Jatropha curcas seed oil as a viable source for biodiesel

Pak. J. Bot., 42(1): 575-582, 2010.
JATROPHA CURCAS SEED OIL AS A VIABLE
SOURCE FOR BIODIESEL

UMER RASHID1,2, FAROOQ ANWAR1,*, AMER JAMIL1
AND HAQ NAWAZ BHATTI1

1Department of Chemistry and Biochemistry, University of Agriculture, Faisalabad-38040, Pakistan
2Department of Industrial Chemistry, Government College University, Faisalabad-38000, Pakistan

Abstract

The purpose of the present study was to explore the utility of Jatropha (Jatropha curcas) seed
oil for biodiesel production. The preliminarily evaluated Jatropha oil was transmethylated under
optimized set of reaction conditions: methanol/oil molar ratio (6:1), sodium methoxide catalyst
concentration (1.00%), temperature (65°C) and mixing intensity (600 rpm) providing 94.00% yield
of Jatropha oil methyl esters (JOMEs)/biodiesel. The gas chromatographic (GC) analysis showed
that JOMEs mainly comprised of six fatty acids: linoleic (49.75%), stearic (16.80%), oleic
(13.00%), palmitic (12.15%), arachidic (5.01%) and gadoleic (2.00%) acids. 1H-NMR spectrum of
JOMEs was also recorded. The thermal stability of the JOMEs produced was assessed by
thermogravimetric analysis (TGA). The fuel properties of the biodiesel produced were found to be
within the standards specifications of ASTM D 6751 and EN 14214.

Introduction

Currently, fossil fuels are the main resources of energy meeting the world
requirements. The fossil-based resources, such as gasoline, petro-diesel and natural gas
are limited and insufficient for the future world’s energy demands. In this connection
there is much concern for search of renewable fuels.
“Biodiesel” is well known chemically as the mono-alkyl esters of long-chain fatty
acids and is produced from several types of conventional and non-conventional vegetable
oils and animal fats including those of used oils from the frying industry, soybean oil,
rapeseed oil, tallow, rubber seed oil and palm oil (Tomasevic & Siler-Marinkovic, 2003;
Shah et al., 2004; Ramadhas et al., 2005; Ahmed et al., 2007). In the situation of rapidly
growing energy requirements, the contribution of new and especially some non-food oils
has to play a significant role (Chitra et al., 2005; Rashid et al., 2008; Chakrabarti &
Ahmad, 2008; Rashid et al., 2009; Harun & Ahmed, 2009).
Jatropha curcas (Linnaeus), belonging to Euphorbiaceae family and the genus
Jatropha is commonly known as Jamalghota (Soomro & Memon, 2007). Jatropha, a crop
native to North American region is now distributed in several regions (Africa, India,
South East Asia and China) across the World (Chitra et al., 2005).
It is reported that Jatropha seeds contain about 30 to 40% of oil (Kandpal & Madan,
1995). The presence of some anti-nutritional factors such as toxic phorbol esters and a
high content of stearic acid (ca 17%) render Jatropha oil unfit for edible purposes (Shah
et al., 2004). The most abundant fatty acid in Jatropha oil is linoleic (47.3%) followed by
stearic (17.0%), oleic (12.8%), palmitic (11.3%) and arachidic (4.7%) acids (Adebowale
& Adedire, 2006). Jatropha oil is looked up on as one of the most appropriate renewable
alternative sources of biodiesel in terms of availability and cost.
*Author for corresponding: E-mail. fqanwar@yahoo.com

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UMER RASHID ET AL.,
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Houfang et al., (2009) investigated a two-step process consisting of pre-esterification
and transesterification to produce biodiesel from crude Jatropha curcas L., oil. The yield
of biodiesel by transesterification was higher than 98% in 20 min using 1.3% KOH as
catalyst and a molar ratio of methanol to oil 6:1 at 64°C (Houfang et al., 2009). As a part
of our systematic investigations of exploring indigenous vegetable oil resources for
biodiesel production, efforts were made to evaluate the utility of Jatropha seed oil for
biodiesel production. Biodiesel was characterized by GLC and 1H-NMR. In addition the
thermal stability and fuel properties of Jatropha oil biodiesel were appraised.

Materials and Methods

Materials: The seeds of Jatropha curcas harvested at botanical garden at University of
Agriculture, Faisalabad (UAF) during 2007 were procured from Department of Botany,
UAF, Faisalabad, Pakistan. Methanol, n-hexane, sodium hydroxide, potassium
hydroxide, sodium methoxide, potassium methoxide and anhydrous sodium sulfate were
purchased from Merck (Darmstadt, Germany). All the chemicals used were analytical
reagent grade. Pure standards of fatty acid methyl esters were obtained from Sigma
Chemical Co. (St. Louis, MO).

Extraction of oil: The crushed seeds (500 g) of each batch of Jatropha were extracted
using a Soxhlet extractor on a water bath for 6 h with 0.8 L of n-hexane. After oil
extraction, the excess solvent was distilled off reduced vacuum using a rotary evaporator
(Eyela, N-N Series, Rikakikai Co. Ltd. Tokyo, Japan) at 45ºC.

Transesterification reaction: The transesterification was carried out in a lab scale
biodiesel reactor following the reaction conditions of our previous study (Rashid &
Anwar, 2008). Briefly, 100 g of Jatropha oil, specified amount of NaOCH3 were placed
in a 250 mL round bottom flask. Mixture was stirred (600 rpm) at a temperature of 65°C
for 120 min., for completion of transesterification reaction. Then the reaction mixture
was transferred to a separating funnel for separation of two phases. Of the two separated
phases; the upper phase consisted of methyl esters with small amounts of impurities such
as residual alcohol, glycerol and partial glycerides, while the lower was the glycerol. The
upper methyl esters layer collected was further purified by distilling residual methanol at
80°C (external bath temperature). Some traces of impurities such as remaining catalyst,
residual methanol and glycerol were removed by successive rinses with distilled water.
Residual water was then removed by drying esters with Na2SO4, followed by filtration
using Whatman filter paper No.42. The yield of methyl esters was calculated using the
following formula;
of

grams

produced

esters

methyl

of

Yield
(%

esters

methyl

) =
×100
of

grams
used

oil

in
reaction


Fatty acid profile by GC: The analysis of the JOMEs/biodiesel was accomplished using
a SHIMADZU gas chromatograph, model 17-A, fitted with a flame ionization detector
(FID) and a methyl-lignocerate-coated polar capillary column SP-2330 (30 m × 0.32 mm
× 0.25 μm; Supelco, Inc., Bellefonte, PA., USA.). The column temperature was
programmed from 180 to 220°C at a linear flow rate of 5°C/min. The initial and final
holds up time were 2 and 10 min, respectively, while the injector and detector were set at
230°C and 240°C, respectively. A sample volume of 1.0 μL was injected onto the column

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JATROPHA CURCAS SEED OIL AS A SOURCE FOR BIODIESEL
577
in split mode (split ratio 1:75). All the quantitative measurements were made by
Chromatography Station for Windows (CSW32) software (Data Apex Ltd. CZ-158 00
Prague 5, the Czech Republic). The fatty acid composition was reported as a relative
percentage of the total peak area.

1H-NMR verification of Jatropha oil methyl esters (JOMEs): 1H-NMR spectrum of
JOMEs was obtained using a Bruker (Billerica, MA) AV-500 spectrometer operating at
500 MHz with a 5-mm broadband inverse Z-gradient probe in CDCl3 (Cambridge Isotope
Laboratories, Andover, MA, USA) as solvent and reference.

Thermal stability of JOMEs: The thermogravimetric (TG) data of the JOMEs were
recorded using TGA apparatus (Gateway Airgas, St. Louis, MO). Dry nitrogen was
flushed over balance chamber at a flow of 40 ml/min, while dry air was used over sample
at flow of 60 ml/min. Using platinum pans, 10 µL of sample was taken. The thermo
balance temperature was equilibrated at 50°C, and then increased to 600°C at a ramp rate
of 10°C/min.

Fuel properties of JOMEs: The fuel properties of the biodiesel/JOMEs produced were
determined following ASTM and EU specifications (ASTM, 2003; EN 14214, 2003).
The determinations of density, kinematic viscosity, lubricity, flash point, cloud point,
pour point, sulfur content, copper strip corrosion, ash content, acid value, ester contents,
free and bound glycerol, mono, di and triglycerides were made in accordance with ASTM
D 5002, ASTM D 445, ASTM D 6079, ASTM D 93, ASTM D 2500, ASTM D 97,
ASTM D 4294, ASTM D 130, ASTM D 874, ASTM D 664, EN 14103 and ASTM D
6584, respectively. All the analysis was performed in triplicate and the data reported as
mean ± standard deviation.

Results and Discussion

Quality of produced biodiesel: Table 1 depicts the fatty acid composition (FAC) of
JOMEs (Fig. 1). Linoleic, stearic, oleic, palmitic, arachidic and eicosanoic acids were the
main component of JOMEs with contribution present at 49.75, 16.80, 13.00, 12.15, 5.01
and 2.00%, respectively. Small amount (0.58%) of minor fatty acid C22:0 was also
detected. The concentration of C18:2 of the investigated JOMEs/biodiesel were in close
agreement with that of cottonseed oil methyl esters (COME). The content of stearic acid
was quite high (16.80%). JOMEs has highest amount (35%) of saturated fatty acids
(SFA) as compared to other vegetable oils methyl esters (Rashid & Anwar 2008; Rashid
et al., 2009a; Rashid et al., 2009b).
1H-NMR spectrum of methyl esters in general should present a signal in δ 3.7 that is
characteristic of oxymethylic hydrogen referent to methylic esters and shouldn’t present
signals between δ 4.0-4.3 and δ 5.3, referent to hydrogen of CH2 and CH glycerol group
(Fig. 2). When compared 1H-NMR spectrum of Jatropha oil with 1H-NMR spectrum of
JOME sample, it can be verified that there is a singlet in δ 3.64 that is characteristic of
oxymethylic hydrogen, and this signal was attributed to esters (biodiesel), multiplet in δ
4.12-4.24 and δ 5.30-5.34 attributed to oxymethylic hydrogen that are characteristic of
triglycerides from Jatropha oil. From the NMR data it could be verified that Jatropha oil
conversion into biodiesel was quite complete.

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UMER RASHID ET AL.,
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Table 1. Fatty acid (FA) composition (g/100g of FA) of Jatropha
oil methyl esters/JOMEs.
FA JOMEs
C16:0
12.15 ± 0.24
C18:0
16.80 ± 0.60
C18:1
13.00 ± 0.26
C18:2
49.75 ± 0.87
C20:0
5.01 ± 0.10
C20:1
2.00 ± 0.04
C22:0
0.58 ± 0.01
SFA 34.54
MUFA 15.00
PUFA 49.75
Values are mean ± SD of triplicate determinations
SFA = Saturated fatty acids; MUFA = Mono unsaturated fatty acids; PUFA = Poly unsaturated fatty acids


Fig. 1. Gas chromatography (GC) chromatogram of Jatropha oil methyl esters (JOMEs).

Thermo-gravimetric analysis (TGA): It is widely known that for any kind of biodiesel,
the boiling point will be the effective average of the types and quantities of esters of fatty
acids present. The TGA analysis is quick and inexpensive technique and can be used to
esters boiling point determination and to monitoring transesterification reaction, when
one compares the parent oil TGA curve and esters TGA curve. Figure 3 shows the
temperatures properties and loss mass that were found to sample JOMEs.
TGA curves of biodiesel/JOMEs showed 3 steps, where the first weight loss started
to decrease at approximately 160°C, and this steps was attributed to a boiling point of
biodiesel, the second one started to decrease at 200ºC and it was attributed to boiling
point of the esters with unsatured bondings, and the third step started to decrease at
218ºC, and it may be due to some Jatropha oil that was not transesterified. TGA curve of
JOMEs were attributed to boiling points of biodiesels/methyl esters with unsatured
bondings, and did not show any step in 589ºC, confirmed that the transesterification
reaction was complete.

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JATROPHA CURCAS SEED OIL AS A SOURCE FOR BIODIESEL
579


Fig. 2. 1H-NMR spectrum of Jatropha oil methyl esters (JOMEs).



Fig. 3. TGA spectrum of Jatropha oil methyl esters (JOMEs).

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UMER RASHID ET AL.,
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Table 2. Fuel properties of Jatropha oil methyl esters (JOMEs) / biodiesel.
Property
JOMEs
ASTM D6751
EN 14214
Kinematic viscosity (mm2/s; 40 °C)
4.80 ± 0.17
1.9-6.0
3.5-5.0
Lubricity (HFRR; µm)
137 ± 1.3
-a)
-a)
Cloud point (°C)
10.0 ± 0.1
Report
-b)
Pour point (°C)
6.0 ± 0.2
-c)
-b)
Flash point (°C)
188 ± 3.0
93 min
120 min
Sulfur content (%)
0.011 ± 0.001
0.05 max
-
Ash content (%)
0.016 ± 0.001
0.02 max
0.02 max
Acid value (mg KOH/g)
0.40 ± 0.03
0.50 max
0.50 max
Copper strip corrosion (50 °C, 3 h)
1a
No. 3 max
No. 1 min
Density (15°C), kg.m-3
880 ± 14.2
-
860-900
Ester contents (%)
96.80 ± 2.53
-
96.5% min
Values are mean ± SD of triplicate determinations
a) Not specified. Maximum wear scar value of 460 and 520 µm are prescribed in petro diesel
standards EN 580 and ASTM D975
b) Not specified. EN 14214 uses time and location-dependent values for the cold filter plugging
point (CFPP) instead
c) Not specified

Fuel properties of Jatropha oil methyl esters (JOMEs): The properties of JOMEs are
summarized in Table 2 alongwith specifications from the biodiesel standards ASTM
D6751 and EN 14214.

Kinematic viscosity: Kinematic viscosity limits are present both in ASTM D6751 (1.9-
6.0 mm2/s @ 40°C) and EN 14214 (3.5-5.0 mm2/s @ 40°C), respectively for biodiesel
fuels. Viscosity is a key fuel property because it persuades the atomization of a fuel upon
injection into the diesel engine ignition chamber and ultimately, the formation of engine
deposits (Knothe & Steidley, 2005). The viscosity of transesterified oil i.e., biodiesel, in
the present study is lower than that of the parent oil. In the current study, JOMEs had
kinematic viscosity (4.8 mm2/s) that fell was within the scope of both the American and
EU biodiesel specification ranges.

Lubricity: Lubricity determination was performed at 60°C according to the standard
method ASTM D6079, with a HFRR lubricity tester obtained from PCS Instruments
(London, England). Biodiesel standards do not currently contain lubricity specifications.
Fuel with poor lubricity can cause failure of diesel engine parts that rely on lubrication by
the fuel (Knothe et al., 2005). As such, lubricity has been included in the European
petrodiesel standard EN 590 (CEN, 2004) and the American petro-diesel standard ASTM
D975. The maximum wear scars are 460 µm in the EN 590 standard and 520 µm in the
ASTM D975 standard. Three tests of JOMEs using the HFRR lubricity tester gave ball
wear scars of 137 µm. These values are below the maximum values prescribed in the
petro-diesel standards ASTM D 975 and EN 590, indicating that material would be
acceptable with regard to lubricity. JOMEs also shows good lubricity, which is in
accordance with the results on lubricity for biodiesel derived from other oils (Knothe &
Steidley, 2005).

Low-temperature properties: Biodiesel is less appropriate for use at low temperature
than petro-diesel. These are static tests that indicate first wax and non-flow temperatures
for the fuel. The cloud point (CP) and pour point (PP) observed for JOMEs (CP 10°C, PP

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JATROPHA CURCAS SEED OIL AS A SOURCE FOR BIODIESEL
581
6°C; Table 2), but, are not as high as observed for methyl tallowate (CP 17°C, PP 15°C)
(Foglia et al., 1997) but almost comparable to yellow grease methyl esters (CP 8°C, PP
6°C) (Wang et al., 2005). Rapeseed methyl esters have better cold flow properties (CP -
3°C, PP -9°C) (Rashid & Anwar, 2008), when compared to JOMEs.

Flash point: Flash point (FP) is an important factor to consider in the handling, storage,
and safety of fuels and flammable materials. In the current work, the flash point
determined for JOMEs (FP 188°C; Table 2), is within the prescribed limits in American
and European biodiesel standards but it is also higher than that of No.2 diesel fuel.

Sulfur and ash contents: The sulfur contents of the JOMEs were analyzed using
wavelength-dispersive X-ray fluorescence spectrometery by ASTM D 4294. The value
was 0.011%, as depicted in Table 2. The presence of sulfur contents in biodiesel may be
from vegetable oils, for example, from phospholipids present in all vegetable oils or
glucosinolates present in Jatropha based biodiesel (Knothe, 2006). Ash content reflects
the contents of inorganic contaminants, such as abrasive solids and catalyst residues, and
the concentration of soluble metal soaps contained in a fuel sample. In the present study,
the JOMEs had 0.016% of ash contents which were within the limits of ASTM standard.

Acid and copper strip corrosion values: The acid value was determined by using the
ASTM D 974. The acid value of the biodiesel synthesized was 0.40 mg KOH/g (Table 1).
The ASTM biodiesel standard D 6751 and European standard approved a maximum acid
value for biodiesel of 0.5 mg KOH/g which was accomplished by the produced JOMEs.
The copper strip corrosion test of the JOMEs was measured using a standard test
specified by ASTM D 130. The degree of tarnish on the corroded strip correlates to the
overall corrosiveness of the fuel sample. As depicted in Table 2, the value was No. 1 for
the JOMEs. The copper strip corrosion property of the investigated methyl esters was
found to be within the specifications of ASTM and EU methods.

Conclusion

The quality characteristics of biodiesel obtained in this work were in good agreement
with ASTM D 6751 and EN 1424 specifications. Therefore, we can conclude that JOMEs
is an acceptable and suitable substitute for diesel fuel. As the Jatropha crop has very good
potential to be grown in Pakistan therefore it is recommended that it should be cultivated
on large scale production to produce non-conventional oil that can be transmethylated
into an acceptable biodiesel.

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(Received for publication 7 March 2009)

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