CeO2/Pd Nanoparticles Incorporated Fly Ash Zeolite: An Efficient and Recyclable Catalyst for Csp2-Csp2 Bond Formation Reactions

Article abstract of DOI:10.1002/aoc.5752

The catalytic activity of CeO₂ and palladium nanoparticles supported fly ash zeolite (CeO₂/Pd@FAZ) for C_sp²-C_sp² bond formation was studied. CeO₂/Pd@FAZ was characterized by FTIR, XRD, EDAX and TEM studies. In the Suzuki-Miyauracross-coupling reaction, biphenyl derivatives with excellent yields were obtained, and the reaction conditions were optimized. The catalytic activity was explored using a wide variety of diversely substituted aryl bromides and chlorides with aryl boronic acid under optimized reaction conditions. The recyclability of the catalyst was established for three cycles, with the conversion rate from 99 to 40percent, which gained the advantage of heterogeneous catalysis.

Full text of DOI:10.1002/aoc.5752

Received: 25 November 2019
DOI: 10.1002/aoc.5752
Revised: 5 April 2020
Accepted: 7 April 2020
F U L L P A P E R
CeO2/Pd Nanoparticles Incorporated Fly Ash Zeolite: An
2
2
Efficient and Recyclable Catalyst for Csp -Csp Bond
Formation Reactions
Seth Sheeba Thavamani1 | Murugesan Sudharsan2 | Anitha Santhana Mariya2
|
Devarajan Suresh2 | Arlin Jose Amali3 | Sanniyasi Rajeswari1
Thomas Peter Amaladhas1
|
1Post Graduate and Research Department
The catalytic activity of CeO2 and palladium nanoparticles supported fly ash
zeolite (CeO2/Pd@FAZ) for Csp2-Csp bond formation was studied. CeO2/
of Chemistry, V.O. Chidambaram College,
Tuticorin, Tamilnadu, 628 008, India
2Department of Chemistry, School of
Chemical and Biotechnology, SASTRA
Deemed University, Thanjavur, Tamil
Nadu, 613 401, India
3Centre for Green Chemistry Processes,
School of Chemistry, Madurai Kamaraj
University, Madurai, Tamil Nadu, 625
021, India
2
Pd@FAZ was characterized by FTIR, XRD, EDAX and TEM studies. In the
Suzuki-Miyauracross-coupling reaction, biphenyl derivatives with excellent
yields were obtained, and the reaction conditions were optimized. The catalytic
activity was explored using a wide variety of diversely substituted aryl bro-
mides and chlorides with aryl boronic acid under optimized reaction condi-
tions. The recyclability of the catalyst was established for three cycles, with the
conversion rate from 99 to 40%, which gained the advantage of heterogeneous
catalysis.
Correspondence
T. Peter Amaladhas, Post Graduate and
Research Department of Chemistry,
V.O. Chidambaram College, Tuticorin,
Tamilnadu, 628 008, India.
K E Y W O R D S
CeO2 nanoparticles, Pd nanoparticles, Suzuki-Miyauracross-coupling, zeolites
Email: peteramaladhas@gmail.com
D. Suresh, Department of Chemistry,
School of Chemical and Biotechnology,
SASTRA Deemed University, Thanjavur,
Tamil Nadu, 613 401, India.
Email: suresh_d@scbt.sastra.edu
1 | INTRODUCTION
significant in catalysis. Homogeneous catalysts get dis-
solved in the reaction medium, thus rendering all cata-
Coal fly ash is a solid waste generated from thermal
power plants, which consists of crystalline aluminosili-
cates, mullite, and metal oxides in trace amounts. The
utilization of fly ash is a matter of global concern from an
environmental and economic point of view. Owing to the
high silica and alumina content, fly ash can be converted
into zeolite by hydrothermal treatment, which finds a
wide range of applications. Recently, metal nanocatalysts
have been extensively studied as model catalysts for
industrially significant reactions. The high surface-to-
volume ratio of nanomaterials makes their role
lytic sites accessible to reactants in solution, which leads
to high activity. However, separation, handling efficiency,
and reusability of homogeneous catalysts need to be
addressed, which opens scope for heterogeneous cataly-
sis. Anchoring nanocatalysts to fly ash zeolite (FAZ)
offers the advantage of heterogeneity, thereby exploring
the possibility of reusability of the catalytic system.
Literature reports reveal that the incorporation of
metal ions and metal complexes in zeolite enhances the
catalytic activity of zeolites. The Advanced Oxidation Pro-
cess (AOP), especially photocatalysis, has been reported
Appl Organomet Chem. 2020;e5752.
wileyonlinelibrary.com/journal/aoc
© 2020 John Wiley & Sons, Ltd.
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https://doi.org/10.1002/aoc.5752

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SHEEBA THAVAMANI ET AL.
by loaded metal nanoparticles in zeolites to degrade con-
taminants in wastewater to stable inorganic compounds
such as carbon dioxide and water.[1]
products and its recyclability are complicated issues that
can be overcome by using solid supports for the catalytic
process. In this context, CeO2 and Pd loaded
nanoparticles supported in fly ash zeolite (CeO2/
Of the rare earth oxides, ceria is most widely used as
catalyst,[2,3] polishing materials[4,5] and so on. The cata-
lytic performance of supported metal nanoparticles
enhances due to specific interactions with CeO2 due to
stabilization.[6] Ru/CeO2 catalyst has been reported to
show excellent activity for the addition of sp2 C-H bonds
of aromatic ketones to vinyl silanes.[7] Pt/CeO2 catalyst
has been reported for CO oxidation,[8] hydrogenation,[9]
methanol decomposition,[10] etc. Hydrosilylation of
organic substrates has been reported using CeO2
supported gold catalysts.[11] The properties of cerium
oxides have been reported to be strongly dependent on
their microstructures, including size, morphology, and
specific surface area.[12] The dispersion of CeO2 on
porous materials could generate small oxide particles and
increase the number of active sites. The incorporation of
CeO2 nanoparticles in FAZ increases its thermal stability
and availability of active sites for catalysis.[13] Zeolites
have been reported as efficient catalysts for several
organic reactions. Transition metals have been used as
catalysts with potential advantages. Metal nanocatalysts
have been extensively studied as model catalysts in fun-
damental research and involve practical applications in
catalysis. Palladium nanocatalysts have been proved to
have effective catalytic activity for hydrogenation[14,15]
and carbon–carbonbond-formingreactions,[16,17] which
2
Pd@FAZ) have been used as catalysts for Csp2-Csp bond
formation. This work aims at studying the activity of
CeO2/Pd@FAZ towards cross-coupling reactions for the
2
formation of Csp2-Csp bonds, establishing the scope of
substrate and recyclability of the catalyst.
2 | EXPERIMENTAL SECTION
2.1 | Materials and methods
Coal fly ash was collected from the electrostatic precip-
itators of Tuticorin Thermal Power Station. (NH4)2Ce
(NO3)6 manufactured by E. Merck (99.0% assay) was
used for preparing CeO2 nanoparticles. Na2PdCl4 and
NaBH4 of 99.5% assay manufactured by E. Merck were
used for the synthesis of Pd nanoparticles. All reagents
and solvents used for studying the catalytic activity
were purchased from commercial suppliers (Sigma-
Aldrich, Alfa Aesar, and Avra Synthesis) and used
without further purification. IR spectra were recorded
from 4000 to 400 cm−1 using JASCO 4600 Infrared
spectrometer. X-Ray Diffraction patterns were recorded
on the XPERT-PRO diffractometer using Cu-Kα radia-
tion of wavelength 1.54 Å. TEM studies were carried
out at SAIF, IIT, Mumbai using PHILIPS, CM
200, TEM microscope operated at 200 kV with a reso-
lution of 2.4 Å. GC analyses were performed on
Agilent 7820A GC fitted with an FID detector and cap-
illary column. EDAX analysis was carried out on
Bruker Nano GmbH using XFlash 5010X detector.
Nuclear magnetic resonance (NMR) spectra were
recorded in deuterated solvents at room temperature
on a Bruker Avance 300 spectrometer operating at
300 MHz. Deuterated solvents were dried by storage
over 4 Å molecular sieves. Chemical shifts (δ) are
expressed in ppm using TMS as internal standard, and
coupling constants (J) are given in Hz. Surface area
and pore size distribution were analyzed using Quan-
tachrome Autosorb iQ2 surface area & pore volume
analyzer. X-ray photoelectron spectroscopic analysis
was performed using an XPS K-Alpha surface analysis,
Thermo Fisher Scientific.
find significant applications in pharmaceutical and fine
2
chemical industries. In particular, the formation of Csp
-
2
Csp bonds through coupling reactions has been demon-
strated to have a broad scope. A coupling reaction is a
process of forming a carbon–carbon bond through the
use of a metal catalyst. Adolphe Wurtz has explored cou-
pling reactions in which sodium metal reacted with an
alkyl halide via metal-halogen exchange followed by
nucleophilic substitution of a second equivalent of the
alkyl halide.[18] Subsequent works involving other metals
in coupling reactions have been reported, including cop-
per, nickel, and palladium.[19] Strong interactions
between metal and metal oxide nanoparticles and that
with the support induce changes in the valence band
structure of the metal nanoparticles, thereby enhancing
their activity.
Cross-coupling reactions of aryl halides (chlorides or
bromides) with aryl boronic acids, known as Suzuki-
Miyaurareaction,[20,21] have been reported as an efficient
2
and less toxic method to form Csp2-Csp bonds. Owing to
their high selectivity and functional group tolerance, the
palladium catalysts have been used extensively for
Suzuki-Miyauracross-coupling reactions. However, sepa-
ration of palladium metal catalysts from the desired
2.2 | Synthesis of FAZ
Fly ash collected from Tuticorin Thermal Power Station
(TTPS) was subjected to hydrothermal treatment to

SHEEBA THAVAMANI ET AL.
3 of 11
synthesize FAZ, as reported in the literature.[22,23] The
cation exchange capacity was determined and was found
to be in accordance with the reported value.[24]
3 | RESULTS AND DISCUSSION
The FAZ prepared by the hydrothermal treatment of fly
ash was characterized by BET, FTIR, XRD, and XRF and
reported to be X-type zeolite. During the hydrothermal
treatment, amorphous aluminosilicate deposits on the
particle surface of coal fly ash gradually, thereby pro-
gressing towards the formation of FAZ. The cation
exchange capacity of the prepared zeolite has been found
to be 457 meq/100 g, which indicates the possibility of
exchanging metal ions, which can be further reduced to
the corresponding metal/metal oxide nanoparticles.[22]
2.3 | Loading of CeO2 nanoparticles
in FAZ
The prepared fly ash zeolite was loaded with CeO2
nanoparticles through the cation exchange process
followed by calcination. The typical procedure is as fol-
lows, 2.0 g of (NH4)2Ce(NO3)6 and 1.0 g of fly ash zeolite
were dispersed in 30 ml of double distilled water and
ꢀ
gently stirred at 60 C for 2 h. The Ce (IV) loaded zeolite
was washed (three times with double distilled water and
one time with ethanol) and dꢀried at 80 ꢀC overnight. The
sample was calcined at 550 C for 4 hr to obtain CeO2
loaded fly ash zeolite.
3.1 | Characterization of CeO2/Pd@FAZ
The XRD pattern of CeO2/Pd@FAZ is presented in
Figure 1. In addition to the XRD peaks of FAZ, character-
istic peaks corresponding to that of CeO2 nanoparticles
are located at 2θ values 29, 33, 47, 56, 64, 79, and
88 which correspond to (111), (200), (220), (311), (400),
2.4 | Synthesis of CeO2/Pd nanoparticles
loaded FAZ (CeO2/Pd@FAZ)
(420),
and
(422)
respectively
(JCPDS
card
no. 34–0394).[25] The broad nature of the XRD patterns
indicates that the crystallite sizes of the samples are tiny.
Peaks due to Pd nanoparticles are feebly located at 2θ
values 46, 68, 81 and 86, which correspond to (200),
(220), (311), and (222) planes respectively (JCPDS card
no 75–8371).[26] The XRD pattern indicates that the
framework of the zeolite is intact, and the major peaks of
FAZ correspond to a higher intensity compared to that of
the incorporated nanoparticles. The loading of CeO2 and
Pd nanoparticles in the framework of zeolite has been
confirmed by matches with the fluorite structure of CeO2
and the fcc structure of Pd nanoparticles, and the
100 mg of CeO2 loaded FAZ is transferred to a 100 ml
beaker and 8 ml of double-distilled water was added. The
dispersed solution was stirred well at room temperature
for 30 min. To this well-dispersed solution, Na2PdCl4
(13 mg in 2 ml of double-distilled water) was added
dropwise under vigorous stirring and continued for one
hour at room temperature. Finally, a solution of NaBH4
(10 mg in 3 ml of double-distilled water) was added into
the solution and stirred at this temperature for further
3 h. Over the period of reaction time, the initial brown
colored solution turned to black, indicating the reduction
of Pd(II) to Pd(0). The material CeO2/Pd@FAZ was
repeatedly washed with double distilled water and dried
under vacuum for 24 hr.
2.5 | Typical procedure for the Suzuki-
Miyaura reaction
A glass vial was sequentially charged with appropriate
amounts of aryl bromide (0.5 mmol), phenylboronic acid
(0.55 mmol), and K2CO3 (1 mmol) and catalyst in metha-
nol (5 ml). The reaction mixture was stirred at 60 ꢀC
under aerobic condition for required time and then
diluted with water (10 ml). Extraction was carried out
with ethyl acetate (3 x 5 ml), dried over anhydrous
sodium sulfate and the solvent was stripped off under
vacuum. GC analysis was performed by dissolving the
solid residue in 2 ml of dichloromethane, and an aliquot
from the solution was injected into the injector port.
FIGURE 1 X-Ray Diffraction pattern of CeO2/Pd@FAZ

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SHEEBA THAVAMANI ET AL.
framework of FAZ remains unaffected after the incorpo-
ration of nanoparticles.
898.40, 901.15, 907.15 and 917.07 eV confirm the pres-
ence of cerium in +4 oxidation state.[33] From the XPS
survey spectrum the amount of palladium is found to be
10.29 at%. Both adsorption and desorption isotherms
presented in Figure 6 exhibit typically type IV pattern
with the relative pressure (P/P0) range between 0.2–0.9,
shows a gradually increased nitrogen adsorption. Both
isotherms of CeO2/Pd@FAZ shows the mesoporous
nature and the surface area is found to be 152.23 m2/g
with the average pore diameter is 10.67 nm.
The FT-IR spectrum of CeO2/Pd@FAZ is presented in
Figure 2. The most intense band at 991 cm−1 corresponds
to the asymmetric stretching of Si-O-Al. The peak at
1341 cm−1 represents the presence of substituted Al
atoms in the tetrahedral forms of silica frameworks. The
band at 3406 cm−1 represents the asymmetric and sym-
metric −OH stretching vibrations suggesting the presence
of possibly hydrated aluminum silicates. The band at
1631 cm−1 corresponds to the bending mode of water
molecules. All these observations correspond to that of
FAZ.[27] In addition to the stretching and bending modes
to that of FAZ, Ce-O stretching frequency is observed at
676 cm−1 showing the loading of CeO2 nanoparticles in
FAZ.[28]
3.2 | Catalytic activity of CeO2/Pd@FAZ
towards Suzuki-Miyauracross-coupling
reactions
The morphological studies of the synthesized CeO2/
Pd@FAZ have been carried out by TEM analysis.
Figure 3 displays the TEM images of CeO2/Pd@FAZ,
which consists of agglomerated nanoparticles comprised
of nanostructures in the range of 1–100 nm. The SAED
pattern indicates a lack of crystallinity owing to the poor
loading of nanoparticles in the porous framework of
FAZ. The loading of CeO2 and Pd in the pores of zeolite
is confirmed by EDAX analysis, which is presented in
Figure 4. The Elemental Analysis spectrum confirms the
presence of Pd at 0.25 keV and 2.8 keV[29,30] besides for
Ce at 0.95 keV and 2.8 keV, which is in accordance with
the EDAX spectrum of CeO2 nanoparticles.[31] Peaks
corresponding to Al and Si present in the FAZ matrix are
located in the EDAX spectrum.[32] To further confirm the
presence of palladium in the CeO2/Pd@FAZ, the sample
was subjected to X-ray photo electron spectroscopy (XPS)
(Figure 5). The presence of peaks at 335.7 and 340.9 eV
confirms the existence of palladium in zero oxidation
state and the peaks corresponding to 882.69, 889.11,
Suzuki-Miyaura cross-coupling reaction is one of the
attractive and highly demanding reactions in synthetic
organic chemistry because of its robust functional group
tolerance. Notably, palladium is an expensive metal but
well known for its transmetalation property, and palla-
dium mediated coupling reactions are successively well
utilized in industrial and academic research for targeted
synthetic methodologies.
Herein, we investigated the catalytic efficiency of the
CeO2/Pd nanoparticles incorporated FAZ towards the
cross-coupling reaction of the aryl halides with boronic
acid derivatives. Initially, a model reaction was per-
formed to optimize the appropriate catalyst for the
Suzuki-Miyaura reaction. FAZ, Pd loaded FAZ
(Pd@FAZ), and CeO2/Pd loaded FAZ (CeO2/Pd@FAZ)
were screened for their activities. A preliminary reaction
with phenylboronic acid, 4-bromoacetophenone, K2CO3
(as base), methanol (as solvent) and catalyst was carried
out at room temperature (Table 1, entries 1–3). At a time
interval of 2.5 h, the catalyst CeO2/Pd@FAZ exhibits
good catalytic conversion to 48% of the cross-coupled
product (Table 1, entry 3). CeO2/Pd loaded FAZ was
identified as a better catalyst and attracted attention to
study its activity towards Suzuki-Miyauracross-coupling
reactions.
CeO2 assists the formation of well-dispersed and
smaller Pd nanoparticles, which results in a larger sur-
face area of the catalyst. Apart from size effect, CeO2
improves the catalytic activity of Pd as CeO2 modifies the
electronic structure of Pd through its synergic interac-
tion.[34] This correlates with the observation that CeO2/
Pd loaded FAZ has better activity compared to FAZ and
Pd loaded FAZ.
To further explore as an efficient catalyst to perform
the Suzuki-Miyauracross-coupling reaction, the base
plays a vital role.[35] To optimize the choice for the base,
the model reaction was further examined by varying the
FIGURE 2 FT-IR spectrum of CeO2/Pd@FAZ

SHEEBA THAVAMANI ET AL.
5 of 11
FIGURE 3 TEM images of CeO2/Pd@FAZ
bases under the optimized reaction conditions. A wide
range of inorganic bases, including K2CO3, NaOAc,
LiOHÁH2O and Cs2CO3, and organic bases including
triethylamine and DABCO (1,4-diazabicyclo[2.2. 2]
octane) have been used under standard reaction condi-
tions (Table 1, entries 3–8). K2CO3 furnished a conver-
sion of 48% (Table 1, entry 3) and hence was chosen as
the base for subsequent reactions. In the absence of base,
there is no evidence for the formation of cross-coupling
reaction (Table 1, entry 19). To evaluate the suitable sol-
vent for the optimization, various polar and non-polar
solvents like H2O, MeOH, DMF, THF, CH3CN and tolu-
ene were examined to choose the best solvent for the
reaction (Table 1, entries 3, 9–13). The result shows that
both methanol and DMF facilitate significant conversion
among the different solvents used for optimization
(Table 1, entries 3 and 13). The solubility of the substrate
and interaction between CeO2/Pd@FAZ and substrate is
very poor in water medium. Hence, the reactions are not
progressing in water.
The effect of catalyst loading was studied by varying
the weight percentage of catalyst (5 to 20) as the amount
of catalyst used in catalytic reaction plays an imperative
role. Under optimized reaction conditions, the catalytic
activity of CeO2/Pd@FAZ was accomplished by varying
the loading of catalyst, reaction temperature, and the
results are summarized in Table 1. It is observed that a
decrease in the catalyst loading (20 to 5 wt.%) increases
the catalytic activity, along with increase in reaction tem-
perature (Table 1, entries 3, 14–18) and in the absence of

6 of 11
SHEEBA THAVAMANI ET AL.
FIGURE 4 EDAX spectrum of CeO2/
Pd@FAZ
FIGURE 5 X-ray photoelectron spectrum of CeO2/Pd@FAZ

SHEEBA THAVAMANI ET AL.
7 of 11
FIGURE 6 BET adsorption isotherm of
CeO2/Pd@FAZ
TABLE 1
Screening of catalysts, bases, and solvents for Suzuki-Miyauracross-coupling
Entry
1.
Base
Catalyst
wt%
20
20
20
20
20
20
20
20
20
20
20
20
20
20
10
10
5
Solvent
MeOH
MeOH
MeOH
MeOH
MeOH
MeOH
MeOH
MeOH
CH3CN
Toluene
THF
Temp (ꢀC)
Time (h)
Yield (%)
K2CO3
K2CO3
K2CO3
NaOAc
LiOHÁH2O
Cs2CO3
DABCO
TEA
FAZ
30
30
30
30
30
30
30
30
30
30
30
30
30
65
30
65
30
65
65
65
2
-
2.
Pd@FAZ
2
39
48
40
40
19
35
-
3.
CeO2/Pd@FAZ
CeO2/Pd@FAZ
CeO2/Pd@FAZ
CeO2/Pd@FAZ
CeO2/Pd@FAZ
CeO2/Pd@FAZ
CeO2/Pd@FAZ
CeO2/Pd@FAZ
CeO2/Pd@FAZ
CeO2/Pd@FAZ
CeO2/Pd@FAZ
CeO2/Pd@FAZ
CeO2/Pd@FAZ
CeO2/Pd@FAZ
CeO2/Pd@FAZ
CeO2/Pd@FAZ
CeO2/Pd@FAZ
-
2
4.
2
5.
2
6.
2
7.
2
8.
2
9.
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
-
10
10
10
10
10
10
10
10
10
10
10
10
3
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
9
3
Water
-
DMF
47
91
63
92
69
97
-
MeOH
MeOH
MeOH
MeOH
MeOH
MeOH
MeOH
5
20
-
K2CO3
-
Reaction condition: 4-bromoacetophenone (1 equiv), phenylboronic acid (1.1 equiv), base (1 equiv), solvent (3 ml). Using
4-bromoacetophenone as an internal standard and the coupled product was determined by GC.

8 of 11
SHEEBA THAVAMANI ET AL.
TABLE 2
Substrate scope in Suzuki Miyaura cross-coupling using CeO2/Pd@FAZ
S.No
Aryl Halide
Boronic acids
Product
Time (h)
Yield (%)a
1.
2
97
2.
3.
4.
5.
21
22
20
22
68
88
82
91
6.
4
91
7.
8.
24
21
51
71
9.
24
21
71
35
10.

SHEEBA THAVAMANI ET AL.
9 of 11
TABLE 2 (Continued)
S.No
Aryl Halide
Boronic acids
Product
Time (h)
Yield (%)a
11.
12.
29
22
69
78b
aReaction condition: aryl halides (1 equiv), phenylboronic acid (1.1 equiv), K2CO3 (1 equiv), (5 wt%) CeO2/Pd@FAZ, DMF (3 ml). b phe-
nylboronic acid (2.1 equiv).
CeO2/Pd@FAZ, (Table 1, entry 20), cross-coupling reac-
tion did not proceed. The CeO2/Pd@FAZ with 5 wt. %
loading afforded the coupled product in excellent conver-
sion (Table 1, entry 18).
Likewise, significant efforts were made to examine
the substrate scope by reaction of phenylboronic acid
Further, the scope of the reaction was extended to less
reactive aryl chloride derivatives. Under optimized reac-
tion conditions, chlorobenzene, 4-chloroacetophenone,
and 4-chloronitrobenzene were coupled with phe-
nylboronic acid. 4-chloroacetophenone gave only 35% of
the coupled product (Table 2, entry 10) while
4-chloronitrobenzene afforded 69% (Table 2, entry 11) of
the cross-coupled product under similar reaction condi-
tion. In addition to that, the reaction of 1,4-dibromo ben-
zene with two equivalents of phenylboronic acids
afforded the corresponding bis-coupled product in good
yields (Table 2, entry 12). The GC yields for the coupling
reactions have been presented in Figures S1-S5. The
products have been confirmed by 1H-NMR and the
results are listed in Figures S6-S8.
To check the recyclability of the catalyst, a series of
reactions were carried out under optimized reaction con-
ditions of 4-bromoacetophenone (0.5 mmol) as reactant,
phenylboronic acid (0.6 mmol) as coupling counterpart,
K2CO3 (0.5 mmol) as base and DMF (3 mL) as solvent
using CeO2/Pd@FAZ (5 wt. %). The results indicate their
conversion rate from 99 to 40% (Figure 7) though there is
considerable leaching of catalyst from cycle I to III. The
catalyst has been efficiently used for three cycles, with an
activity of 40% conversion in the third cycle. In this study,
up to 97% conversion has been observed in ten hours
with recyclability up to three cycles by loading CeO2 and
with
a wide variety of diversely substituted aryl
bromides/chlorides under the optimized reaction condi-
tion, and the results are compiled in Table 2. The cou-
pling reaction between 4-bromoacetophenone and
phenylboronic acid using MeOH as solvent affords a
conversion of 91% coupled product under reflux condi-
tion (Table 1, entry 14), whereas in the case of other
all substrates, MeOH as solvent shows lesser catalytic
conversion compared to DMF (data not shown). In this
regard, DMF is fixed as optimum solvent for the fur-
ther reactions to study the substrate scope of the aryl
halides. All the reactions progressed efficiently to
afford the biaryls in good to excellent yields. The elec-
tronic nature of aryl halides has significant effects on
catalytic conversion. Aryl bromides with electron with-
drawing groups proceed much faster with high conver-
sion (Table 2, entries 1–3) compared to that of
electron releasing groups in the aryl bromides
(Table 2, entries 7 and 8). In addition, the electroni-
cally neutral substrate also incurred excellent yields
(Table 2, entries 4–6).

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SHEEBA THAVAMANI ET AL.
on reductive elimination affords the coupled biaryl prod-
uct and regenerates the catalyst.
4 | CONCLUSION
CeO2/Pd nanoparticles incorporated in FAZ has been
proved as an efficient heterogeneous catalyst towards
2
cross-coupling reactions involving Csp2-Csp bond forma-
tion reactions between aryl halides and phenylboronic
acid. Reaction conditions including the catalyst, base, sol-
vent and substrate scope have been optimized. The pres-
ence of electron-withdrawing groups in the aryl halides
enhances the rate of the reaction with good conversion
while the electron releasing groups affect the rate of reac-
tion with reasonable yields. Further, the catalyst has been
recycled and reused up to two times. Apart from postulat-
ing a sophisticated method for the utilization of fly ash,
this work suggests a cost-effective catalyst for Suzuki
Miyaura cross-coupling reaction.
FIGURE 7 Recyclability test of catalyst CeO2/Pd@FAZ
Pd nanoparticles in FAZ, which is at par with the yields
reported in literature with commercial zeolites.[36,37]
Though the mechanistic details are not ascertained, a
plausible catalytic cycle for the Palladium-catalyzed cross
coupling reaction of aryl halide and aryl boronic acid
using K2CO3 as base is shown Scheme 1. The aryl halide
undergoes oxidative addition reaction with Pd(0) (I) in
the catalyst CeO2/Pd@FAZ. Presence of CeO2 in the cata-
lyst enhances the easier oxidation of Pd(0) to Pd
(II) during the oxidative addition reaction with aryl
halide. The in-situ formed chlroboronic acid facilitates
transmetallation reaction to afford intermediate II which
ACKNOWLEDGEMENT
S. Sheeba Thavamani acknowledges the financial support
provided by University Grants Commission under Minor
Project Scheme. [Ref. No: F MRP-5645/15 (SERO-UGC)].
CONFLICT OF INTEREST
The authors declare no conflict of interest.
ORCID
Thomas Peter Amaladhas https://orcid.org/0000-0002-
4469-0643
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SCHEME 1 Plausible mechanism for the formation of biaryls
catalyzed by CeO2/Pd@FAZ

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SUPPORTING INFORMATION
Additional supporting information may be found online
in the Supporting Information section at the end of this
article.
How to cite this article: Sheeba Thavamani S,
Sudharsan M, Santhana Mariya A, et al. CeO2/Pd
Nanoparticles Incorporated Fly Ash Zeolite: An
[27] S. Sheeba Thavamani, T. Peter Amaladhas, J. Mater. Environ.
Sci 2016, 7(7), 2314.
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2
Efficient and Recyclable Catalyst for Csp2-Csp
Bond Formation Reactions. Appl Organomet Chem.
2020;e5752. https://doi.org/10.1002/aoc.5752