SUPPLEMENTARY INFORMATION
Seed Oils from Non-conventional Sources in North-east India: Potential Feedstock for
Production of Biodiesel
Priyanka Baruaa, Kajal Duttaa, Sanjay Basumatarya, Dinesh C. Dekab and Dibakar C. Dekaa*
a
Department of Chemistry, Gauhati University, Guwahati 781014, Assam, India.
b
Department of Botany, Birjhora Mahavidyalaya, Bongaigaon 783380, Assam, India.
Abstract
A total of 9 oilseeds with more than 15 wt% oil have been investigated for evaluating
them as feedstock for biodiesel industries. Fatty acid profiles of all the 9 oil samples
have been determined by GC-MS analysis. The saponification numbers, gross heats of
combustion of the oils and those of corresponding fatty acid methyl esters (FAMEs) as
well as cetane indices of the FAMEs have been calculated empirically. Iodine values
have been determined experimentally. These values have been used for predicting the
quality of the corresponding biodiesels. If prepared from these oils biodiesels are likely
to meet the major specification of biodiesel standards of USA, Germany and European
Standard Organization. Seed oil, from Cucumis sativus is found rich in linoleic acid,
which is considered an essential fatty acid of biological significance.
Keywords: Oilseeds, biodiesel, saponification number, iodine value, cetane index,
north-east India
Experimental
Materials
The plant seeds were collected from the states of Assam and Manipur in the north-eastern part
of India at different time of the year depending on the flowering season of the species. Seeds
containing a hard shell were manually hulled to get the kernels which were sun-dried before
being crushed for solvent extraction. Solvents and chemicals used were of analytical grade and
used without further purification.
Oil extraction
Seed oils were extracted from the crushed kernels by stirring magnetically a mixture of the kernel
with light petrol (40-60 °C, 10 mL/g) at room temperature (30-32 °C). The solid residue was removed
by filtration and the solvent from the filtrate was evaporated under vacuum in a rotavapor to yield the
crude oil which was purified by column chromatography over silica gel (60-120 mesh) using a
mixture of light petrol (40-60 °C) and ethyl acetate (20:1) as the eluent. Statistical averages of yields
with deviation from triplicate experiments are shown in Table S1.
Transesterification of the purified oils
Transesterification of the seed oils was carried out at room temperature with methanol (MeOH). The
catalyst used for transesterification was prepared in the laboratory from the trunk of Musa balbisiana
plant (Deka & Talukdar, 2007; Deka & Basumatary, 2011). A mixture of oil, MeOH (10 mL/g of
purified oil) and catalyst (20 wt% of oil) was stirred magnetically in a round bottom flask at room
temperature (30-32 oC). Reaction was monitored by Thin Layer Chromatography (TLC). After
completion of the reaction, the product mixture was partitioned between water and petroleum ether (at
least twice) and the combined organic phase was washed with brine, dried over anhydrous Na2SO4
and the solvent removed under vacuum to yield the crude Fatty Acid Methyl Ester (FAME) mixture.
The product was purified by column chromatography over silica gel (60-120 mesh) using a mixture of
light petrol and ethyl acetate (25:1) as the eluent. Yields shown in Table S2 are arithmetic averages of
duplicate experiments. Deviation is less than one in all the cases, and not shown in the table.
GC-MS analysis
The fatty acid methyl esters were identified using Perkin-Elmer Clarus 600 GC-MS analyzer. The
column used was Elite 5 MS with dimension 30.0 m x 250 μm. The oven temperature was initially
held at 140 °C for 5 minutes, increased to 240 °C at 4 °C/min and finally held for 5 min at 240 °C.
The injector, transfer and source temperatures were 250 °C, 200 °C and 150 °C respectively. Helium
was used as the carrier gas. The mass spectrum was scanned from 20 to 400 Da. The FAMEs were
identified by comparison with NIST library mass spectrum database. Random check on data shown in
Table S3 was carried out by repeating GC-MS analysis. Results are reproducible. The percentage
composition of the FAMEs was determined based on the peak area of the individual component
relative to the total peak area of all the components present in the sample (Abdulkadir & Tsuchiya,
2008).
Determination of Iodine Value (IV)
Procedure for determination of iodine value of oils (Wijs method; AOAC Official Method 993.20)
The required amount of test sample was weighed into dry 500 mL iodine flask. 15 mL acetic acidcyclohexane solvent (1:1 v/v) was added to each test sample and swirled to ensure complete
dissolution. 25 mL of Wijs solution (8.25 g ICl dissolved in 500 mL acetic acid) was added to the
flask containing test sample and swirled to mix. The flask was stoppered and kept in a dark place for
1h after which it was removed from the dark, 20 mL of 15% KI solution was added and mixed. 150
mL water was added and the mixture was gradually titrated with 0.1 M standard Na2S2O3 solution
with constant and vigorous stirring until yellow color almost disappears. 1 to 2 mL starch solution was
added to the flask and titration is continued until blue colour just disappears (S ml of thiosulfate
solution). Blank titration was also done with the test sample (B mL of thiosulfate solution). The iodine
value was calculated as given in equation (1) below:
𝐼𝑉 (g I2/100g oil) =
(B-S)×M×12.69
wt. of oil or fat
(1)
where, M is the molarity of Na2S2O3 solution determined by standardizing sodium thiosulfate solution
with K2Cr2O7.
Calculation of Saponification Number (SN), Cetane Index (CI) and Gross Heat of Combustion
(HG)
Saponification number (SN) of the FAME mixture was calculated from Eq. (2) given by
Kalayasiri et al (1996):
𝑆𝑁 = ∑ (560×Ai)/MWi
(2)
where, Ai= percentage of the ith component in the mixture, MWi= molecular weight of the ith
component.
For calculating cetane indices (CI) of the FAMEs, the Eq.(3) given by Krisnangkura (1986) was used:
𝐶𝐼 = 46.3 +
5458
− 0.225IV
SN
(3)
Lastly, the gross heats of combustion of both the triglycerides as well as FAMEs have been calculated
using the Eqs. (4) and (5) respectively (Krishnangkura, 1991).
𝐻𝐺 𝑜𝑓 𝑡𝑟𝑖𝑔𝑙𝑦𝑐𝑒𝑟𝑖𝑑𝑒 =
1,896,000
− 0.61IV − 1600
SN
where, IV and SN are as calculated from equations (1) and (2) respectively.
(4)
𝐻𝐺 𝑜𝑓 𝑖𝑛𝑑𝑖𝑣𝑖𝑑𝑢𝑎𝑙 𝐹𝐴𝑀𝐸, 𝐻𝐺i =
where, SNi = (560/MWi)100,
618,000
− 0.081IVi − 430
SNi
(5)
IVi = (254 x Di/MWi)100, Di = number of double bonds in the ith
component and MWi = molecular weight of the ith component
𝐻𝐺 𝑜𝑓 𝑡ℎ𝑒 𝐹𝐴𝑀𝐸 𝑚𝑖𝑥𝑡𝑢𝑟𝑒 = ∑ (HGi×Ai)/100
where Ai is the percentage of the ith component in the mixture.
Table S1. Oil contents of plant seeds.
Entry
1
Scientific name of
the plant
Citrus maxima
Oil content (wt%,
before column)
50.50 ± 1.34
Oil content (wt%,
after column)
47.5
Loss after column
(wt%)
3.0
2
Jatropha curcas
45.80 ± 1.03
39.9
5.9
3
Cucurbita
44.90 ± 0.47
42.8
2.1
moschata
4
Anisomeles indica
45.27 ± 1.25
41.8
3.5
5
Luffa acutangula
34.5 0± 0.53
32.4
2.1
6
Cucumis sativus
30.20 ± 1.48
28.1
2.1
7
Parkia timoriana
22.52 ± 0.74
21.6
0.9
8
Meyna spinosa
22.30 ± 1.44
19.8
2.5
9
Abelmoschus
moschatus
17.90 ± 1.04
17.4
0.5
Table S2. Transesterification of seed oils with methanol.
Entry
a Reactions
b
1
Scientific name of the
plant
Citrus maxima
2
Reaction time (h)a
3.5
Yield of FAMEs
(wt%)b
96
Jatropha curcas
3
90
3
Cucurbita moschata
4
91
4
Anisomeles indica
2.5
94
5
Luffa acutangula
4
92
6
Cucumis sativus
4
90
7
Parkia timoriana
4.5
93
8
Meyna spinosa
3.5
95
9
Abelmoschus
moschatus
3.5
94
were carried out at ambient temperature of 30 to 35 oC.
Yield based on purified seed oil.
Table S3. Fatty acid composition of the FAME mixtures derived from the seed oils.
Entry
1
2
3
4
5
6
7
8
9
@
16:1
16:0
Composition of FAME (wt%)@
18:2 18:1 18:0 20:2 20:1
0.8
-
29.7
16.5
59.2
9.6
61.6
19.2
23.4
46.2
27.8
25.7
33.2
16.1
65.5
30.4
28.9
Seed oil
Citrus maxima
Jatropha curcas
Cucurbita moschata
Anisomeles indica
Luffa acutangula
Cucumis sativus
Parkia timoriana
Meyna spinosa
Abelmoschus
moschatus
39.6
43.8
15.6
70.5
14.2
15.2
24.7
35.5
37.4
4.9
5.6
25.2
3.7
24.1
13.6
16.3
4.1
-
-
20:0 22:0
3.0
1.9
-
4.8
-
Individual FAME is indicated by the ratio of the number of carbon atoms in the acid component to the number
of double bonds in the fatty acid chain.
Table S4. Calculated SN, CI, HG and observed IV values of the oils and FAME mixtures.
Entry
Seedoil
SN (mg
KOH/g oil)
194.8
IV (g I2 /100g
oil
91.8
HG (MJ/kg) of
Oil
Biodiesel
38.0
38.4
CI
(biodiesel)
56.7
1
Citrus maxima
2
Jatropha curcus
192.8
104.6
38.4
38.8
53.0
3
198.7
37.1
37.2
37.3
67.0
190.6
115.2
39.0
39.2
58.2
5
6
Cucurbita
moschata
Anisomeles
indica
Luffa acutangula
Cucumis sativus
199.7
193.4
35.6
108.7
37.1
38.2
37.6
38.6
70.6
46.1
7
8
Parkia timoriana
Meyna spinosa
191.6
197.0
80.56
59.0
38.8
37.6
39.2
37.9
58.2
67.2
9
Abelmoschus
moschatus
191.0
92.9
38.9
37.7
56.4
4
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