Development of Process Technology to Produce Low Cost Biofuel I -

Minimization of Operating Parameters during Preparation of Biodiesel

Soumya Parida, Sunasira Misra, Debendra Kumar Sahu*

Dept. of Chemistry, C.V. Raman College of Engineering, Bidyanagar, Mahura, Janla, Bhubaneswar-
752054, India
* Corresponding author. Tel: 91-674 2460043, Fax: 91-674 2460093,Mobile: 91-9937141191, E-mail:
drdksahu62@rediffmail.com

Abstract: Fatty acid methyl ester (FAME), a renewable liquid biofuel popularly known as biodiesel, is emerging
as a suitable replacement to common diesel fuel (CDF) in unmodified Compression Ignition (CI) engine. Present
article reports the development of a process to reduce the operating cost during the conversion of vegetable oil to
biodiesel through the application 1kW sonication techniques at various stages of the composite process. Around
98 % yield was achieved by employing minimum quantity of excess alcohol and alkali catalyst in
transesterification reaction. After the completion of reaction, instantaneous separation of FAME from glycerol is
a noticeable advantage. Its reaction parameters such as time and temperature have been reduced drastically. The
ultrasound energy had also produced excellent benefit during purification of crude FAME through the efficient
removal of mono and diglyceride from FAME. The analysis of the products was done as per ASTM methods and
its fuel characteristics were evaluated using a research engine.

Keywords: FAME, Biodiesel, Transesterification, Ultrasonication, Compression Ignition engine

1. Introduction
Stupendous efforts have been made during the last few decades on bio-fuel chemistry.
Amongst these, biodiesel in particular, has captured the world attention as an impressive
substitute to common diesel fuel (CDF). It is the monoalkyl esters of long chain fatty acids
(FAME) derived from vegetable oil and animal fats. The feedstock composed of mainly
triglycerides with high viscosity, very low vapor pressure and impurities like free fatty acid
(FFA), phospholipids, moisture, vegetable sediments and gum hence cannot act as ideal fuel
for CI engine [1]. On being converted to FAME (having both carbon and viscosity equivalent
to CDF) through a chemically reversible reaction called transesterification [1, 2], it becomes
suitable to replace CDF, hence called biodiesel. Transesterification reaction is the vital step of
the composite process where the vegetable oil (triglyceride) is treated with a short chain
alcohol viz. methanol, in presence of a catalyst (acidic/basic) at a suitable temperature and
reaction time to produce corresponding FAME as per gross reaction (1). It is renewable,
biodegradable with relatively less emission profile, admissible viscosity, flash point and a
high cetane number [3].

Triglycerides + 3 CH 3 OH - Glycerol + FAME (1)

Even though the synthesis of FAME from vegetable oil is relatively facile its economization
is challenging. The major drawback of the composite process lies largely on the costly
feedstock, inefficient extraction of oil from seed, complicated purification of crude oil and
product, high reaction parameters of transesterification, ineffective separation of products and
loss of homogeneous catalyst. The difficulty involved with purification step of FAME
comprises utilization of vast quantity of fresh water, loss of small quantity of the product with
water followed by waste water treatment.

The present paper attempts to develop a process to produce biodiesel from refined soybean oil
and sunflower oil by overcoming major hurdles involved in both transesterification and

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purification steps. Reduction of reaction parameters and other improvements in the various
working steps have been tried with the help of ultrasonic waves [4, 5]. The purified biodiesel
was subjected for exploration of its fuel characteristics in an unmodified CI engine.

2. Materials and methods

2.1. Materials
Refined soybean oil of nature fresh brand and sunflower oil of fortune brand were procured
from local dealers. Anhydrous methanol (MeOH) (99.5%) and sodium hydroxide (NaOH)
pellets were procured from M/s Finar, Ahmedabad. Fatty acid profile of the feedstock was
evaluated by Gas Chromatography while moisture by using Karl Fischer (Systronics make)
and phospholipids by classical method. Refined vegetable oil are found to contain negligible
quantity of free fatty acid, moisture phospholipids, and used as feedstock for biodiesel
preparation without further purification. The Ultrasonic Processor of Sonapros PR-1000
model of 1kW was used to generate sonication in a special designed three necked glass
reaction vessel housed in a sound dampener. Gas Chromatograph of model CERES 800 plus
of M/s Thermo Electron LLS Pvt. Ltd was used for the analysis of glycerol, monoglycerides,
diglycerides, triglycerides, methyl esters of various fatty acids. Kirloskar make compression
ignition engine with variable compression ratio was procured to study its performance with
different biodiesel and evaluate their respective fuel properties.

2.2. Method
2.2.1. Transesterification reaction for the conversion of vegetable oil to FAME
All the ingredients of transesterification such as vegetable oil, anhydrous methanol was kept
over freshly dried anhydrous sodium sulphate for over 10hours before use. Clearly
homogeneous stock solution of desired strength of sodium hydroxide-methanol was prepared
and also stored over freshly dried anhydrous sodium sulphate to remove any possibility of
moisture formation. Exactly weighed quantity of vegetable oil was taken in the sonication
vessel and preheated to a temperature 5oC below the operating temperature. Methanol-sodium
hydroxide catalyst solution was added into the sonication vessel very slowly without lowering
the pre set temperature of the vessel. Appropriate horns/probes of the ultrasonic processor
were inserted into the sonicator vessel so that its tip dips about 5mm into the alcohol phase.
Reflux condenser, thermocouple, and dropper to draw sample time to time were placed with
the reactor and appropriate sonication energy was applied. The experiments were conducted
over wide range of methanol and oil molar ratio between 3:1 to 15:1, varying quantity of
sodium hydroxide catalyst ranging from 0.1% to 1.5% with respect to oil and reaction times
varying from 5 minutes to 45 minutes as well as wide temperature range of 30 to 70°C. After
the completion of the reaction, heavier glycerol was gravity separated instantaneously from
the reacted mixture leaving FAME as upper layer in a separating funnel.

2.2.2. Purification of Products

Crude FAME containing free glycerol, small amount of alkali and partial unconverted portion
of triglycerides usually are usually done complicated water washing or vacuum distillation
methods [6]. Disadvantages associated with such classical process is the partial loss of
biodiesel and poisonous methanol, total loss of costly homogeneous catalyst, use of large
quantity of fresh water followed by adopting costly waste water treatment process. While
purification through distillation under reduced pressure was found to make partial oxidation
of biodiesel due to the presence of double bond with fatty acids of FAME. Moreover, both
methods failed to reduce mono- and diglycerides impurities from it [7]. In order to overcome
the difficulties a novel method was adopted to purify FAME after its separation from reaction

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mixture. The neutralization of the alkali content of the product was done with dilute sulphuric
acid [8] followed by counter current water washing to remove entire unreacted alcohol and
residual free glycerol. By this way the requirement of fresh water was reduced to only 2 liters
per litre of FAME in compare to large quantity of water utilized earlier [9]. The methanol was
recovered from the waste water by distillation. About 90% methanol content of washed water
was recovered by distillation. The waste of small quantity of FAME through washed water
was minimized by reusing the distillate as washing fluid. The purified product was dried
under by purging dried air. The mono- and diglycerides were reduced from the product by
treating with silica gel of particular surface property and of particular mesh size under
ultrasonication for 15-20 minutes. This purification method without thermal treatment
prevents partial decomposition of the relatively unstable FAME containing un-conjugated
double bonds.

2.2.3. Analysis of biodiesel

The ester content of soybean oil methyl ester and sunflower oil methyl ester was determined
using Gas Chromatography with Flame Ignition Detector (FID), % yield was calculated
following ASTM: D 6584-00 and moisture, viscosity, flash-fire point, density, etc as per the
ASTM6547 method and GC graph is shown in Fig. 1.

[ m V]
0.607 1

FAME C:\IRIS32 LITE\WORK1\CHROMATOGRAMS\SOME4

8.593 4

80

60
Voltage

40
7.487 3

triglycerides
int. std2
20
int.std1 monoglycerides diglycerides
21.903 8
13.530 5

19.297 7
17.020 6
4.177 2

0
0 5 10 15 20 25 30 35
Time [ m in.]

Fig. 1. Soy-FAME Gas Chromatogram

3. Results and Discussion

3.1. Effect of alcohol oil molar ratio:
The theoretical molar ratio of alcohol to oil in the transesterification reaction is 3:1. The
higher molar ratio of methanol to oil is involved with catalytic braking of carbonyl bond with
glycerides under strong thermal turbulence created by sonication. Availability of more solvent
brings poorly soluble oil slowly into the homogeneous reaction phase. The nascent fatty acids
after its liberation from glyceride are highly acidic for esterifiation with vast quantity of
methanol available as medium. The presence of alkali catalyst in the reaction mixture
probably helps the esterification. It is observed that with 5:1 to 9:1 molar ratio of alcohol-oil,
ester formation (shown in Fig. 2) is more than 98%. When it is increased to 15:1 the yield of
esters dropped to 80%. Such higher molar ratio of alcohol to oil probably reduces the

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adequate homogeneous catalytic concentration by dilution as well as interferes with the
separation of glycerin as it is dispersed in large volume of solution thereby lowers the yield of
esters. FAME yield is drastically reduced when molar ratio goes down from 5:1 which may be
due to the fact that insufficient solvent fails to bring poorly soluble oil for reaction zone.
Sonication technique proved to be more beneficial leading to an enhancement in the yield.

100

80

60
% yield

40 5:1
6:1
20
9:1
15:1
0
0 10 20 30 40 50
time (min.)

Fig. 2. Percentage yield of soy-FAME at varied methanol-oil molar ratios and different interval

3.2. Effect of catalyst concentration:

Methanolysis of soybean and sunflower oil is done by taking low cost NaOH as catalyst over
the concentration range of 0.3 to 1.2 % wt with respect to oil. With alcohol-oil molar ratio 6:1
and temperature 60°C the product is analyzed at different time intervals starting from 5 min to
45 minutes. The results are displayed in Fig. 3. It is observed that the reaction has shown a
yield of around 85% even with a low catalyst concentration of 0.3% in 45 minutes. Unlike the
mechanical stirring method where the yield of products with low catalyst concentration is
quite low, the sonication technique proved to be more beneficial leading to an enhanced
increase in yield of methyl esters. However the maximum 98% yield is obtained at catalyst
concentration of 1% wt. of oil in less than 15 minutes time. Longer reaction time found to
increase the viscosity of FAME may be due to back reaction of FAME with glycerol.

100
90
80
70
% yield

60
50 0.3%
40 0.5%
30
0.75%
1%
20
10
0
0 10 20 30 40 50
time (min.)

Fig. 3. Percentage yield of soy-FAME at varied catalyst concentrations and different time intervals

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3.3. Effect of temperature:
It is observed that transesterification under sonication is temperature dependent. At
temperature 60-65°C more than 90% conversion is achieved in just 5 min (shown in Fig. 4).
The gas chromatogram for this conversion is shown in Fig. 1. The ultrasound technique
involves the formation of a fine dispersion between oil and alcohol due to micro-turbulence
generated by cavitations bubbles creating enormous interfacial area. Thermal input between
two immiscible liquids under sonication forms more dispersion and thus accelerates chemical
reactions especially between two immiscible ingredients.

100

90

80

70

60
%yield

50

40

30

20

10

0
0 10 20 30 40 50
time (min.)

Fig. 4. % yield of soybean oil methyl ester at varied temperature and different time intervals

3.4. Performance of biodiesel in IC engine

The biodiesel with maximum conversion (98%) after purification and analysis is taken up for
the evaluation of its fuel properties in a CI research engine. Due to low vapour pressure of
FAME the flash point is found to be more than 1300C. Hence it cannot be used as a direct fuel
in the unmodified CI engine. Hence, FAME is blended with CDF in the proportion of 5% and
10%, called as B-05 and B-10 and used as fuel [6] in the unmodified CI engine.

The density and kinematic viscosity of FAME is equivalent to CDF. The gross calorific value
(GCV) is 1-2% lower than diesel. The brake specific fuel consumption (BSFC) i.e. the ratio of
fuel mass flow of an engine to its output power were drawn for soybean FAME-CDF blended
B-05 and B-10 at low engine load under variable compression ratio (CR). BSFC is found to
be higher at lower loads and as the load increased its value decreased. It is also noticed that
the BSFC for B-05 is greater than that of B-10. The difference between BSFC values for both
the blends is reduced with rise in load (Fig. 5 & 6). Due to higher flash point and lower
calorific value, the BSFC should rise with biodiesel content in the biodiesel-diesel blended
fuel, but at lower loads this does not happen. It may be due to the presence of oxygen
(attached to carbonyl carbon) content in biodiesel as well as its better spray characteristics
(due to its lower viscosity) and comparable energy density for which the brake power is
improved [10]. Overall, BSFC of biodiesel is at par with CDF, may be due to the presence of
un-conjugated double bonds with fatty acids of FAME.

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 Brake Specific Fuel Consumption (kg/kW-hr)
1.5
1.4
1.3
1.2
B-5
1.1 B-10
1.0 CR=17
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
0 1 2 3 4 5 6 7 8 9 10
load (kg)

Fig. 5. Variation of Brake Specific Fuel Consumption with different loads at CR of 17 for B-05 & B-10
Brake Specific Fuel Consumption (kg/kW-hr)

1.5
1.4
1.3
1.2 B-5
1.1
1.0
B-10
0.9
CR=18
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
0 1 2 3 4 5 6 7 8 9 10
load (kg)

Fig. 6. Variation of BSFC with different loads at compression ratio 18 for B-05 & B-10

4. Conclusion
The paper puts up a composite process to produce biodiesel from vegetable oil with reduced
operating parameters such as the reduction of reaction time, reaction temperature, reduction in
quantity of unrecoverable homogeneous catalyst, utilization of lesser amount of excess
methanol for achieving excellent yield by the application of low energetic (1kW)
ultrasonication. However, the transesterification reaction under sonication is found to be

77
temperature dependent. The separation of FAME from glycerol under the present working
condition is instantaneous. The complicated purification step has been simplified. Use of
silica gel along with sonication found to reduce the impurities of crude FAME such as free
glycerol, mono and diglycerides. Hence, the application of sonication is found to be beneficial
with composite process of synthesizing biodiesel from refined vegetable oil. Brake Specific
Fuel Consumption of biodiesel prepared through the application of ultrasonication found to be
at par with that of Common Diesel Fuel although the gross calorific value of biodiesel is 1.5%
lower than CDF, which may be due to the presence of un-conjugated double bonds with many
fatty acids of FAME that could replace it in CI engine.

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