Ultrasonic-assisted preparation of nano eggshell powder: A novel catalyst in green and high efficient synthesis of 2-aminochromenes

Article abstract of DOI:10.1016/j.ultsonch.2013.04.008

The nano eggshell powder (NESP) has been prepared by ultrasound irradiation and used as a novel and biodegradable catalyst with high catalytic activity and reusability in green synthesis of 2-aminochromenes via condensation of α- or β-phathol, malononitri

Full text of DOI:10.1016/j.ultsonch.2013.04.008

Accepted Manuscript
Ultrasonic-assisted preparation of nano eggshell powder: A novel catalyst in
green and high efficient synthesis of 2-aminochromenes
Elaheh Mosaddegh
PII:
S1350-4177(13)00101-6
DOI:
http://dx.doi.org/10.1016/j.ultsonch.2013.04.008
ULTSON 2299
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To appear in:
Ultrasonics Sonochemistry
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Revised Date:
Accepted Date:
9 February 2013
10 April 2013
17 April 2013
Please cite this article as: E. Mosaddegh, Ultrasonic-assisted preparation of nano eggshell powder: A novel catalyst
in green and high efficient synthesis of 2-aminochromenes, UltrasonicsSonochemistry (2013), doi: http://dx.doi.org/
10.1016/j.ultsonch.2013.04.008
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Ultrasonic-assisted preparation of nano eggshell powder: A novel catalyst in green and
high efficient synthesis of 2-aminochromenes
Elaheh Mosaddegh
Department of New materials, Institute of science and High Technology and Environmental
sciences, Graduate University of advanced Technology, PO Box 76315-117, Kerman, Iran.
Tel.: +98 3426226617; fax: +98 3426226611-12; E-mail addresses:
emosaddegh@gmail.com

Abstract
The nano eggshell powder (NESP) has been prepared by ultrasound irradiation and used as a
novel and biodegradable catalyst with high catalytic activity and reusability in green
synthesis of 2-aminochromenes via condensation of α- or β-phathol, malononitrile and
aromatic aldehydes at 125 °C under solvent-free conditions. The reaction proceeds to
completion within 10-35 min in 91-98% yield. Nano eggshell catalyst was characterized by
scanning electron microscopy, X-ray powder diffraction, IR spectroscopy and X-ray
fluorescence, thermal gravimetric, surface area and elemental analyses. In addition, the
catalytic activity and chemical structure of nano-sized eggshell were compared with pure
CaCO3.
Keywords: Nano eggshell powder, Sonochemical preparation, natural catalyst, XRD, 2-
aminochromenes, green chemistry
1. Introduction
Eggs are consumed worldwide because they contain all essential amino acids, vitamins, and
minerals. Eggshell waste primarily contains calcium, magnesium carbonate (lime) and
protein [1] and is the significant solid waste produced from food processing and
manufacturing plants [2]. This natural solid waste, although non-hazardous, is commonly
disposed in landfills without any pretreatment because it was traditionally useless [3]. As a
consequence, a huge problem of pollution is generated. In addition, it can attract rats and
worms due the organic protein matrix, resulting in a problem of public health [4]. However,
special attention has been devoted to industrial sectors that are sources of pollution of the
environment [5, 6]. A topical area of great importance related to the waste processing and
recycling approach is the proper characterization of the material [6]. In recent years, a great
deal of effort has been conducted for the application of eggshell as value-added products.
These major applications included a possible bone substitute [7], the starting material for
preparing calcium phosphate bioceramics (e.g. hydroxyapatite) [8], coating pigments for
inkjet printing paper [9], a low-cost adsorbent for removal of ionic pollutant and dyes from
the aqueous solution [10,11] and lactose isomerisation [12]. Also, calcined eggshell (CaO)
was used for biodiesel fuel production [13] and dimethyl carbonate [2] synthesis.
Currently, there is a trend toward simple, low temperature and green method for the
preparation of nanoparticle. One of the novel, powerful and simple method for the synthesis
of nanomaterial is sonochemistry [14,15] that led to high activity in catalysis due to their

particles size and high surface area [16]. Also, the ultrasonic irradiation provides a clean
media to prepare nanomaterials in short reaction time. The chemical and physical effects of
ultrasonic irradiation originate from acoustic cavitations [17, 18].
2-Aminohromenes are widely employed as pigments, cosmetics, potential biodegradable
agrochemicals and also as components of many natural products [19-21]. Also, They show
antidepressant, antihypertensive, anti-tubulin, antiviral and antioxidative activity [22,23]. The
most straightforward synthesis of this heterocyclic system involves a three-component
coupling of aromatic aldehyde, malononitrile and activated phenol in the presence of organic
bases like piperidine in an organic solvent such as ethanol or acetonitrile for several hours
[24]. Although a number of modifications of this reaction conditions have been reported [25-
40], but, all these methods include some or other drawbacks such as low yields, prolonged
reaction time, tedious catalyst preparation and workup, and exhaustive usage of energy
sources and solvents. So, the development of an efficient and green methodology for the
synthesis of 2-aminochromenes is highly essential.
Heterogeneous base catalyzed organic synthesis is a promising field of research with
potential application in pharmaceuticals and related fine chemical industries [41–46].
Recently, we found that waste eggshell could be used as an active heterogeneous and micro-
porous catalyst for 4H-benzo[b]pyrans synthesis [47]. It was proved that eggshell was an
interesting unconventional heterogeneous biocatalyst for organic synthesis. Since eggshell
has a little porosity, we decided to explore ultrasonic assisted preparation of nanopowder
catalyst based on eggshell waste and investigate its catalytic properties as a solid base
mesoporous catalyst for 2-aminochromenes synthesis via one pot multi-component
condensation of aryl aldehydes, malononitrile and α or β-naphthol in solvent-free and thermal
conditions. The other aim was to compare the catalytic activity of pure CaCO3 and nano-
sized mesoporous eggshell catalysts.
2. Experimental
2.1. Materials and Instruments
All chemicals were of analytical grade, purchased from Merck and used as received.
Ultrasonic irradiation was performed in an ultrasound cleaning bath (FALC instrument, Italy)
with a frequency of 60 Hz and voltage of 220 V. Melting points were determined on a
Gallenkamp melting point apparatus and are uncorrected. NMR spectra were recorded at 500
(1H) and 125.77 (13C) MHz on Bruker DRX-500 Avance spectrometer at 500 and 125.77
MHz, respectively. IR spectra were obtained with MATSON 1000 FT-IR spectrophotometer.

X-ray diffraction (XRD) with a D8 Bruker diffractometer (40kV and 40mA) and Cu Kα
radiation (λ=0.154 nm) was used to analyze the crystal structure of the milled powders. The
XRD patterns were recorded in the 2θ range of 20-80º with the step size of 0.01º. The mean
size and size distribution of the eggshell powder were measured by a dynamic laser light
scattering (DLS) apparatus (FRITSCH Analysette 22 NanoTec Laser Particle Sizer). The
chemical composition of the catalyst was determined using a X-ray fluorescence (XRF)
Microanalyser (Unisantis XMF-104, Germany) with 40kV, 300mA and Mo radiation. TGA
experiments were carried out using a STA 409 PC Luxx thermal analysis machine
(NETZSCH, Germany) under a flow of nitrogen. The sample weight used was about 20 mg,
and the temperature ranged from 25 to 900 °C with a ramping rate of 10 °C/min. The
morphology of the cross section of the film was examined with a field emission scanning
electron microscope (FESEM) after being fractured in liquid nitrogen. Dried samples were
coated with gold ions using an ion coater at 150 s. Surface structure was visualized by field
emission scanning electron microscope (Hitachi S4160) using a 15 kV accelerating voltage.
TEM images were obtained on a LEO912-AB (LEO, Germany) transmission electron
microscope with an accelerating voltage of 120 kV. Particles were deposited onto a carbon
foil supported by a copper grid. The Milling was carried out in a planetary ball mill using
hardened chromium steel vial (250 ml) at room temperature under argon atmosphere. It was
performed using hardened chromium steel vial (250 ml). The ball-to-powder weight ratio and
the rotation speed of the vial were 350 rpm and 10:1 respectively.
2.2. Catalyst preparation
Empty chicken eggshells were collected from the household and washed with tap warm
water. The adhering membrane was separated manually. Then, the eggshells were washed
with distilled water and dried at 120°C for 1 h. Then the eggshells were milled in a planetary
ball mill for 2 h. Next, the eggshell powder was mixed with CH2Cl2 and placed in an
ultrasonic cleaning bath with a frequency of 60 Hz at 50oC for 1 h. Since eggshell is a
hydrophobic compound, an organic and aprotic solvent is needed to dissolve and remove the
rest of the organic materials from the eggshell. These impurities often remain in the eggshell
even after washing and drying in oven. It is likely that the presence of these impurities in the
eggshell, affect the average surface area and catalytic activity of the eggshell catalyst. So, a
purification process such as that described above may remove these impurities. Also, it was
observed that a small amount of solvent (CH2Cl2, 5 mL) was necessary to stabilize the
suspension of eggshell nanocrystals to avoid high agglomeration. After ultrasonication, the

powder was filtered from the solvent and dried at room temperature. The eggshell particle
size was obtained with laser particle sizer.
2.3. General procedure for the preparation of 2-aminochromene-2-carbonitriles
In a typical general procedure, a mixture of 3-nitrobenzaldehyde (0.15 g, 1 mmol),
malononitrile (0.07 g, 1 mmol) and α or β-naphthol (0.14 g, 1 mmol) in solvent-free
condition at 125 °C, were stirred thoroughly in the presence of a catalytic amount of NESP
(0.1 g) to afford the corresponding 2-aminochromene in excellent yields. After completion of
the reaction (TLC), hot EtOH was added to the reaction mixture and stirred for 5 min. Then
the solid catalyst was filtered from the soluble products and washed with hot EtOH. After
cooling, the crude products were precipitated. Pure 2-aminochromenes were obtained in high
yields without any use of more purification. All compounds were known in the literature [25-
40] and the NMR and IR spectra of the products were in agreement with earlier data [25-40].
The selected spectral data of two representative 2-aminochromene derivatives are given
3-Amino-1-(3-nitrophenyl)-1H-benzo[f]chromene-2-carbonitrile (Table 3, entry 7). IR (KBr):
3455, 3336, 2196, 1669, 1600, 1571, 1415, 1377, 1100 cm-1; 1H NMR (400 MHz, DMSO) δ
= 8.15 4.86 (s, 2H, NH2); 5.32 (s, 1H, CH), 7.41–7.20 (m, 5H), 7.45–7.51 (m, 1H), 7.86–7.89
(m, 2H), (d, J = 9.7 Hz, 2H),
2-Amino-4-(4-chlorophenyl)-4H-benzo[h]chromene-3-carbonitrile (Table 3, entry 2). IR
(KBr): 3454, 3336, 2192, 1669, 1601, 1575, 1414, 1378, 1100, 878 cm-1; 1H NMR (400
MHz, DMSO) δ = 4.78 (br s, 2H, NH2), 4.85 (s, 1H, CH), 7.01 (d, J= 8.7 Hz, 1H, Ar), 7.19-
7.47 (m, 5H, Ar), 7.50-7.58 (m, 2H, Ar), 7.78 (d, J=7.1 Hz, 1H, Ar); 8.15 (d, J= 8.2 Hz, 1H);
3. Results and Discussion
3.1. Characterization of nanocatalyst
3.1.1. Chemical composition of nano eggshell powder
XRF and Elemental analysis of mesoporous eggshell showed high levels of Ca (35.2%) and
carbon (13%), P (0.75%), O (48.01%), with small amounts of Mg (1.61%), Sr (0.6%), Si
(0.3%), K (0.075%), Na (0.054%), Fe (0.03%), Zn (0.03%), Ni (0.01%), Cl (0.028%),
nitrogen (0.30%), and hydrogen (0.05%).
3.1.2. Particle size and BET surface area analysis
The higher SBET with smaller size of catalyst particles could provide higher reaction
conversion [48]. Table 1 presents the particle size and the nitrogen physisorption data of

natural eggshell and pure CaCO3. The surface area of just ballmill treatment eggshell was
0.0253 m2 g-1 with the average particle size of 35 µm, whiles they are 3.5421 m2 g-1 and 3
µm for NESP (Table 1, entry 1,2) that proved a decrease in crystal size of the powder due to
ultrasonic irradiation. As shown in Table 1, the low surface area with larger particle size of
pure CaCO3 and its sonicated ones (entries 3-6) processed low porosity. Since, the catalytic
activity of the catalysts agreed well with the specific surface area and catalyst particle size, it
is logical that mesoporous sonicated eggshell with downsized crystal can catalyze the
reaction more effective than ballmilled eggshell powder and CaCO3. Also, there was
interested that we tried to prepare NESP using microwave irradiation, but our attempt was not
successful.
Table 1.
3.1.3. Thermo Gravimetric Analysis (TGA)
Nanocatalyst was further analyzed by thermal gravimetric analysis in order to explain the
effect of high temperature on its thermal stability (Fig. 1). DSC thermal curves representing
the carbonate mineral are characterized by exothermic peaks with ∆Hf° = 1194 J/g caused by
the evolution of carbon dioxide. TGA result showed the temperatures, at which the eggshell
precursors decomposed when heated in a controlled environment at a given ramp rate. The
weight loss below 1.3 % at 600°C was related to release of physisorbed H2O from the
sample. Complete calcination was observed between 600-847°C with the weight loss of
46.2%, resulting in phase-change due to decomposition of CaCO3 to CO2 and CaO. So, the
catalyst remained stable in the reaction temperature (125 °C) and CaO phase was found when
the eggshell was calcined at 900 °C for 1 h.
Fig. 1.
3.1.4. XRD and FTIR analysis
Also, the prepared catalyst was characterized by infrared spectroscopy (FT-IR) and X-ray
diffraction (XRD). The same XRD pattern of the nano eggshell powder and the commercially
available CaCO3 with 2Ө = 29.4 angles, indicating that calcite (CaCO3) is a major phase of
the waste eggshell (Fig. 2), and the NESP and the commercially available CaCO3 have a very
similar chemical nature. High XRD peak intensities of commercially available CaCO3 than
those of the eggshell catalyst are related to its larger CaCO3 particle size [49]. The XRD
patterns of pure CaCO3 are the same as its ultrasonic treatment one . The major peak of

calcite phase (2Ө = 29.4) was not shown in XRD pattern of the calcined eggshell, implying
that the CaCO3 phase was completely transformed to CaO phase (Fig. 2c).
Fig 2.
Fig 3.
Fig. 3 shows the same strong characteristic carbonate bands of the nanocatalyst and the
sonicated CaCO3 in IR spectra. IR spectra of pure CaCO3 and its ultrasonic treatment are
exactly the same. The broad transmission band at approximately 3410 cm-1 can be attributed
to OH stretching vibration from residual water [47]. The weak band at 1798 cm-1 corresponds
to CO bonds from carbonate [50]. Two well-defined infrared bands at 1422 and 710 cm-1 are
characteristic of the C–O stretching and bending modes of calcium carbonate, respectively
[51]. The strong band at 876 cm-1is related to OCO out of plane of vibration mode [47]. A
medium broad band in 2517 cm-1 shows the presence of HCO3. This data confirms the
presence of CaCO3 in the egg shell powder [51] and compare with published data of 1455-
1470/1420-1425 cm-1 (ν ), 1065-1075 cm-1 (ν ), 863-873 cm-1 (ν ) for CaCO3 [52–55]. Fig 3c
3
1
2
shows the existence of peak at 3640 cm-1 is due to OH in Ca(OH)2 formed during adsorption
of water by CaO. So, the FTIR spectrum of eggshell powder indicates this product is
hygroscopic and clearly has moisture water [56].
3.1.5. Electron microscope images
Transmission electron microscope (TEM) and Field Emission Scanning Electron Microscope
(FESEM) are another useful tool for the analysis of the surface morphology of a catalyst.
SEM images of just ballmilled treatment eggshell, sonicated calcium carbonate and NESP
were given in fig 4. A comparative SEM images study was shown an increase in porosity of
NESP and obviously illustrate the mesoporous nature of the catalyst with many distributed
pores and pits over the entire eggshell surface. In general, the high porosity of the nano
eggshell powder provides a large contact area for catalyzing the reaction (Fig. 4a ,b). The
average size of the nanocrystals obtained from the TEM and FESEM images analysis is 50
nm.
Fig. 4.
3.2. General synthesis of 2-aminochromene derivatives
The activity of the green nanocatalyst was tested using a one-pot three-component
condensation of α or β-naphthol (1 mmol) with different aromatic aldehydes (1 mmol) and
malononitrile (1.5 mmol) under solvent-free and thermal conditions to obtain the

corresponding 2-aminochromenes. Without the addition of a catalyst, the reaction produced
only alkene 5 and no 2-aminochromenes 4 was formed even after 10 h in the reaction
conditions (Fig. 5).
Fig. 5.
To develop optimum conditions, first, the effect of temperature and solvent on the rate of the
reaction was studied for the preparation of 2-aminochromenes (Table 2). At 125 °C, the
reactions proceeded to completion very rapidly. A decrease in temperature leads to
decreasing product yields and rate of the reaction. It was observed that the reaction did not
proceed at room temperature. In order to show the effect of ultrasonic irradiation on the
catalytic activity of the NESP, next, a comparative reaction was carried out by using just
ballmill treatment eggshell. As shown in Table 2 (entry 8 ), the reaction proceeds to
completion in 75 min with product yield of 84%, while they are 35 min and 91% for its
ultrasonic treatment one. This proves the essential effect of ultrasonic irradiation on the
catalytic activity of eggshell powder as a mild and efficient catalyst in the reaction.
Table 2.
Next, the optimum amount of nanocatalyst was evaluated in the range of 0.02-0.2 g. The
highest yield was obtained with 0.1 g of the catalyst. A further increase in the amount of
catalyst up to 0.2 g did not have any significant effect on the product yield or reaction time.
The generality of this reaction was examined using different aldehydes (Table 3). In all cases,
the reactions gave the corresponding products in good to excellent yields (91-98%) and in
very short reaction times (10-35 min). This method offers significant improvements with
regard to the scope of the transformation, simplicity, and green aspects by avoiding
expensive, hazardous or corrosive catalysts.
Table 3.
Among several heterogeneous basic catalysts, the alkali and alkaline earth metals are most
promising [42,57]. Calcium carbonate is an interesting basic carbonate which shows well
defined surface basicity and catalytic activity [32]. Since almost 90% of the eggshell is
composed calcium carbonate and it is the main active site of eggshell catalyst, we carried out
a comparative reaction in the presence of CaCO3 (0.1 g) in the same conditions. It was
interested that different byproducts with trace amounts of the desired product can be obtained
after 24 h. In addition, the catalytic reactions by using CaCO3 powder prepared under
ultrasonic irradiation from 1 to 3 h were carried out and compared with the subject reaction
using NESP. As shown in Table 2 (entry 10-12), the catalytic activity of CaCO3 was
increased with irradiation time because of downsize the powder due to ultrasonication.

However, compared with NESP catalyst, the reaction time was very long and the product
yield was low. The eggshell product has an average porosity naturally and ultrasonic
irradiation causes an increase in its porosity. It is probably because of the vapor of the solvent
from the catalyst pores in high pressure and temperature that makes it more porous catalyst.
As seen in BET and SEM analysis, NESP is very porous and its calcium carbonates have
much higher surface area. Also, eggshell contains small amount of different ions (Mg, Sr, P,
Si, K, Na, Fe, Ni and Cl) which can catalyze the reaction. But, as is clear, these small
amounts of chemicals have low catalytic activity. However, a comparative reaction was
carried out using sonicated MgCO3 which has the highest amount after CaCO3 (Table 2, entry
13). The result was shown the low catalytic activity of sonicated MgCO3. This proved the
highest catalytic activity of the NESP due to increase in porosity and decrease in crystal size
of the catalyst because of ultrasonic irradiations.
3.3. Catalyst Recovery and Reusability
The reusability of catalysts is one of the most important benefits and makes them useful for
commercial and industrial applications. The reusability of the catalyst was examined in the
synthesis of 2-aminochromene-2-carbonitrile 4b (Table 3, entry 7). The catalyst was
recovered after each run, washed three times with hot EtOH, dried in an oven at 120 °C, and
tested for its activity in subsequent runs.
Fig. 6.
It was found that the catalyst could be reused six times without any loss of activity. Thus, the
new procedure is eco-friendly, cost effective, clean and more efficient than reported methods.
4. Conclusion
In summary, easily and rapidly sonochemical preparation of nano eggshell powder in a
CH2Cl2 solution and its comparison with sonicated CaCO3 structure has been explored. Also,
a green, rapid and highly efficient protocol for the one-pot synthesis of 2-amino-4H-
chromens has been described under thermal solvent-free conditions using eggshell waste as a
heterogeneous nanocatalyst with high catalytic activity and reusability. This eggshell is a
novel nanocatalyst base on eggshell waste which can catalyze the organic transformation and
reduce environmental problems and it is the first use of this waste material as the nano-sized
catalyst in organic synthesis.

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Figure Caption:
Scheme 1. Synthesis of 2-aminochromene derivatives catalyzed by nano eggshell powder
(NESP)
Fig. 1. TGA curves of nano eggshell powder (NESP)
Fig. 2. XRD pattern of (a) black line: commercially available CaCO3; (b) red line: NESP; (c)
blue line: calcined eggshell
Fig. 3. FTIR spectra of NESP (a), sonicated CaCO3 (b) and calcined eggshell (c).
Fig. 4. TEM and SEM images of NESP (a); ballmill treatment eggshell powder (b); sonicated
calcium carbonate for 3 h (c).
Fig. 5. Benzilidene malononitrile intermediate
Fig. 6. Recycling experiment of NESP

Table 1. BET surface area (SBET), and average particle size of eggshell powder and pure
CaCO3.
Entry
Sample
Surface areaa (m2g-1)
3.5421
Average particle sizeb (µm)
1
2
3
4
5
6
eggshell
3
ballmilled eggshell 0.3265
35
49
47
44
41
CaCO3
0.0145
0.0215
0.0823
0.1061
CaCO3,c US 1 h
CaCO3,c US 2 h
CaCO3,c US 3 h
a Determined by N2 adsorption analysis.
b Determined by laser particle sizer.
c Pure CaCO3 were irradiated in ultrasonic for appropriate time according to experimental
section.

Table 2. Effect of solvent, temperature and type of catalyst in the reaction condensation of 3-
nitrobenzaldehyde, α-naphthol and malononitrile.
Entry Conditions
Catalyst
Time
24 h
Yield (%)a
1
H2O, r.t
NESP (0.1 g)
NESP (0.1 g)
NESP (0.1 g)
NESP l (0.1 g)
___
__
2
H2O, 45°C
24 h
trace
trace
trace
__
3
EtOH, r.t
24 h
4
EtOH, 45°C
10 h
5
solvent-free, 125 °C
solvent-free, 80 °C
solvent-free, 125 °C
solvent-free, 125 °C
solvent-free, 125 °C
solvent-free, 125 °C
solvent-free, 125 °C
solvent-free, 125 °C
solvent-free, 125 °C
10 h
6
NESP l (0.1 g)
NESP (0.1 g)
95 min
35 min
85
7
91
8
ballmilled eggshell (0.1 g) 75 min
84
9
CaCO3 (0.1g)
24 h
19 h
16 h
14 h
24 h
trace
69
10
11
12
13
CaCO3 (0.1g),b US 1 h
CaCO3 (0.1g),b US 2 h
CaCO3 (0.1g),b US 3 h
MgCO3 (0.005g),b US 3 h
77
80
trace
a Yields refer to the isolated products.
b Pure CaCO3 and MgCO3 were irradiated in ultrasonic bath for appropriate time.

Table 3. Synthesis of 2-aminochromene derivatives catalyzed by NESP under thermal and
solvent-free conditions.
Entry Product
R
Time (min)
Yielda (%)
1
4a
4a
4a
4a
4a
4a
4b
4b
4b
4b
4b
4b
3-NO2-C6H4
4-Cl- C6H4
3-Br- C6H4
2-CH3O- C6H4
2,4-Cl2- C6H3
4-OH- C6H4
3-NO2-C6H4
4-Cl- C6H4
3-Br- C6H4
2-CH3O- C6H4
2,4-Cl2- C6H3
4-OH- C6H4
20
25
30
10
20
15
35
20
25
10
15
15
94
93
98
97
96
93
91
92
97
95
95
94
2
3
4
5
6
7
8
9
10
11
12
aYield refers to isolated pure product.

Figure
Fig. 1. TGA curves of nano eggshell powder (NESP).

Figure
(c)
(b)
(a)
Fig. 2. XRD pattern of (a) black line: commercially available CaCO3; (b) red line: NESP; (c)
blue line: calcined eggshell.

Figure
(c)
(b)
(a)
Fig. 3. FTIR spectra of NESP (a), sonicated CaCO3 (b) and calcined eggshell (c).

Figure
a
a
b
c
Fig. 4. TEM and SEM images of NESP (a); ballmill treatment eggshell powder (b); sonicated
calcium carbonate for 3 h (c).

Figure
Ar
CN
CN
5
Fig. 5. Benzilidene malononitrile intermediate

Figure
100
80
60
40
20
0
Fig. 6. Recycling experiment of NESP

Scheme 1. Synthesis of 2-aminochromene derivatives catalyzed by nano eggshell powder
(NESP)

Highlights:
• Ultrasonic-assisted preparation of nano eggshell powder (NESP) has been developed
• Eggshell Characterization with XRD, XRF, IR spectra, BET, TGA, TEM and
FESEM.
• Green and rapid synthesis of 2-aminochromenes in the presence of nanosized eggshell
• High catalytic activity and reusability of nano catalyst even after five cycles
• Catalytic activity comparison of pure CaCO3 and NESP as heterogeneous catalyst

NH2
OH
CN
O
X
CHO
CN
CN
+
X
CN
O
X
NH2
OH
Nano eggshell powder
Graphical Abstract