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Improving the Yield of Biodiesel Production Using Waste Vegetable Oil
Considering the Free Fatty Acid Content
Saanyol Ityokumbul Igbax, Daniel Swartling, Ahmed ElSawy, and Stephen Idem
Tennessee Technological University
Cookeville, TN, U.S.A.
ABSTRACT
This paper investigates the use of waste vegetable oil
(WVO) for production of biodiesel. The goal of this study was
to explore the improvement of biodiesel production to achieve
high yields. Different oil streams, including virgin canola oil and
WVO, were used as the raw material for the transesterification
processes. These oils had different fatty acid contents as a result
of environmental or previous processing conditions. The main
objective of this study was to assess the impact of free fatty acid
(FFA) content on the resulting yield. In addition, the yield was
influenced by production parameters such as reaction time,
reaction temperature, molar/volume ratios of oil to alcohol,
catalyst amount, and mechanical mixing. This was accomplished
by automating the biodiesel production from WVO, thereby
achieving improved processing and requiring minimal direct
human involvement. A biodiesel production apparatus was
developed with a Raspberry Pi 3 microcomputer to control the
process. It was shown that the particular choice of these process
parameters depended on the particular oil type. This research
used mixtures of virgin and waste vegetable oils at different
volume ratios (oil to alcohol) of 4:1, 6:1, and 8:1, which was
determined by the FFA content of the oil. In addition to
mechanical mixing, ultrasonication rated at 500W, 20kHz was
used to enhance mixing by adding 450 kJ to the process, thereby
reducing both the processing time and the amount of methoxide
needed to perform a base-catalyzed transesterification. The
production temperature was held within the range of 50-65C.
This research demonstrated that optimal yield depends on
temperature, catalyst concentration, FFA content of the oil, and
the energy introduced by sonication. A 96% yield was achieved
with the following parameters: an oil to methanol volume ratio
of 6:1, 0.6% weight concentration of catalyst (NaOH) at 6.25 g,
and FFA values of approximately 5%. It was determined that the
proposed system can produce acceptable quality biodiesel.
INTRODUCTION
This paper considers the use of waste vegetable oil (WVO)
for production of biodiesel. The goal of this study was to explore
the improvement of biodiesel production to achieve high yields.
Different waste oil streams were used as the raw material for the
transesterification processes. These oils had different fatty acid
contents as a result of environmental or previous processing
conditions. This study examined the impact of FFA content of
the WVO on yield. The yield was also influenced by production
parameters such as reaction time and temperature, molar ratio of
oil to alcohol, catalyst amount, and mechanical mixing. An
automated biodiesel production apparatus was utilized to achieve
improved processing that required minimal direct human
involvement. The production apparatus used a Raspberry Pi 3
microcomputer to control the process. In a bid to accomplish
high yields the energy input (including heating and sonication)
was adjusted to meet the production demands while maintaining
product quality.
An original contribution of this investigation is that it
provides extensive details regarding the magnitude of the
sonication energy added to the reactant mixture during the
biodiesel production process. This research utilized a
transesterification process that can be applied to any virgin or
waste vegetable oil to produce biodiesel. A complete description
of the sonication mixing schedules and the oil-to-alcohol volume
ratios that were employed is presented. The procedure to assess
the fatty acid content and the required catalyst amount is
thoroughly elucidated. As noted in [1-3], transesterification is a
widely accepted process that provides good fatty acid conversion
and produces acceptable viscosity values suitable for biodiesel.
Transesterifcation is straightforward to employ for small-batch
biodiesel production because the processes, apparatus, and
materials needed do not require sophisticated equipment or
complex procedures. Sustainability, practicality, applicability,
and costs were key factors that influenced the decision to use the
transesterification process described in this paper. Other
biodiesel production methods were deemed to be beyond the
scope of the present investigation.
Previous studies on biodiesel production often utilized
approaches unique to the researcher's operation. In many
instances details of the processes were not provided, and as a
result the literature often reports seemingly inconsistent results.
For example, [4] described the effect of FFA content related to
1
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Proceedings of the ASME 2022
International Mechanical Engineering Congress and Exposition
IMECE2022
October 30-November 3, 2022, Columbus, Ohio
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biodiesel yield specifically for neem oil. Research by [5]
addressed the effect of free fatty acid content on biodiesel
quality, but primarily focused on the glyceride content as a
measure for the reaction. The existing literature linked to the
amount of auxiliary energy needed to optimize biodiesel
production is scanty. The difficulty in evaluating the amount of
energy needed was noted by [6], and it was further emphasized
that other researchers had likewise provided few relevant details.
Production optimization was also researched by [7], but they
provided no significant discussion of the added energy. Biodiesel
production using eucalyptus oil was investigated in [8]. They
showed that parameters such as ultrasonic frequency, ultrasonic
power, molar ratio, and reaction temperature and time all
affected the reaction efficiency for that particular process.
Ultrasonic mixing is regarded as a time-efficient and
economical method for biodiesel production, and is capable of
reducing the process time to a few hours [9]. Likewise, careful
control of the reaction temperature is needed to energize the
mixture for completing the reaction in due time. Biodiesel is
produced by basic transesterification chemical reactions, using
different kinds of oils, including edible and non-edible vegetable
oils, waste vegetable oils, animal fats, and algae oils. Biodiesel
is a natural substitute for mineral diesel. The chemical name for
glycerin is glycerol, which is a form of the reaction byproduct.
Biodiesel is biodegradable, non-toxic, free of sulfur and
aromatics, and has significantly fewer emissions than petroleum-
based diesel when burned [10]. However, the high cost of
biodiesel is a significant barrier to its commercialization
compared to petroleum-based diesel [11,12]. The cost of the raw
materials comprises approximately 70% - 85% of the total
biodiesel production cost. Every day there is an enormous
amount of WVO generated from restaurants and food processing
industries. Using this under-utilized resource can help make
biodiesel competitive in price with petroleum-based diesel fuel.
Biodiesel has the potential to reduce the dependence on imported
fuel, support the local economy, and reduce environmental
impacts. Vegetable oil is available abundantly and helps in the
recycling of waste products. Among the renewables, biodiesel
ranges high in terms of sustainability and accessibility.
Furthermore, the technology can be accessed and used in remote
locations, as well as in urban centers. Due to this, biodiesel is
favored for the ease of production, relative cost, and the
production of the by-product glycerin, which has use in the
therapeutic and agricultural industries [13].
There are many advantages to the use of WVO to fuel
automobiles [14]. Vehicles that utilize WVO-based biodiesel
exhibit higher mileage compared to diesel and petrol vehicles.
Biodiesel lubricates the engine more efficiently, which in turn
helps to lower maintenance costs. Compared to petroleum-based
diesel fuels, the utilization of biodiesel in internal combustion
engines reduces the emissions of CO, HC, and particulate matter
in the exhaust gas. Furthermore, the lack of sulfur extends the
life of catalytic converters. Biodiesel may be blended with other
fuels and can be used in diesel engines without making any
modifications. The properties of biodiesels are described by such
characteristics as viscosity, FFA content, cetane number, and
combustibility. For wide-scale acceptability, material
specification and biodiesel properties should satisfy criteria
prescribed in such standards as ASTM 6751 and EN 14214, as
described in [15-17].
Vegetable oil consists of triglycerides that are composed of
three chains of fatty acids, all connected by a glycerin molecule.
The biodiesel reaction requires three molecules of fatty acid to
one molecule of glycerol. A triglyceride is an ester comprised of
a chain of glycerol and three fatty acids. Vegetable oil or animal
fat is reacted with methanol in the presence of the catalyst
sodium hydroxide (lye) to produce a mixture of glycerin and
fatty acid esters. The most significant factor affecting production
efficiency and yield is the catalyst to oil volume ratio [18,19].
Optimum FFA content is needed to achieve increased product
profits [20,21]. Fully refined biodiesel is completely mixed,
pure, and devoid of impurities. Careful analysis of the molecular
reaction is vital. The reaction can be enhanced by means of
kinetic and thermal energy addition, which impacts the chemical,
physical, and mechanical components of the process. Although
several reactions are associated with the biodiesel process, the
main one is the transesterification. The transesterification
reaction can be catalyzed by either acids or bases, although the
base-catalyzed reaction is more common. Catalysts serve to
lower the activation energy and increase the rate of a reaction by
enabling more successful molecular collisions. Increased
mechanical action involves stirring, circulation, and sonication,
which has been proven to enhance the biodiesel production
process [22-24].
BIODIESEL PRODUCTION
The experimental apparatus and procedures utilized in this
investigation was designed for optimal production (i.e.
maximum yield while attempting to maintain minimal cost) of
biodiesel from WVO. In some instances virgin canola oil was
also utilized to produce biodiesel, thereby serving as a baseline
case for comparison to WVO. The setup consisted of four tanks,
i.e., a reaction tank, a methoxide (i.e., a mixture of NaOH and
CH3OH) tank, and two separation tanks, all of which were
connected with pipes and valves. An in-line temperature-
controlled heater and an ultrasound mixing device were
incorporated in the apparatus to reduce the operation time and
control the quality of product. Enhanced mixing by sonication
created a more homogenous mixture of methoxide and oil. This
created nano-sized vacuum bubbles, which helped to overcome
the forces of cohesion and adhesion in the relatively immiscible
fluids. The production system was automated using code written
in Python programming language to control the process.
The reactants were transferred to the tanks via pumps and
valves, which were designed to open and close depending on the
flow situation. The WVO was initially filtered to remove loose
particles, and then heated to 55-65C in a storage drum to
facilitate subsequent pumping. The pumping process was
2
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regulated by means of a user interface Raspberry Pi 3 controller,
which sent signals to the pumps and valves through a set of relays
to transfer the fluids. Methanol, which had been pre-mixed in a
prescribed ratio with sodium hydroxide (NaOH), was heated to
55C to form a sodium methoxide solution. Both the methoxide
and the WVO were mixed in the reaction tank and continuously
circulated through an ultrasonic mixer and the in-line heater.
This process was intended to mix the reactants thoroughly, so
that the transesterification could be completed within the shortest
time possible. The heater was adjusted to maintain a reaction
temperature of 60C. Sonication was provided using a Hielscher
Ultrasonic Technology BS4d40 sonotrode, which had a full-
scale rating of 500W at a frequency of 20 kHz. The ultrasound
was set at a fixed amplitude, in this case 75% of its peak value
(31 µm). Typically, this investigation employed 20 minutes of
ultrasonic mixing, where sonication was applied with either
pulse-modulation or continuous operation. For pulse sonication,
the ultrasonic mixer was operated at 75% of full power for the
first 10 minutes of the production run. This was followed by a 10
minute period where no sonication was utilized. Thereafter the
ultrasonic mixer was again run at 75% of full power for 10
additional minutes, such that a total of 450 kJ of energy were
imparted to the reactants over the entire course of testing. For
continuous sonication, the ultrasonic mixer was operated at 75%
of full power for varying time periods, without any intervening
idle period. Within 25 minutes of initiating the production
process the mixture showed a deep color separation, which
indicated the reaction/transformation was taking place.
Recirculation of the reactants was maintained for a maximum of
70 minutes. Subsequently the reacted mixture was pumped to the
separation tanks, where it was is allowed to settle by gravity.
After that the glycerin was decanted while the biodiesel was
transferred into finished product containers. The procedures
employed in this study focused on achieving biodiesel that
conformed to ASTM D6751 and EN 14214. These standards
have been accepted worldwide, and can be used to certify various
aspects of biodiesel quality [25-27].
Material Testing and Measurements
Biodiesel quality is highly dependent on the type of
feedstock used. Thus the first stage of the production process
required selecting, sourcing, and characterizing the reactants.
The WVO color was observed, since that provided some
indication of the history of the oil. Based on past experience, this
provided some guidance regarding the potential duration of the
production run, and tended to indicate how much heating and
sonication was potentially needed to optimize yield. A
significant performance parameter in the consideration of
biodiesel production is the fatty acid content, which plays a role
in determining the thermophysical properties of the oil, i.e., the
viscosity and density. Free fatty acids in oils largely are
responsible for these properties. Some oils appear different in
color, texture and other physical/chemical properties, based on
how they were previously used in frying applications, and under
what circumstances they were stored. Hence in this investigation
chemical titration was employed to ascertain the FFA content,
and to calculate optimum reactant mixture ratios and amounts of
catalyst. Viscosity measurement of the WVO (as well as virgin
canola oil) and biodiesel was performed using both a rotating
spindle viscometer, and calibrated capillary tube viscometers.
Product quality was checked using the Warnquist 27/3 test
[28,29] which give a subjective confirmation of biodiesel
quality. Yield measurements were then utilized to assess the
success of each production run, to deduce the operational
parameters that minimized inefficient use of the reactants and
catalysts.
Titration Procedure
Titration was performed to calculate the amount of free fatty
acids present in an oil sample. The goal was to determine the
ideal amount of catalyst required to neutralize the oil, which
contains the amount of fatty acids detached from the carbon
chain. The free fatty acid per cent content generally ranges from
0.1-40% FFA for biodiesel production [30]. The procedure
followed in this investigation is described as follows. Typically,
one mL of oil and 10 mL of alcohol (methanol) was mixed with
three drops of phenolphthalein indicator in a beaker. Likewise,
another sample comprised of an NaOH solution (with a molarity
of 0.1M) was prepared using 4 four grams of NaOH salt (solute)
in 1000 mL of distilled water as the titer. The lye mixture was
then placed into a burette to allow for accurate measurement
during the test. Thereafter 10 mL of isopropyl alcohol, one mL
of vegetable oil (either virgin canola oil or WVO) and 2–3 drops
of phenolphthalein were mixed in an Erlenmeyer flask to prepare
the sample for testing. The lye solution (titer) was slowly
dropped (titrated) into the flask until a distinct pink color
lingered for 10 seconds or more. The solution remained clear
until the free fatty acids in the alcohol/oil solution had been
neutralized, wherein the color changed to pink. This titer,
measured in (mL), was then used to determine the free fatty acid
content in the virgin canola/WVO sample.
Warnquist 27/3 Biodiesel Quality Test
When biodiesel is produced, it needs to be tested for quality,
and to determine if the reaction was completed. This can be done
in various ways, but for simplicity the 27/3 test was utilized in
this investigation for a quick qualitative assessment. It was
performed by pouring 27 mL of methanol and 3 mL of the
produced biodiesel maintained at 24C into a test tube. The
mixture was then vigorously shaken for approximately one
minute. After allowing the products to settle by gravity for 15
minutes, the quality was determined by visual inspection of the
mixed solution. If the solution had colloidal solids or particulates
floating inside (refer to Figure 1), the biodiesel was deemed to
have low quality, and thus did not pass the test. This meant the
reactants had not fully reacted, and that some of the available
triglycerides still needed to be further reacted with methanol. If
the solution was transparent and had no appearance of colloidal
solids floating in it, then the biodiesel quality was regarded as
being satisfactory. All samples were checked by this method to
establish the efficacy of the production procedures.
3
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Figure 1. Test Indication for Failed/Passed Biodiesel
27/3 Test
Viscosity Measurements
Biodiesel viscosity influences the quality of the product.
Hence viscosity measurements of the biodiesel produced in this
investigation were performed, using either a Brookfield
viscometer or a capillary tube viscometer. This was done to
ensure the values resided within the acceptable range 1.9
6.0 mm2/s, per [30]. In every instance the viscosity
measurements were performed over temperatures that ranged
from 50C to 60C. These temperatures were maintained
constant during the measurement process using a
thermostatically-controlled water bath.
FFA Assessment
Oils are made up of triglycerides and glycerol-bonded free
fatty acids (FFA). The hydroxyl groups from the alcohol dissolve
the triglycerides and complete the reaction to form esters and
glycerol. The FFA in oils influence their viscosity and density.
FFA content was estimated by determining the quantity of alkali
that was added to the FFA in the oil to render it neutral. The free
fatty acid value was converted to a percentage by comparing the
molar masses of the solvent used (NaOH) and the oil. The
determination of free fatty acids in the oil was determined using
the titration procedure, which measured the amount of catalyst
needed to neutralize/dissolve the FFA in the oil in order to
complete the transesterification reaction. To calculate the FFA
by titration, the molarity of the titer solution was calculated per
Equation 1:
(1)
For example, since the molecular weight of NaOH is 40 g/mol,
and 4 g of the solute was dissolved in 1000 mL of distilled water,
the molarity of the titer solution was 0.1 M. Therein the FFA
calculation was based on neutralizing 1.0 mL of oil, having a
measured density ρ = 0.92 g/mL, implying the mass of the oil
sample was 0.92 g. Oil consists primarily of triglycerides, which
are mostly oleic in nature. Therefore, assuming the molecular
weight of oleic acid to be 282 g/mol, the FFA% in an oil sample
was evaluated by measuring the titer solution volume that was
needed to produce a color change, i.e.,
(2)
Hence, if 1.1 mL of titer solution yielded a color change, then
the FFA percentage determined using Eq. (2) was 3.37%. The
catalyst employed in the present investigation was
sodium/potassium hydroxide. The amount of catalyst utilized in
the reaction was calculated as a function of the oil sample mass
using Eq. (3):
(3)
In this investigation the catalyst concentration described how
much catalyst was present in a fixed volume of solution, while
maintaining the prescribed oil to alcohol volume ratios. For
example, assuming 1 L of virgin canola oil/VWO was mixed
with 0.25 L of methanol (to achieve a 4:1 volume ratio), the
resulting solution mass was evaluated as follows:
= (4)
Assuming that 5.6 g of catalyst was dissolved in this solution,
the resulting weight percent was calculated as follows:
(5)
In this investigation the resulting weight fraction fractions of
catalyst were reported on a per unit liter of oil basis. Evaluation
of catalyst weight fractions for other oil-to-alcohol volume
fractions and catalyst amounts was performed similarly.
Reactant Mixtures
Having determined the FFA content and the required
catalyst amount, it was necessary to evaluate the respective
volumes of vegetable oil and methanol needed to achieve the
desired stoichiometry. In that case, the number of moles of the
reactants present in a one liter volume was determined by
dividing the mass of each species by its respective molecular
weight. For example, that implied that one liter of vegetable oil
having a mass of 930 g (and possessing a presumed molecular
weight for unused canola oil of 877 g/mol, which is based on a
weighted average of the percent composition of fatty acids in the
oil) consisted of 1.06 moles. Likewise, one liter of methanol
4
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having a mass of 790 g and a molecular weight 32.04 g/mol
comprised 24.66 moles. Hence for a 1:1 volume ratio of oil to
methanol the molar ratio was 23.26. Therein to achieve a 6:1
volume ratio of vegetable oil to methanol required a
corresponding molar ratio of 3.88:1; the extension to other
volume ratios was performed similarly. For example, in this
investigation the volume ratio of vegetable oil to methanol was
typically maintained at either 8:1, 6:1, or 4:1. These ratios
implied methanol to vegetable oil molar ratios of 2.91:1, 3.88:1,
and 5.82:1, respectively.
RESULTS AND DISCUSSION
Table 1 summarizes the test conditions maintained in this
investigation, and describes the biodiesel yield obtained for each
case. The biodiesel viscosity measured at the end of each
production run is also reported in Table 1. For a given volume of
oil (either virgin canola oil or WVO obtained from a cafeteria
facility) used in a given test, approximately one liter of methanol
was utilized. This yielded prescribed methanol/oil volume and
molar ratios for the test regimen. In every instance the reaction
temperatures were carefully controlled. As demonstrated by
[31,32], this was done to enhance the reaction rates, and to ensure
that significant methanol evaporation did not occur, due to the
resulting safety concerns. Likewise, the test durations were
limited, based on observations reported in [33,34]. For tests
involving WVO, all biodiesel production runs used the same
pulse sonication schedule. However for tests that utilized virgin
canola oil, continuous sonication was employed in every
instance. For those cases the sonication application period was
increased as a function of increasing FFA content, although the
reaction times and temperatures were maintained at constant
values throughout the test. Where sonication was employed, it
was restricted to the initial portion of a production run. This was
based on prior experience, where performing sonication
throughout the entire production run led to increased times
needed for gravitational settling of the biodiesel/glycerin
mixture.
Referring to Figure 2, for WVO the catalyst amount used
(ranging from 5.4-9.66 g) was increased as the FFA content
increased from 4.13% to 7.42%. This was required to account for
the greater volume of sodium hydroxide needed for the acid to
react with the base to form a neutral salt. The yield for WVO
decreased with increasing FFA (in spite of the use of more
catalyst) when such factors as reaction time/temperature and
sonication schedules were maintained at constant values. In
contrast, for virgin canola oil it was observed that increasing
FFA content was associated with increasing yield when the
reaction time/temperature was kept constant. However, the
virgin canola tests were performed using progressively greater
continuous sonication duration, as the FFA increased from
3.37% (no sonication) to an FFA of 4.8 %. In the latter instance
20 minutes of pulse sonication was used, which coincided with
the schedule utilized for the WVO tests. It was determined that
the highest yield of 96% yield was achieved under the following
circumstances: an oil to methanol volume ratio of 6:1 (for both
virgin canola oil and WVO), a 0.60-0.67 weight percent
concentration of catalyst (NaOH), and FFA values ranging from
4.8-5.3%.
In this investigation it was observed that for greater FFA
percentages in the oil, more catalyst was needed. For instances
where the catalyst amount used exceeded the calculated
optimum value, additional energy from sonication was required
to improve the processing. For example, in the case where virgin
canola oil with 3.37% FFA was utilized, the production was
performed without ultrasound. In that instance, 4.39 g were
prescribed by the analysis. Since no additional energy from
sonication was used to complete the operation, a total of 6.25 g
of catalyst was used. However, this resulted in the lowest yield
observed for any case in this study. Careful selection of the
catalyst amount is important as it helps to drive the reaction
towards completion.
The flow rate of the reactants was limited by the capacity of
the pump utilized in the apparatus. The achievable flow rate was
likewise affected by the system curve of the piping system and
valves, which was not quantified in this study. Hence the flow
rate of the reactants through the apparatus was neither measured
nor controlled in this investigation. This warrants further
investigation to establish whether reaction rates can be optimized
by controlling the flow rate through the apparatus. Utilizing
sonication generally improved the production process, although
as noted the use of too much sonication can be detrimental. The
amount of energy added to reactants was limited in the present
investigation. Presumably, for larger batch volumes of
methanol/oil, more sonication would be beneficial to overcome
the resistance to mixing of the oil and methanol associated with
their viscosity, inherent immiscibility, FFA%, and the presence
of contaminants. The variable sonication periods employed with
biodiesel production from pure canola oil led to difficulty in
directly comparing the measured yields to those resulting
obtained from WVO, where a consistent sonication schedule was
employed. It is recommended that any future testing utilizing
pure canola oil should employ the same sonication procedures
used for the WVO tests to facilitate comparable yield
assessments. The energy added by sonication to the reactants
throughout the transesterification process for all tests was
restricted, due to the observation that excessive sonication
yielded soap formation, such that the biodiesel produced failed
to pass the 27/3 test.
The present research program is a preliminary study. It is
proposed to expand the scope of this investigation to further
assess the influence of sonication power and schedule on
biodiesel yield from WVO. It is likewise anticipated that a
detailed inquiry comparing the efficacy of electrostatic
separation of biodiesel/ glycerin versus gravitational settling will
be performed.
5
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Table 1. Test Conditions and Biodiesel Yield
Oil Sample
Sample
FFA
(%)
Oil
Volume
(L)
Alcohol
Volume
(L)
Catalyst
Amount
(g)
Wt%
Reaction
Time
(minutes)
Reaction
Temperature
(C)
Ultrasound
Time/Schedule
(minutes)
Continuous/Pulse
Yield
(%)
Biodiesel
Viscosity
(mm2/s)
Virgin Canola
3.37
4.0
1.12
6.5
0.58
70
55
0
89
3.8
Virgin Canola
4.13
4.0
1.02
5.4
0.53
55
55
5 (C)
91
4.2
Virgin Canola
4.33
4.0
1.02
5.6
0.55
55
55
10 (C)
93
4.4
Virgin Canola
4.50
5.0
1.11
6.3
0.57
55
55
10 (C)
94
4.7
Virgin Canola
4.80
6.0
1.03
6.3
0.61
55
55
20 (P)
96
5.1
WVO
5.30
6.0
1.03
6.9
0.67
60
58
20 (P)
96
5.6
WVO
6.00
7.0
1.04
7.8
0.75
60
58
20 (P)
95
4.7
WVO
6.60
8.0
1.02
8.5
0.83
60
55
20 (P)
92
5.1
WVO
7.42
8.0
1.01
9.7
0.96
60
55
20 (P)
91
3.4
6
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Figure 2. Biodiesel Yield Versus Ultrasound Time and Catalyst Amount
0
5
10
15
20
25
30
35
40
45
50
70
75
80
85
90
95
3.37 4.13 4.33 4.5 4.8 5.3 6 6.6 7.42
Catalyst Amount (g) and Ultrasound Time (minutes)
Yield %
Free Fatty Acid (%)
Yield % Ultrasound Time Catalyst Amount (g)
7
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CONCLUSIONS
This paper investigated a consistent test procedure to obtain
maximum yields of biodiesel from a transesterification process
involving a mixture of either waste vegetable oil or virgin canola
oil, methanol, and sodium hydroxide catalyst. It was
demonstrated that the free fatty acid content had a profound
impact on the yield. The yield was likewise influenced by
controllable production parameters such as reaction time,
reaction temperature, molar/volume ratios of oil to alcohol,
catalyst amount, and sonication. When 20 minutes of pulse
sonication was employed in a production run, a yield of 96% was
obtained for an oil to methanol volume ratio of 6:1 (for both
virgin canola oil and WVO). In those instances, the FFA values
ranged from 4.8-5.3%, and a 0.60-0.67 weight percent
concentration of catalyst was used.
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