.3
7.9
60
90
120
150
30
60
6.5
10.1
20.2
25.1
11.0
11.9
18.1
16.9
19.9
21.7
20.0
Ce–NiFe2O4
NiFe2O4
90
120
150
30
60
90
120
150
29.0 15.8
a(Ep)oxidation of 1,2-cyclooctene (1.0 mmol) by an aqueous H2O2 (3.0 mmol) or TBHP (1.7 mmol), catalyst (0.10 g) in 10 mL solvent for
150 min
1 3

Journal of the Iranian Chemical Society
Ce–NiFe2O4 and Nd–NiFe2O4, respectively. With a short
time of the catalytic protocol catalyzed by Nd–NiFe2O4,
Ce–NiFe2O4 or NiFe2O4, the yield of the chemoselective
product was low. Prolongation of the reaction time from 60,
90, 120 to 150 min, the yield was improved remarkably and
gradually to the optimized amount of the formed chemose-
lective with all catalysts afording excellent conversion with
t-BuOOH (~ 95, 95 and 96%, catalyzed by Nd–NiFe2O4,
Ce–NiFe2O4 and NiFe2O4, respectively). But, with an aque-
ous H2O2, the conversion was good giving 65, 49 and 80%
with Nd–NiFe2O4, Ce–NiFe2O4 and NiFe2O4, respectively
(Table 1). Longer time, i.e., more than 150 min, caused fx-
ing in the conversion with reducing in the amount of the
epoxy product with an enhancement of the other side prod-
uct amounts, due probably to the further (ep)oxidation of
epoxy-1,2-cyclooctane with the excess amount of the oxi-
dant [44].
However, the high loaded amount of the catalysts (0.10 g)
was catalyzed the (ep)oxidation process, the low yield and
selectivity of the welcomed epoxy product were observed
(Table 1). Accordingly, new tests of the (ep)oxidation of
1,2-cyclooctene were studied with low loaded amounts
of the heterogeneous catalysts (0.01, 0.02 and 0.05 g) in
order to improve the yield percentages of the desired
product. Table 2 assigns the various loaded amount of the
Nd–NiFe2O4, Ce–NiFe2O4 or NiFe2O4 to the reaction system
compared to that of the results in Table 1. The low amount
of the catalysts (0.01 g) aforded very low catalytic reactiv-
ity dramatically, whereas the increased amount, i.e., 0.02 g,
enhanced the yield percentage at the optimal reaction condi-
tions. The best-inserted amount of the catalysts (NiFe2O4,
Fig. 6 Catalytic (ep)oxidation of 1,2-cyclooctene using Ce–NiFe2O4.
The conversion percentages of 1,2-cylooctene presented in plot A;
the product selectivity percentage of epoxy-1,2-cyclooctane and
2-cyclooctane-1-one presented in plot B, with aqueous H2O2 or
TBHP at 85 °C as a function of time
Ce–NiFe2O4 and NiFe2O4) was reported with 0.05 g, which
gave excellent yield percentages of epoxy-1,2-cyclooctane,
94, 90 and 87%, respectively, with t-BuOOH. The yield
amount of the wanted product was less than that within
t-BuOOH when an aqueous H2O2 was used as the oxidant.
The yields were good with NiFe2O4, Ce–NiFe2O4 and
NiFe2O4 awarding 83, 88 and 73%, respectively (Table 2).
Fig. 7 Catalytic (ep)oxidation of 1,2-cyclooctene using Nd–NiFe2O4.
The conversion percentages of 1,2-cylooctene presented in plot A;
the product selectivity percentage of epoxy-1,2-cyclooctane and
2-cyclooctane-1-one presented in plot B, with aqueous H2O2 or
TBHP at 85 °C, as a function of time
Fig. 5 Catalytic (ep)oxidation of 1,2-cyclooctene using NiFe2O4.
The conversion percentages of 1,2-cylooctene presented in plot A;
the product selectivity percentage of epoxy-1,2-cyclooctane and
2-cyclooctane-1-one presented in plot B, with aqueous H2O2 or
TBHP at 85 °C as a function of time
1 3

Journal of the Iranian Chemical Society
Table 2 Catalytic (ep)oxidation
products conversion percentages
of 1,2-cyclooctene oxidation
using an aqueous H2O2 or
Catalysta
Amount of
catalyst (g)
Amount of the
Epoxy-1,2-cy-
clooctane
Conversion (%)
Selectivity (%)
Epoxy-1,2-cy-
clooctane
Other productsc
TBHP catalyzed by NdNiFe2O4,
CeNiFe2O4 and NiFe2O4 at
85 °C for with diferent loaded
amounts in acetonitrile
H2O2
TBHP
H2O2
TBHP
H2O2
TBHP
H2O2
TBHP
Nd–NiFe2O4
Ce–NiFe2O4
NiFe2O4
0.01
0.02
0.05
0.10
0.01
0.02
0.05
0.10
0.01
0.02
0.05
0.10
30
47
83
40
29
46
88
28
27
40
73
32
45
72
94
52
40
69
90
48
36
62
87
38
40
73
93
65
41
69
96
49
39
58
89
79
52
86
100
95
50
84
100
95
48
77
98
75
64
89
61
70
66
90
57
69
69
82
41
86
83
94
54
80
82
92
50
75
80
89
40
25
36
11
39
30
34
10
43
31
31
18
59
14
17
6
46
20
18
8
50
25
20
11
60
96
a(Ep)oxidation of 1,2-cyclooctene (1.0 mmol) by an aqueous H2O2 (3.00 mmol) or TBHP (1.7 mmol) in
10 mL acetonitrile for 150 min
t-BuOOH is reported here as an excellent oxidizing agent
for the conversion and selectivity (with 0.05 g of the catalyst)
of 1,2-cyclooctene catalyzed by Nd–NiFe2O4, Ce–NiFe2O4
and NiFe2O4 compared that with the aqueous H2O2. The
rich amount of water with H2O2 molecules could vigorously
compete with H2O2 molecules to bond to the catalyst and
so impeded the electron and oxygen transfer processes in
the catalytic system [57]. Moreover, water molecules could
occupy the active sites on the surface of the probed catalysts,
so water could reduce the catalytic activity of the ferrite
catalysts by aqueous hydrolysis [42, 58].
respectively. The high formed amounts of 2-hydroxycy-
clooctanone with an aqueous H2O2 could be resulted from
the presence of a high amount of water of the aqueous H2O2
in the reaction media causing, probably an aqueous hydroly-
sis of the chemoselective product [58].
Efect of solvent
Various solvents, e.g., ethanol, acetone, chloroform,
1,2-dichloroethane and dimethyl sulfoxide (DMSO), were
applied to investigate the catalytic activity of Nd–NiFe2O4,
Ce–NiFe2O4 and NiFe2O4 in the (ep)oxidation of
1,2-cyclooctene by an aqueous H2O2 or t-BuOOH. The per-
centages of conversion and selectivity are listed in Table 3.
Among the studied solvents, chloroform and 1,2-dichloro-
ethane were found to be better than acetonitrile, ethanol,
acetone and DMSO for those catalytic systems at the opti-
mized conditions (150 min and 85 °C), which gave the maxi-
mum conversion and epoxy selectivity percentages with both
oxidants (H2O2 and t-BuOOH) (Table 3).
On the other hand, t-BuOOH presented lower selectivity
percentages, i.e., lower amounts of the epoxy product, com-
pared to that with aqueous H2O2 (when 0.10 g used of the
catalysts). The internal alcoholysis of the oxidation product
of t-BuOOH, i.e., tert-BuOH, could carry out for the epoxy
product percentages, as reported elsewhere [59]. This could
explain the large loaded amount of the catalysts that cause
the opposite behavior. In reality, the low loaded amounts
of the catalysts could prevent such a phenomenon of the
oxidant, i.e., t-BuOOH.
The high power of coordination ability of acetonitrile,
ethanol and acetone could have strong competition with the
oxidant (H2O2 or t-BuOOH) to coordinate to the metal ion of
the catalyst within occupying the active coordination sites on
the catalyst surface [46, 48]. This could explain why the cat-
alytic reactivity of the current catalysts was reduced in those
polar solvents compared to those solvents with less coordi-
nation ability (chloroform and dichloromethane). Moreover,
the high coordination capability of DMSO could diminish
the catalytic efciency of the studied catalyst materials, due
to the high probability of DMSO to coordinate to the central
metal ion of Nd–NiFe2O4, Ce–NiFe2O4 and NiFe2O4.
The second detected formed product, after the selective
epoxy-1,2-cyclooctene (for 0.10 g of the loaded catalysts,
Table 1), was diferent according to the type of oxidant.
With t-BuOOH, the second percentage of the product was
2-cyclooctene-1-one catalyzed by Nd–NiFe2O4, Ce–NiFe2O4
and NiFe2O4 with percentages 22, 23 and 29%, respectively,
after 150 min. The amounts of 2-cyclooctene-1-one were
very high at 60 after 90 and 120 min (Table 1). With an
aqueous H2O2, the second formed product was 2-hydrox-
ycyclooctanone with percentages 10, 18 and 29% yields
catalyzed by Nd–NiFe2O4, Ce–NiFe2O4 and NiFe2O4,
1 3

Journal of the Iranian Chemical Society
Table 3 Catalytic (ep)oxidation
products conversion percentages
of 1,2-cyclooctene oxidation
using an aqueous H2O2 or
Catalysta
Solvent
Conversion (%)
Selectivity (%)
Epoxy-1,2-cyclooc- Other productsc
tane
TBHP catalyzed by NdNiFe2O4,
CeNiFe2O4 and NiFe2O4 at
85 °C in diferent solvents
H2O2
TBHP
H2O2
TBHP
H2O2
TBHP
Nd–NiFe2O4
Acetonitrile
Ethanol
Acetone
Chloroform
Dichloromethane
DSMO
Acetonitrile
Ethanol
65
63
59
85
84
79
49
48
48
82
78
72
79
65
61
82
79
68
95
91
89
97
95
88
95
90
88
90
84
79
96
90
87
87
81
78
61
58
55
84
81
54
57
51
44
81
76
51
41
40
35
71
67
46
54
50
48
68
65
44
50
45
41
65
60
42
40
39
34
56
51
37
39
42
45
16
19
46
43
49
56
19
24
49
59
60
65
29
33
54
46
50
52
32
35
56
50
55
59
35
40
58
60
61
66
44
49
63
Ce–NiFe2O4
NiFe2O4
Acetone
Chloroform
Dichloromethane
DSMO
Acetonitrile
Ethanol
Acetone
Chloroform
Dichloromethane
DSMO
a(Ep)oxidation of 1,2-cyclooctene (1.0 mmol) by an aqueous H2O2 (3.00 mmol) or TBHP (1.7 mmol), cata-
lyst (0.10 g) in 10 mL solvent for 150 min
Additionally, low polarity and high covalence properties
of chloroform and 1,2-dichloroethane compared to acetoni-
trile, ethanol and acetone interpreted the low polarity of the
reaction system, i.e., the reaction could probably take place
with electron parking mechanism [60, 61]. The most com-
mon mechanistic pathway of such (ep)oxidation reaction
progresses within electron and oxygen transfer processes
[61], and the low polar solvents are the best reaction media.
This phenomenon has been observed previously [46, 62].
characterization results. This could probably promote their
chemoselectivity of 1,2-cyclooctene (ep)oxidation com-
pared to that of the free NiFe2O4. The doping of nickel
ferrite with Nd or Ce as a lanthanide element enriches
slightly the catalytic potential of NiFe2O4 toward the (ep)
oxidation of 1,2-cyclooctene. The various oxidation num-
ber interchange and the high Lewis acid feature [65–67]
of the central metal ion in the catalyst could strongly force
the catalytic potential of the considered catalyst in such
(ep)oxidation processes [58, 68]. This could not be taken
place easily with the doped Nd and Ce, as lanthanides
or f-block elements [69], with the electron and/or oxy-
gen transfer processes in the catalytic cycles [61, 70].
Additionally, the presence of Nd or Ce in nickel ferrite
increased the heterogeneous nature of nickel ferrite and
so might reduce its progressing of their reactivity (Figs. 5,
6, 7) [71].
Efect of type of catalysts
The homogeneous or heterogeneous inorganic cata-
lytic processes depend mainly on the type and charge of
the central metal ion in its material [63, 64]. However,
NiFe2O4 showed the highest conversion of 1,2-cyclooc-
tene (ep)oxidation compared to those Nd–NiFe2O4 and
Ce–NiFe2O4 (Figs. 5, 6, 7), and it awarded the lowest cat-
alytic selectivity with both t-BuOOH and H2O2 (40 and
41%, respectively) (Table 1). Hence, the presence of the
Nd- or Ce-doped species in nickel ferrite showed a some-
what infuence on the catalytic potential of NiFe2O4, espe-
cially in the selectivity. Both doped Ce– and Nd–NiFe2O4
reduced the particle size of NiFe2O4 (10, 11 and 8 nm for
NiFe2O4, Ce–NiFe2O4, and Nd–NiFe2O4) with an improve-
ment of their surface areas, as observed by the above
The coordination chemical feature of the central metal
in the catalyst toward the oxidant and the substrate could
play notably a major action in its catalytic afectivity within
the electron and/or oxygen transfer processes to cause (ep)
oxidation of the substrate [29]. Such a system could not be
touched with lanthanides, i.e., Ce and Nd, as rare earth ele-
ments [24, 69]. Particularly, the low coordination capability
of the doped Ce and Nd (as lanthanide elements), compared
to the transition element, i.e., Ni and Fe in NiFe2O4 toward
1 3

Journal of the Iranian Chemical Society
the oxidizing agent and the substrate could be a considerable
reason for the less observable enhancement in the catalytic
potential of NiFe2O4 [20–26, 72].
an (ep)oxidation reactivity more than that of the acyclic or
aliphatic alkenes (Table 4) [75, 76]. Such behavior could be
resulted from the inner double bonding in the cyclic alkenes
compared to the terminal double bonding in the aliphatic
alkenes. Type of double bonding of alkene might infuence
the coordination to the central metal ion of the catalyst and
so could afect the reactivity of the alkene toward the (ep)
oxidation [46].
Although Ce and Nd have low coordination chemical
behavior, the catalytic selectivity was enhanced of doped
Ce– and Nd–NiFe2O4 nanospecies by increasing the yield
of the epoxy product. The reason is that the surface area
of nickel ferrite was enhanced by the doped Ce and Nd.
Furthermore, Nd could progress the catalytic afectivity of
NiFe2O4, as Nd–NiFe2O4, more than that in the presence
of Ce in Ce–NiFe2O4 within the development of the active
sites on the surface of nickel ferrite [73]. The particle size of
the nanoparticles of nickel ferrite was decreased remarkably
with the doping of Nd more than that with Ce, as reported
form the XRD and TEM obtains. So, this could promote the
catalytic active sites on the surface of nickel ferrite toward
homogeneity [74].
Recyclability
The recyclability of the novel catalysts was registered with
repeating of the (ep)oxidation of 1,2-cyclooctene with
t-BuOOH at the optimum reaction conditions, magnetically
(Table 5). The easy extraction of the catalysts was accom-
plished by a magnet for further catalytic tests. In particular,
Nd–NiFe2O4, Ce–NiFe2O4 and NiFe2O4 showed high cata-
lytic reactivity for 5 times of recycling experiments with
long-time durability.
(Ep)oxidation of other aliphatic and cyclic alkenes
After 6 times of the recycling, the new catalysts pre-
sented a remarkable loss of their potential was almost 20%,
as shown in Table 5. The reason for the deactivation of
the catalysts could be considered as the diminution of the
active sites and the active centers. Figure 8 presents the EDS
analyses of the reused of Nd–NiFe2O4 after 6 times, repre-
sentatively, as observed elsewhere [77]. Clearly, there was
no considered change in the morphology of Nd–NiFe2O4 to
lose its catalytic potential. So, there is no obvious reason for
The catalysts screening for the (ep)oxidation of various alk-
enes within cyclic and acyclic chains at the optimization was
studied, and the obtained results are recorded in Table 4. All
catalysts were efciently capable of catalyzing the (ep)oxi-
dation of those alkenes to their corresponding epoxy prod-
ucts by an aqueous H2O2 or t-BuOOH. Cyclic alkenes, e.g.,
1,2-cyclooctene, 1,2-cyclohexene and styrene with higher
electron-donating power by the C=C double bond estimated
Table 4 (Ep)oxidation of some cyclic and acyclic alkenes catalyzed by Nd–NiFe2O4, Ce–NiFe2O4 and NiFe2O4 using an aqueous H2O2 or TBHP
Entry
Alkenea
Product
Conversion, %
(Selectivity, %)
NdNiFe2O4
CeNiFe2O4
H2O2
NiFe2O4
H2O2
H2O2
TBHP
TBHP
TBHP
1
2
87 (85)
96 (72)
85 (81)
92 (70)
82 (83)
88 (60)
O
80 (75)
89 (69)
77 (70)
88 (68)
77 (69)
79 (60)
O
3
4
5
6
84 (78)
71 (58)
64 (49)
88 (45)
90 (74)
81 (56)
71 (49)
85 (43)
81 (76)
67 (53)
52 (42)
79 (41)
88 (71)
74 (52)
65 (41)
80 (39)
78 (67)
62 (49)
48 (38)
72 (29)
78 (63)
61 (45)
54 (40)
77 (37)
O
O
O
O
HO
HO
aReaction carried out in chloroform (10 mL), alkene (1.0 mmol), H2O2 (3.0 mmol) or TBHP (1.7 mmol) and catalyst (0.10 g) at 85 °C after
150 min
1 3

Journal of the Iranian Chemical Society
Table 5 Number of recycling of
the catalysts (Nd–NiFe2O4, Ce–
NiFe2O4 and NiFe2O4) in the
(ep)oxidation of 1,2-cyclooctene
by an aqueous H2O2 and TBHP
No. of recyclinga Conversion, % (Selectivity, %)
NdNiFe2O4
CeNiFe2O4
H2O2
NiFe2O4
H2O2
TBHP
TBHP
H2O2
TBHP
1
2
3
4
5
6
85 (84)
85 (84)
83 (84)
83 (82)
82 (81)
75 (70)
97 (68)
97 (68)
95 (68)
95 (68)
91 (68)
84 (48)
82 (81)
82 (80)
82 (80)
82 (79)
80 (80)
71 (59)
90 (65)
90 (65)
89 (65)
89 (65)
87 (65)
62 (47)
82 (71)
82 (71)
82 (69)
82 (69)
80 (67)
58 (49)
87 (56)
87 (55)
87 (55)
85 (55)
84 (54)
58 (39)
aReaction carried out in chloroform (10 mL), 1,2-cyclooctene (1.0 mmol), H2O2 (3.0 mmol) or TBHP
(1.7 mmol) and catalyst (0.10 g) at 85 °C after 150 min
Fig. 8 EDS analysis of
Nd–NiFe2O4 after the recy-
cling of the (ep)oxidation of
1,2-cyclooctene with aqueous
H2O2
its deactivation, which could be found elsewhere or could
explain that behavior.
was accomplished by proton transmission from H2O2 or
t-BuOOH molecule to the oxygen atom of the spinel ferrite
catalyst. A generation of OH− anion with Lewis acidic center
of the metal in spinel ferrites could subsequently react with
alkene C=C double bond to give the epoxy product in good
yields (within the oxygen transfer process) [24]. Then, the
leaving catalyst could start a new catalytic cycle.
Overall possible mechanism
A representative mechanism of 1,2-cyclooctene (ep)oxida-
tion could be displayed within current catalysts of NiFe2O4
and its doped Ce and Nd nanoparticles, as mixed spinel
structures. A fast electron exchange between M2+ and M3+
ions occurred (electron transfer process) of Nd–NiFe2O4,
Ce–NiFe2O4 and NiFe2O4 [78]. NiFe2O4 and its doped were
oxidized with H2O2 or t-BuOOH and through the changes
of Fe2+ and Ni3+ to Fe3+ and Ni2+ ions (within the elec-
tron transfer process), respectively, generate and OH− or
tBuO− anions [79]. The liberating of OH− or tBuO− anions
The selectivity of the spinel ferrite catalysts toward the
(ep)oxidation processes is based upon the distribution of
the cation ions of the dopant Ce and Nd ions in octahedral
Oh sites [80]. This could be discussed as the catalyst active
centers in the octahedral active sites, which mainly local-
ized at the spinel ferrite surface. Signifcantly, Nd–NiFe2O4
showed slightly more selectivity toward the (ep)oxidation of
1,2-cyclooctene, as interpreted above.
1 3

Journal of the Iranian Chemical Society
5. W. Zhang, Y. Xu, H. Wang, C. Xu, S. Yang, Sol. Energy Mater.
Sol. Cells 95, 2880 (2011)
Conclusions
6. N. Senthilkumar, M. Pannipara, A.G. Al-Sehemi, G.G. Kumar,
New J. Chem. 43, 7743 (2019)
Free nickel ferrite and its doped Ce–NiFe2O4 and
Nd–NiFe2O4 nanoparticles were successfully synthesized
through the sol–gel route. The physicochemical charac-
terizations including FTIR, XRD, FE-SEM, TEM, SAED
and EDS were investigated to distinguish the morphology,
chemical bonds, crystallinity and chemical analyses of the
fabricated NiFe2O4, Ce–NiFe2O4 and Nd–NiFe2O4. The
XRD patterns emphasized the existence of the tetrahedral
and octahedral spinel-type of nickel ferrite for all samples
without any further impurities. The obtained crystallite sizes
were estimated as 8.5, 10 and 7 nm for NiFe2O4, Ce–NiFe2O4
and Nd–NiFe2O4, respectively. SAED patterns emphasized
the crystalline nature of the prepared nanomaterials. FE-
SEM images illustrated the uniform and homogenous dis-
tribution of Nd–NiFe2O4 nanoparticles by an average size
of 14.5–18.4 nm. All catalysts show excellent conversion
with t-BuOOH at 85 °C (~ 95, 95 and 96%, catalyzed by
Nd–NiFe2O4, Ce–NiFe2O4 and NiFe2O4, respectively) after
150 min in the (ep)oxidation of 1,2-cyclooctene. With all
catalysts, t-BuOOH showed higher oxidation infuence on
the conversion of 1,2-cyclooctene than that with an aqueous
H2O2. With t-BuOOH, the catalytic system aforded lower
chemoselectivity due to the alcoholysis efect with the high
loaded amounts of the catalysts (0.10 g). But, with lower
loaded amount of the catalysts (0.05 g), the catalytic activity
of Nd–NiFe2O4, Ce–NiFe2O4 and NiFe2O4 was optimized
to give an excellent yield of the epoxy product. Cyclic alk-
enes awarded higher conversion and selectivity more than
the acyclic alkenes. Doping of Nd and Ce enhanced the ion
ratio at the octahedral Oh sites and hence enhanced their
activity and selectivity toward the alkenes (ep)oxidation.
The reusability of the magnetic catalysts was probed and
exhibited a maximum 5 times of catalyst cycling under the
easy separation by exposing to an external magnet. This sys-
tematic report introduces novel nanocatalysts Nd–NiFe2O4
and Ce–NiFe2O4 toward the alkenes (ep)oxidation.
7. K.M. Reddy, L. Satyanarayana, S.V. Manorama, D.K. Misra,
Mater. Res. Bull. 39, 1491 (2003)
8. A.P. Alivisatos, Science 271, 933 (1996)
9. M. Junaid, M.A. Khana, M.N. Akhtar, A. Hussain, M.F. Warsi,
Ceram. Int. 45, 13431 (2019)
10. A.A. Ensaf, A.R. Allafchian, Colloids Surface B 102, 687 (2013)
11. S. Payra, A. Saha, S. Banerjee, RSC Adv. 6, 52495 (2016)
12. A. Sheoran, M. Dhiman, S. Bhukal, R. Malik, J. Agarwal, B. Chu-
dasama, S. Singhal, Mater. Chem. Phys. 222, 207 (2019)
13. X. Guo, D. Wang, J. Environ. Chem. Eng. 7, 102814 (2019)
14. B. Behdadfar, A. Kermanpur, H. Sadeghi-Aliabadi, Molares M.
del Puerto, M. Mozafari, J. Solid State Chem. 187, 20 (2012)
15. A.K. Gupta, M. Gupta, Biomaterials 26, 3995 (2005)
16. S. Mosivand, I. Kazeminezhad, Ceram. Int. 41, 8637 (2015)
17. A. Javidan, S. Rafzadeh, S.M. Hosseinpour-Mashkani, Mater. Sci.
Semicond. Process. 27, 468 (2014)
18. M. Hashim, K.S. Alimuddin, B.H. Koo, S.E. Shirsath, E.M.
Mohammed, J. Shah, R.K. Kotnala, H.K. Choi, H. Chung, R.
Kumar, J. Alloys Compd. 518, 11 (2012)
19. K.V. Babu, G.V.S. Kumar, K. Jalaiah, P.T. Shibeshi, J. Phys.
Chem. Solids 118, 172 (2018)
20. E. Uyanga, D. Sangaa, H. Hirazawa, N. Tsogbadrakh, N. Jargalan,
I.A. Bobrikov, A.M. Balagurov, J. Mol. Struct. 1160, 447 (2018)
21. B.I. Kharisov, H.V.R. Dias, O.V. Kharissova, Arab. J. Chem. 12,
1234 (2019)
22. R. Galindo, E. Mazario, S. Gutiérrez, M.P. Morales, P. Herrasti,
J. Alloys Compd. 536S, S241 (2012)
23. R. Galindo, S. Gutiérrez, N. Menéndez, P. Herrasti, J. Alloys
Compd. 586, S511 (2014)
24. A.M. Kulkarni, U.V. Desai, K.S. Pandit, M.A. Kulkarni, P.P. Wad-
gaonkar, RSC Adv. 4, 36702 (2014)
25. R. Saranya, R.A. Raj, M.S. AlSalhi, S. Devanesan, J. Supercond.
Nov. Magn. 31, 1219 (2018)
26. I.T. Cunha, I.F. Teixeira, A.S. Albuquerque, J.D. Ardisson,
W.A.A. Macedo, H.S. Oliveira, J.C. Tristão, K. Sapage, R.M.
Lago, Catal. Today 259, 222 (2015)
27. J. He, S. Yang, A. Riisager, Catal. Sci. Technol. 8, 790 (2018)
28. A. Goyal, S. Kapoor, P. Samuel, S. Singhal, Anal. Chem. Lett. 6,
98 (2016)
29. P. Samoila, C. Cojocaru, L. Sacarescu, P.P. Dorneanu, A.-A.
Domocos, A. Rotaru, Appl. Catal. B 202, 21 (2017)
30. N. Velinov, T. Petrova, R. Ivanova, T. Tsoncheva, D. Kovacheva,
I. Mitov, Hyperfne Interact. 241, 31 (2020)
31. Y. Choi, B.S. Seong, S.S. Kim, Phys. B 404, 689 (2009)
32. M. Chithra, C.N. Anumol, B. Sahu, S.C. Sahoo, J. Magn. Magn.
Mater. 401, 1 (2016)
Acknowledgements The authors acknowledge the Deanship of Scien-
tifc Research at King Faisal University for the fnancial support under
the annual research project (Grant No. 180074).
33. J. Zhou, J. Ma, C. Sun, L. Xie, Z. Zhao, H. Tian, Y. Wang, J. Tao,
X. Zhu, J. Am. Ceram. Soc. 88, 3535 (2005)
34. Y. Wang, L. Li, J. Jiang, H. Liu, H. Qiu, F. Xu, React. Funct.
Polym. 68, 1587 (2008)
35. S. Thakur, S.C. Katyal, M. Singh, J. Magn. Magn. Mater. 321, 1
(2009)
References
36. J. Wang, T. Deng, Y. Lin, C. Yang, W. Zhan, J. Alloys Compd.
450, 532 (2008)
37. P.E. Meskin, V.K. Ivanov, A.E. Barantchikov, B.R. Churagulov,
Y.D. Tretyakov, Ultrason. Sonochem. 13, 47 (2006)
38. A. Katelnikovas, J. Barkauskas, F. Ivanauskas, A. Beganskiene,
A. Kareiva, J. Sol-Gel Sci. Technol. 41, 193 (2007)
39. J.D. Mackenzie, E.P. Bescher, Acc. Chem. Res. 40, 810 (2007)
40. X. Zhao, Y. Wang, W. Feng, H. Lei, J. Li, RSC Adv. 7, 52738
(2017)
1. T. Tolaymat, A. El Badawy, A. Genaidy, W. Abdelraheem, R.
Sequeira, J. Clean. Prod. 143, 401 (2017)
2. K. Ueda, M. Tsuji, J. Ohyama, A. Satsuma, ACS Catal. 9, 2866
(2019)
3. G. Kaur, P. Devi, S. Thakur, A. Kumar, R. Chandel, B. Banerjee,
ChemistrySelect 4, 2181 (2019)
4. W. Wang, D. Zhang, RSC Adv. 8, 32221 (2018)
1 3

Journal of the Iranian Chemical Society
61. J. Du, C. Miao, C. Xia, Y.-M. Lee, W. Nam, W. Sun, ACS Catal.
8, 4528 (2018)
41. F. Yan, K. Han, G. Zhao, X. Shi, N. Song, Z. Jiao, Mater. Charact.
124, 90 (2017)
62. S.M. Hosseini, H. Hosseini-Monfared, V. Abbasi, M.R. Khoshroo,
Inorg. Chem. Commun. 67, 72 (2016)
42. M.F.I. Al-Hussein, M.S.S. Adam, Appl. Organometal. Chem. 34,
e5598 (2020)
63. X. Liu, C. Manzur, N. Novoa, S. Celedón, D. Carrillo, J.-R.
Hamon, Coord. Chem. Rev. 357, 144 (2018)
43. M.S.S. Adam, Appl. Organometal. Chem. 32, e4234 (2018)
44. M.S.S. Adam, A.D.M. Mohamad, Polyhedron 151, 118 (2018)
45. J. Li, H. Gao, L. Tan, Y. Luan, M. Yang, Eur. J. Inorg. Chem. 30,
4906 (2016)
64. M. Maurya, C. Haldar, A. Kumar, M.L. Kuznetsov, F. Avecilla,
J.C. Pessoa, Dalton Trans. 42, 11941 (2013)
65. G. Licini, V. Conte, A. Coletti, M. Mba, C. Zonta, Coord. Chem.
Rev. 255, 2345 (2011)
46. F.M. Golkhatmi, B. Bahramian, M. Mamarabadi, Mater. Sci. Eng.
C 78, 1 (2017)
66. L. Gomez, I. Garcia-Bosch, A. Company, J. Benet-Buchholz, A.
Polo, X. Sala, X. Ribas, M. Costas, Angew. Chem. Int. Ed. 48,
5720 (2009)
47. D.T. Bregante, N.E. Thornburg, J.M. Notestein, D.W. Flaherty,
ACS Catal. 8, 2995 (2018)
48. N.M.R. Martins, A.J.L. Pombeiro, L.M.D.R.S. Martins, Catal.
Commun. 116, 10 (2018)
67. M.R.M. Bisht, A. Kumar, M.L. Kuznetsov, F. Avecilla, J.C. Pes-
soa, Dalton Trans. 40, 6968 (2011)
49. G. Dixit, J.P. Singh, C.L. Chen, C.L. Dong, R.C. Srivastava,
H.M. Agrawal, W.F. Pong, K. Asokan, J. Alloys Compd. 581,
178 (2013)
68. M.S.S. Adam, K.A. Soliman, H.M. Abd El-Lateef, Inorg. Chim.
Acta 499, 119212 (2020)
69. W. Yan, G. Zhang, H. Yan, Y. Liu, X. Chen, X. Feng, X. Jin, C.
Yang, ACS Sustain. Chem. Eng. 6, 4423 (2018)
70. D.-H. Zhang, G.-D. Li, J.-X. Li, J.-S. Chen, Chem. Commun. 29,
3414 (2008)
50. K.N. Harish, H.S.B. Naik, P.N.P. Kumar, R. Viswanath, ACS Sus-
tain. Chem. Eng. 1, 1143 (2013)
51. S. Sagadevana, Z.Z. Chowdhuryb, R.F. Rafque, Mater. Res. 21,
e20160533 (2018)
71. Y. Zhang, Z. Li, W. Sun, C. Xia, Catal. Commun. 10, 237 (2008)
72. G. Mata, R. Trujillano, M.A. Vicente, S.A. Korili, A. Gil, C.
Belver, K.J. Ciuf, E.J. Nassar, G.P. Ricci, A. Cestari, S. Naka-
gaki, Micropor. Mesopor. Mat. 124, 218 (2009)
73. H. Mirzazadeh, M. Lashanizadegan, Solid State Sci. 79, 48 (2018)
74. F. Shi, M.K. Tse, M.-M. Pohl, A. Bruckner, S. Zhang, M. Beller,
Angew. Chem. Int. Ed. 46, 8866 (2007)
52. R. Nivetha, C. Santhosh, P. Kollu, S.K. Jeong, A. Bhatnagar, A.N.
Grace, J. Magn. Magn. Mater. 448, 165 (2018)
53. M.M. Khalaf, H.M. Abd El-Lateef, G. Farghal, E.M.M. Ibrahim,
Measurement 132, 99 (2019)
54. E.M.M. Ibrahim, G. Farghal, M.M. Khalaf, H.M. Abd El-Lateef,
Appl. Phys. A 123, 533 (2017)
55. T.J. Shinde, A.B. Gadkari, P.N. Vasambekar, J. Alloys Compd.
513, 80 (2012)
75. S. Rayati, F. Ashouri, C. R. Chim. 15, 679 (2012)
76. S. Huber, M. Cokoja, F.E. Kühn, J. Organomet. Chem. 751, 25
(2014)
56. L. Chauhana, N. Singh, A. Dharb, H. Kumar, S. Kumar, K. Sreeni-
vas, Ceram. Int. 43, 8378 (2017)
77. M. Nasrollahzadeh, M. Sajjadi, H.A. Khonakdar, J. Mol. Struct.
1161, 453 (2018)
57. M.S.S. Adam, A.M. Hafez, I. El-Ghamry, React. Kinet. Mech.
Cat. 124, 779 (2018)
78. D.G. Reithwisch, J.A. Dumesic, Appl. Catal. 21, 97 (1986)
79. A.M. Dumitrescu, P.M. Samoila, V. Nica, F. Doroei, A.R. Iordan,
M.N. Palamaru, Powder Technol. 243, 9 (2013)
80. K. Omata, T. Takado, S. Kasahara, M. Yamada, Appl. Catal. A
146, 255 (1996)
58. M.S.S. Adam, M.S.M. Ahmed, O.M. El-Hady, S. Shaaban, Appl.
Organometal. Chem. 34, e5573 (2020)
59. J.J. Plata, L.C. Pacheco, E.R. Remesal, M.O. Masa, L. Vega, A.M.
Márquez, J.A. Odriozola, J.F. Sanz, Mol. Catal. 459, 55 (2018)
60. B.J. Hofmann, S. Huber, R.M. Reich, M. Drees, F.E. Kühn, J.
Organomet. Chem. 885, 32 (2019)
1 3