Potassium Halides - Impregnated Eggshell as a Heterogeneous Nanocatalysts for Biodiesel Production

Journal of Environmental Treatment Techniques

2019, Volume 7, Issue 1, Pages: 103-108

J. Environ. Treat. Tech.

ISSN: 2309-1185

Journal web link: http://www.jett.dormaj.com

Potassium Halides - Impregnated Eggshell as a

Heterogeneous Nanocatalysts for Biodiesel

Production

Mansoor Anbia*, Sholeh Masoomi, Sotoudeh Sedaghat, Mohammad Sepehrian

Research Laboratory of Nanoporous Materials, Faculty of Chemistry, Iran University of Science and Technology, Tehran 16846-

13114, Iran

Received: 23/11/2018

Accepted: 08/01/2019

Published: 30/03/2019

Abstract

In this study, Potassium halides-doped Calcium Oxide (CaO) was synthesized as heterogeneous nanocatalysts for

transesterification of waste cooking oil. The chicken eggshell wastes were used as raw materials to synthesize calcium oxide. The

calcium carbonate (CaCO ), principal constituent in the eggshell, was changed to calcium oxide by calcining at 873 K for 4 h.

After that, the calcium oxide was impregnated with potassium iodide (KI) and potassium fluoride (KF) via wet impregnation

method. The textural properties of the solid oxide catalyst were characterized by base strength, field emission scanning electron

microscopy (FE-SEM), powder X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). The basic

strengths of the catalysts were determined applying Hammett indicator. The yield of nanocatalysts evaluated by using the

prepared catalysts in waste cooking oil transesterification with methanol for at 338 K 2 h. the catalytic activity depends on

several factors such as, base strength, Impregnation and calcination processes and impregnated Compound. The formed KCaF3

was the major active element for the catalytic activity in KF/CaO nanocatalyst, however, this activity was not observed in

KI/CaO nanocatalyst. For the reason of presenting of this component, the Ca2+ in KF/CaO acts as a stronger Lewis acid and

exhibits high catalytic activity. Biodiesel yield for KF/CaO catalyst and KI/CaO was 91.18 % and 87.69%, respectively.

Keywords: Heterogeneous nanocatalyst, Eggshell wastes, Basic nanocatalyst, Biodiesel Production

influential parameter in preparation of biodiesel. Catalysts

Introduction

can be either heterogeneous or homogeneous and basic or

acidic. The reaction is carried out by homogeneous base

catalysts faster than acidic catalysts. Homogeneous

catalysts which are commonly used include sodium

hydroxide and potassium hydroxide [3]. The homogeneous

catalyst has many drawbacks such as instrument

corrosiveness, difficulty in catalyst recovery, and health

dangers to the operators because of the generation of

enormous waste stream in washing steps [6].

In comparison, heterogeneous catalysts have the

advantage that separation and regeneration of the catalyst is

easy and inexpensive, making the production process more

economical, causing less environmental problems and the

product is pure [7-10]. Heterogeneous basic catalysts

contain alkaline earth metal oxides, like hydrotalcites,

magnesium oxide (MgO) and calcium oxide (CaO) [11,

Renewable energy expansion has been focused

universal, because of the limited reserve of fossil fuels and

increase in oil prices and the increasing emissions of

polluting [1]. Biodiesel is one of the most substituted

energy resources and is environmental friendly. Biodiesel

can be synthesized by different methods such as Trans-

esterification. In this method the material is converted to a

desired product at a reasonable rate, using a catalytic

process [2, 3]. Biodiesel, identified as the fatty acid methyl

esters, is made by Trans-esterification of renewable

biological resources such as for example vegetable oils

with an alcohol in the presence of the catalysts and in this

technique glycerol is really a useful byproduct [4, 5]. A

novel approach in this process is to use “green” method

based on heterogeneous catalyst. Nature of catalyst is an

12].

Corresponding Author: Mansoor Anbia, Research

Laboratory of Nanoporous Materials, Faculty of Chemistry,

Iran University of Science and Technology, Tehran 16846-

Recently the application of natural calcium resources

from waste materials for biodiesel production has been

considered as a novel trend [13]. By using eggshell wastes

as raw material to synthesize the desired catalysts, the

heterogeneous catalysts can be produced with low cost and

3114, Iran. Mobile: 0098 912 1104931; Tel: 0098 21

7240516; Fax: 0098 21 772491204; Email:

anbia@iust.ac.ir

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Journal of Environmental Treatment Techniques

2019, Volume 7, Issue 1, Pages: 103-108

eliminate the wastes [14]. The eggshells contain a network

of protein fibers, in communication with crystals of

comparable. The prepared CaO was powdered and

immersed in 15–20 mL potassium halides solution by the

mass ratio of 0.25 (mass proportion of potassium halides to

CaO) for 1 h. Finally, the samples were heated at 373 K for

7 h followed by 4 h calcination in muffle furnace at 873 K

[29].

magnesium carbonate (MgCO

CaCO ), calcium phosphate (Ca (PO

and water. CaCO , the key constituent of the eggshell

96%), can be an amorphous crystal that happens generally

), calcium carbonate

(

4 2

) ), organic materials

(

in the form of calcite [15, 16]. Using wastes draw great

interest because of the eggshell waste as a renewable, low

cost, Eco-material for synthesis of catalyst and eggs are

part of daily meal the majority of the countries [17-19]. The

catalytic activity of CaO can be enhanced with

modification of CaO surface with potassium halides to

create strong active basic sites [20-22].

2.3 Characterization

FT-IR spectra was recorded on Shimadzu

-1

spectrometer 8400 spectrometer in the 4000–400 cm

scanning range (KBr pellet technique). PXRD patterns

were attained by a JDX-8030 diffractometer using Cu-K

radiation operating at 30 kV and 20 mA over a wide angle

Although the solid phase catalytic techniques have

already been studied generally, the industrial applications

are restricted [23, 24]. Heterogeneous catalytic techniques

are often time consuming and mass transfer resistant [25].

New research indicates that nanocatalysts may solve above

problems, because they have numerous active sites and

high catalytic activities [26, 27].

The deposition of potassium halide nanoparticles

increases the surface area of the catalyst and basic strength.

Basic phases (like K O) are obtained from decomposition

of potassium halides at high temperatures, associated with

potassium halides which increase the activity of the catalyst

(2θ range of 5–80°) with a step size of 0.015° at a scanning

-1

speed of 0.6° min . The morphology and surface features

of the nanocatalysts and calcined eggshells were tested by a

scanning electron microscope (SEM Camscan- Mira 3-

XMU).

Hammett indicator were applied to determine the basic

strengths of the catalysts. The sample (100 mg) was shaken

with cyclohexane (5 mL), then three drops of a Hammett

indicator (0.1% w/w in benzene) was added to a suspended

sample during shaking vigorously. After equilibration,

indicators undergo the following color changes in the

presence of the basic samples: Benzidine (H_ = 22)

colorless to purple, 4-nitroaniline (H_ = 18.4) yellow to

orange, 2,4-dinitroaniline (H_ = 15) yellow to violet, and

Phenophtalein (H_ = 9.8) colorless to red.

[28].

herein, an eggshell has been utilized as a costless mean

to introduce a heterogeneous catalyst for biodiesel synthesis

of waste cooking oil. As mentioned earlier, potassium

halides-doped CaO catalysts were well synthesized by wet

impregnation method. The calcination and impregnation

with particle sizes of (30–40 nm) improved the activity of

catalyst surface. The high activity of KF/CaO revealed by

the transesterification at 338 K, 400 rpm, 12:1 methanol

ratio, owing to the formation of KCaF3 as a novel

crystalline phase, enhanced the activity and stability of

catalyst. This paper is a sample of comprehensive report for

management of municipal solid waste, which led to

produce green fuel.

2.4 Transesterification reaction

The laboratory scale transesterification of waste

cooking oil was carried out using a thermometer, magnetic

stirrer and 250-mL 3-necked flask equipped with a water

cooled condenser, in oil bath at a temperature of 338 K. At

first 7.0 ml methanol was added to 0.2 g catalyst and stirred

at 400 rpm. After a few minutes, 12.5 g heated refined oil

was added to flask, this reaction lasted for 2 h. All

experiments were performed under atmospheric pressure

and repeated several times. Eventually, centrifuge is

employed to separate the prepared catalyst.

. Material and Methods

.5 Methyl ester analysis

A gas chromatograph equipped with a mass selective

.1 Materials

Eggshells were obtained as wastes from university

detector (Agilent 7890/5975C VLMSD) was used to

analyze the biodiesel samples and HP-5 MS column was

applied to separate the FAMEs. FAMEs samples were

diluted (1:1000) in N-Heptan that contains an internal

standard (GLC 90, SUPELCO). The chromatographic

conditions included: detector: 523 K, injector: 513 K,

dormitory. To remove impurities and dust, the eggshell was

washed with water. Finally, the eggshells were dried an

oven. Waste cooking oil was purchased from Pastry factory

in Tehran, Iran. Both potassium iodide and potassium

fluoride were analytical grade (Merck, Germany).

Methanol 99.5% and acetone 99.5% were purchased from

Merck company, too. All solutions were prepared by using

deionized water.

-1

column: 232-270 at 303 K min , 200-232 at 275 K min

-1

and 100-200 at 323 K min . The methyl ester band area

ratio to the internal standard band area was estimated for

each run [30].

2.2 preparation of Catalyst

In the CaO catalyst production, calcination method was

used. The dried eggshell waste (100 mesh) was calcined in

the atmosphere pressure at 1273 K for 4 h (heating rate

3 Results and Discussion

3.1 Characterization

C/min). Before usage, the resulting white powder was

The activities of catalysts were related to their basic

strength, i.e. the higher base strength of the catalyst can

lead to the higher biodiesel yields [28]. Impregnated

catalysts showed intense increase (87.69% and 91.18%) in

biodiesel yield. In contrast, oil percent conversion of CaO

preserved in the fastened vessel to prevent reacting with

moisture and carbon dioxide in air. Subsequently, the CaO

catalyst was impregnated with potassium halides. All

Catalysts were synthesized under the same conditions to be

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Journal of Environmental Treatment Techniques

2019, Volume 7, Issue 1, Pages: 103-108

catalyst is 20.62%. While the base strengths of catalysts are

nearly average and identical about 9.8 to 15. KF/CaO

revealed base strength less than 15.0 while it exhibited high

catalytic activity. Therefore, higher base strength is needed

for the catalytic transesterification reaction, but it's not

enough Thus, the catalytic activity depends on other factors

that there is no external mass transfer limitation for

impregnated catalysts.

Figure 2 has shown the XRD pattern of CaO, KF/CaO

and KI/CaO, in three catalysts which confirmed the

existence of crystalline phase of CaO. Catalyst is composed

of CaO (32.3º, 37.28º 53.9º, 64.2º, 67.34º) Ca(OH)2 (18º,

29º, 47.2º, 50.82º, 63º) [31]. As can be seen, diffraction

peaks of KF and KI in KF/CaO and KI/CaO, are

disappeared respectively, and a new diffraction peak is

detected which is attributed to KCaF3 (20º, 28.4º, 32.12º,

37.28º, 40.5º, 79.7º) and KF (34.1º, 71.8º). This phase was

created during the impregnation of the Potassium fluoride

in the supported lattice through capillary action and later

activation process [21]. The existence of other forms, such

[21].

Impregnation and calcination processes have allowed

the creation of nanostructures with an average pore size that

is recorded in Table 1. SEM analysis shows a layered

structure of the calcined shells with a same irregular shapes

Figure

1 (A), and two images of nanostructured

impregnated catalysts Figure 1 (B,c) . As can be ssen the

crystal morphologies of KF/CaO) Figure 1 (B) and KI/CaO

Figure 1 (C) are totally different.

2 3

as KO and KO in KF/CaO and KO3 in KI/CaO is owing

In addition, the enormous catalytic active site could

enhance the contact between oil and alcohol, leading to

improve catalytic efficiency. These results also indicated

that Potassium halide doped-CaO catalyst can inmprove

higher TONs compared to that of CaO catalyst, meaning

to the interaction between CaO and potassium halides.

XRD patterns of nanocatalysts indicated the existence of

calcium hydroxide, Ca(OH)2, which is completely

vanished at 873 K and converted to CaO.

Table 1: Basic strengths, particle size and catalytic performances of solid base catalysts

Catalyst

Tc (K)

Basic strength

Particle size (nm)

Conversion (%)

CaO

1000

600

H_< 15.0

28.72

29.96

20.62

91.18

KF/CaO

9.8 < H_< 15.0

KI/CaO

600

9.8 < H_< 15.0

42.97

87.69

Figure 1: SEM images of catalysts; CaO (A), KF/CaO (B), KI/CaO (C).

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2019, Volume 7, Issue 1, Pages: 103-108

However, this phase was generated by the reaction

between water and calcined shells during wet impregnation.

The crystallite sizes determined by XRD patterns of

catalysts were all in the range of 30-40 nm [31, 32].

Moreover, the occurrence of stretching vibrations of O\C\O

in carbonates was established by the broad band appeared

−1

at 1460 cm and two stretching band at 712 cm and 875

−

cm [30].

Figure 3 has depicted the FT-IR spectrums of prepared

−

catalysts over the range of 4000-400 cm . It can be seen

−

that the sharp band at 3645 cm is assigned to the OH

groups of Ca(OH) of each sample, which was primarily

3.2 Catalytic activity

−1

The catalytic activity of CaO loaded with two

potassium compounds in the waste cooking oil

transesterification was done. For the suitable comparison,

the same reaction conditions were applied for each

prepared catalyst in all experiments (Table 1). Formation of

Ca(OH)2, KO2 and KO3 enhanced Connecting locations

for alcohol molecules, therefore increases catalytic activity.

identified by the XRD results. Although this phase has an

ability to improve the catalytic activity but a high amount

of Ca(OH) could simply cause saponification in biodiesel

preparation [32, 33]. Also, Broad band in the range of

−1

100–3400 cm and band at 1640 cm are attributed to

physically-sorbed water stretching vibrations [30].

Figure 2: XRD patterns of catalysts, blue spectra for CaO, red spectra for KI/CaO and yellow spectra for KF/CaO

Figure 3: FT-IR spectra of catalysts.

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2019, Volume 7, Issue 1, Pages: 103-108

It can be suggested that the obtained active sites are

sufficient to react with triglyceride, leading to the

completion of the reaction. “F” element has higher

electronegativity than “I”, for this reason “F” tends to form

new structures with “Ca” and “K”, and the new structure is

KCaF3 as active site. Based on eley-rideal mechanism,

alcohol chemisorbed on to the single site of the catalyst

surface, so presence of “F” causes the Ca2+ in KCaF3 to be

a stronger Lewis acid that has stronger attraction for

CH3O- [20]. The catalytic activity depends on ability to

form methoxide ion. Also, F- is a stronger Lewis base with

stronger attraction to H+, which makes it better to attack

carbonyl group (C=O) and leads to further improve in rate

and efficiency of transesterification. Accordingly, the

KF/CaO with nanostructure and active KCaF3 has higher

catalytic activity than KI/CaO. Superior activity and

stability are because of active component and its structure.

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