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Transesterification of Castor Oil for Biodiesel Production Using
H
2
SO
4
Wet Impregnated Snail, Egg and Crab Shell Catalyst.
*Nwanekwu Akunna Maureen, *Okoye Patrice-Anthony Chudi, Vincent Ishmael Egbulefu Ajiwe,
Omuku Patrick Enuneku, Onyeije Ugomma Chibuzor.
Department of Pure and Industrial Chemistry, Nnamdi Azikiwe University, Awka, Nigeria.
*Corresponding Author
DOI : https://doi.org/10.51583/IJLTEMAS.2024.130520
Received: 19 May 2024; Accepted: 28 May 2024; Published: 21 June 2024
Abstract: Biodiesel does not only provide a sustainable alternative for diesel fuel but also enables the transformation and utilization
of wastes into high value products. Therefore, the aim of this study is to use heterogeneous catalysts derived from wet-impregnated
snail, crab and egg shell waste in the production of biodiesel using castor oil. The use of castor oil as the preferred non-edible oil is
due its high ricinoleic acid concentration as well as its high solubility in alcohol. The uncalcined egg, snail and crab shell catalysts
were identified as E, S and C respectively while CS
800
o
C
/H
2
SO
4
, CC
900
o
C
/H
2
SO
4
, and CE
900
o
C
/H
2
SO
4
represents
calcined/impregnated
snail, crab and egg shell catalysts respectively. The BET and SEM were used to determine the surface morphology and
microstructure of the catalysts while the structure of the crystalline materials and the elemental composition of the catalysts were
determined using the XRD and XRF respectively. GC-MS was used to analyze the free fatty acid composition of the oil and FTIR to
obtain the organic and polymeric materials present. The physical and chemical analysis of the crude castor oil was carried out so as
to determine the percentage of FFA contained in the oil. Each of the calcined/impregnated snail, crab and egg shells were reacted
singly with castor oil in the biodiesel production where CS, CC and CE are acronyms that stands for castor oil-snail shell, castor oil-
crab shell and castor oil-egg shell biodiesel products respectively. All three castor oil biodiesel products were produced at various
specifications or reaction conditions lettered from A – I usually written as a subscript after the biodiesel product and as a result, 27
samples of biodiesel was produced. The optimal conditions required for the production of the biodiesel were obtained and the fuel
properties of all 27 samples of biodiesel produced were determined. The crude castor oil gave acid value and FFA of 5.87mgKOH/g
and 3.25 respectively which were above the ASTM standards at 0.4 – 4 mgKOH/g and 0.2 – 2 respectively. The highest surface area
was produced from calcined/impregnated crab shell at 170.21 m
2
/g. The result from the FTIR analysis showed the presence of O – C
– O and O – H bonds in the uncalcined spectra and a strong S ═ O bond after calcination/impregnation. Castor oil-egg shell biodiesel
product obtained with H-specification (CE
H
) produced the highest biodiesel yield of 95.3 %. This was obtained at optimal conditions
of 1:12 oil to methanol ratio, 5 wt% catalyst loading, 60
O
C reaction temperature for 60 min reaction time. Results from the
characterization of biodiesel products obtained showed 70, 9.80 mm
2
/s and 945 kg/m
3
as maximum values of cetane number,
kinematic viscosity and density traced from castor oil-egg shell biodiesel product obtained with H-specification (CE
H
), castor oil-
snail shell biodiesel product obtained with A-specification (CS
A
) and castor oil-egg shell biodiesel products obtained with A-
specification (CE
A
) respectively.
Keywords: Transesterification, Heterogeneous, Catalysts, Wet-Impregnation
I. Introduction
With lots of developing countries depending directly or indirectly on energy being the principal propeller of a booming economy and
social advancement, hike in the cost of fossil fuel and certain environmental adverse effect such as the increase in the average
temperature of the earth, emission of detrimental air stressors and greenhouse gases among others will continuously result in the
threats the 21
st
century is being confronted with. This can be attributed to the endless rise in global population and world energy
demand. However, this source is insubstantial and will be used up in subsequent time [1].
Studies has relayed that among the green energy technologies listed above, bio-energy has proven to be more reliable as energy
produced from plants can be captured and stored thereby providing a more cost effective economic approach and no detrimental
threat to humans and the environment [2]. Irrespective of the jeopardy created by the use of fossil fuel for energy generation, the use
of biodiesel as a surrogate for fossil fuel replacement till date still remains almost impossible. [3,4]. It is with the above listed
setbacks that this waste to energy investigation process is relayed on as the possibility and the effectiveness of utilizing waste derived
solid catalyst in the presence of non-edible feedstock’s in the production of biodiesel is determined.
Homogeneous catalysts are effective but the set-backs associated with them such as; high energy consumption, wastewater treatment
due to unreacted chemicals among others has qualified the use of heterogeneous catalyst especially the CaO –base catalyst [5].
However, in some catalysts, particularly CaO, leaching takes place that adversely influences the reaction [6,7]. Therefore, charging a
heterogeneous base catalyst by wet impregnation can help to design and modify the catalyst’s surface to meet the requirements of
specific applications and solve the issues associated with the use of homogeneous as well as heterogeneous catalyst [8]. This can be
achieved to build a CaO catalyst with both acidic and basic reactive sites with zero limitations as there is total involvement of both
internal and external surface active species in the reaction [9]. The use of edible vegetable oil results in competition between the
food and fuel oil market and as such, triggers a hike in the cost of purchase of vegetable oil and biodiesel. With zero competition,
easy accessibility and unique adaptive features, castor oil has been found worthy, attractive and attainable by researchers and energy
enthusiasts to be used as a surrogate in place of edible oil [10]. Therefore the aim of this study is to carry out transesterification of
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castor oil using H
2
SO
4
wet-impregnated crab, egg and snail shell. Optimization was carried out to determine the best reaction
conditions that supports the production of a high biodiesel yield.
II. Materials and Methods
2.1. Materials
Separating funnel, reflux condenser, muffle furnace, desiccators, water bath, soxhlet extractor, centrifuge, retort stand, conical flasks,
beakers, pipette & burette, magnetic stirrer heating mantle, thermocouple, 500 mL round bottom 3 neck glass reactor. Scanning
electron microscope (SEM), x-ray diffraction (XRD), fourier transform infrared radiation (FTIR), x-ray fluorescence spectroscopy
(XRF), gas chromatography-mass spectroscopy (GC-MS), Brunauer-Emmett-Teller (BET).
2.2. Reagents
All reagents used in this study were all of analytical grade; ethyl alcohol, chloroform, potassium iodide solution, hanus solution,
isopropyl alcohol, n- hexane, methanol, tetraoxosulphate (VI) acid, potassium hydroxide, phenolphthalein indicator, hydrochloric
acid,
2.3 Methods
2.3.1 Sample Collection
The castor seeds were brought in bags from a major castor seed dealer. The egg shell was collected from a campus restaurant in
Yabatech, Lagos State. While the crab shells were collected at bariga market, Lagos State. The snail shells were collected from a
dumpsite at the popular mile one market.
2.3.2 Sample Pretreatment
2.3.2.1 Catalyst pretreatment
The catalysts were pretreated by means of calcination, impregnation and recalcination. Firstly, the shells were brought in and washed
thoroughly with warm water to remove impurities and organic matter present in them. To ensure they are completely dried, they
were placed in an oven at 105
O
C for 24 hr. With the aim of increasing the surface area, the shells were blended separately and sieved
in a 60 mesh size sieve to properly separate the crystals from the fine particles. The egg and crab shells were calcined at 900
O
C for 2
hr while the snail shell was calcined at 800
O
C for 4 hr. For the impregnation process, 500 ml H
2
SO
4
was added
in drops to 100 g of
each of the calcined catalysts with simultaneous stirring, the mixture was stirred with magnetic stirrer for 6 hr and placed in an oven
to dry at 105
O
C for 24 hr. Lastly, the egg and crab shells were recalcined at 900
O
C for another 2 hr and the snail shell at 800
O
C for
2 hr.
2.3.2.2 Catalyst Identification
The pattern of identifying the catalyst after pretreatment is shown in table 2.1 below;
Table 2.1: Identification of Catalysts after Pretreatment
Catalysts
Uncalcined
Catalysts
Calcined
Catalysts
Calcined/Impregnated
Catalysts
Snail Shell
S
CS
800
o
C
CS
800
o
C
/H
2
SO
4
Crab Shell
C
CC
900
o
C
CC
900
o
C
/H
2
SO
4
Egg Shell
E
CE
900
o
C
CE
900
o
C
/H
2
SO
4
2.3.2.2 Oil Pretreatment
The castor seeds were washed thoroughly with distilled water and sundried for 48 hr. With the aim of deshelling, they were cracked
to remove the shells from the seeds. The white seeds were placed in an oven at 90
O
C for 45 minutes and on cooling, they were
crushed and placed in a thimble for soxhlet extraction of the oil from the seeds.
2.3.3 Sample Characterization
Both the uncalcined and the calcined/impregnated crab, snail and egg shell catalysts were characterized using various analytical
instruments such as; BET, XRF, SEM, FTIR and XRD while the castor oil was subjected to physiochemical analysis and also
characterized using GC-MS to quantitatively determine the free fatty acid present in them.
2.3.4 Esterification and Transesterification Processes
A feedstock shown to have a high FFA is first subjected to acid esterification were it is being catalyzed by an acid. About 0.14 ml of
H
2
SO
4
is added into a conical flask containing 55 ml of methanol. The mixture is heated in a water bath to attain a temperature of 60
O
C. On the other hand, 100 g of the crude feedstock is also weighed accurately into the glass reactor and heated to attain same
temperature. Upon attaining that temperature, the content of the conical flask is emptied into the glass reactor and heated at 60
O
C
with stirring at a speed of 800 rpm for 1 hr. On cooling, it is placed in a separatory funnel and the esterified oil recovered. For the
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transesterification process, a known weight percent of the catalyst is weighed accurately into a known volume of methanol and
heated to attain a temperature of 55
O
C while on the other hand, 100 g of the esterified oil is also weighed into the glass reactor and
heated to attain same temperature. The content of the conical flask is again emptied into the glass reacted and heated for 1 hr at a 300
rpm stirring speed. The biodiesel produced is separated from the layer of catalyst, glycerol and methanol in a separatory funnel,
centrifuged and wet washed with warm water. Its percentage yield is determined by;
% Biodiesel Yield = (Weight of biodiesel/Weight of esterified oil) × 100
The biodiesel produced was characterized according to the various methods proposed by the ASTM standards.
III. Result and Discussion
Table 3.1. Physiochemical Evaluation of Castor oil
Properties
Units
ASTM Value
Moisture content
%
0.05
Acid value
mgKOH/g
0.4 – 4
Saponification value
mgKOH/g
175 – 187
Iodine value
mgI
2
/100g
82 – 88
Free fatty acid
-
0.2 – 2
Density
g/ml
-
Viscosity at 40
O
C
mm
2
/sec
0.957 – 0.968
As seen from table 3.1 above, all values obtained were higher than that of the ASTM standard value with exception to iodine value.
The high acid value as well as moisture content can be attributed to poor seed handling from processing to harvesting. While the
presence of OH and double bond in the ricinoleic structure of the castor oil can initiate both oxidation and hydrolysis thereby
increasing the FFA content of the oil. This is answerable to the compulsory subjection of the crude castor oil to esterification before
the main transesterification process.
3.1 Characterization of the Uncalcined and Calcined/Impregnated Snail, Crab and Egg Shell
The results obtained from the BET analysis to determine the surface area, pore volume as well as the pore diameter of the catalysts
are analyzed in table 3.2 below;
Table 3.2. BET Analysis of Catalyst Samples
Catalysts
Surface Area
(m
2
/g)
Pore Volume
(cm
3
/g)
Pore Size
(Å)
Uncalcined snail shell
3.80
0.0062
2.015
Calcined snail shell/H
2
SO
4
(CS
800
o
C
/H
2
SO
4
)
2.60
3.461
2.513
Uncalcined egg shell
3.260
2.580
2.105
Calcined egg shell/H
2
SO
4
(CS
800
o
C
/H
2
SO
4
)
3.925
5.50
2.621
Uncalcined crab shell
9.78
0.03
2.46
Calcined crab shell/H
2
SO
4
(CS
800
o
C
/H
2
SO
4
)
170.21
2.08
5.84
From the BET result obtained, it can be deduced that all calcined/impregnated catalyst samples produced higher values for surface
areas, pore volumes and pore sizes as compared to their uncalcined counterparts but with exception to calcined/impregnated snail
shell with a surface area of 2.60 m
2
/g lower than that of its uncalcined state. This can be attributed to the filling of the CaO pores
with CaSO
4
owing to the long calcination temperature applied.
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3.1.1. SEM Analysis of Uncalcined and Calcined/impregnated Samples
A = Uncalcined B= Calcined/impregnated
Figure 3.1: SEM Image of Uncalcined and Calcined/ Impregnated Crab Shell
The SEM image of the uncalcined and calcined/impregnated crab shell revealed that for the calcined and impregnated shell, there is a
distortion in the surface of the catalyst owing to the evaporation of the volatile phases from the surface of the catalysts. However, this
distortion led to an increase in its porosity, micropores and mesopores. Whereas in the case of the uncalcined crab shell, there is an
uneven arrangement of spherical structural particles with varying sizes and shapes.
A = Uncalcined B= Calcined/impregnated
Figure 3.2: SEM Image of Uncalcined and Calcined/ Impregnated Snail Shell
As seen from figure 3.2 above, upon calcination and impregnation, there is a well-structured arrangement which showed increase in
the porosity of the shell. While among all uncalcined and impregnated samples analyzed, only the uncalcined snail shell catalysts
displayed a rod-like structural particle owing to the low values of surface area, pore volume and pore size it possesses as seen from
the BET analysis reported. However, same structural pattern was also affirmed by [11].
A = Uncalcined B= Calcined/impregnated
Figure 3.3: SEM Image of Uncalcined and Calcined/ Impregnated Egg Shell
The result obtained above shows that the uncalcined egg shell showed an uneven distribution as well as an unstructured arrangement
of spherical-shaped particles of various sizes while that of the calcined and impregnated shell shows slight disorderliness in the
surface of the catalyst owing to the loss of H
2
O and CO
2
from the surface of the catalyst which builds up the concentration of CaO
after all the CaCO
3
has been successfully removed by means of thermal decomposition.
3.1.2. XRF Analysis of Uncalcined and Calcined/Impregnated Catalysts
The results of the XRF analysis of the uncalcined as well as calcined and impregnated crab, snail and egg shell is summarized and
discussed below;
A
B
A
B
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Table 3.3: XRF Results of Uncalcined and Calcined/Impregnated Snail Shell
Element
Atomic Conc.
Uncalcined Snail
Shell
Weight Conc.
Uncalcined
Snail Shell
Atomic Conc.
CS
900
O
C
/H
2
SO
4
Weight Conc.
CS
900
O
C
/
H
2
SO
4
Ca
90.70
89.52
89.38
88.57
Y
0.92
2.02
0.96
2.10
Ag
0.73
1.94
0.75
1.99
Nb
0.54
1.23
0.66
1.52
K
1.21
1.16
1.30
1.25
Cl
0.86
0.75
1.06
0.93
S
0.88
0.70
57.93
55.32
The XRF results displayed above delineates that calcium remained the most dominant element in all uncalcined and
calcined/impregnated catalyst samples. The result for uncalcined and calcined/impregnated snail shell sample as seen from table 3.3
above shows the very low concentration of sulphur obtained before calcination and its high concentration attained after
calcination/impregnation can be attributed to the charging of H
2
SO
4
into the catalyst after wet impregnation. While the high atomic
concentration of calcium in the uncalcined catalyst decreased after calcination and impregnation because the recalcination
temperature applied in the catalyst gradually decomposes all the volatile phases in the catalyst thereby building up the concentration
of calcium in the catalyst.
Table 3.4: XRF Result of Uncalcined and Calcined Egg Shell
Elements
Atomic Conc.
Uncalcined Egg Shell
Weight Conc.
Uncalcined Egg
Shell
Atomic Conc.
CE
900
o
C
/H
2
SO
4
Weight Conc.
CE
900
o
C
/H
2
SO
4
Ca
85.38
85.55
88.84
89.35
Y
1.03
2.29
0.88
1.94
Al
3.38
2.28
0.99
0.67
Ag
0.83
2.23
0.78
2.08
Ni
0.75
1.74
0.60
1.38
K
1.47
1.44
1.37
1.33
S
1.47
1.18
64.30
61.80
The XRF results displayed in table 3.4 above also depicts that calcium still remained the most dominant element in all uncalcined
and calcined/impregnated catalyst samples. The high atomic concentration of calcium obtained from their uncalcined state even
became higher after calcination and impregnation. This can be attributed to the high calcination temperature of 900
O
C which
initiated the evaporation of the volatile components from the surface of the CaCO
3
thereby leading to the increase in the
concentration of calcium in the catalyst. Whereas the concentration of sulphur moved from almost not been detected in the
uncalcined states to attaining a high atomic concentration after calcination and impregnation. This is answerable to the gradual fading
away of the CaCO
3
which led to the buildup of the sulphur in the catalyst.
Table 3.5: XRF Results of Uncalcined and Calcined/Impregnated Crab Shell
Elements
Atomic Conc.
Uncalcined Crab
Shell
Weight Conc.
Uncalcined Crab
Shell
Atomic Conc.
CC
900OC
/H
2
SO
4
Weight
Conc. CC
900OC
/H
2
SO
4
Ca
79.54
81.94
85.05
87.82
P
4.38
3.49
4.08
3.26
Y
0.70
1.93
0.74
1.68
Ni
2.20
0.38
0.29
0.69
C
40.33
21.30
26.50
24.54
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S
4.19
1.29
66.70
61.58
O
48.32
44.28
53.97
50.87
The XRF results for uncalcined and calcined/impregnated crab shell displayed in table 3.5 above shows that after
calcination/impregnation, elements such as calcium, sulphur and oxygen attained higher atomic concentration values of 85.05, 66.70
and 53.97 respectively while other elements such as yitrium, Niobium and phosphorus were seen to be present but at very low
concentrations.
3.1.3 XRD Analysis of Uncalcined and Calcined/Impregnated Catalysts
The results of the XRD analysis determined for both the uncalcined as well as calcined/impregnated crab, egg and snail shell
catalysts is summarized and discussed below;
Figure 3.4: XRD Pattern for Uncalcined and Calcined/Impregnated Crab Shell
The spectrum representation of the XRD result of uncalcined crab shell shows the presence of both aragonite and calcite crystalline
phases. Figure 3.4 above, clearly shows that the uncalcined crab shell catalyst produced trace amount of calcite but was largely
dominated by the aragonite crystal phase at a 2𝜃 range of 26.103
O
, 32.398
O
and 34.013
O
. For the impregnated and calcined crab
shell, a 2𝜃 range presented general diffraction peaks at 23.00
O
, 26.41
O
, 29.30
O
, 39.33
O
, 43.09
O
, 47.40
O
, 48.40
O
. The
crystallization of the calcite CaCO
3
in crab shell at the initial stage of calcination displays very strong diffraction peaks at 29.33
O
,
35.92
O
, 39.34
O
, 43.09
O
, 47.36
O
and 48.39
O
.
Figure 3.5: XRD Pattern for Uncalcined and Calcined/Impregnated Snail Shell
The result revealed that the crystalline nature of the uncalcined snail shell was that of the aragonite CaCO
3
phase which was the most
dominating phase produced. This was observed at the theta range of 23.36
o
, 34.22
o
37.19
o
, 38.16
o
and 44.22
o
. The spectrum
displayed by the calcined/impregnated snail shell catalyst showed very rough diffraction peaks. The qualitative result of the analysis
was determined using the phase data view which showed the various phases produced by the spectrum.
CS
800
o
C
/H
2
SO
4
Uncalcined Snail Shell
Uncalcined Crab Shell
CC
900
o
C
/H
2
SO
4
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Figure 3.6: XRD Pattern for Uncalcined and Calcined/Impregnated Egg Shell
For the calcined/impregnated egg shell, sharp and intense peak of 29.40 was revealed which connotes the presence of the trigonal
crystalline phase of the calcite. This further depicts the disappearance of calcite CaCO
3
and the emergence of CaO. While others
were reported at 31.43
O
, 35.98
O
, 39.42
O
, 57.42
O
. The x-ray diffraction patterns obtained for the calcined and uncalcined eggshell
particles shows diffraction peaks which suggested a crystalline phase of the main material calcium carbonate in the form of calcite
(CaCO
3
). The major intense peak was traced at a 2θ angle of 27.2° while 22.2°, 30.5°, 37.1°, 36.6°, 41.9°, 46.9°, and 47.7° were
minor peaks discovered.
3.1.4 FTIR Analysis of Uncalcined and Calcined/Impregnated Catalysts
The results of the FTIR analysis determined for both the uncalcined as well as calcined/impregnated crab, egg and snail shell
catalysts is summarized and discussed below;
(a) Calcined/impregnated snail shell (b) Uncalcined snail shell
Figure 3.7: FTIR Analysis for Uncalcined and Calcined/Impregnated Snail Shell
For the uncalcined snail shell, the sharp and intense infrared band was attained at 1750 cm
-1
which shows the presence of asymmetry
stretching vibration of the O–C–O bond thereby communicating the presence of CO
3
-2
present in the catalyst. For the snail shell
impregnated and calcined at 800
O
C (CS
800
o
C
/H
2
SO
4
), a major absorption band of 1304 cm
-1
was also spotted which also shows the
complete thermal decomposition of the CaSO
4
to CaO.
(a)
Uncalcined Egg Shell
CE
900
o
C
/H
2
SO
4
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(a) Calcined/impregnated crab shell (b) Uncalcined crab shell
Figure 3.8: FTIR Analysis for Uncalcined and Calcined/Impregnated Crab Shell
As seen in figure 3.8 above, the spectrum of the uncalcined crab shell shows the presence of a sharp peak detected at 1100 cm
-1
which indicates the stretching vibration of the Ca – O bond. This is answerable to the high atomic and weight concentrations of
calcium in the uncalcined crab shell as seen in the XRF result in table 3.5 above. On the other hand, the FTIR spectrum for crab shell
impregnated and calcined at 900
O
C (CC
900
o
C
/H
2
SO
4
) revealed an intense infrared band of 1036 cm
-1
which delineates the presence of
asymmetry stretching vibration of a strong S ═ O which signifies the successful thermal dissociation of the sulphite ion from the
CaSO4 to give calcium oxide which is the end product [12].
Figure 3.9: FTIR Analysis for Uncalcined and Calcined/Impregnated Egg Shell
The FTIR spectra analysis for uncalcined egg shell revealed the presence of a very wide stretching peak at 3553 cm
-1
band which
connotes the presence of weak stretching vibration of the O – H bond and affirms the presence of gaseous water from the CaCO
3
. On
the other hand, the major absorption band of the egg shell impregnated and calcined at 900
O
C (CE
900
o
C
/H
2
SO
4
) was detected at a
peak of 1394 cm
-1
which depicts the asymmetry stretching vibration of the O–C–O bond.
3.1.5 GC-MS Analysis of Castor Oil
Table 3.6: Percentage Concentration of Free Fatty Acid from Castor oil
Free Fatty Acid
Composition
Common Name
Molecular
Formula
Concentration (%)
9-Octadecenoic acid
Oleic acid
C
18
H
32
O
2
5.30
9,12-Octadecadienoic acid
Linoleic acid
C
18
H
31
O
2
6.10
Octadecanoic acid
Stearic acid
C
18
H
34
O
2
7.20
Hexadecanoic acid
Palmitic acid
C
16
H
32
O
2
8.90
12-Hydroxy,
9- Octadecenoic acid
Ricinoleic acid
C
18
H
33
O
3
72.50
(a)
355
3.1:
1
33
00
.8:
43
2
800.
7:90
11
223
0:76
.112
I850
.7:8
53
(b)
(a)
(b)
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It is observed from the table 3.6 above, ricinoleic acid emerged as the most dominant free fatty acid present at 72.50 % in the oil.
With such high percentage concentration, castor oil will continuously maintain its stance as the only prevailing vegetable oil whose
fatty acid is embedded with a hydroxyl group at position 12 of the fatty acid chain. Therefore it isn’t out of place to conclude that the
castor oil used in this research is a highly reactive one because the disappearance of the hydroxyl group paves way for the emergence
of the double bond which serves as a reactive channel through which the oil engages in several reactions. Higher ricinoleic value of
84.2 % has also been reported [13].
3.1.6 Characterization of the Biodiesel Produced from Castor Oil
CC
,
CS and CE = Castor oil crab, snail and egg shell biodiesel products. Subscripts A, C, D, E = various reaction specification as
seen from table 3.7 below.
Figure 3.10: Summary of some Characterization of Biodiesel Produced
Figure 3.10 above shows the summary of some fuel properties analyzed in the biodiesel produced. The result showcased some of the
biodiesel products with the highest FFA, kinematic viscosity at 40
O
C as well as acid value amongst other properties analyzed
obtained from castor oil. The highest FFA value of 0.90 mgKOH/g was produced from CE
C
biodiesel product while the highest
kinematic viscosity value of 9.80 mm
2
/s was spotted from CS
A
biodiesel product. Also a value of 0.91 was recorded as the highest
acid value traced from CE
C
product. All values were higher than the ASTM stipulated standard value while other values are said to
fall within the standard value.
3.2 Optimization of Process Parameter for Transesterification Reaction
The optimization process used in this study is governed by the Taguchi Orthogonal array design as seen from the table 3.7 below;
Table 3.7: Array Design of the Effect of Various Reaction Conditions on Castor Oil Egg, Snail and Crab Shell Biodiesel Yields
Reaction
Specif.
Oil to
Methanol
Ratio
Reaction
Temp
(
O
C)
Catalyst
Loading
(wt%)
Reaction
Time
(min)
Castor
Oil
Biodiesel
A
1:6
55
1
60
CS
A
B
1:6
60
3
90
CS
B
C
1:6
65
5
120
CS
C
D
1:9
55
1
120
CS
D
E
1:9
60
5
120
CS
E
F
1:9
65
3
60
CS
F
G
1:12
55
3
90
CS
G
H
1:12
60
5
60
CS
H
I
1:12
65
1
90
CS
I
0
2
4
6
8
10
12
FFA KINEMATIC
VISCOSITY
ACID VALUE
Summary of Some Characterization of
Biodiesel Products
CRAB SNAIL EGG
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Where A, B, C….I = various reaction specifications for the reaction conditions applied in batches for each of the biodiesel
production. CS
A
, CS
B
…..CS
I
= castor oil-snail shell biodiesel products produced using the various reaction specifications.
Table 3.7 above shows the array design governing the transesterification of biodiesel products from castor oil using
calcined/impregnated snail shell. This table will be replicated for biodiesel products from calcined/impregnated crab and egg shell
making a total of 27 samples of biodiesel produced in the study. The effect of reaction temperature, reaction time, catalyst loading
and oil to methanol ratio on the various yields of biodiesel were determined to aid in the optimization process.
3.2.1. Effect of Oil to Methanol Ratio on Biodiesel Yields
Table 3.8: Effect of Oil to Methanol Ratio on the Yields from Castor oil
Oil
Methano
l Ratio
Reaction
Time
(min)
Catalyst
Loading
(wt%)
Reaction
Temp.
(
O
C)
EggShell
Biodiesel
Product
Snail Shell
Biodiesel
Products
Crab Shell
Biodiesel
Products
1:6
60
1
55
CE
A
81.51
CS
A
75.33
CC
A
89.97
1:6
90
3
60
CE
B
83.10
CS
B
89.40
CC
B
90.53
1:6
120
5
65
CE
C
87.50
CS
C
87.10
CC
C
91.26
1:9
120
1
55
CE
D
84.76
CS
D
88.80
CC
D
92.64
1:9
120
5
60
CE
E
89.20
CS
E
84.00
CC
E
83.00
1:9
60
3
65
CE
F
88.00
CS
F
92.70
CC
F
92.77
1:12
90
3
55
CE
G
93.68
CS
G
- 93.50
CC
G
90.33
1:12
60
5
60
CE
H
95.30
CS
H
- 94.20
CC
H
90.11
1:12
90
1
65
CE
I
94.00
CS
I
- 86.00
CC
I
90.00
Figure 3.11: Effect of Oil to Methanol ratio on Castor oil --Egg, Snail and Crab shell Biodiesel Yields
From the result obtained in Figure 3.11 above, it can be deduced that the highest biodiesel yield of 95.30 % was obtained at a 1:12 oil
to methanol ratio as seen from castor oil egg shell biodiesel product CE
H
. The high yield of biodiesel produced can also be attributed
to the fact that each mole of biodiesel produced is accounted for every mole of methanol used up in the reaction [14]. While CC
B
emerged third with a biodiesel yield of 90.53 % and a 1:6 oil to methanol ratio.
CC
B
CC
F
CE
H
88
89
90
91
92
93
94
95
96
1:06 1:09 1:12
% FAME YIELD
Oil to Methanol Ratio
Series 1
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3.2.2. Effect of Catalyst Loading on Biodiesel Yields
Table 3.9: Effect of Catalyst Loading on the Yields from Castor oil
Catalyst
Loading
(wt%)
Reactio
n
Time
(min)
Oil to
Methanol
Ratio
Reactio
n
Temp.
(
O
C)
EggShell
Biodiesel
Products
Snail Shell
Biodiesel
Products
Crab Shell
Biodiesel
Products
1
60
1:6
55
CE
A
81.51
CS
A
75.33
CC
A
89.97
1
120
1:9
55
CE
D
84.76
CS
D
88.80
CC
D
92.64
1
90
1:12
65
CE
I
94.00
CS
I
86.00
CC
I
90.00
3
90
1:6
60
CE
B
83.10
CS
B
89.40
CC
B
90.53
3
60
1:9
65
CE
F
88.00
CS
F
92.70
CC
F
92.77
3
90
1:12
55
CE
G
93.68
CS
G
93.50
CC
G
90.33
5
60
1:12
60
CE
H
95.30
CS
H
94.20
CC
H
90.11
5
120
1:6
65
CE
C
87.50
CS
C
87.10
CC
C
91.26
5
120
1:9
60
CE
E
89.20
CS
E
94.20
CC
E
83.00
Figure 3.12: Effect of Catalyst Loading on Castor oil -Egg, Snail and Crab shell Biodiesel Yields
The result displayed on figure 3.12 above depicts that among all biodiesel products obtained, castor oil egg shell product CE
H
produced the highest yield at 95.30 % at a catalyst loading of 5 wt%. As seen from table 3.7 above, H specification is embodied with
a high concentration of the products which are oil and methanol at 1:12. Therefore it can be said that the high product ratio matches
the 5 wt% used. This is in agreement with the report communicated by [15] that when the weight of the catalyst greatly outweighs
that of the oil and methanol, it creates an imbalance thereby distorting the rate of effective collision. While a slightly low yield of
94.00 % was obtained from castor oil egg shell biodiesel product CE
I
at 1 wt% catalyst loading. Also the highest biodiesel yield at 5
wt% catalyst loading accompanied by a temperature of 60
O
C only depicts that a high catalyst loading and temperature increases the
enthalpy of the reaction which automatically increases the activation energy of the reaction [16].
3.2.3. Effect of Reaction Time on Biodiesel Yield
Table 3.10: Effect of Reaction Time on Yields from Castor oil
Reaction
Timw.
(min)
Reactio
n
Temp.
(
O
C)
Catalyst
Loading
(wt%)
Oil to
Methanol
Ratio
EggShell
Biodiesel
Products
Snail Shell
Biodiesel
Products
Crab Shell
Biodiesel
Products
CE
I
CE
G
CE
H
92.5
93
93.5
94
94.5
95
95.5
1 wt% 3 wt% 5 wt%
% FAME YIELD
Catalyst Loading (wt%)
Series 1
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60
55
1
1:6
CE
A –
81.51
CS
A
- 75.33
CC
A
– 89.97
60
60
5
1:12
CE
H –
95.30
CS
H
- 94.20
CC
H
– 90.11
60
65
3
1:9
CE
F –
88.00
CS
F
- 92.70
CC
F
– 92.77
90
55
3
1:12
CE
B-
83.10
CS
B
- 89.40
CC
B
– 90.53
90
60
3
1:6
CE
G –
93.68
CS
G
- 93.50
CC
G
- 90.33
90
65
1
1:12
CE
I-
94.00
CS
I
- 86.00
CC
I
– 90.00
120
65
5
1:9
CE
C-
87.50
CS
C
- 87.10
CC
C
- 91.26
120
55
1
1:9
CE
D-
84.76
CS
D
- 88.80
CC
D
– 92.64
120
60
5
1:6
CE
E –
89.20
CS
E
- 84.00
CC
E
– 83.00
Figure 3.13: Effect of Reaction Time on Castor oil- Egg, Snail and Crab shell Biodiesel Yields
Among all biodiesel samples produced, the highest yield of 95.30 % was obtained from CE
H
biodiesel product with a retention time
of 60 min as seen from figure 3.13 above. Meanwhile at 94.00 %, castor oil – egg shell biodiesel product CE
I
recorded a yield
slightly lower than that of CE
H
at a retention time of 90 min. Extending the retention time above 90 min would give room for loss of
methanol via evaporation thereby decreasing the yield of biodiesel as seen from castor oil crab shell biodiesel product CC
D
emerging
third with a 92.64 % biodiesel yield at a reaction time of 120 min. Furthermore, at 120 min reaction time, there is an increase in
production cost as much amount of energy will be lost in the process of conversion. [17].
3.2.4. Effect of Reaction Temperature on Biodiesel Yield
Table 3.11: Effect of Temperature on Yields from Castor Oil
Reaction
Temp.
(
O
C)
Reaction
Time
(min)
Catalyst
Loading
(wt%)
Oil to
Methanol
Ratio
EggShell
Biodiesel
Products
Snail Shell
Biodiesel
Products
Crab Shell
Biodiesel
Products
55
60
1
1:6
CE
A
81.51
CS
A
75.33
CC
A
89.97
55
90
3
1:9
CE
D
84.76
CS
D
88.80
CC
D
92.64
55
120
3
1:12
CE
G
93.68
CS
G
93.50
CC
G
90.33
60
120
1
1:6
CE
B
83.10
CS
B
89.40
CC
B
90.53
60
120
5
1:9
CE
E
89.20
CS
E
84.00
CC
E
83.00
60
60
5
1:12
CE
H
95.30
CS
H
94.20
CC
H
90.11
65
90
3
1:9
CE
F
88.00
CS
F
92.70
CC
F
90.33
65
60
5
1:6
CE
C
87.50
CS
C
87.10
CC
C
91.26
65
90
1
1:12
CE
I
94.00
CS
I
86.00
CC
I
90.00
CE
H
CE
I
WC
C
92.5
93
93.5
94
94.5
95
95.5
60 90 120
% FAME YIELD
Reaction Time (min)
Column1
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Figure 3.14: Effect of Reaction Temperature on Castor oil- Egg, Snail and Crab shell Biodiesel Yields
The highest biodiesel yield of 95.30 % was produced at a temperature of 60
O
C from CE
H
. It is said that the effectiveness of
temperature is highly dependent on the surface area provided as seen from calcined/impregnated egg shell in the BET analysis
displayed in table 3.2 above. Also at 60
O
C reaction temperature, the temperature was high enough to initiate a translational energy
within the molecules of the compound which is said to be equal or even higher than the activation energy. Castor oil egg shell
biodiesel product CE
I
produced a 94.00% biodiesel yield at a temperature of 65
O
C because a temperature above the boiling point of
methanol will decrease the yield of the biodiesel and vice versa [18].
IV. Conclusion
In this study, transesterification of castor oil using H
2
SO
4
wet-impregnated crab, egg and snail shell produced various biodiesel
yields as seen from figure 4.1 below;
Figure 4.1: Summary of Biodiesel Yields from Castor oil- Snail, Egg and Crab shell Biodiesel Products
From the result displayed above, biodiesel yields of 95.30, 94.20 and 92.77 % were produced from castor oil- egg, snail and crab
shell biodiesel products CE
H
, CS
H
and CC
H
respectively. The highest biodiesel yield of 95.30 % was produced from castor oil-egg
shell biodiesel product CE
H
at optimal conditions of 5 wt%, 1:12, 60
O
C and 60 min as seen from figure 4.1 above.
V. Recommendations
The common problem generally faced by the energy sector and the green energy enthusiasts has and will continue to be the existence
of high FFA feedstock’s which totally affects biodiesel from its production, utilization as well as its economic stance. Therefore, it is
highly recommended that a more dynamic approach be developed in the improvement of the genetic evolution of crop species so as
to obtain crops with better varieties and yield. Such crops must possess low FFA while enhancing a high biodiesel yield. Also to
discover an appropriate catalyst with high internal and external adsorption and reactivity, capable of annulling all limitations while
CE
G
CE
H
CE
I
92.5
93
93.5
94
94.5
95
95.5
55 60 65
% FAME YIELD
Temperature (OC)
Column1
94.2 CS
H
95.30 CE
H
92.77 CC
H
91.5
92
92.5
93
93.5
94
94.5
95
95.5
Castor
- Snail
Castor
- Egg
Castor
- Crab
% BIODIESEL YIELD
BIODIESEL PRODUCTS
Castor - Snail
Castor - Egg
Castor - Crab
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promoting high biodiesel yield. Lastly develop a technology for the containing of the CO
2
released after thermal decomposition so as
to promote resource recovery as well as greenhouse gas reduction.
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