Handbook of plant based biofuels - Chapter 20 (end) ppt

281
20
Biodiesel Production
from Rubber Seed Oil
Arumugam Sakunthalai Ramadhas, Simon Jayaraj,
and Chandrashekaran Muraleedharan
ABSTRACT
Rubber seed oil is a high free fatty acid content, nonedible vegetable oil. The acid
value of unrened rubber seed oil is about 34. Neither alkaline-catalyzed transes-
terication nor acid-catalysed esterication alone is suitable. A two-step esterica-
tion process, that is, acid esterication followed by alkaline transesterication was
developed to convert the unrened rubber seed oil to its methyl esters and glycerol.
The process parameters, such as quantity of catalyst and methanol used, reaction
temperature, and reaction duration, are analysed. The properties of methyl esters
of rubber seed oil are comparable to that of diesel. The performance and emission
characteristics of biodiesel-diesel blends provide evidence that methyl esters of rub-
ber seed oil are a suitable alternative fuel to diesel.
CONTENTS
Abstract 281
20.1 Introduction 282
20.2 Potential of Rubber Seed Oil as an Alternative Fuel 282
20.2.1 Transesterication 283
20.2.1.1 Acid Esterication 284
20.2.1.2 Alkaline Transesterication 285
20.3 Properties of Methyl Esters of Rubber Seed Oil 287
20.4 Engine Tests with Biodiesel 287
20.4.1 Brake Thermal Efciency 287
20.4.2 Specic Fuel Consumption 288
20.4.3 Carbon Monoxide Emission 288
20.4.4 Carbon Dioxide Emission 289
20.4.5 Smoke Density 289

20.4.6 Exhaust Gas Temperature 290
20.5 Conclusions 290
References 291
© 2009 by Taylor & Francis Group, LLC
282 Handbook of Plant-Based Biofuels
20.1 INTRODUCTION
Recent concerns over the environment, increasing fuel prices, and scarcity of supply
have promoted interest in the development of alternative sources to petroleum fuels.
The vegetable oils are a promising alternative fuel to diesel as their fuel properties
approximate those of diesel. The sources of the vegetable oils, seeds, grow renew-
ably in oil-yielding crops. Diesel fuel consists of saturated, nonbranched hydrocar-
bon molecules, with carbon ranging between 12 and 18, whereas the vegetable oil
molecules are of triglycerides, generally nonbranched chains of different lengths and
different degrees of saturation. Important properties such as energy density, cetane
number, heat of vaporization, and stoichiometric air-fuel ratio of vegetable oil are
comparable to those of diesel (Montague 1996). Currently biodiesel is produced
mainly from eld crop oils, such as rapeseed, sunower, and soybean oil (Zhang
1996; Zeiejerdki and Pratt 1986). The prices of the edible oils are several-fold higher
than nonedible oils. Nonedible oils also have potential for the production of biodie-
sel, including jatropha oil, karanji oil, rubber seed oil, etc. Biodiesel production from
the nonedible oils would reduce the overall biodiesel cost. This chapter describes
the biodiesel production method from unrened rubber seed oil, its physiochemical
properties, cost analysis, and evaluation of engine performance and emission char-
acteristics with biodiesel-diesel blends.
20.2 POTENTIAL OF RUBBER SEED OIL AS AN ALTERNATIVE FUEL
The rubber tree (Hevea brasiliensis) is indigenous to the Amazon in Brazil. It grows
quickly and is a fairly sturdy perennial tree of 25 to 30 m in height. The young plant
shows its characteristic growth pattern of alternating periods of rapid elongation and
consolidated development. The leaves are trifoliate with long stalks. The rubber tree
may live for a hundred years or even more. However, its economic life period on

plantations, is generally about 32 years, that is, seven years of immature phase and
25 years of productive phase. It owers during the months of February and March.
The fruits mature in the months between July and September, and have ellipsoidal
capsules with three carpels, each containing a seed. These open up during the sun-
shine and the seeds fall on the ground and are normally hand picked. The rubber
seeds resemble castor seeds but are slightly larger in size and each weighs 2 to 4 g.
The seeds, which fall on the ground, deteriorate very rapidly due to moisture and
infection. These lead to rapid increase in the free fatty acid (FFA) content of the oil.
Therefore, it is essential to collect the seeds as quickly as possible and dry them, so
as to reduce the moisture to a value less than 5% in order to arrest increase in the
FFA. The rubber seed oil is normally obtained by expelling of the seeds. Depending
on the pre-extraction history of the kernels, the color of the oil ranges from water
white to pale yellow for low FFA content (about 5%) to dark color for high FFA
content (about 10 to 40%). The fatty acid composition of rubber seed oil is given
in Table 20.1 (Aigbodion and Pillai 2000; Aigbodion et al. 2003). The molecular
formula of rubber seed oil is C
18
H
32
O
2
and its molecular weight is 278. The impor-
tant physiochemical properties of rubber seed oil and diesel are shown in Table 20.2
(Ramadhas, Jayaraj, and Muraleedharan 2005a). The specic gravity of rubber seed
© 2009 by Taylor & Francis Group, LLC
Biodiesel Production from Rubber Seed Oil 283
oil is higher than that of diesel; hence it has almost the same caloric value as diesel
on a volumetric basis. The ash point of rubber seed oil is much higher than that of
diesel and hence, from a storage point view, it is much safer than diesel. One of the
undesirable properties of the oil is its viscosity, which is several times higher than

that of the diesel. The caloric value of rubber seed oil is about 12% lower than that
of the diesel. However, the lower caloric value of oil is compensated for by the
enhanced lubrication.
20.2.1 tr a n S e S t e r i f i c at i o n
For alkaline transesterication, triglycerides should have lower acid value and all
reactants should be substantially anhydrous. The difculty with processing noned-
ible oils and fats is that these often contain large amounts of FFA that cannot be
converted to biodiesel using the alkaline catalysis method. The addition of excess
sodium hydroxide catalyst with oil can compensate the higher acidity but the result-
ing soap would increase its viscosity or formation of the gels that interfere with
TABLE 20.1
Fatty Acid Composition of Rubber Seed Oil
Fatty Acid Formula Structure Composition (%)
Palmitic c C16H32O2O
2
16:0:0 10.2.2
Stearic C18H36O2O
2
18:0:0 8.7.7
Oleic C18H34O2O
2
18:1:1 24.6.6
Linoleic C18H32O2O
2
18:2:2 39.6.6
Linolenic C18H30O2O
2
18:3:3 13.2.2
(Reprinted from Aigbodion, A. l., Pillai, C. K. S. [2000]. Preparation, analysis and applications of
rubber seed oil and its derivatives as surface coating material, Progress in Organic Coatings, 38,

187–192, Elsevier Publications, with permission.)
TABLE 20.2
Properties of Rubber Seed Oil in Comparison with Diesel
Property Test Method Rubber Seed Oil Diesel
Specic gravity ASTM D4052 0.91 0.835
Viscosity (mm2/s) at 40(C°) ASTM D445 66 4.5
Flash point (ºC) ASTM D93 198 48
Fire point (ºC) ASTM D93 210 55
Caloric value (MJ/kg) ASTM D240 37.5 42.5
Saponication value ASTM D94 206 -
Acid value ASTM D664 34.0 0.062
(Reprinted from Ramadhas, A. S., Jayaraj, S., Muraleedharan, C. [2005], Chacterization and effect of
using rubber seed oil as fuel in the compression ignition engines, International Journal of Renewable
Energy 30 (5), 795–803, Elsevier Publications, with permission.)
© 2009 by Taylor & Francis Group, LLC
284 Handbook of Plant-Based Biofuels
the forward reaction as well as with separation of the glycerol. The yield of the
transesterication process would decrease considerably with increase in FFA. The
acid value of unrened rubber seed oil is 34 mg KOH/g, that is 17% FFA content.
It is known that alkaline-catalyzed transesterication does not occur if FFA content
in the oil is more than 3% (Canakci and Van Gerpen 2001, 1999). Nevertheless,
the rening process reduces the acid value of the oils but it increases the overall
biodiesel production cost. The acid esterication process can be used to produce
biodiesel from oils having FFA content higher than 3%. But this reaction is much
slower than that of alkaline transesterication. A two-step esterication process is
developed to produce biodiesel from unrened rubber seed oil. The rst step, acid
esterication, converts FFA to esters and reduces the acid value of the oil to about 4.
The second step is the alkaline-catalyzed transesterication process.
20.2.1.1 Acid Esterification
A measured quantity of the rubber seed oil is stirred and heated in the reactor to

about 60˚C. The calculated quantity of the methanol is mixed with the preheated
rubber seed oil and the mixture is stirred vigorously for a few minutes and allowed
to run at medium speed. Then a precise quantity of the concentrated sulfuric acid is
added in the mixture. The heating and stirring are continued for 20 min and then the
products are poured into the separating funnel. The excess alcohol with the sulfuric
acid and impurities, if any, move to the upper layer and the lower layer is separated
for the second step.
20.2.1.1.1 Effect of the Amount of Acid Catalyst
The quantity of the acid catalyst used in the process is an important parameter that
affects the yield and quality of the biodiesel. The methanol is used in excess with
varying amounts of concentrated sulfuric acid (0.25 to 2%). It was found that 0.5%
concentrated sulfuric acid (v/v) gave the maximum yield (Figure 20.1). An excess
amount of sulfuric acid does not increase the yield but darkens the color of the prod-
uct and adds to the cost. However, an insufcient amount of the sulfuric acid lowers
the yield.
20.2.1.1.2
Effect of the Amount of Methanol
The quantity of the methanol used is an important factor that affects the yield of the
process and the production cost of the biodiesel. The molar ratio is dened as the
ratio of number of moles of alcohol to number of moles of triglycerides. Theoreti-
cally, 3 mol of alcohol is required for the conversion of 1 mol of triglyceride to 3
mol of the ester and 1 mol of the glycerol. However, in practice, an excess methanol
is required to drive the reaction towards completion. Experiments carried out with
the optimal catalyst quantity (0.5% v/v) revealed the maximum yield with 20 ml of
methanol for 100 ml of the rubber seed oil (Figure 20.2). With further increase in
the amount of methanol, there was only little improvement in the yield. However,
reduction in viscosity of the mixture was observed with increase in the quantity of
methanol. Excess methanol in the biodiesel would reduce the ash point of the fuel.
© 2009 by Taylor & Francis Group, LLC
Biodiesel Production from Rubber Seed Oil 285

20.2.1.1.3 Effect of Reaction Temperature
The reaction temperature strongly inuences the reaction rate and the yield of the
process. The yield of biodiesel from the rubber seed oil was very low (about 10%)
when the reaction was carried out at room temperature. The optimum temperature
was in the range of 45 ± 5°C. The boiling point of the methanol is 60°C and hence
higher temperature results in loss of the methanol and darkens the color of the prod-
uct. Furthermore, higher reaction temperature consumes more energy and thus
increases the overall production cost of the biodiesel.
20.2.1.2 Alkaline Transesterification
The product of the rst step, that is, the oil-ester mixture (the lower layer in the
separating funnel) was heated to the reaction temperature. The catalyst (anhydrous
sodium hydroxide pellet) was dissolved in the methanol and added to the preheated
mixture. Heating and stirring were continued for 30 min at the required tempera-
ture. The reaction produced two liquid phases: ester in the upper layer and crude
glycerol in the lower layer. The phase separation was observed within 10 to 15 min
after stirring was stopped but the complete separation required a longer time (2 to
10 h). The catalyst-glycerol mixture, settled at the bottom, was drained for further
processing. The ester layer was washed with water (about 25% volume of the oil) by
0
0.4 0.5 11.5 2
20
40
60
80
100
120
Sulphuric Acid (% v/v)
Yield of Esters (%)
FIGURE 20.1 Effect of amount of acid catalyst on yield.
0

20
40
60
80
100
120
10 15 20 30 40
Methanol (% v/v)
Yield of Esters (%)
FIGURE 20.2 Effect of methanol quantity on yield of rst step.
© 2009 by Taylor & Francis Group, LLC
286 Handbook of Plant-Based Biofuels
gentle agitation several times until the washed water was clear, that is, the pH value
was neutral.
20.2.1.2.1 Effect of the Amount of Alkaline Catalyst
In order to study the effect of the amount of alkaline catalyst on the production of
biodiesel from rubber seed oil, sodium hydroxide pellets in the range of 0.3 to 1%
by weight (weight of NaOH/weight of oil) were dissolved in the excess methanol.
The yield of the process with respect to amount of catalyst is shown in Figure 20.3.
The maximum yield was achieved with the use of 0.5% NaOH. Excess amounts of
catalyst increased the viscosity of the mixture and led to the formation of soap. Also,
insufcient amounts of catalyst did not initiate the reaction.
20.2.1.2.2 Effect of the Amount of Methanol
Figure 20.4 shows the yield of biodiesel with respect to the quantity of methanol
used in the process. The maximum ester yield was obtained with 30% methanol
by volume. With further increase in the molar ratio or methanol quantity, the yield
remained almost the same. On settling of the mixture, excess methanol moved over
the ester layer.
0
20

40
60
80
100
0.3 0.4 0.45 0.5 0.55 0.60.7 0.8
Sodium Hydroxide (% w/w)
Yield of Esters (%)
FIGURE 20.3 Effect of alkaline catalyst on yield.
0
20
40
60
80
100
10 20 30 40 50
Methanol (% v/v)
Yield of Esters (%)
FIGURE 20.4 Effect of methanol amount on yield of second step.
© 2009 by Taylor & Francis Group, LLC
Biodiesel Production from Rubber Seed Oil 287
20.3 PROPERTIES OF METHYL ESTERS OF RUBBER SEED OIL
The physiochemical properties of the biodiesel in comparison with the ASTM biod-
iesel standards, ASTM D 6751, are given in Table 20.3. The properties of the methyl
esters are comparable to those of diesel and match the ASTM biodiesel standard. C,
H, and O compositions of the rubber seed oil methyl esters were 76.85%, 11.82%,
and 11.32%, respectively. The fuel analysis showed that the transesterication pro-
cess improved the fuel properties of the oil, particularly the viscosity and ash point.
The viscosity of the methyl esters of rubber seed oil was found to be closer to that of
diesel, and hence, no hardware modications are required for storage and handling
of biodiesel.

20.4 ENGINE TESTS WITH BIODIESEL
The engine tests were conducted with the blends of biodiesel and diesel as fuel at
the rated speed of 1500 rpm. Here, B20 represents a blend that contains 20% biod-
iesel and 80% diesel. The engine performance and emission characteristics obtained
using biodiesel-diesel blends as fuel are described below (Ramadhas, Jayaraj, and
Muraleedharan 2005b).
20.4.1 Br a K e tH e r m a l ef f i c i e n c y
Figure 20.5 shows the variation in the brake thermal efciency of the engine with
respect to its brake mean effective pressure (BMEP) operating with various blends
of biodiesel and diesel. Increase in brake thermal efciency of the engine with load
was observed due to reduction in heat loss and increase in power. The brake thermal
efciency of 28% was achieved with B10 as compared to 25% with diesel. The lower
percentage concentration of biodiesel in the blends improved the brake thermal ef-
ciency of the engine. The additional lubricity provided by the biodiesel that reduced
frictional power and the presence of the oxygen makes complete combustion. But, at
the higher blends, the brake thermal efciency of the engine decreased because of
its lower caloric value.
TABLE 20.3
Properties of Methyl Esters of Rubber Seed Oil in Comparison with Diesel
Property
Test
Procedure
Biodiesel
Standard ASTM
D6751-0202
Rubber Seed Oil
Methyl Ester Diesel
Specic gravity ASTM D4052 0.87–0.90 0.874 0.835
Caloric value (MJ/kg) ASTM D240 – 36.50 42.5
Viscosity (mm2/s) at 40°C ASTM D445 1.9-6.0 5.81 3.8

Flash point (°C) ASTM D93 >110 130 48
Cloud point (°C) ASTM D2500 -3–12 4 -1
Pour point (°C) ASTM D97 -15–10 -8 -16
© 2009 by Taylor & Francis Group, LLC
288 Handbook of Plant-Based Biofuels
20.4.2 SP e c i f i c fu e l co n S u m P t i o n
The variation of specic fuel consumption with respect to the BMEP for the dif-
ferent fuels tested is depicted in Figure 20.6. The specic fuel consumption of the
engine fueled with the lower concentration of biodiesel in the blend was lower than
that of diesel at all the loads. The specic fuel consumption of B50 to B100 was
found to be higher as compared to diesel because of their lower caloric values.
About 12% increase in fuel consumption with neat biodiesel was observed as com-
pared to neat diesel.
20.4.3 ca r B o n mo n o x i d e em i S S i o n
CO emission was found to be lower at lighter load conditions and increased with
load for all the fuels tested. CO emission increased as the air-fuel ratio became lower
than that of the stoichiometric air-fuel ratio (Figure 20.7). CO emission was found
to be negligibly small at the stoichiometric air-fuel ratio or on the lean side of the
stoichiometric. The diesel-fueled engine emitted more CO as compared to that of the
biodiesel blends under all the loading conditions.
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.55
0.6
0 100 200 300 400500 600700 800

Brake Mean Effective Pressure (kPa)
Specific Fuel Consumption
(kg/kWh)
Diesel B5
B10 B20
B100
FIGURE 20.6 Comparison of specic fuel consumption of the engine at various BMEP values.
0
5
10
15
20
25
30
35
0 100 200 300 400 500600 700800
Brake Mean Effective Pressure (kPa)
Brake ermal Efficiency (%)
Diesel
B5
B10
B20
B100
FIGURE 20.5 Comparison of brake thermal efciency of the engine at various brake mean
effective pressure (BMEP) values.
© 2009 by Taylor & Francis Group, LLC
Biodiesel Production from Rubber Seed Oil 289
20.4.4 ca r B o n di o x i d e em i S S i o n
CO
2

emission increased with the increase in the load, as expected. The lower per-
centage of biodiesel in the blends emit very low amounts of CO
2
in comparison with
that of the diesel (Figure 20.8). It was observed that neat biodiesel operation emit-
ted slightly higher amounts of the carbon dioxide as compared to that of the diesel
operation. This indicated the complete combustion of the fuel and hence higher com-
bustion chamber temperature.
20.4.5 Sm o K e de n S i t y
The variation of the smoke density for different fuels tested in the engine is depicted
in Figure 20.9. The smoke density of the biodiesel blends was found to be lower than
that of the diesel. These results support the better combustion of biodiesel blends as
compared to diesel.
0
2
4
6
8
10
12
14
Diesel B5 B10B20 B100
Fuel
Carbon Dioxide (%)
0 kPa
200 kPa
350 kPa
500 kPa
575 kPa 700 kPa
FIGURE 20.8 Comparison of CO

2
emission of the engine at various BMEP values.
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
Diesel B5 B10B20 B100
Fuel
Carbon Monoxide (%)
0 kPa
200 kPa
350 kPa
500 kPa
575 kPa 700 kPa
FIGURE 20.7 Comparison of CO emission of the engine at various BMEP values.
© 2009 by Taylor & Francis Group, LLC
290 Handbook of Plant-Based Biofuels
20.4.6 ex H a u S t Ga S te m P e r a t u r e
The variation of the exhaust gas temperature with respect to BMEP of the engine
for different fuels tested is shown in Figure 20.10. The exhaust gas temperature
increased with increase in the load for all the fuels tested. It was observed that with
increase in the concentration of biodiesel in the blend, the exhaust gas tempera-
ture increased marginally. The nitrogen oxides emission was directly related to the
engine combustion chamber temperatures, which in turn indicated the prevailing
exhaust gas temperature.

20.5 CONCLUSIONS
Low-cost, high-FFA feedstocks for the production of biodiesel were investigated.
High-FFA vegetable oils such as rubber seed oil could not be transesteried with the
alkaline-catalyzed transesterication process. A two-step transestercation process
was developed to convert the high-FFA vegetable oil to its methyl esters. The rst
step, acid-catalyzed esterication, followed by the second step, alkaline-catalyzed
transesterication, converts vegetable oils into mono-esters and glycerol. This two-
0
100
200
300
400
500
600
700
800
Diesel B5 B10B20 B100
Fuel
Exhaust Gas Temperature (°C)
0 kPa 200 kPa 350 kPa 500 kPa 575 kPa 700 kPa
FIGURE 20.10 Comparison of exhaust gas temperature of the engine at various BMEP values.
0
5
10
15
20
25
30
35
40

45
50
Diesel B5 B10B20 B100
Fuel
Smoke Density (%)
0 kPa
200 kPa
350 kPa 500 kPa
575 kPa 700 kPa
FIGURE 20.9 Comparison of smoke density of the engine at various BMEP values.
© 2009 by Taylor & Francis Group, LLC
Biodiesel Production from Rubber Seed Oil 291
step esterication method reduces the overall production cost of the biodiesel, as
it uses low-cost, unrened nonedible oils. The effects of alcohol to oil molar ratio,
catalyst amount, reaction temperature, and reaction duration were analyzed for each
step. The fuel properties of biodiesel are comparable to those of diesel. The per-
formance and emissions characteristics support the use of biodiesel-diesel blends
in engines. Use of nonedible oils for fuel purposes reduces fuel insecurity and air
pollution also.
REFERENCES
Aigbodion, A. I. and C. K. S. Pillai. 2000. Preparation, analysis and applications of rubber
seed oil and its derivatives as surface coating material. Progress in Organic Coatings
38: 187–192.
Aigbodion, A. I., F. E. Okieimen, E. O. Obazee, and I. O. Bakare. 2003. Utilization of
maleinized rubber seed oil and its alkyd resin as binders in water-borne coatings. Prog-
ress in Organic Coatings 46: 28–31.
Canakci, M. and J. Von Gerpen. 1999. Biodiesel production via acid catalysis. Transactions
of American Society of Agricultural Engineers 42 (5): 1203–1210.
Canakci, M. and J. Von Gerpen. 2001. Biodiesel production from oils and fats with high
free fatty acids. Transactions of American Society of Agricultural Engineers 44:

1429–1436.
Montague, X. 1996. Introduction of rapeseed methyl ester in diesel fuel – French National
program. 962065. Society of Automotive Engineers. Warrendale, PA: SAE Publication
Group.
Ramadhas, A. S., S. Jayaraj, and C. Muraleedharan. 2005a. Characterization and effect of
using rubber seed oil as fuel in the compression ignition engines. International Journal
of Renewable Energy 30 (5): 795–803.
Ramadhas, A. S., S. Jayaraj, and C. Muraleedharan. 2005b. Performance and emission evalu-
ation of a diesel engine fueled with methyl esters of rubber seed oil. International
Journal of Renewable Energy 30: 1789–1800.
Zeiejerdki, K. and K. Pratt. 1986. Comparative analysis of the long term performance of a
diesel engine on vegetable oil. 860301. Society of Automotive Engineers. Warrendale,
PA: SAE Publication Group.
Zhang, Y. 1996. Combustion analysis of esters of soyabean oil in a diesel engine. 960765.
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© 2009 by Taylor & Francis Group, LLC