BATCH PRODUCTION OF FATTY ACID PROPYL ESTERS
(BIODIESEL) FROM OILSEED CROPS
BY
LATEEF, FATAI ABIOLA
PG/M.Sc./07/43230
A THESIS
SUBMITTED TO THE SCHOOL OF POST GRADUATE STUDIES
IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE
AWARD OF THE DEGREE OF MASTER OF SCIENCE IN THE
DEPARTMENT OF PURE AND INDUSTRIAL CHEMISTRY,
UNIVERSITY OF NIGERIA, NSUKKA,
ENUGU STATE
MARCH, 2010
ii
APPROVAL PAGE
LATEEF, Fatai Abiola a postgraduate student in the Department of
Pure and Industrial Chemistry with Registration Number PG/M.Sc/07/43230
has satisfactorily completed the requirements for course and research work
for the degree of M.Sc. in Industrial Chemistry.
__________________ ____________________
Prof. O.D. Onukwuli Dr. U.C. Okoro
Supervisor Supervisor
_____________________
Dr. P.O. Ukoha
Head of Department
iii
DEDICATION
This work is dedicated to God and to Popoola Folarin (SAN),
Opaluwa E.H.O and Abeh T. for their financial and moral support.
iv
ACKNOWLEDGEMENTS
I would like to thank my supervisors, Prof. O.D. Onukwuli and Dr.
U.C. Okoro for firstly, giving me this opportunity to have a part in this
project and more importantly giving me support throughout both my course
and project work. I would also like to say that their faith in me has given me
confidence in my ability to be an industrial chemist from this work, I have
learnt to appreciate hard work as the basis of success in all human
endeavuors. I appreciate the spirit of hardwork that they have instilled in me.
I would also like to thank Mr. P.M. Ejikeme for his assistance and
input on cloudy issues and the many offer of much needed help in writing
this thesis. Also in this category are all the lecturers (both academic and non-
academics) of the department of Pure and Industrial Chemistry, UNN;
Departments of Science Laboratory Technology, and Food Science and
Technology, Federal Polytechnic, Idah.
I would also like to say thank you to Mr. B.I.D. Obidiegwu of
Analytical laboratory, Soil Science department, UNN for his input in
analytical chemistry work and Mr. Fidelis Eze of Fluid Mechanics
Laboratory, Civil Engineering Department, UNN.
I thank all my well wishers and admirers who stood by me during my
masters programme till the end. Thanks to Mr. M.K. Egbekun, Dr.E.M Odin,
Late I.E.O. Salawo, Mr Okorie, E., Oresanya Adebisi, Daodu Niyi, Afolabi
Safara, Adeyemo Nurudeen, Atiga Simeon, Eguda Felix, Ajayi Ebenezer,
Dosunmu Oladipupo, Tijani Memuna, the entire Muslim Community UNN,
Osayuki Godwin and Joseph Jesuorobo of ICT unit, FPI Idah for the
provision of materials used in writing this thesis free of charge.
Finally, I would like to thank my parents, my extended family
members for standing by me, without them I would not have been able to
complete much of what I have done and become who I am. They are the
light that shines my way and the drive for my ever persistent determination.
v
ABSTRACT
Biodiesel fuels were prepared from castor, palm kernel and groundnut oils
through alkali transesterification reaction using sodium hydroxide (NaOH)
as the catalyst at 65oC, residence time of 60 minutes, 0.50g optimal catalyst
weight for castor oil and palm kernel oil and 0.40g for groundnut oil in an
air-tight 250ml batch reactor at 1:6 oil/alcohol molar ratio. The biodiesels
produced were characterized as alternative diesel fuels through ASTM D
6751, EN 14214 specification standards for the fuel properties: specific
gravity, viscosity, calorific (combustion) value, saponification value, iodine
value and acid value. The castor oil (CSO), palm kernel oil (PKO) and
groundnut oil (GNO) biodiesels displayed temperature dependent behaviour
when their respective viscosities were measured at 30, 45, 60 and 75oC. In
the kinetic studies, biodiesels were produced at 5, 10, 20 and 60 minutes, the
volume of biodiesel and their various percentage (%) conversions evaluated
at different temperatures of 30, 45, 60 and 75oC. The CSO, PKO and GNO
biodiesels were also measured for their storage/oxidative stabilities
compared with commercial petrodiesel. The biodiesels produced were of
good fuel properties with respect to ASTM D 6751 and EN 14214
specification standards (except kinematic viscosity of castor oil biodiesel).
The viscosities of castor oil biodiesel at different temperatures were in the
range of 6.89-8.12 mm2/s which were higher than that of European biodiesel
standards (EN 14214 : 3.5–5.0) and American Society of Testing Material
Standards (ASTM D 6751 : 1.9-6.0). However, promising results which
conforms to above specification standards were realized when castor oil
biodiesels were blended with commercial petrodiesel. The specific gravities
recorded for CSO, PKO and GNO biodiesel were higher than the values
obtained for petrodiesel: 1.049 times that of the petrodiesel for CSO, 1.086
times that of petrodiesel for PKO and 1.078 times that of petrodiesel for
GNO at 28oC. In the oxidative storage stability test, commercial petrodiesel
has the highest oxidative stability than biodiesel produced from CSO, PKO
and GNO oils. The infrared spectra result of a B100 biodiesel shows that the
strong ester peaks near 1750 (the C=O vibration) and around 1170-1120cm-1
(C-O vibration).
vi
TABLE OF CONTENTS
Title Page - - - - - - - - - i
Certification - - - - - - - - ii
Dedication - - - - - - - - - iii
Acknowledgements - - - - - - - iv
Abstract - - - - - - - - - v
Table of Contents - - - - - - - - vi
List of Figures - - - - - - - - x
List of Tables - - - - - - - - xii
CHAPTER ONE
INTRODUCTION
1.1 Preamble - - - - - - - - 1
1.2 Justification of Study - - - - - - 4
1.3 Aim and Objectives of Research - - - - 5
CHAPTER TWO
LITERATURE REVIEW
2.1 History of Biodiesel - - - - - - 7
2.2 Chemical Foundations of Biodiesel-Making - - - 7
2.3 Biodiesel Production: Process Overview - - - 12
2.3.1 Direct Use and Blending - - - - - - 12
2.3.2 Microemulsion - - - - - - - 13
2.3.3 Thermal Cracking (Pyrolysis) - - - - - 15
2.3.4 Transesterification - - - - - - 16
2.3.5 Alcohols - - - - - - - 17
2.3.6 Esterification - - - - - - - 17
2.3.7 Aminolysis - - - - - - - 18
2.3.8 Biocatalyst - - - - - - - 18
vii
2.4 Oil Extraction and Expression Methods - - - - 19
2.5 Oil Purification Methods - - - - - - 20
2.6 Lipid Chemistry - - - - - - 22
2.6.1 Fats and Oils - - - - - - 23
2.6.2 Transesterification of Glycerides - - - - 24
2.6.3 Fatty Acids - - - - - - - 25
2.7 Physical and Chemical Properties of Lipids - - - 28
2.7.1 Physical Properties - - - - - - 28
2.7.2 Chemical Properties of Fats and Oil - - - - 29
2.8 Rancidity - - - - - - - 31
2.9 Storage and Oxidative Stability of Fatty acid Esters - 32
2.10 Additization of Esters - - - - - - 34
2.11 Rheological Properties of Fluids - - - - - 35
2.11.1 Biodiesel Rheology: Fluid flow phenomena - - 35
2.11.2 Viscosity - - - - - - 36
2.11.3 Kinematic Viscosity - - - - - - 36
2.12 Biodiesel Specifications and Properties - - - - 37
2.13 Biodiesel Production Process Options - - - - 39
2.13.1 Batch Processing - - - - - - - 40
2.13.2 Continuous Process Systems - - - - - 43
2.14 Spectroscopy for Biofuel Analysis - - - - 43
2.14.1 Use of Molecular Spectra as Aids in the Identification of
Organic Structures - - - - - - 43
2.14.2 Infrared Spectra - - - - - - - 45
CHAPTER THREE
RESEARCH METHODOLOGY
3.1 Raw materials - - - - - - - 46
3.2 Apparatus - - - - - - - 46
3.3 Extraction of Oil from Various Seeds and Solvent Recovery 46
viii
3.3.1 Extraction of Oil from Castor Seed - - - - 46
3.3.2 Extraction of Oils from Palm-Kernel Seed - - - 47
3.3.3 Extraction oil Oils from Groundnut Seed - - - 47
3.4 Pre-treatment of Oils - - - - - - 47
3.5 Determination of the Optimal Catalyst Weight - - 48
3.6 Determination of Kinematic Viscosity of Crude, Kinetics
Biodiesel Samples - - - - - - 49
3.7 Alkali-Catalyzed Batch Production of Biodiesel - - 50
3.8 Characterization of the Crude, Refined Oils, Biodiesel and
Petrodiesel - - - - - - - 51
3.8.1 Saponification Value (SV) Determination - - - 51
3.8.2 Acid Value (AV) Determination - - - - - 51
3.8.3 Iodine Value (IV) Determination - - - - - 51
3.8.4 Specific Gravity Determination - - - - - 52
3.8.5 Peroxide Value Determination - - - - - 52
3.8.6 Calorific (heating/combustion) Value Determination using
Bomb Calorimeter - - - - - - 53
3.9 Investigation of Temperature Dependence of Biodiesel Kinematic
Viscosity and Specific Gravity / Biodiesel-Petrodiesel Blending 54
3.10 Transesterification Kinetics in a Batch Reactor - - 55
3.11 Infrared Spectroscopy-Biodiesel Product Analysis Procedure 56
CHAPTER FOUR
RESULTS AND DISCUSSION
4.1 Extraction of Crude Plant Oils - - - - - 58
4.2 Pre-treatment of Oils - - - - - - 58
4.3 Optimal Catalyst Weight Test - - - - - 59
4.4 Properties of Crude, Refined and Biodiesel Obtained - 61
4.4.1 Saponification Value - - - - - - 61
4.4.2 Iodine Value - - - - - - - 62
4.4.3 Acid Value - - - - - - - 62
ix
4.5 Physical Characterization of Castor, Palm Kernel and Groundnut
Oils Biodiesel in Comparison with Conventional Diesel
(Petrodiesel) - - - - - - - 62
4.5.1 Specific Gravity - - - - - - - 63
4.5.2 Calorific Value - - - - - - - 63
4.5.3 Kinematic Viscosity - - - - - - 64
4.6 Alkali-Catalyzed Batch Production of Biodiesel at 65oC - 64
4.7 Kinematic Viscosity of Biodiesel at Different Temperatures 66
4.8 Castor Oil Biodiesel/Petrodiesel Blending - - - 72
4.9 Kinetic Studies Result at Various Temperatures - - 73
4.10 Biodiesel Storage/Oxidative Stability Measurement - 76
4.11 Infrared Spectroscopy-Biodiesel Product Analysis Result - 78
CHAPTER FIVE
CONCLUSION AND RECOMMENDATIONS
5.1 Conclusion - - - - - - - - 85
5.2 Recommendation - - - - - - - 86
References - - - - - - - - 88
Appendices
x
LIST OF FIGURES
Fig. 1.1: Transesterification Reaction of Triglycerides - - 3
Figure 2.1: Molecule Structure of an Idealized Fatty Acid - 8
Figure 2.2: Molecular Structure of Soap - - - - 8
Figure 2.3: Molecular Structure of Glycerol - - - - 8
Figure 2.4: Molecular structure of methanol, ethanol, 1–propanol, and
1–butanol - - - - - - - - 9
Figure 2.5: Biodiesel molecules (a) methyl ester (b) propyl ester - 9
Figure 2.6: Molecular structure of triglycerides - - - - 10
Figure 2.7: Molecular structures of octadecanoic acid (a) cetane
(hexadecane) molecule (b) ethyl ester 10
Fig. 2.8: Transesterification of Triglycerides - - - - 16
Figure 2.9: Esterification - - - - - - - 18
Fig 2.10: Aminolysis of triglycerides - - - - - 18
Figure 2.11: Typical Oil Extraction Process - - - - 19
Fig 2.12: Fats and Oils - - - - - - - 24
Figure 2.13: Three consecutive and reversible reactions - - 24
Figure 2.14: Part of the hydrocarbon chain of a saturated fatty acid 25
Figure 2.15: Part of the hydrocarbon chain of a unsaturated fatty acid 25
Figure 2.16: Oxidation Behaviour of Vegetable Oils and Animal Fats 33
Fig 2.17: Butylated Hydroxyanisole (BHA) - - - - 34
Figure 2.18: Antioxidants for oils and fats - - - - 35
Figure 2.19: Batch Reaction Process - - - - - 42
Figure 2.20: Plug Flow Reaction System - - - - 43
Fig. 4.1: Variation of Percentage (%) Yield of Biodiesel with % (w/v)
of Catalyst (CSO, PKO and GNO) - - - - 60
Fig. 4.2: Graph of lnV CSO against 1/T (K-1
) - - - 67
Fig. 4.3: Graph of lnV PKO against 1/T (K-1
) - - - 68
Fig. 4.4: Graph of lnV GNO against 1/T (K-1
) - - - 69
xi
Fig. 4.5: Graph of Specific Gravity of CSO, PKO and GNO
at different temperatures - - - - 71
Fig 4.6: Graph of Percentage (%) Conversion of biodiesel against
time (min) Kinetic result at 30oC - - - - 74
Fig 4.7: Graph of % Conversion of biodiesel against time (min)
Kinetic result at 45oC - - - - - - 74
Fig 4.8: Graph of Percentage (%) Conversion of biodiesel against
time (min) Kinetic result at 60oC - - - - 75
Fig 4.9: Graph of Percentage (%) Conversion of biodiesel against
time (min) Kinetic result at 75oC - - - - 75
xii
LIST OF TABLES
Table 1.1: Nigeria Vegetable Oil Profile - - - - 6
Table 1.2: Nigeria’s Palm Kernel Oil Profile - - - - 6
Table 2.1: Known problems, probable cause and potential solutions for
using straight vegetable oil in diesels - - - 14
Table 2.2 Compositional data of pyrolysis of oils - - - 15
Table 2.3: Typical Assay Showing the Percentage of Constituent Fatty
Acids - - - - - - - - 26
Table 2.4: Castor Oil fatty acids - - - - - 27
Table 2.5: Biodiesel Chain Length - - - - - 27
Table 2.6: Some common fatty acid - - - - - 28
Table 2.7: Iodine values of various groups of oils and fats - 30
Table 2.8: ASTM Biodiesel Standard D 6751a - - - 38
Table 2.9: European Biodiesel Standards EN 14214 for Vehicle Use
and EN 14213 for Heating Oil Use - - - 39
Table 2.10: Kinematic Viscosity of Oils - - - - 40
Table 4.1: Yield of Oils - - - - - - 58
Table 4.2: Percentage loss on Pretreatment - - - - 58
Table 4.3 Result for the Characterization of Crude, Refined and
Biodiesel - - - - - - - 61
Table 4.4 Physical Characterization of Biodiesel and Petrodiesel 63
Table 4.5 Results of Alkali-Catalyzed Batch Production of Biodiesel
at 65oC - - - - - - - 64
Table 4.6: Variation of Kinematic Viscosity of Biodiesel with
Temperature - - - - - - - 66
Table 4.7: Simplification of Andrade Equation of Biodiesel Sample 66
Table 4:8: Variation of Specific Gravity of Biodiesel Samples with
Temperatures - - - - - - 70
Table 4.9: Comparison of Kinematic viscosity and Specific Gravity
of Castor oil Biodiesel and Petrodiesel Blend with
Unblended Biodiesel - - - - - 73
Table 4.10: Peroxide Values of Castor, Palm kernel, Groundnut Oils
and Petrodiesel - - - - - - 76
1
CHAPTER ONE
INTRODUCTION
1.1 Preamble
The high energy demand, pollution problems, as well as global
consensus that fossil energy sources are finite, make it increasingly
necessary to develop the renewable energy source of limitless duration,
smaller environmental impacts, technically feasible and readily available
(Gupta et al, 2008; Meher et al., 2004; Alamu et al, 2008; Bamgboye and
Hansen, 2007; Fukuda et al, Sharma et al, 2008). Biodiesel have been
reported as a promising long-tern renewable energy source (Tapasvi et al,
2005).
Biodiesel is pursued not only for the consideration of the future
shortage of petroleum supplies but also for the well being of the environment
(Zhao et al, 2007; Ma and Hanna, 1999). Diesel fuels have an essential
function in the industrial economy of a developing country and used for
transport of industrial and agricultural goods and operation of diesel tractor.
Various plant oils have been converted into biodiesel and they work well in
diesel engines (Pimentel and Patrick, 2005). One possible alternative to
fossil fuel is the use of oil of plant origin like vegetable oil (Wenzel et al,
2006; Meher et al, 2004; Gerpen, 2005; Noureddini and Zhu, 1997) waste fat
and oil (Refaat et al, 2008, Gupta et al, 2007; Zhang et al, 2003); although
other crops such as mustard, hemp, jatropha and even algae show great
potential as a source of raw materials for biodiesel production (Baroutian et
al, 2008; Chhetri et al, 2008).
Available statistical data ranked Nigeria as one of the twenty largest
oil producers in the world with a whooping 36.220 million barrels of
proven oil reserves, 184.160 Trillion cubic feet natural gas reserves at the
beginning of year 2009 and end of the year 2007 respectively (EIA, 2009).
2
Nigeria is the eight largest producer of oil and nineth largest producer of
natural gas. Fossil fuels account for over ninety percent of its revenue
generation (NNPC Newsletter, 2009). This amazing oil wealth
notwithstanding, the Energy Commission of Nigeria (ECN) expressed fears
over future depletion of these fossil fuels and its severe environmental
impacts (Alamu et al, 2007a).
Petroleum-based energy sources pose severe threats to the
environment from hazardous emissions. Huge level of fossil fuel combustion
have resulted in the concentration of carbondioxide which causes dramatic
global climate change, air pollution (Kyu-Wan et al, 2007).
Biodiesel, an environmental friendly fuel, has many merits. It is
derived from renewable, domestic resource (thereby relieving reliance on
petroleum fuel imports), biodegradable and non-toxic (Zhang et al, 2003;
Gerpen, 2004; Canakci and Gerpen, 2001). Compared to petroleum-based
diesel, biodiesel has a more favourable combustion emission profile, such as
low emissions of carbon monoxide, particulate emission and unburned
hydrocarbons. Biodiesel has a relatively high flash point, lubricating
properties that reduce engine wear and extend engine life (Zhang et al, 2003,
Gerpen, 2004; Alamu et al, 2007a).
Plant-oils occupy a prominent position in the development of
alternative fuels although, there have been many problems associated with
using it directly in diesel engine (especially in direct ignition engine). These
include carbon deposits, oil ring stickening, thickening of lubricants and high
viscosity (Knothe et al, 2005; Krisnangkura et al, 2005; Knothe, 2001;
Alamu et al, 2008).
Biodiesel is produced by transesterifying the parent oil or fat with an
alcohol (Knothe, 2006; Darnoko et al, 2000). Alcohols such as methanol,
ethanol, 1-propanol and butanol have been used for biodiesel production.
Using alcohol of higher molecular weight improves the cold flow properties
3
of the resulting ester, at the cost of a less efficient transesterification reaction
(Wikipedia, the free encyclopedia: Biodiesel). Alkaline catalyst such as
sodium hydroxide (NaOH) and potassium hydroxide (KOH) are the most
commonly used in transesterification, since their reaction is much faster than
an acid-catalyzed reaction (Titipong, 2006).
Two approaches for transesterification of plant-oils for production of
biodiesel are suggested: chemical one using alkali catalyst (NaOH, KOH or
alkoxides) or acid catalyst (strong acids H2SO4, H3PO4) (Jitputti et al, 2004;
Shah et al, 2004; Zhang et al, 2003). The product of the reaction is a mixture
of esters, which is known as biodiesel and glycerol, which is a high value co-
product. The second approach is enzymatic one, in which lipase-catalyzed
transesterification is carried out in non-aqueous environment.
H2C – OCOR1 ROCOR1 H2C – OH
H2C – OCOR2 + ROH ROCOR2 + H C – OH
H2C – OCOR3 ROCOR3 H2C – OH
Triglyceride Alcohol Mixtures of Glycerol
Alkyl ester
Fig. 1.1: Transesterification reaction of triglycerides
R1, R2 and R3 are long hydrocarbon chains, sometimes called fatty
acid chains.
Triglycerides, as the main component of plant oil, consist of three long
chain fatty acids esterified to a glycerol backbone. When triglycerides react
with an alcohol (e.g 1-propanol), the three fatty acid chains are released from
the glycerol skeleton and combine with alcohol to yield fatty acid alkyl
esters. Glycerol is produced as a by-product. The transesterification reaction
is a reversible reaction and the transformation occurs essentially by mixing
the reactants. However, the presence of a catalyst considerably accelerates
Catalyst
4
the adjustment of the equilibrium (Ma and Hanna, 1999). Stoichiometric
reaction requires 1mol of a triglycerides and 3mol of alcohol. However an
excess of alcohol is used to increase the yields of the alkyl esters and to
allow its phase separation to be formed (Schuchardt et al, 1998).
There are two major methods available for biodiesel production: batch
transesterification processes and continuous process (Leevijit et al, 2004).
The batch reactor has the advantage of high conversions that can be obtained
by leaving the reactant in the reactor for long periods of time (Fogler, 2006).
1.2 JUSTIFICATION OF STUDY
Various plant oils have been converted into biodiesel and they work
well in diesel engines. Several researchers have used biodiesel as alternative
fuel in the existing compression engine (CE) without any modification.
Promising results have been obtained by running CE on plant oil based
biodiesels: soybean (US), rapeseed (Europe), oil palm (South-East Asia) e.t.c.
which are commercialized in these countries (Alamu, 2007b). However,
Nigeria, having the greatest potential in this area, because of the availability
of these raw materials for the production of biorenewable and
environmentally friendly fuel (biodiesel), is yet to make remarkable impact
on its production and usage.
Plant oil is an important renewable feedstock in the long-term (2016–
2025) vision of providing secure, abundant, cost effective and clean source
of energy for Nigeria. Common plant oil in the country includes palm oil,
palm kernel oil, groundnut oil, cottonseed, soybean bean oil etc. Profile for
these oils is presented in Tables 1.1 and 1. 2.
Nigeria is rated to be the second world’s largest producer of palm-
kernel oil and groundnut oil after Malaysia and India respectively (Asiedu,
1989). It was also reported that castor oil plant originates in Africa. However,
industrial use of these plants oil has been limited to soap, detergent,
5
lubricants, paints e.t.c. This shows that despite the abundance of these plant
oils, it has been underutilized in Nigeria. Successful reports on
transesterification of some Nigerian oils in the preparation of biodiesel is an
indication of better industrial utilization of these plant oils in Nigeria, as
considerable research efforts are now focusing on this alternative diesel fuel
worldwide (Knothe, 1999).
1.3 AIM AND OBJECTIVES OF RESEARCH
This project is aimed at the production of biodiesel using various plant
oils: castor oil, palm kernel and groundnut oils on 6:1 propanol-oil molar
ratio and optimal weight of sodium hydroxide as the catalyst.
• To carryout physical and chemical characterization on the biodiesel
produced.
• To determine the optimal catalyst weight for the transesterification
reaction.
• To evaluate biodiesel kinematic viscosity at various temperatures.
• To investigate how biodiesel production reaction proceeds at different
time (Reaction Kinetics).
• To determine the oxidative stability of the biodiesel produced.
• To analyze the biodiesel sample by Fourier Series Infra-red
Spectroscopy.
• To make recommendations based on the findings from the study.
6
Table 1.1: Nigeria Vegetable Oil Profile (2006)
Commodity Quantity (tons) Percentage Share
Palm oil 800,000 50
Palm kernel oil 270,000 17
Others: peanuts, cottonseed, soybean 260,000 16
Imports 270,000 17
National requirement 1,600,000 100
Source: Alamu et al, 2007a
Table 1.2: Nigeria’s Palm Kernel Oil Profile
Commodity USDA Revised
Estimate (2004)
USDA Revised
Estimate (2005)
USDA Revised
Estimate (2006)
(1000 tons)
Beginning stock 10 10 10
Production 272 272 275
Imports 1 1 1
Total supply 283 283 286
Exports 1 1 1
Industrial domestic
consumption
86 86 86
Food use domestic
consumption
186 186 189
Total domestic
Consumption
272 272 275
Source: Alamu et al, 2007a
7
CHAPTER TWO
LITERATURE REVIEW
2.1 HISTORY OF BIODIESEL
The diesel engine was invented by Otto Diesel in 1982. His engine
was designed to run on a wide variety of fuels. Although he demonstrated a
diesel engine running on peanut oil at the Paris exhibition of 1900, the first
commercial diesel engines ran on kerosene. The new engine first appeared in
transportation vehicles in ships in the 1900’s. They showed up in trains in
1914, but “did not seriously displace the steam engine until after World
War”. Diesels were first used in automobile in 1924 (Turner, 2005).
On August 31,1937, G. Chavanne of the University of Brussels
(Belgium) was granted a patent for a procedure for the transformation of
vegetable oils for their uses as fuels (Belgian Patent 422,877). This patent
described the alcoholysis (often referred to as transesterification) of
vegetable oils using ethanol (an alcohol) in order to separate the fatty acids
from the glycerol by replacing the glycerol with short linear alcohols. This
appears to be the first account of the production of what is known as
‘biodiesel’ today (Wikipedia, the free encyclopedia, 2008).
2.2 Chemical Foundations of Biodiesel-making
Biodiesel is a renewable, biodegradable, environmentally benign fuel
use in diesel engine (Titipong, 2006). Either virgin vegetable oil or waste
vegetable oil (wvo) can be used to make quality fuel. Fats are converted to
biodiesel through a chemical reaction involving alcohol and a catalyst.
It is instructive to think of the chemistry of biodiesel in terms of
building blocks that comprise the larger molecules involved in the biodiesel-
making reactions. Fatty acids are a component of both vegetable oil and
biodiesel. In chemical terms, they are carboxylic acids of the form:
8
H2 H2 H2 H2 H2 H2 H2 H2 O C C C C C C C C H3C C C C C C C C C OH H2 H2 H2 H2 H2 H2 H2 H2
Figure 2.1: Molecule structure of an idealized fatty acid
Fatty acids which are not bound to some other molecule are known as
free fatty acids. When reacted with base, a fatty acid loses a hydrogen atom
to form soap.
H2 H2 H2 H2 H2 H2 H2 H2 O C C C C C C C C H3C C C C C C C C C O H2 H2 H2 H2 H2 H2 H2 H2
Figure 2.2: Molecular structure of soap
Chemically, soap is the salt of a fatty acid. The structures of the fatty
acids shown in this section are highly idealized. Real fatty acids vary in the
number of carbon atoms, and in the number of double bonds. Glycerol, a
component of vegetable oil and a by-product of biodiesel production, has the
following form:
HO CH2
HO CH
CH2 HO
Figure 2.3: Molecular structure of glycerol
Alcohols are organic compound of the form R–OH, where R is a
hydrocarbon. Typical alcohols used in biodiesel-making are methanol,
ethanol, 1-propanol, and 1-butanol:
9
H2 H2 H2 H2
H3C–OH C C OH C C
H3C OH H3C C H3C C OH H2 H2
Figure 2.4: Molecular structure of methanol, ethanol, 1–propanol, and 1–
butanol
Transesterification is sometimes called alcoholysis, or if by a specific
alcohol, by corresponding names such as methanolysis, or ethanolysis or
propanolysis. Chemically, biodiesel is a fatty acid alkyl ester:
H2 H2 H2 H2 H2 H2 H2 H2 O H3 C C C C C C C C C _ (a) H3C C C C C C C C C O H2 H2 H2 H2 H2 H2 H2 H2
H2 H2 H2 H2 H2 H2 H2 H2 O H2 H3 C C C C C C C C C C (b) H3C C C C C C C C C O C H2 H2 H2 H2 H2 H2 H2 H2 H2
Figure 2.5: Biodiesel molecules (a) methyl ester (b) propyl ester
The biodiesel ester contains a fatty acid chain on one side, and a
hydrocarbon called an alkane on the other. Thus, biodiesel is a fatty acid
alkyl ester. Usually, the form of the alkane is specified as in “methyl ester”,
“ethyl ester” or “propyl ester”.
Vegetable oil is a mixture of many compounds, primarily triglycerides
and free fatty acids. Triglyceride is a tri-ester of glycerol and three fatty
acids.
10
H2 H2 H2 H2 H2 H2 H2 H2 O C C C C C C C C H3C C C C C C C C C O H2 H2 H2 H2 H2 H2 H2 H2
H2 H2 H2 H2 H2 H2 H2 H2 O C C C C C C C C CH _ H3C C C C C C C C C O H2 H2 H2 H2 H2 H2 H2 H2
H2 H2 H2 H2 H2 H2 H2 H2 O C C C C C C C C CH2 _ H3C C C C C C C C C O H2 H2 H2 H2 H2 H2 H2 H2
Figure 2.6: Molecular structure of triglycerides
Virgin oil contains a low percentage of free fatty acids. Waste
vegetable oil contains a higher amount of FFA’s because the frying process
breaks down triglycerides molecules (Turner, 2005).
Petroleum diesel and biodiesel are both mixtures of organic
compounds. The idealized petroleum molecule is cetane, a pure paraffin.
Compared to cetane, alkyl esters are somewhat longer, and more importantly,
contain two oxygen atoms.
H2 H2 H2 H2 H2 H2 H2 C C C C C C C CH3 (a) C C C C C C C C H3 H2 H2 H2 H2 H2 H2 H2
H2 H2 H2 H2 H2 H2 H2 H2 O H2 C C C C C C C C C (b) H3C C C C C C C C C O CH3 H2 H2 H2 H2 H2 H2 H2 H2
Figure 2.7: (a) cetane (hexadecane) molecule
(b) ethyl ester of octadecanoic acid
Since combustion is an oxidation reaction, the heating value of cetane,
which contains no oxygen atoms, is higher than that of biodiesel. For this
reason, diesel engines running biodiesel, experience a loss of power on the
order of 5% (Turner, 2005).
CH2
11
The principal ways of making biodiesel are by transesterification of
triglycerides and esterification of free fatty acids.
The esterification reaction of triglycerides is as follows:
Tryglyceride + 3Alcohol 3Biodiesel + Glycerol
The esterification reaction of free fatty acids:
FFA + Alcohol Biodiesel + Water
In the first reaction, a tri-ester is converted to three individual esters,
thus the term transesterification. In the second reaction, a new ester is
created, thus it is called esterification.
Transesterification reaction can be base-catalyzed, acid catalyzed, or
enzymatic. The base-catalyzed reaction takes about one hour or more at
room temperature (Gerpen et al, 2004; Ma & Hanna 1999). It suffers from
competing saponification reactions, which convert the same ingredients as
well as any free fatty acid to soap. Acid-catalyzed and enzymatic
transesterification require three to four days to complete (Turner, 2005). The
acid-catalyzed reaction also requires heat.
There is no competing saponification reaction with acid-catalyzed and
enzymatic reactions. In fact, even free fatty acids are converted to biodiesel
by esterification.
The associated acid-catalyzed esterification reaction requires only
about two hours to completion (Turner, 2005). A combined strategy called
the two-stage process can be used to maximize the amount of biodiesel
produced, while minimizing the amount of soap produced (Turner, 2005).
The first stage is acid-catalyzed esterification of the free fatty acids. This is
followed by base-catalyzed transesterification. This approach is especially
effective for waste vegetable oil and animal fats, which have high free fatty
acid content.
This thesis only deals with base-catalyzed transesterification.
acid catalyst
catalyst
12
2.3 BIODIESEL PRODUCTION: PROCESS OVERVIEW
There are several generally accepted ways to make biodiesel, some
more common than others e.g. transesterification and blending, and several
others that are more recent developments e.g. reaction with supercritical
methanol. An overview of these processes is as follows:
1. Direct use and Blending, which is the use of pure vegetable oils or the
blending with diesel fuel in various ratios,
2. Micoremulsions with simple alcohols,
3. Thermal cracking (pyrolysis) to alkanes, alkenes e.t.c.,
4. Transesterification (alcoholysis) which consists of several sub
categories;
(i) Esterification
(ii) Aminolysis
5. Other forms of catalysis
(i) Biocatalysis
(ii) Catalyst free
2.3.1 Direct Use and Blending
The direct use of vegetable oil (palm kernel oil, groundnut oil e.t.c) in
diesel engines is problematic and has many inherent failings. It has only
been researched extensively for the past couple of decades, but has been
experimented with for almost a hundred years. Although some diesel engines
can run pure vegetable oils, turbocharged direct injection engines such as
trucks are prone to many problems (Khan, 2002). Direct use has not been
satisfactory because of viscous nature of vegetable oil. However, methyl,
ethyl, propyl and butyl esters of fatty acids present in oils have proved
promising enough to be called biodiesel (Shah et al, 2003).
13
Neat vegetable oils (such as palm oil, groundnut oil e.t.c) were
primarily considered as alternatives for diesel fuel but their very high
viscosity, at room temperature made them unsuitable in diesel engine
(Krisnangkura et al, 2005). Even after heating to around 80oC, it is still six
times as viscous as diesel. This leads to problems with flow of oils from the
fuel tank to the engine, blockages in filters and subsequent engine power
losses. Even if preheating is used to lower the viscosity, difficulties may still
be encountered with starting due to the temperatures required for oils to give
off ignitable vapour. Further, engines can suffer coking and gumming which
leads to sticking of piston rings due to multibonded compounds undergoing
pyrolysis. Polyunsaturated fatty acids also undergo oxidation in storage
causing gum formation and at high temperatures where complex oxidative
and thermal polymerization can occur (Ma and Hanna, 1999). See table 2.1.
2.3.2 Microemulsion
A microemulsion is designed to tackle the problem of the high
viscosity of pure vegetable oils by reducing the viscosity of oils with
solvents such as simple alcohols. Microemulsions are defined as colloidal
equilibrium dispersions of optically isotropic fluid microstructures, with
dimensions generally in 1–150nm range formed spontaneously from two
normally immiscible liquids and one or more ionic or non-ionic compounds
(Khan, 2002).
14
Table 2.1
Known problems, probable cause and potential solutions for using straight vegetable oil in diesels (Ma and Hanna,1999).
Problem Probable cause Potential solution
Short-term
1. Cold weather starting
High viscosity, low cetane, and low flash point
of vegetable oils
Preheat fuel prior to injection. Chemically alter fuel
to an ester
2. Plugging and gumming of filters,
lines and injectors
Natural gums (phosphatides) in vegetable oil.
Other ash
Partially refine the oil to remove gums. Filter to
4-microns
3. Engine knocking
Very low cetane of some oils. Improper injection
timing.
Adjust injection timing. Use higher compression
engines. Preheat fuel prior to injection. Chemically
alter fuel to an ester
Long-term
4. Coking of injectors on piston
and head of engine
High viscosity of vegetable oil, incomplete
combustion of fuel. Poor combustion at part
load with vegetable oils
Heat fuel prior to injection. Switch engine to diesel
fuel when operation at part load. Chemically alter
the vegetable oil to an ester
5. Carbon deposits on piston
and head of engine
High viscosity of vegetable oil, incomplete
combustion of fuel. Poor combustion at part
load with vegetable oils
Heat fuel prior to injection. Switch engine to diesel
fuel when operation at part load. Chemically alter
the vegetable oil to an ester
6. Excessive engine wear
High viscosity of vegetable oil, incomplete
combustion of fuel. Poor combustion at part
load with vegetable oils. Possibly free fatty acids
in vegetable oil. Dilution of engine lubricating
oil due to blow-by of vegetable oil
Heat fuel prior to injection. Switch engine to diesel
fuel when operation at part load. Chemically alter
the vegetable oil to an ester. Increase motor oil
changes. Motor oil additives to inhibit oxidation
7. Failure of engine lubricating
oil due to polymerization
Collection of polyunsaturated vegetable oil
blow-by in crankcase to the point where
polymerization occurs
Heat fuel prior to injection. Switch engine to diesel
fuel when operation at part load. Chemically alter
the vegetable oil to an ester. Increase motor oil
changes. Motor oil additives to inhibit oxidation.
14
15
Table 2.2: Compositional data of pyrolysis of oils (Ma and Hanna, 1999)
Percent by weight
High Oil safflower Soybean
Alkanes 40.9 29.9
Alkenes 22.0 24.9
Alkadienes 13.0 10.9
Aromatics 2.2 1.9
Unresolved unsaturates 10.1 5.1
Carboxylic acids 16.1 9.6
Unidentified 12.7 12.6
The performances of ionic and non-ionic microemulsions were found
to be similar to diesel fuel, over short term testing. They also achieved good
spray characteristics, with explosive vapourization which improved the
combustion characteristics (Ma and Hanna, 1999). In longer-term testing, no
significant deterioration in performance was observed, however significant
injector needle sticking, carbon deposits, incomplete combustion and
increasing viscosity of lubricating oils were reported (Ma and Hanna, 1999).
2.3.3 Thermal Cracking (Pyrolysis)
Pyrolysis is defined as the conversion of one substance into another by
means of heat or by heat with the aid of a catalyst (Ma and Hanna, 1999).
The pyrolysis of fats has been investigated for more than 100 years,
especially in countries where there is shortage of petroleum deposits. Typical
catalysts that can be employed in pyrolysis are SiO2 and Al2O3 (Khan, 2002).
Unlike direct blending, fats can be pyrolysed successfully to produce many
smaller chain compounds. Typical breakdown of compounds found from
pyrolysis of safflower and soybean oil are listed in Table 2.2 above.
16
2.3.4 Transesterification
Transesterification of triacylglycerols (triglycerides) is a simple
process that converts vegetable oils into fuel for diesel engine (Warzyniak et
al, 2005). The stoichiometry for the reaction is 3:1 alcohol to oils (lipids),
however in practice this is usually
H2C – OCOR1 ROCOR' H2C – OH
H2C – OCOR2 + 3R'OH ROCOR' + H C – OH
H2C – OCOR3 ROCOR' H2C – OH
Triglyceride Alcohol Esters Glycerol
Fig. 2.8: Transesterification of Triglycerides
The raw materials for biodiesel production are: vegetable oils and
animal fat, alcohols and catalysts.
Oils and fats are essentially esters of glycerol and fatty acids, derived
from plant and animal sources. Different oils have different acid
compositions and hence different viscosities. Oils are normally liquid at
ambient temperature, fats are normally solid (Lewis, 1987). Vegetable oil is
an important renewable feedstock in the long term (2016 – 2025) vision of
providing secure, abundant, cost effective and clean source of energy for
Nigeria (Alamu et al, 2007a). Common vegetable oil in the country includes
palm oil, palm kernel oil, groundnut oil, peanuts, cottonseed and soybean.
Animal fat such as tallow, lard, chicken fats are useful in biodiesel
production.
Catalysts are necessary to reduce the time and energy requirement for
the transesterification reaction. The catalyst lowers the activation energy of
the reaction by providing an alternative path that avoids the slow, rate-
determining step of the uncatalyzed reaction (Atkins and Paula, 2002).
Catalysts are classified as alkali, acid or enzyme. Alkali-catalyzed
transesterification is much faster than acid catalyzed. However, if a glyceride
Catalyst
17
has a higher free fatty acid content and more water, acid-catalyzed
transesterification is suitable. The acids could be sulfuric acid, phosphoric
acid, hydrochloric acid or organic sulfonic acid. Alkali includes sodium
hydroxide, sodium methoxide, potassium hydroxide, potassium methoxide
e.t.c. Sodium hydroxide is cheaper and also chosen because is used widely in
large-scale processing (Ma and Hanna, 1999).
Transesterification will occur without the aid of catalyst, however at
temperatures below 300oC the rate is very slow. It has been said that there
are, from a broad perspective, two methods to producing biodiesel and that is
with and without a catalyst (Khan, 2002).
2.3.5 Alcohols
Aliphatic monohydric alcohols are monohydroxyl derivatives of
alkanes and have a general molecular formula CnH2n+1OH, or simply ROH
(Murray, 1997). Generally, in biodiesel production a large excess of alcohol
is used to shift the equilibrium to the right (Zhang et al, 2003). The most
commonly used primary alcohol in biodiesel production is methanol,
although other alcohols such as ethanol, propanols, butanols and amyl
alcohol can also be used. The major factors that influence the choice of
alcohol for transesterification are: cost of the alcohol, amount of the alcohol
needed for the reaction, ease of recovery, and recycling of the alcohol and
fuel tax incentives.
2.3.6 Esterification
The formation of esters occurs through a condensation reaction known
as esterification. This requires two reactants, carboxylic acids (fatty acid)
and alcohols (Khan, 2002). Esterification reactions are acids catalyzed and
proceed slowly in the absence of strong acids such as sulphuric acid,
18
phosphoric acid, sulfonic acids and hydrochloric acid. The equation for the
esterification reaction is shown below.
R– C – OH + R'OH R – C – OR' + H2O
Free fatty acid Alcohol Esters Water
Figure 2.9: Esterification
2.3.7 Aminolysis
Esters undergo nucleophilic substitution at their acyl carbon atoms
when they are treated with primary or secondary amines. These reactions are
slow but are synthetically useful (Khan, 2002).
O
R1 – C – N – R
5
H2C – COO – R1 R4 O H2C – OH
H2C – COO – R2 + 3 H – N – R3 R
2 – C – N – R
5 + H2C – OH
H2C – COO – R3 O H2C – OH
R3 – C – N – R
5
Triglycerides Amine Amides Glycerol
Fig 2.10: Aminolysis of triglycerides
2.3.8 Biocatalyst
Biocatalysts are usually lipases; however conditions need to be well
controlled to maintain the activity of the catalyst (Khan, 2002). Hydrolytic
enzymes are generally used as catalysts as they are readily available and are
easily handled. They are stable, do not require co-enzymes and will often
tolerate organic solvent. The second approach in producing biodiesel is
enzymatic one, in which lipase-catalyzed transesterification is carried out in
nonaqeous environments. The main problem of enzyme catalyzed process is
the high cost of the lipases used as catalyst (Royon et al, 2006). Chemical
transformation is efficient in terms of reaction. Though, biocatalysts allow
H+
heat
19
synthesis of specific alkyl esters, easy recovery of glycerol, and
transesterification of glycerides with high free fatty acid content (Shah et al,
2003) but recent patents and articles have shown that reaction yields and
times are still unfavourable compared to base-catalyzed transesterification
for commercial application.
2.4 OIL EXTRACTION AND EXPRESSION METHODS
Fats and oils are derived from oil seed and animal sources. In order to
get high quality oil, various techniques are used in the processing. The
process of obtaining oil from seeds involves the separation of oil from oil-
bearing material by mechanical means, chemical means e.t.c.
There are generally three broad techniques or methods of oil
extraction – Distillation, Solvent extraction and Expression (Eckhardt and
Kawaguchi, 1997).
Distillation:
Most essential oils are extracted using steam distillation. As the steam
break down the plant, its essential oils are released in a vapourized form.
When these pass through cooling tanks, the volatile essential oil return to
liquid form and are separated and is easily isolated as pure essential plant oil.
Figure 2.11: Typical Oil Extraction Process
Whole seed Cleaning Mechanical press
Purification processing Crude oil Seed meal
Usable oil
20
Solvent Extraction
It is very common in large-scale operations to remove the oil from
cracked seeds at low temperature with a non-toxic fat solvent such as hexane.
When a plant contains very little oil or when the odorous properties of
flavour and plant materials would be destroyed or altered by steam or water
distillation, solvent extraction is used. The solvent is percolated through the
plant (seed) material in order to produce concrete. The plants (seeds)
constituents including essential oils, fatty acids and waxes are dissolved by a
solvent. After the solvent is distilled off, the remaining constituents make up
the concrete. Alcohol is used to extract the essential oil from the other
constituents. Since the waxes and fatty acids are not alcohol soluble, they are
separated. The alcohol is then released through secondary distillation,
leaving the absolute oil behind.
Expression
Expression, also known as cold pressing, can also be used for the
extraction of oil. Various types of mechanical presses are used to squeeze oil
from oil seeds. The oil-bearing material is squeezed through a tapering outlet
in the mechanical pressing and filtered to get pure essential oil.
2.5 OIL PURIFICATION METHODS
Crude fats and oils are obtained directly from the extraction of the oil
seed. Crude fats and oils contain varying substances that may influence
undesirable flavour, colour, or quality. These substances are removed
through a series of processing steps. The purification processing can be
divided into seven types.
1. Degumming:
Most oils undergo treatment known as degumming. The bulk of
certain phosphatides such as lecithin are separated through this operation.
21
The processing consists of mixing the oil with water or steam for 30mins.
The gummy residue is dehydrated and the oil is then passed through
centrifugal separators. Larger amounts of water or steam are used to prepare
oil which is more gummed.
2. Refining:
The process of refining reduces the free fatty acid, phospholipids,
carbohydrates, or proteins. The most widely practices form of refining
method is alkali treatment. By treatment of the fats and oils with an alkali
solution, the free fatty acid converts into water soluble soaps. After the alkali
treatment, the fats and oils are washed with water to remove residual water
soluble soaps.
3. Bleaching:
The bleaching process is removing colouring materials such as
chlorophyll and carotene and purifying the fats and oils. The method is by
adsorption of the colour producing substances on an adsorbent material.
Bentonite, silical gel and activated carbon are used as bleaching adsorbent.
4. Deodourization
Deodourization is a vacuum steam distillation process for the purpose
of removing undesirable flavours and odours, mostly arising from oxidation,
in fats and oils. Using steam under reduced pressure, the volatile compounds
are removed from fats and oils. The deodourization utilizes the differences in
volatility between off-flavour and off-odour substances and the triglycerides.
5. Fractionation:
Fractionation is the removal of solids at a given temperature. There are
three kinds of fractionation process such as crystallization, winterization, and
pressing. Crystallization is the widespread technique. A mixture of
triglycerides is separated into different melting points based on solubility at
selected temperature. Next, a small quantity of material is crystallized to
avoid hazes of liquid fractions at refrigeration temperatures, this process is
22
called winterization. Many oils, including cottonseed and hydrogenated
soyabean oils, are winterized. Pressing process is used to separate liquid oil
from solid fat. The process squeezes or presses the liquid oil. This process is
used to produce hard butter.
6. Hydrogenation
In hydrogenation, hydrogen is added directly to react with unsaturated
(double bond) oil in the presence of nickel catalyst. The need for the
hydrogenation is based on: (1) converting liquid oils to the semi-solid forms
and (2) increasing the oxidation and thermal stability of fats and oils. This
process greatly influences the desired stability and properties of many edible
oil products. The hydrogenation process is easily controlled and can be
stopped at any point. A gradual increase in the melting point of fat and oil is
one of the advantages. If the double bonds are eliminated entirely with
hydrogenation, the product is a hard brittle solid at room temperature.
Margarines are typical examples.
7. Interesterification
Interesterification is a rearrangement or redistribution of the fatty
acids on the glycerol. The fatty acids can be described in random or directed
under some conditions. In addition, this process does not change the degree
of unsaturation or the isomeric state of the fatty acids.
2.6 LIPID CHEMISTRY
LIPIDS
Lipids are group of compounds soluble in organic solvents such as
hexane, benzene, carbontetrachloride, ether e.t.c. but sparingly soluble in
water. They contain carbon, hydrogen and oxygen.
23
CLASSIFICATION OF LIPIDS
Lipids are classified into:
1. Simple (neutral) lipids
(a) Fats and oils (b) Waxes
2. Compound lipids
(a) Phospholipids (phosphatides)
(i) Lecithins (ii) Cephalins (iii) Sphingomyelins
(b) Glycolipids
(i) Cerebrosides (ii) Sialic acid (iii) Gangliosine
3. Derived lipids
(a) Sterols (b) Bile acids
2.6.1 FATS AND OILS
Fats and oils are esters of fatty acids and glycerol. Glycerol is a
trichydric alcohol, that is, it has 3OH groups. Each OH group of glycerol
reacts with the COOH group of fatty acid to form a molecule of fat and oil.
When one molecule of glycerol reacts with a molecule of fatty acid, a
monoglyceride is formed. When two molecules of fatty acids combine with a
molecule of glycerol, diglyceride is formed. While three molecules of fatty
acids reacting with a glycerol molecule give rise to triglycerides (Onimawo
and Akubor, 2005).
24
O O
CH2OH HO – C – R1 CH2 – O – C – R1
O O
CH2OH + HO – C – R2 CH2 – O – C – R2
O O
CH2OH HO – C – R3 CH2 – O – C – R3
(1 mole of glycerol) (3 molecules of fatty acids) (1 molecule of
triglycerides)
R1 = R2 = R3 (identical FA)
R1 ≠ R2 ≠ R3 (different FA)
Fig 2.12: Fats and Oils
Fats and oils are principally mixture of triglycerides. It may be
composed of glycerol combined with three different or with three molecules
of the same kind. The simplest type of triglyceride is one in which all three
fatty acids are the same as shown in the scheme above.
2.6.2 TRANSESTERIFICATION OF GLYCERIDES
Transesterification, also called alcoholysis, is the displacement of
alcohol from an ester by another alcohol. Suitable alcohols include methanol,
ethanol, propanol, butanol and amyl alcohol. This process has been widely
used to reduce the viscosity of triglycerides, thereby enhancing the physical
properties of renewable fuels to improve engine performance (Fukuda et al,
2001).
Triglyceride (TG) + R'OH Diglyceride (DG) + R'COOR1
Diglyceride (DG) + R'OH Monoglyceride (MG) + R'COOR2
Monoglyceride (MG) + R'OH Glycerol (GL) + R'COOR3
Figure 2.13: Three consecutive and reversible reactions. R1, R2, R3 and R'
represent alkyl group since naturally occurring fats and oils are mixtures of
different triglycerides, they may contain a number of different fatty acids.
Catalyst
Catalyst
Catalyst
25
O
– C
OH
2.6.3 FATTY ACIDS
The essential components of lipids are carboxylic acids, known as
fatty acids. The general formula of a fatty acid (alkanoic acid is RCOOH
where R represents a hydrocarbon chain. The carboxyl functional group,
contains both a carbonyl and hydroxyl functional group (Murray, 1985).
They are divided into two groups, that is saturated and unsaturated. In
saturated fatty acids, the hydrocarbon chain is saturated with hydrogen.
O H H H H H H H
HO – C – C – C – C – C – C – C – C – R
H H H H H H H H
Figure 2.14: Part of the hydrocarbon chain of a saturated fatty acid
The end carbon atom to which the oxygen atom and hydroxyl (OH)
radical are attached to form a carboxyl group gives the molecule its acid
name. Saturated fatty acids, are characterized by single bonds. Unsaturated
fatty acid, on the other hand, do not have the hydrogen chain saturated with
hydrogen and has one or more double bond.
O H H H H H H H
HO – C – C – C – C – C – C – C – C – R
H H H H H H H H
Figure 2.15: Part of the hydrocarbon chain of a unsaturated fatty acid
26
Table 2.3: Typical Assay Showing the Percentage of Constituent Fatty Acids
27
Table 2.4: Castor Oil Fatty Acids
Average Composition of Castor seed oil/fatty acid chain
Acid name Average percentage Range
Ricinoleic acid 85 – 95%
Oleic acid 6 – 2%
Linoleic acid 5 – 1%
Linoleic acid 1 – 0.5%
Stearic acid 1 – 0.5%
Palmitic acid 1 – 0.5%
Dihydroxystearic acid 0.5 – 0.3%
Other 0.5 – 0.2%
Source: Wikipedia, the free encyclopedia from http://en.wikipedia.org/
wiki/castoroil
Table 2.5: Biodiesel Chain Length
Fatty Acid Composition (%)
Carbon
chain length
Soy oil Castor oil Palm oil Palm
kernel oil
Animal fat
C8 4.4
C10 3.7
C12 48.3
C14 1.1 15.6 3.0
C16 11.0 44.0 7.8 26.0
C18 87.6 97.5 53.8 19.8 70.0
C20
Source: PAC catching the wave – IR Application for Biofuel
28
Table 2.6: Some common fatty acid
Type Common
name
Systematic
name
Formula No. of
double
bond
Position
of
double
bond
Saturated
Butyric Butanoic C3H7COOH
Caproic Hexanoic C5H11COOH
Caprylic Octanoic C7H15COOH
Capric Decanoic C9H19COOH
Lauric Dodecanoic C11H23COOH
Myristic Tetradecanoic C13H27COOH
Palmitic Hexadecanoic C15H31COOH
Stearic Octadecanoic C17H35COOH
Arachidic Eicosani C19H39COOH
Mono
unsaturated
Oleic 9-
octadecanoic
C17H33COOH 1 9
Poly
unsaturated
Linoleic 9,12-
octadecanoic
C17H31COOH 2 9, 12
Linolenic 9, 12, 15-
octadecanoic
C17H29COOH 3 9, 12, 15
Arachidonic 5,8,11,14-
eicosatetranoic
C19H31COOH 4 5,8,11,14
Source: Onimawo and Akubor (2005)
2.7 PHYSICAL AND CHEMICAL PROPERTIES OF LIPIDS
Some of the important physical and chemical tests that shall be
considered in this work are: refractive index, specific gravity, viscosity,
iodine value, saponification value, peroxide value.
2.7.1 PHYSICAL PROPERTIES
The physical properties of the fats and oils are often used to identify
them. Physical and chemical properties characterization of oils are of
practical importance in understanding of the components of the lipids, and
29
their determination will usually be sufficient for confirming the identity and
uses of most oils and fat (Meyer, 2004). These properties of lipids depend on
factors such as sources, degree of saturation, length of carbon chains,
molecular structures of the triglycerides and processing method.
Specific Gravity (S.G) of oils
Specific gravity is one of the analytical constant used in identifying
oils and fats. Specific gravity is a measure of the ratio of the weight gravity
or mass gravity of a substance to that of a given standard, usually water.
The specific gravity of oils is related to the degree of unsaturation of
the component fatty acids and their average molecular weight. The higher
their degree of unsaturation and the lower the molecular weight. The specific
gravity of individual oils, however, does not vary widely, it lies between
0.910 – 0.924. The degree of unsaturation of component of fatty acids has
but little effect on specific gravity (Joslyn, 1970).
2.7.2 CHEMICAL PROPERTIES OF FATS AND OIL
IODINE VALUE
The iodine value of oil is defined as the weight of iodine absorbed by
100 parts by weight of the sample. The glycerides of the unsaturated fatty
acids present (particularly of the oleic acid series) unite with a definite
amount of halogen and the iodine value is therefore a measure of the degree
of unsaturation. It is constant for a particular oil or fat, but the exact figure
obtained depends on the particular technique employed. The ranges of
figures for the iodine values of the various groups of oils and fats are as
follows:
30
Table 2.7: Iodine values of various groups of oils and fats
Groups Examples Range of iodine values
Waxes – Very small
Animal fats Butter, dripping, land 30 – 70
Non-drying oils Olive oil, arachis oil 80 – 110
Semi-drying oil Cottonseed oil, soya oil 80 – 140
Drying oils Linseed oil, sunflower
oil
125 – 200
Source: David (1976)
The iodine value is often the most useful figure for identifying an oil
or at least placing it into particular group. It should be noted that the less
unsaturated fats with low values are solid at room temperature, or conversely,
oils that are more highly unsaturated are liquids. Further point of interest is
that, in general, the greater the degree of unsaturation (i.e. the higher the
iodine value), the greater is the liability of the oil or fat to go rancid by
oxidation.
The iodine value is usually determined by Wij’s method.
SAPONIFICATION VALUE
The saponification value of an oil or fat is defined as the number of
milligram of potassium hydroxide required to saponify one gram of the oil or
fat. Saponification value (S.V) is a good indicator of the average molecular
weight of the constituent fatty acids (Gupta et al, 2007). It gives the number
in milligram potassium hydroxide of the base required to neutralize the free
fatty acids in the lipid, and to saponify the triglycerides in 1gram of the lipid.
As many oils have somewhat similar values (e.g. those in the olive oil
series fall within the range 188 – 196), the saponification value is not, in
general, as useful for identification purposes as the iodine value. The
saponification value is of most use for detecting the presence of palm-kernel
31
oil (SV 247) and coconut oil (SV 255), which contain a high proportion of
the lower fatty acids (David, 1976).
ACID VALUE OR FREE FATTY ACIDS (FFA)
The acid value of an oil or fat is defined as the number of mg of
potassium hydroxide required to neutralize the free acid in 1g of the sample.
The result is often expressed as the percentage of free acidity.
The acid value is a measure of the extent to which the glycerides in the
oil have been decomposed by lipase action. The decomposition is
accelerated by heat and light. As rancidity is usually accompanied by free
fatty acid formation, the determination is often used as general indication of
the condition and edibility of oils (David, 1976).
2.8 RANCIDITY
Fats and oil undergo changes during storage which result in the
production of an unpleasant taste and odour, which is commonly referred to
as rancidity. Rancidity is brought about by the action of air (oxidative
rancidity) or by micro-organisms (Ketonic rancidity). Oxidative rancidity is
accelerated by exposure to heat and light, by moisture and by the presence of
traces of certain metals (e.g. copper, nickel, iron). It is now generally
accepted that oxygen is taken up by the fat (or oil) with the formation of
compounds which react as peroxides. In general, the greater the degree of
unsaturation (the higher the iodine), the greater is the liability of the fat (or
oil) to oxidative rancidity. When the concentration of ‘peroxides’ reaches a
certain level, complex chemical changes occur and volatile products are
formed which are mainly responsible for the rancid taste and odour
(David,1976).
With most oils and fats, the free fatty acidity increases during storage
but, with refined oils particularly, the free fatty acidity figure is not
32
necessarily related to the extent to which rancidity has progressed. On the
other hand, although the ‘peroxides’ are possibly not directly responsible for
the taste and odour of rancid fats, the concentration of them as represented
by the peroxide value is often useful for assessing the extent to which
spoilage has advanced (David, 1976). Fortification of fats and oils with
antioxidants extends the storage time and protect essential nutrients (Krause
and Hunscher,1999). The main substrates for oxidation of lipids are the
unsaturated fatty acids which generally oxidize faster in a free state than
when they form part of triglycerides or phospholipids (Alais and Linden,
1999).
2.9 STORAGE AND OXIDATIVE STABILITY OF FATTY ACID
ESTERS
Storage stability refers to the ability of the fuel to resist chemical
changes during long term storage. The changes usually consist of oxidation
due to contact with oxygen from the air (Ferrari et al, 2005). Fatty acid
composition of the biodiesel fuel is an important factor in determining
stability towards air. Generally, the polyunsaturated fatty acids (C18:2,
linoleic acid; C18:3 linolenic acid) are most susceptible to oxidation. The
changes can be catalyzed by the presence of certain metals (including those
making up the storage container) and light. If water is present, hydrolysis can
also occur. The chemical changes associated with oxidation usually produce
hydroperoxides that can, in turn, produce short chain fatty acids, aldehydes
and ketones. Under the right conditions, the hydroperoxides can also
polymerize. Therefore, oxidation is usually denoted by an increase in acid
value and viscosity of the fuel. Often these changes are accompanied by a
darkening of the biodiesel colour from yellow to brown and the development
of a “paint” smell. When water is present, the esters can hydrolyse to long
chain free fatty acids which can also cause the acid value to increase.
33
There is currently no generally accepted method for measuring the
stability of biodiesel, the techniques generally used for petroleum-based
fuels, such as ASTM D 2274, have shown to be incompatible with biodiesel.
Other procedures, such as the oil stability index or the Rancimat apparatus,
which are widely used in the fats and oils industry, seem to be more
appropriate for use with biodiesel. However, the engine industry has no
experience with these tests and acceptable values are not known. Also, the
validity of accelerated testing methods has not been established or correlated
to actual engine problems. If biodiesel’s acid number, viscosity or sediment
content increase to the point where they exceed biodiesel’s ASTM limits, the
fuel should not be used as transportation fuel.
Figure 2.16: Oxidation Behaviour of Vegetable Oils and Animal Fats
34
2.10 Additization of Esters
Biodiesel, because it contains large numbers of molecules with double
bonds, is much less oxidatively stable than petroleum-based diesel fuel
(Gerpen et al, 2004).
Additives such as BHT (Butyl hydroquinone) and TBHQ (t-butyl
hydroquinone) are common in the food industry and have been found to
enhance the storage stability of biodiesel. Biodiesel produced from oils
naturally contain some antioxidants (tocopherols, i.e vitamin E), providing
some protection against oxidation (some tocopherol is lost during refining of
the oil prior to biodiesel production). Thermal process during biodiesel
pretreatment can also degrade some naturally occurring antioxidants in oils
and fats (Ferrari et al, 2005). Any fuel that will be store for more than 6
months, whether it is diesel fuel or biodiesel, should be treated with an
antioxidant additive.
Figure 2.17 shows typical antioxidants in oils and fats.
3 BHA (3-tert-butyl-4-hydroxyanisole 2BHA(2-tert-butyl-4-, hydroxyanisole
2 tert-butyl-4-methoxyphenol) 3 tert-butyl-4-methoxyphenol)
Fig 2.17: Butylated Hydroxyanisole (BHA)
OH
OCH3
C(CH3)3
C(CH3)3
OH
OCH3
35
Butylated Hydroxytoluene (BHT) Propyl Gallate (PG)
(2, 6 – di-tert-butyl-o-cresol; 4- methyl (Propyl gallate (n-propyl-
– 2, 6 – di-tert-butylphenol) 3,4,5 – trihydroxybenzoate)
Mono-tert-butylhydroquinone (TBHQ)
Figure 2.18: Antioxidants for oils and fats
2.11 Rheological Properties of Fluids
2.11.1 Biodiesel Rheology: Fluid flow phenomena
Rheology is defined as the science of the deformation and flow of
matter (Jacobs, 1999). The behaviour of a flowing fluid depends strongly on
whether the fluid is under the influence of solid boundaries. In the region
where the influence of the wall is small, the shear stress may be negligible
and the fluid behaviour may approach that of an ideal fluid, one that is
incompressible and has zero viscosity. The flow of such an ideal fluid is
called potential flow and is completely described by the principles of
Newtonian mechanics and conservation of mass. The relationship between
the shear stress and shear rate in a real fluid are part of science and Rheology.
Gases and most liquid are Newtonian. In a Newtonian fluid, the shear stress
(CH3)3 – C
CH3
OH
C(CH3)3
C – ( CH3)3
CH3
COOC3H7
OH HO
C(CH3)3
OH
OH
36
is proportional to the shear rate, and the proportionality constant is called the
viscosity.
τv = µ (du/dy)
where τv – shear stress
µ - viscosity
du/dy – shear rate
In SI unit τv is measured in Newton per square meter and µ is
kilograms per meter second or pascal-second. Viscosity data are generally
reported in millipascal-seconds or in centipoises (cP = 0.01P = 1m Pa.s)
(McCabe et al, 2005)
2.11.2 Viscosity
Viscosity can be simply defined as the internal friction acting within a
fluid, that is, its resistance to flow. A fluid in a glass, when inverted, is
subjected to gravitational forces, some fluids flow easily out of the glass,
some with difficulty and some not at all. Viscosity is therefore, the measure
of the rate of flow (Lewis, 1987). The viscosity generally increases with
molecular weight and decreases rapidly with increasing temperature. The
main effect of temperature change comes not from the increase in average
velocity, but from the slight expansion of the liquid, which makes it easier
for the molecules to slide past each another.
The viscosity is a strongly non-linear function of the temperature, but
a good approximation for temperatures below the normal boiling point is
ln µ = A + B
T
2.11.3 Kinematic Viscosity
This is the ratio of absolute viscosity to the density of a fluid µ/ ρ. The
property is called the kinematic viscosity and designated by υ. In SI, the unit
for υ is square meter per second. For liquids, kinematic viscosities vary with
37
temperature over a somewhat narrower range than absolute viscosities
(McCabe et al, 2005).
BACKGROUND: VISCOSITY OF BIODIESEL
Neat vegetable oils were primarily considered as alternatives for diesel
fuel but their very high viscosity at room temperature made them unsuitable
in diesel engines. Esters of lower alcohol (methanol, ethanol, propanol) of
plant or animal oils are very much lower in viscosities than neat oils.
Reducing viscosity is the major reason why vegetable oils or fats are
transesterified to biodiesel because the high viscosity of neat vegetable oils
or fat ultimately lead to operational problems such as engine deposits
(Knothe and Steidley, 2005; Krisnangkura et al, 2005). The viscosity of
biodiesel is slightly greater than that of petrodiesel but approximately an
order of magnitude less than that of the parent vegetable oil or fat.The best
known equation that correlates liquid viscosity and temperature is the
Andrade equation, given by:
µ = AeB/T
where A and B are constants. T is the
absolute temperature. The equation can be used for predicting viscosity up to
approximately the normal boiling point of the fluid (Krisnangkura et al,
2005).
The viscosity values are recorded for some common vegetable oils in
table 2.10.
2.12 Biodiesel Specifications and Properties
The biodiesel standard is framed as a set of property specifications
measured by specific ASTM test methods. The standard of biodiesel is
ASTM 6751 – 02.
ASTM D 6571 – 02 sets forth the specifications that must be met for a
fatty acid ester product to carry the designation “biodiesel fuel” or “B100” or
38
for use in blends with any petroleum-derived diesel fuel defined by ASTM D
975, Grades 1-D, 2-D, and low sulfur 1-D and 2-D.
The values of the various biodiesel properties specified by ASTM D
6751 are listed in Table 2.8. Each of these properties and the test method
used to measure it are also in Table 2.8. Also, Table 2.9 is for European
Biodiesel Standards EN 14212 for vehicle use and EN 14213 for heating oil
use.
Table 2.8:
39
Table 2.9:
39
40
Table 2.10: Kinematic Viscosity of oils
Oil Temperature (oF) Kinematic Viscosity (cSt)
Almond 100 43.2
Olive 100 46.7
Rapeseed 100 50.6
Cottonseed 100 35.9
Soyabean 100 28.5
Linseed 100 29.6
Sunflower 100 33.3
Castor 100 293.4
Coconut 100 29.8
Palm-kernel 100 30.9
Source: Levis, J. M. (1987).
2.13 Biodiesel Production Process Options
There are two major ways in which biodiesel can be produced. These
are: Batch processing and Continuous processing.
2.13.1 Batch Processing
The simplest method for producing alcohol esters is to use a batch,
stirred tank reactor. Alcohol to triglyceride ratios from 4:1 to 20:1
(mole:mole) have been reported with a 6:1 ratio most common (Sharma et al,
2008). The reactor may be sealed or equipped with a reflux condenser. The
operating temperature is usually about 65oC, although temperatures from
25oC to 85
oC have been reported (Gerpen et al, 2005). The most commonly
used catalyst is sodium hydroxide, with potassium hydroxide also used.
Typical catalyst loading range from 0.3% to about 1.5% (Gerpen et al, 2005).
Thorough mixing is necessary at the beginning of the reaction to bring
the oil, catalyst and alcohol into intimate contact. Towards the end of the
41
reaction, less mixing can help increase the extent of reaction by allowing the
inhibitory product, glycerol, to phase separate from the ester-oil phase.
Completions of 85% to 94% are reported (Gerpen et al, 2005).
Some groups use a two-step reaction, with glycerol removal between
steps, to increase the final reaction extent to 95+% (Sharma et al, 2008).
Higher temperature and higher alcohol:oil ratios can enhance the percent
completion. Typical reaction times range from 20 minutes to more than one
hour (Sharma et al, 2008).
Figure 2.19 shows a process flow diagram for a typical batch system.
The oil is first charged to the system, followed by the catalyst and alcohol
(methanol, ethanol, 1-propanol or butanol). The system is agitated during the
reaction time. Then agitation is stopped. In some process, the reaction
mixture is allowed to settle in the reactor to give an initial separation of the
esters and glycerol. In order processes, the reaction mixture is pumped into
settling vessel, or is separated using a centrifuge.
The alcohol is removed from both the glycerol and ester stream using
an evaporator or a flash unit. The esters are neutralized, washed gently using
warm, slightly acid water to remove residual methanol and salts, and then
dried. The finished biodiesel is then transferred to storage. The glycerol
stream is neutralized and washed with soft water. The glycerol is then sent to
the glycerol refining section.
42
Figure 2.19: Batch Reaction Process
For yellow grease and animal fats, the system is slightly modified with
the addition of an acid esterification vessel and storage for the acid catalyst.
The feedstock is sometimes dried (down to 0.4% water) and filtered before
loading the acid esterification tank. The sulphuric acid and alcohol (e.g
methanol, 1-propanol) mixture is added and sometimes the system is
pressurized or a co-solvent is added. Glycerol is not produced. If a two-step
acid treatment is used, the stirring is suspended until the alcohol phase
separates and is removed. Fresh alcohol is added and the stirring resumes.
Once the conversion of the fatty acids to methyl esters has reached
equilibrium, the alcohol/water/acid mixture is removed by settling or with a
centrifuge. The remaining mixture is neutralized or sent straight into
transesterification where it will be neutralized using excess base catalysts.
Any remaining free fatty acids will be converted into soaps in the
transesterification stage.
43
2.13.2 Continuous Process Systems
Continuous process of biodiesel production uses a Continuous Stirred
Tank Reactors (CSTRs) in series. The CSTRs can be varied in volume to
allow for a longer residence time in CSTR to achieve a greater extent of
reaction. Glycerol is usually decanted from the stream leaving the first CSTR
before charging the stream into the second CSTR. An essential element in
the design of a CSTR is sufficient mixing input to ensure that the
composition throughout the reactor is essentially constant. This has the effect
of increasing the dispersion of the glycerol product in the ester phase.
Continuous stirred tank reactor however, has disadvantage of low conversion
per reactor volume (Gerpen et al, 2004).
Figure 2.20: Plug Flow Reaction System
2.14 SPECTROSCOPY FOR BIOFUEL ANALYSIS
2.14.1 Use of Molecular Spectra as Aids in the Identification of Organic
Structures
The absorption of electromagnetic radiation by some part of the
molecule may be used to help gain precise information about structure. In
44
the case of infrared (I.R) spectroscopy, the radiation is passed through the
sample under analysis and the spectrum is recorded.
During the early stages of analysis, it if often advantageous to study
first the infrared spectrum, bearing in mind the evidence already obtained
from the infrared spectrum. Consideration of the molecular formula will
often allow the rejection of a number of alternative interpretations consistent
with the sample piece of spectroscopic evidence (Murray, 1985). Molecules
have different bond structures which absorb unique wavelength of light. I.R
measures how light interact with fuel components. The amount of light
absorbed is proportional to that components concentration in the fuel.
Infrared (I.R) region produces primary absorbances that give
fundamental knowledge of the types of chemical groups presents in the fuel.
The benefits include fast analysis, no sample preparation, no waste
chemicals, no consumables, portable/automated instruments. I.R application
for biofuel includes feedstock analysis, determination of product blends,
final product quality and contamination (Ritz and Nash, 2004)
Spectroscopic methods are being increasingly utilized for quality
control purposes (Knothe, 1999). The analytical issues with biodiesels have
two sources. The production facilities and terminal facilities need to ensure
quality (completion of transesterification, glycerol removal etc) while testing
laboratory and regulatory agents must ensure the labeled blend levels are
present. Infrared provides a rapid, precise and accurate tool for this analysis
when these needs are taken into account (Bradley, 2007).
45
2.14.2 Infrared Spectra
Carbonyl stretching vibrations Wavenumber range/cm-1
1. Aldehyde, aliphatic, saturated 1470 – 1720
aromatic 1715 – 1695
2. Ketone, R – CO – R’ 1725 – 1705
R – CO – Ar 1700 – 1680
Cyclic, saturated 1775 – 1750
3. Carboxylic acid, R – COOH (diver) 1725 – 1700
Ar – COOH 1700 – 1680
(O - C - - - O, intermolecularity 2700 – 2500
hydrogen bonded (several bonds)
4. Ester, R – COOR’ 1750 – 1735
Ar – COOR 1730 – 1715
R – COOAr 1800 – 1730
(Murray, 1985)
46
CHAPTER THREE
MATERIALS AND METHODS
3.1 Raw Materials
Castor seeds, Palm kernel seeds and groundnut seeds were obtained
from Ogige market in Nsukka, Enugu State.
3.2 Apparatus
The apparatus used in the laboratory are as follows:
Centrifuge (Hettich Universal II, Serial number 27712), Oven (Labor
Muszeripari Muvek, Type: LP-301), Thermostated water-bath (Laboratory
Thermal Equipment, Serial no: 72294150), Electronic weighing balance
(Electronic Scale High Precision Mettler Toledo, Model AD01), Manual
blender (Lander YCIASA 2E), Mechanical grinder, Extraction column,
Viscometer (Ferranti Portable Viscometer, Model: VL,VH), Rotary
evaporator (Rotavapor-R), Electric heater (STC Model no: 0016), and
Nicolet Avartar 310FTIR (Fourier Transform Infrared Spectroscopy, Model
no:310).
3.3 Extraction of Oil from Various Seeds
3.3.1 Extraction of Oils from Castor Seed
The castor seeds were de-shelled by hand picking and the shell were
separated from the seed. The seeds were spread and sundried for three
consecutive days. The seeds of initial weight 5.735kg reduced to 5.435kg
after sun drying. The sun-dried seeds were left in the oven for three hours for
dehydration (removal of moisture present in the seed) and then chopped into
smaller bits with hand and later with mortal pestle. This was done in order to
create large surface area of contact with the solvent for maximum extraction.
Absolute ethanol (2.5 litres) was used as the extracting solvent and
47
extraction column (cold extraction method) was used for the extraction of oil
from the seeds.
3.3.2 Extraction of Oils from Palm-Kernel Seed
Palm kernel seeds (3.281kg) were ground with mechanical grinder.
The ground palm kernel seeds were soaked with the 2.5 litres of solvent (n-
hexane) in an extraction column and left standing for 72 hours, after which
the tap was opened and the oil collected.
3.3.3 Extraction oil Oils from Groundnut Seed
Groundnut seeds (4.298kg) were sundried, after which it was ground
with the aid of manual blender, and then soaked with the 2.5 litres solvent
(n-hexane) in an extraction column. The extraction column was left standing
for 72 hours after which the tap was opened and the oil collected.
The solvent from the three seeds (castor, palm-kernel and groundnut)
were recovered with rotary evaporator (model ROTAVAPOR–R). The
solvent recovered were stored for further use.
3.4 Pre-treatment of Oils
Measuring cylinder was used to measure 300ml of oil and the oil was
heated to 75oC in a 500ml beaker using electric heater (STC Model no:
0016). The oil was mixed with 0.1 (v/v)% of 85% phosphoric acid, distilled
water to about 0.2 wt % of the oil. Magnetic stirrer was placed at the bottom
of the 500ml beaker and it was used to homogenized the oil for about 30
minutes. Gum which result from the homogenization was allowed to settle
and the oil was decanted into another 500ml beaker for refining.
In the refining step, temperature of the oil was restored to 75oC under
magnetic stirrer and 9.5wt% of NaOH solution was added gradually, as the
mixture was continuously homogenized. This process converts the free fatty
48
acids into soaps. 15 wt% distilled water of the total mixture was used to
wash the oil free of soap in a 500ml separating funnel. The washed oil was
later dried at 105oC using oven (LP-301) for about 30 minutes.
3.5 Determination of the Optimal Catalyst Weight
The alkali used for transesterification affects the yield of oil samples
into biodeisel. Hence, the optimal catalysts tests were studied for each oil
sample. (See table B2 in Appendix II for the process parameters).
Transesterification
The laboratory scale transesterification reactors (batch reactor) to
produce propyl esters from castor oil, palm kernel oil and groundnut oil were
carried out in a 200ml conical flask (air-tight flask) and mounted on a
magnetic stirrer. The magnetic stirrer was set to a constant speed throughout
the experiment, to ensure uniform agitation and thorough homogenization of
the reaction mixture.
Optimal catalyst tests were determined for each oil sample using 50ml
of the refined oils and the volume of 1-propanol used on the basis of 3:1, 1-
propanol to oil molar ratio. The catalyst used is sodium hydroxide (NaOH)
pellet. The weights of the catalyst were varied from 0.05, 0.10, 0.15, 0.20,
0.25, 0.30, 0.35 and 0.40g.
NaOH pellets was dissolved in 15ml of 1-propanol and the mixture
stirred for 15 minutes to form sodium methoxide (CH3ONa) in an air-tight
conical flask.
This sodium methoxide was introduced gently into the heated oil in
the reactor and the entire content was brought to a temperature of 55oC and
then held at this temperature for 60 minutes. The reaction product mixture of
the transesterification were allowed to separate into two phases by standing
for 6 hours in a separating funnel (100ml) so as to separate glycerol from the
biodiesel. The two layers – superior (biodiesel) and inferior (glycerol) were
separated by washing with warm distilled water to remove impurities. The
49
denser soapy mixtures was carefully drained from the bottom of the 100ml
separating funnel, leaving behind the superior biodiesel layer. The volumes
of the biodiesel obtained were determined in a measuring cylinder. Graphs of
biodiesel yield fraction against catalyst weight per volume of oil were
estimated and the graphs plotted.
Note: from the volume ratio of sample at 3:1 alcohol/oil molar ratio, it
was observed that 50cm3 of refined oil requires 15cm
3 of alcohol.
3.6 Determination of Kinematic Viscosity of Crude Plant oils and
Biodiesel Samples
Kinematic viscosity values of biodiesel samples was determined with
Ferranti portable viscometers (Model VL for PKO and GNO, Model VH for
CSO) at 30oC following the standard method as outlined in the Ferranti
portable viscometer manual. About 150ml of sample were measured into a
300ml beaker and placed under an outer cylinder. The outer cylinder was
immersed in the sample fluid by allowing the cylinder to rotate until the
reading was stable. The viscometer was raised above the fluid and tilted to
allow the sample to flow from the annulus back into the container and the
readings were taken from the Ferranti Portable Viscometer calibrations by
selecting the appropriate speed.
Dynamic and kinematic viscosity data which are related by density as
a factor were determined for crude plant oils (castor oil, palm kernel oil and
groundnut oil) and biodiesel produced from these oils. The viscosities in
poises, at a given speed and cylinder combination, were obtained by
multiplying the instrument reading by the appropriate Multiplying Factor
given on the calibration chart.
50
3.7 Alkali-Catalyzed Batch Production of Biodiesel
The transesterification reaction was carried out by reacting oils (castor,
palm kernel and groundnut oils) with 1-propanol in the presence of a basic
catalyst - sodium hydroxide (NaOH) pellet, analytical grade (Joechem UNN)
and the biodiesel fuels were processed in a batch type reactor at 6:1 alcohol
to oil molar ratio. Excess alcohol was used in order to shift the equilibrium
to the right. (See table B3 in Appendix II for the process parameters).
Procedure:
One hundred milli-litre each of the three oil samples (castor, palm
kernel and groundnut oils) was heated to 65oC and placed in a 250ml flat
bottom flask-batch reactor (at 6:1 alcohol to oil molar ratio, 100ml of castor
and palm kernel oil requires 60ml of 1-propanol and 100ml of groundnut oil
requires 50ml of 1-propanol). The optimal catalyst (NaOH) weight earlier
calculated for the three oils (0.50g for castor and palm kernel oils and 0.40g
for groundnut oil) was dissolved into the alcohol by vigorous stirring in a
separate air-tight container of 200ml. The alcohol-optimal catalyst weight
mixtures were poured into the oils and the final mixture stirred vigorously
for 60 minutes in an air-tight container. The reaction product mixture wass
allowed to separate into two phases at the end of the reaction; ester and crude
glycerol, by standing for 15 hours in a separating funnel so as to separate
glycerol from the biodiesel. The tap of the separating funnel was opened to
evacuate the lower layer (glycerol) and the crude biodiesel was left in the
separating funnel.
Fifty milli-litre warm distilled water at 45oC was used to wash the
crude biodiesel thrice and dried in the oven at 105oC for 60 minutes. The
volumes of the biodiesel obtained were recorded and samples were used for
characterization.
51
3.8 Characterization of the Crude, Refined Oils, Biodiesel and
Petrodiesel
3.8.1 Saponification Value (SV) Determination
One gram of sample was dissolved in 20ml of the alcoholic potassium
hydroxide solution and put into a conical flask which was attached to a
reflux condenser and the flask was heated in boiling water for 10 minutes,
shaking frequently. Two drops of phenolphthalein indicator were added into
the hot solution and it was titrated with 0.5M hydrochloric acid, shaking
frequently to colourless end point (titration = a ml). A blank was equally
carried out at the same time (titration = b ml).
Saponification value = (b – a) x 28.05
Weight in g of sample
The procedure was repeated two more times and the average titre
values calculated.
3.8.2 Acid Value (AV) Determination
One gram of sample was dissolved and mixed with 25ml diethylether
with 25ml ethanol and 2 drops of phenolphthalein indicator and was
carefully neutralized with 0.1M sodium hydroxide, shaking constantly until a
pink colour which persists for 15 seconds was obtained.
Acid value = Titration (ml) x 5.61
weight of sample used (g)
The procedure was repeated two more times, and the average titre
values calculated.
3.8.3 Iodine Value (IV) Determination
One gram of our sample was dissolved in 5ml carbon tetrachloride
(CCl4) and 5ml Wijs’ solution in a 250ml stoppered conical flask and
allowed to stand in the dark cupboard for 30 minutes. 10ml of the potassium
iodine solution and 25ml of distilled water mixed and titrated with 0.1M
52
thiosulphate solution using 2ml starch as indicator. Titration of the solution
was continued until the blue black colouration due to iodine was discharged
(titration = a ml). The procedure was repeated twice and the average titre
was calculated. Blank at the same time commenced with 10ml of carbon
tetrachloride (titration = b ml)
Iodine Value = (b – a) x 1.269
weight (in g) of sample
3.8.4 Specific Gravity Determination
Twenty five milli-litre density bottle (Wb) was thoroughly washed
with detergent, water and petroleum ether, dried and weighed (Wb). The
density bottle was filled with water, corked and weighed again (W1). The
water in the density bottle was discharged, cleaned with the diethyl ether.
After drying the bottle, it was filled with oil/biodiesel/petrodiesel samples
and the weight (W2) was taken.
Specific gravity = W2 – Wb
W1 – Wb
3.8.5 Peroxide Value Determination
One gram of biodiesel sample was weighed into a 100ml conical flask
containing 20ml of solvent mixture (2:1 volume of glacial acetic acid and
chloroform), 20ml of 50% potassium iodide (KI) solution and 1.0g of
potassium iodide (KI) crystals and the whole mixture agitated. The mixture
was then placed in a boiling water at 100oC for 30 seconds. About 5 drops of
starch solution was added to the mixture which turned the yellow colour of
the mixture to black and then titrated against 0.1M sodium thiosulphate
(Na2S2O3) until the black colour turns white (colourless). This procedure was
repeated two more times, and the average titre value was calculated (Ibitoye,
2006).
53
Peroxide Value (P.V) = T x M x 100
Sample weight (g) mmol peroxide/kg sample
where T = titre value of Na2S2O3
M = Molarity of Na2S2O3
3.8.6 Calorific (heating/combustion) Value Determination using Bomb
Calorimeter (Model: XRY – 1A)
Castor, palm kernel and groundnut oils biodiesel sample were
characterized for their combustion values – and compared to conventional
diesel fuel (Petrodiesel).
Procedure:
The outer canister of the bomb calorimeter was filled with water. The
inner canister was filled with 3 litres of distilled water. 1g of biodiesel/
petrodiesel sample to be evaluated was measured and placed in a mould
(small metal crucible). 10cm ignition thread (wire) connected to the
electrodes of the oxygen bomb, was placed and allowed to keep in touch
with the sample. The bomb was filled in with oxygen at a pressure of 2.8 –
3.0 mPa and then transferred into the inner canister (filled with 300cm3 of
distilled water). The necessary wires were connected and the temperature
sensor was placed into inner canister.
The power was switched on and the water inside the inner canister was
stirred for about 2 minutes and the initial temperature of the water was noted
and denoted To. The Bomb calorimeter was fired and the final temperature
(Tf) was recorded when the time got to 31 minutes. Length of the pieces of
unburnt firing wire was measured (l) and the inner lining of the oxygen
bomb and crucible were washed with distilled water into a conical flask. The
wash solution was titrated against 0.0709N Na2S2O3, using 2 drops of methyl
red indicator.
54
Calorific values of the samples were calculated from the expression:
W = E∆T – Φ – V
m
where w = heat of combustion of sample (calorie/g)
m = mass of sample to be evaluated (g)
E = 13,039.308 calories/g , Benzoic acid standard
T = change in temperature = Tf – To
Φ = 2.3l (where l = length of the unburnt wire)
V = volume of alkali (Na2S2O3 solution) cm3
The combustion value were converted to Joules from the expression
1 calorie = 4.148 Joules
3.9 Investigation of Temperature Dependence of Biodiesel Kinematic
Viscosity and Specific Gravity / Biodiesel-Petrodiesel Blending
The viscosity of fatty acid propyl esters (biodiesel) were measured at
various temperatures. The esters were analyzed for viscosity at temperatures
of 32, 45, 60, 75oC (using samples of alkali catalyzed biodiesel for the
production of biodiesel at 6:1 alcohol to oil molar ratio as in section 3.8 and
allowed to cool to room temperature 30oC) using Ferranti portable
viscometer (Model: VL, VH).
Procedure
The temperatures of the biodiesel samples (castor, palm kernel and
groundnut) and petrodiesel (commercial) were taken each and recorded at
room temperature 30oC. About 150ml of biodiesel/petrodiesel sample was
measured into a 300ml beaker. The outer cylinder was immersed in the
biodiesel/petrodiesel sample, the speeds required were selected and the
motor was switched on. The motor allows the cylinder to rotate until the
reading was stable. The viscometer was raised above the
biodiesel/petrodiesel sample and tilted, to allow the sample to flow from the
55
annulus back into the container. The viscosity was read on the calibrated dial
at the top of the portable viscometer.
Using the method for the determination of specific gravity described
earlier, biodiesels (fatty acid propyl esters) were found to be temperature
dependent. The same temperature intervals used for the determination of
kinematic viscosity were repeated for the specific gravity. In order to reduce
castor oil kinematic viscosities so as to meet ASTM standards, castor oil
biodiesels were blended with petrodiesel in the following manner:
Petrodiesel (90%) – biodiesel (10%) : B10
Petrodiesel (80%) – biodiesel (20%) : B20
Biodiesel (Propyl esters) : B100
Petrodiesel : P100
3.10 Transesterification Kinetics in a Batch Reactor
Transesterification reactions were performed in a 250ml round bottom
flask (herein referred to as batch reactor) on castor, palm kernel and
groundnut oils at 6:1 alcohol to oil molar ratio in a thermostated water bath
that was capable of varying temperature between 0–120oC. The reaction
temperatures were varied at 32, 45, 60 and 75oC (referred to desired
temperature in the procedure) at various time interval 5, 10, 20, 60 seconds.
(See table B4 in Appendix II for the process parameters).
Procedure:
The batch reactor (250ml round bottom flask was filled with 100ml of
refined oil sample (castor, palm kernel and groundnut oils) was heated to the
desired temperature using optimal catalyst weight–NaOH pellet required
for each oil (0.50g for castor and palm kernel oil and 0.40g for groundnut
oil), and a measured amount of 1-propanol (60ml for CSO and PKO and
50ml for GNO) were mixed and heated to the desired temperature with the
aid of thermostated waterbath. The reacting mixture (1-propanol and sodium
56
hydroxide (NaOH pellet)) were heated to 65oC in a separate 100ml capacity
container (air-tight) which was then added to the oil originally in the batch
reactor. Mechanical stirrer was inserted and the reacting mixture agitated
(air-tight). At this point, the reaction was assumed to have started and timed.
At various times; 5, 10, 20, 60 seconds, 10ml of the sample was
withdrawn quickly from the reactor with a syringe and then placed in the test
tubes containing 3 drops of 0.1M hydrochloric acid, which was added to
neutralize the catalyst (Darnoko and Cheryan, 2000).
The sample was then centrifuged (Centrifuge-Hetich Universal II,
Speed 0 to 100%). The centrifuge was set at 90% for 20 minutes. Two layers
(phases) were observed after centrifugation – the top layer, consisting of
biodiesel and a semi-solid viscous layer at the bottom. The biodiesel layer
(superior layer) was carefully decanted into a container (50ml capacity).
Volume of biodiesels were recorded as in Table 4.10 This procedure
was repeated for the three oils.
3.11 Infrared Spectroscopy-Biodiesel Product Analysis Procedure
Biodiesel produced at 65oC as outlined in section 3.7 using optimal
catalyst weights were analyzed using Fourier Transform Infrared
spectrophotometer (Model: 310FT-IR). The purpose of this analysis was to
measure how light interacts with fuel components.
Procedure:
A Nicolet Avartar 310FT-IR (Fourier Transform Infrared
Spectrophotometer) equipped with KBr beam splitter. The smart ARKTM
attenuated total reflection sensory was used to collect the data. About 0.4ml
of biodiesel samples were smeared to cover the sampling crystal. Spectra
were collected in 40 seconds.
57
The data were collected using OMNICTM
spectroscopy software
showing spectrum region, absolute threshold, sensitivity, peak list-positions
as shown in figures 4.10 - 4.15.
58
CHAPTER FOUR
RESULTS AND DISCUSSION
This is the section in which the data obtained for the project/thesis are
presented, analyzed and discussed. Calculation involved in the
determinations are contained in Appendices I, II, III and IV.
4.1 EXTRACTION OF CRUDE PLANT OILS
The results obtained from the extraction of various plant oils (Castor
seed, palm kernel and groundnut oils) are shown in Table 4.1.
Table 4.1: Yield of oils
Sample Weight of seeds
(Kg)
Weight of extracted
oil (Kg)
Percentage (%)
yield
Castor seed oil 7.80 3.80 48.72
Palm kernel oil 6.56 2.78 42.38
Groundnut oil 8.10 3.76 46.42
The three oil samples showed good yield, with castor seed, having
highest percentage (%) yield.
4.2 PRE-TREATMENT OF OILS
It is a well known fact that crude plant oils contain some free fatty
acids and phospholipids. The three oil samples used for biodiesel production
were pretreated. The pre-treatment (processing) result is shown in Table 4.2
Table 4.2: Percentage Loss on Pre-treatment
Sample Weight of unrefined
oil (kg)
Weight of refined
oil (kg)
Percentage (%)
loss on pre-
treatment
Castor seed oil 3.80 3.58 5.78
Palm kernel oil 2.78 2.61 6.12
Groundnut oil 3.76 3.52 6.38
59
The free fatty acids and phospholipids are responsible for the
significant losses recorded during pre-treatment. The oil extracted from
groundnut has high acid values which is responsible for its high percentage
loss during pre-treatment with 6.38%, followed by palm kernel oil (6.12%).
4.3 OPTIMAL CATALYST WEIGHT TEST
The graphical relationship between the biodiesel yield (%) and
percentage weight per volume of the catalyst (% wt/v) are depicted in the
Figure 4.1.
From Appendix IV (see Table D1 in Appendix IV for the result of the
optimal catalyst weight test), it is observed that the product volume
(biodiesel yield) increased steadily from 0.10% wt/v of the catalyst (NaOH)
until it peaked at 0.5% wt/v of catalyst and thereafter, a decrease was
witnessed for CSO and PKO. But GNO peaked at 0.4% wt/v but witnessed
decrease thereafter. It is clear therefore that increment in percentage weight
per volume of the catalyst would not yield further volume increase in
biodiesel obtained from castor seed, palm kernel and groundnut oils. The
optimal catalyst weight test helps to confirm that increase in the amount of
catalyst only leads to production of soaps and no biodiesel.
60
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.810
20
30
40
50
60
70
80
Percentage[%] (wt/v) of catalyst
Pe
rce
nta
ge
[%]
Bio
die
se
l Y
ield
CSOCSO
GNOGNO
PKOPKO
Fig. 4.1: Variation of Percentage (%) Yield of Biodiesel with Percentage
(%) (w/v) of Catalyst for CSO, PKO and GNO
61
4.4 Properties of Crude, Refined and Biodiesel Obtained
Different properties like saponification value (S.V), iodine value (I.V)
and acid value (A.V) were determined for crude, refined and biodiesel
produced from castor, palm kernel and groundnut oils. These results were
discussed in the following sections.
Table 4.3: Result for the Characterization of Crude, Refined and Biodiesel
Sample S.V
(mg KOH/g)
A.V
(mg NaOH/g)
I.V
g of Iodine/g
Crude CSO 183.70 3.02 12.33
Crude PKO 242.80 3.04 12.69
Crude GNO 189.70 3.78 75.45
Refined CSO 181.00 0.74 11.23
Refined PKO 238.40 0.79 12.38
Refined GNO 182.30 0.98 74.15
CSO biodiesel 168.20 0.44 11.11
PKO biodiesel 204.54 0.48 12.11
GNO biodiesel 180.08 0.52 74.05
CSO – Castor oil, PKO – Palm kernel oil and GNO – Groundnut oil
4.4.1 Saponification Value
Saponification values of propyl esters prepared from castor, palm
kernel and groundnut oils were less than those prepared from crude oils. This
could be due to the presence of phosphatides which were removed during
degumming and refining process. The saponification values of propyl esters
were within the range of 168.20 to 242.80 mgKOH/g. The average molecular
weight of oil can be calculated by multiplying the inverse of saponification
value by 168000 (Titipong, 2006). Therefore, the higher the saponification
value, the lower the molecular weight.
62
4.4.2 Iodine Value
The iodine value of the conventional diesel fuel was approximately 10
(Gupta et al, 2007). Therefore, the biodiesel had significantly higher degree
of unsaturation than diesel fuel (10.11g of iodine/g for castor biodiesel,
12.11g of iodine/g for palm kernel biodiesel and 74.05g of iodine/g for
groundnut oil biodiesel), though the iodine values of the refined and
unrefined oils did not show any appreciable difference. This implies that
diesel engine utilizing biodiesel is more susceptible to gum formation than
that utilizing conventional diesel fuel due to the higher iodine values of
biodiesel.
4.4.3 Acid Value
The acid value of propyl esters prepared from castor, palm kernel and
groundnut oils were 0.44, 0.48 and 0.52 mg NaOH/g respectively and 3.02,
3.04, 3.78 mg NaOH/g for unrefined oil and 0.74, 0.79, 0.98 mg NaOH/g for
refined oils. The results shows that both refined and unrefined oils could not
be used directly as fuel in diesel engine since their acid value is above the
ASTM requirement while the results of biodiesel produced from these oils
conform to ASTM D 6751 standards.
4.5 Physical Characterization of Castor, Palm Kernel and Groundnut
Oils Biodiesel and Petrodiesel
In assessing the suitability of the castor, palm kernel and groundnut
oils biodiesel produced as alternative diesel fuel, the CSO, PKO, GNO
biodiesel and the commercial grade fossil diesel (petrodiesel) were analyzed
for heat of combustion (heating/calorific value), specific gravity and
kinematic viscosity.
Results obtained are presented in the Table 4.4.
63
Table 4.4: Physical Characterization of Biodiesel and Petrodiesel
Specific gravity at
28oC
Calorific
value MJ/kg
Kinematic
Viscosity (mm2/s) at
40oC
CSO biodiesel 0.87 37.54 7.21
PKO biodiesel 0.90 38.64 3.56
GNO biodiesel 0.89 37.52 4.12
Petrodiesel 0.83 45.52 2.85
4.5.1 Specific Gravity
The specific gravity recorded for CSO, PKO and GNO biodiesels
were higher than the values obtained for petrodiesel. 1.049 times that of
petrodiesel for CSO, 1.048 times that of petrodiesel for PKO and 1.078 times
that of petrodiesel for GNO.
The specific gravity obtained for the castor, palm kernel and
groundnut oils biodiesel falls within the limit specified for biodiesel fuel in
Europe (EN 14214:086–0.90). Specific gravity (also known as relative
density) refers to the ratio of the density of a fuel to the density of water at
the same temperature. The level of agreement recorded in specific gravities
for the CSO, PKO and GNO biodiesels is an important pointer to suitability
of the biodiesel fuel substitute as important fuel performance indicators such
as heating values, fuel storage are correlated with specific gravity (Yuan et al,
2004; Ajav and Akingbehin, 2002).
4.5.2 Calorific Value
The petrodiesel presented the highest calorific value – 45.52 MJ/kg,
which are far higher than the biodiesel produced from castor, palm kernel
and groundnut oils. Calorific value is the quantity of heat energy, which is
emitted by fuel at the time of combustion under set conditions of experiment.
It was found that overall, that castor, palm kernel and groundnut oils propyl
64
esters (biodiesel) behaved comparably to diesel fuel (petrodiesel) in terms of
rate of heat release.
4.5.3 Kinematic Viscosity
Fuel viscosity is regulated by the standards at 40oC. From Table 4.4,
CSO, PKO and GNO biodiesel has higher viscosity than conventional diesel
fuel (petrodiesel) in agreement with reports from several researchers (Alamu
et al, 2007; Ajav and Akingbehin, 2002). Kinematic viscosity is defined as
the resistance to flow of a fluid under gravity. The viscosity of biodiesel
from castor oil is thrice the viscosity of fossil diesel (petrodiesel) and for
groundnut oil biodiesel, viscosity is twice the viscosity of petrodiesel.
The kinematic viscosity for PKO and GNO biodiesel falls within the
specified limits by ASTM D6571 (3.5-5.0) but that of castor oil biodiesel
does not. Knothe and Steidley (2005), reported that castor oil biodiesel, in its
neat form exceeds all kinematic viscosity specifications in biodiesel
standards due to the high content of ricinoleic acid. The reported technical
implication of higher viscosity biodiesel is that it decreases the linkages of
fuel in a plunger pair and in turn it changes the parameters of a fuel supply
process (Lebedevas and Vaisekauskas, 2006).
4.6 Alkali-Catalyzed Batch Production of Biodiesel at 65oC
Table 4.5: Results of Alkali-Catalyzed Batch Production of Biodiesel at 65oC
Pre-
treated oil
sample
Volume
of oil
(cm3)
Volume of
1-propanol
(CH3CH2CH2OH)
Volume
of
biodiesel
(cm3)
Conversion Percentage
(%)
Conversion
Castor oil 100.00 60.00 89.50 0.895 89.5
Palm
kernel oil
100.00 60.00 87.00 0.870 87.0
Groundnut
oil
100.00 50.00 81.80 0.818 81.8
65
The biodiesel was produced by transesterifying refined oil samples
(castor oil, palm kernel and groundnut oils) at 6:1 1-propanol to oil molar
ratio in the presence of their various optimal catalyst weight earlier
calculated (0.50 wt/v for castor and palm kernel oils, and 0.40 wt/v for
groundnut oil) at 65oC for 60 minutes. The process for the production of
biodiesel using an alkali (sodium hydroxide – NaOH) catalyzed method in a
batch reactor was composed of glycerol separation steps (after each
transesterification step) and an ester purification step.
As can be seen from table 4.5 , the process proved to be successful for
the production of biodiesel from a high quality feedstock (refined oils).
Castor oil gave the highest conversion (89.5%) followed by palm kernel
87.0% and groundnut 81.8%. The result proved to be consistent within the
limit of experimental errors. The problems of saponification was greatly
reduced because the feedstock (castor, palm kernel and groundnut oils) used
were pre-treated. The pre-treatment greatly reduced the free fatty acid which
reacts with sodium hydroxide to form soap which could have in turn reduced
the conversion of oil, alcohol (1-propanol) and catalyst (NaOH) into
biodiesel.
66
4.7 Viscosity of Biodiesel at Different Temperatures
Table 4.6: Variation of Kinematic Viscosity of Biodiesel with Temperature
Temperature Kinematic Viscosity
T
(oC)
T
(K)
1/T
(K-1
)
1/T
(K-1
)
V (mm2/s) ln V
CSO PKO GNO CSO PKO GNO
32 303 0.0033 3.30x10-3
8.12 4.05 5.13 2.09 1.40 1.64
45 318 0.0031 3.14x10-3
7.14 3.54 4.08 1.97 1.26 1.41
60 333 0.0030 3.00x10-3
7.02 3.50 4.01 1.95 1.25 1.39
75 348 0.0029 2.87x10-3
6.89 3.46 3.64 1.93 1.24 1.29
The graphs obtained (Figures 4.2 – 4.4) using Andrade equation shows
relationship between kinematic viscosity V and temperature T (K). In
studying the kinematic viscosity dependence on temperature, variation in
viscosity were analyzed using Andrade Equation (V=AexpB/T
) to establish
the relationship between the viscosities of the sample, with temperature. The
result showed that as the temperature increases, kinematic viscosity
decreases.
From the graphs, Andrade equation was simplified to obtain constants
A and B.
Table 4.7: Simplification of Andrade Equation of Biodiesel Sample
Sample A B
CSO biodiesel 1.76 466.67
PKO biodiesel 1.05 500.00
GNO biodiesel 1.35 599.10
67
1/T (K-1
)
Fig. 4.2: Graph of lnV CSO against 1/T (K-1
)
1.70
1.60
2.00
1.90
ln V
2.20
1.80
2.10
0.0027 0.0029 0.0027 0.0030 0.0031 0.0032 0.0033 0.0034
68
Fig. 4.3: Graph of lnV PKO against 1/T (K-1
)
1.20
1.10
1.50
1.40
ln V
1.70
1.30
1.60
0.0027 0.0029 0.0027 0.0030 0.0031 0.0032 0.0033 0.0034
69
1/T (K-1
)
1.20
1.10
1.50
1.40
ln V
1.70
1.30
1.60
0.0027 0.0029 0.0027 0.0030 0.0031 0.0032 0.0033 0.0034
Fig. 4.4: Graph of lnV GNO against 1/T (K-1
)
70
A is evaluated from the intercept of the graph of lnV against 1/T (K-1
)
and B is evaluated from the slope of the graph as follows.
B = lnV
(1/T) (K-1
)
Similarly, using the same biodiesel samples, the specific gravities are
recorded at room temperature as shown in the table 4.8.
Table 4:8: Variation of Specific Gravity of Biodiesel Samples with
Temperature
Temperature Specific Gravity
(oC) CSO PKO GNO
32 0.86 0.88 0.82
45 0.84 0.87 0.81
60 0.81 0.85 0.80
75 0.80 0.84 0.80
The graph of specific gravity against temperature (oC) is shown in
Figure 4.5.
The specific gravities of biodiesel fuel displays a linear specific
gravity temperature relationship. Though there is less significant decrease in
specific gravity with respect to biodiesel produced as temperature increases.
Viscosity and specific gravity of biodiesel samples were found to be
temperature dependent. As the temperature increases from 32 to 75oC, their
specific gravities slightly decreases.
71
Sp
ecif
ic g
rav
ity
T (oC)
Fig. 4.5: Graph of Specific Gravity of CSO, PKO and GNO at different
temperatures
GNO
CSO
PKO
0.80
0.78
0.86
0.84
0.90
0.82
0.88
40 30 50 60 70 80
PKO
CSO
GNO
72
The viscosities of castor oil biodiesel esters were in the range of 6.89 –
8.12 mm 2
/s (see table 4.6) which were higher than that of European
biodiesel standards (EN 14214:3.5 – 5.0) and American Society of Testing
Material Standards (ASTM D6751. 1.9 – 6.0). Knothe and Steidley (2005)
reported that the introduction of an OH group significantly increases
viscosity and this is of significance for production of castor oil-based
biodiesel, a fuel that in its neat form exceeds all kinematic viscosity
specifications in biodiesel standards due to the high content of ricinoleic acid
in castor oil. In order to solve this problem, biotechnological interventions
for improving castor for biofuels have evolved. In castor oil, though beyond
the limit of this experimental work, transgenic technology approach has been
proposed for reduction of the toxic protein ricin and conversion of ricinoleic
(12-hydroxyoleic acid) rich castor oil to oleic rich oil (Sujatha, 2009).
However, the limit values of viscosity can be met through
transesterification followed by dilution or blending with conventional diesel
fuel and vegetable oil (Sujatha, 2009). Meanwhile palm kernel and
groundnut biodiesel esters conform to ASTM D 6751 standards.
4.8 CASTOR OIL BIODIESEL/PETRODIESEL BLENDING
In order to obtain acceptable kinematic viscosity result for castor oil,
the biodiesels produced were blended with petrodiesel in the following
manner.
Petrodiesel (90%) – biodiesel (10%) : B10
Petrodiesel (80%) – biodiesel (20%) : B20
Biodiesel (propyl esters) : B100
Results obtained are shown in Table 4.9.
73
Table 4.9: Comparison of Kinematic viscosity and Specific Gravity of
Castor oil Biodiesel and Petrodiesel Blend with Unblended Biodiesel
Properties B10 B20 B100 P100
Specific gravity (28 oC) 0.85 0.86 0.87 0.83
Kinematic viscosity mm2/s (40
oC) 4.24 4.98 7.21 2.85
The properties of the B100, B20 and B10 mixtures are comparable to
those of petroleum diesel P100 and acceptable within what is specified for
biodiesel in the ASTM D6751 standards (with the exception of viscosity of
B100).
4.9 Kinetic Studies at Various Temperatures
This section discusses the effects of temperature and reaction time on
biodiesel yield and conversion. As evident from Appendix III, volume of
biodiesel and percentage (%) biodiesel conversion increases with respect to
time and temperature. Figures 4.6 - 4.9 shows the progress of the biodiesel
conversion for castor, palm kernel and groundnut oils.
With the reaction time increased to 20mins, an improved biodiesel
conversion of 66% was achieved for castor oil (CSO) biodiesel at 32oC. This
trend continued with reaction time up to 60mins with conversion of 89%.
Similar results were achieved for PKO and GNO and the same trend of the
graph obtained. This implies that within the time range of 5–60 mins, CSO,
PKO and GNO biodiesels yield increased with reaction time. It was also
observed that biodiesel conversion of oils were higher as temperature was
increased to 45, 60 and 75oC for the biodiesels (CSO, PKO and GNO).
The graphs of percentage conversion of oils against time were shown
in Figures 4.6 – 4.9.
74
0 10 20 30 40 50 6030
40
50
60
70
80
90
100
Time [Min]
Pe
rce
nta
ge
[%]c
on
ve
rsio
n a
t 3
0[d
eg
]
GNOGNOPKOPKO
CSOCSO
0 10 20 30 40 50 6040
50
60
70
80
90
100
Time [Min]
Pe
rce
nta
ge
[%]c
onve
rsio
n a
t 4
5[d
eg
]
GNOGNOPKOPKO
CSOCSO
Fig 4.6: Graph of Percentage (%) Conversion of biodiesel against time (min)
Kinetic result at 32oC
Fig 4.7: Graph of Percentage (%) Conversion of biodiesel against time (min)
Kinetic result at 45oC
75
0 10 20 30 40 50 6040
50
60
70
80
90
100
Time [Min]
Pe
rce
nta
ge
[%]c
on
ve
rsio
n a
t 6
0[d
eg
.]
CSOCSO
PKOPKOGNOGNO
0 10 20 30 40 50 6040
50
60
70
80
90
100
Time [Min]
Pe
rce
nta
ge
[%]c
on
ve
rsio
n a
t 7
5[d
eg
.]
GNOGNO
CSOCSO
PKOPKO
Fig 4.9: Graph of Percentage (%) Conversion of biodiesel against time (min)
Kinetic result at 75oC
Fig 4.8: Graph of Percentage (%) Conversion of biodiesel against time (min)
Kinetic result at 60oC
76
4.10 Biodiesel Storage/Oxidative Stability Measurement
In the oxidative stability test, the biodiesels produced at 65oC using
alkali-transesterification methods (see section 3.7) were exposed to light and
air. The peroxide value were determined at one month interval each (herein
referred to as run)
The most significant and undesirable change in liquid fuel with time is
the formation of solids, also termed filtrate sediments. During long-term
storage oxidation due to contact with air (autooxidation) presents a
legitimate concern with respect to maintaining fuel biodiesel quality (Ferrari
et al, 2005). The progress of the oxidation was monitored by measuring the
peroxide value or the fraction of the biodiesel/petrodiesel that has been
converted to a peroxide molecule.
Table 4.10 shows oxidative stability results of the biodiesel from
castor, palm kernel, groundnut oils and conventional diesel (Petrodiesel)
samples evaluated through their peroxide values. The results were taken over
a period of three months (a month interval for each run) at room temperature
28–30oC. Gerpen et al (2004) reported that biodiesel have no conversion for
a period of time, due to presence of natural antioxidant in the biodiesel oil
sample (three months – called the induction period) but then oxidize quickly.
Table 4.10: Peroxide Values of Castor, Palm kernel, Groundnut Oils and
Petrodiesel
Peroxide Value (mmol peroxide/kg sample)
Sample Run I Run II Run III
CSO Biodiesel 80 80 81
PKO Biodiesel 20 40 50
GNO Biodiesel 10 50 60
Petrodiesel Neutral Neutral Neutral
CSO – Castor oil, PKO – Palm kernel oil and GNO – Groundnut oil
77
The results obtained showed that conventional diesel (Petrodiesel)
showed greater stability than the biodiesel produced from castor, palm kernel
and groundnut oils – as it showed no result (trace) when peroxide value was
determined. This is because petroleum based diesel fuels (Petrodiesel) are
treated with a wide range of additives to improve lubricity, oxidative
stability, corrosion resistance and many other properties unlike biodiesel
which contain more or less unsaturated fatty acids in its compositions which
are susceptible to oxidation reactions, accelerated by exposition to oxygen,
being able to change to polymerize compounds (Meher et al, 2004).
Next to the petrodiesel which showed greater stability is castor oil
biodiesel, followed by palm kernel and groundnut oils diesel. For castor oil
biodiesel, the peroxide values remained constant for run I and II – 80mmol
peroxide/kg sample and increases slightly at run III – 81mmol peroxide/kg
sample. Sujatha (2009) reported that the presence of hydroxyl group and
double bonds impacts unique chemical and physical properties that make
castor oil a vital raw material and stabilizes the oil against oxidation. Castor
oil has a good shelf life when compared to other vegetable oils and it does
not turn rancid when subjected to excessive heat.
The peroxide value results taken for the samples shows that castor oil
biodiesel can withstand oxidation after two months of production unlike
palm kernel oil biodiesel whose peroxide value increases sharply from
20mmol peroxide/kg sample (run I) to 40mmol peroxide/kg sample (run II)
and then in the third run increases to 50mmol peroxide/kg sample. The
results from groundnut oil biodiesel show the worst oxidative stability as its
peroxide value increase sharply from 10mmol peroxide/kg sample to
50mmol peroxide/kg sample in the second run and the 60mmol peroxide/kg
sample in the third run. Gerpen et al (2004) reported that, oxidation is an
autocatalytic process so that when it starts, it progresses at ever-increasing
rate and this were exhibited by PKO and GNO biodiesel, but the presence of
78
hydroxyl group and double bonds in castor oil stabilizes the oil against
oxidation.
4.11 Infrared Spectroscopy-Biodiesel Product Analysis Results
The infrared spectra of a B100 biodiesel (Fatty Acid Propyl Esters
FAPE) from castor, palm kernel and groundnut oils are shown in Figures
4.10-4.15. The strong ester peaks near 1750 cm-1
(the C=O vibration) and
around 1170-1200 cm– 1
(the C–O vibration) were clear and are the basis for
the procedure. There is no interference in the spectra for CSO, PKO and
GNO.
The spectrum, region, Absolute threshold, sensitivity, peak list
positions are shown in Figures 4.10– 4.15.
79
Fig. 4.10: Percentage Transmittance versus Wavenumber (cm-1
) for CSO
79
80
Fig. 4.11: Esters, Olefins and Aliphatic Hydrocarbons Percentage Transmittance versus
Wavenumber (cm-1
) for CSO
80
81
Fig. 4.12: Percentage Transmittance versus Wavenumber (cm-1
) for PKO
81
82
Fig. 4.13: Esters, Olefins and Aliphatic Hydrocarbons Percentage Transmittance versus
Wavenumber (cm-1
) for PKO
82
83
Fig. 4.14: Percentage Transmittance versus Wavenumber (cm-1
) for GNO
94
94
83
84
Fig. 4.15: Esters, Olefins and Aliphatic Hydrocarbons Percentage Transmittance versus
Wavenumber (cm-1
) for GNO
84
85
CHAPTER FIVE
CONCLUSION AND RECOMMENDATIONS
5.1 CONCLUSION
The population growth, ever increasing use of transport fuels, rising
prices of fossil fuel, climate change and environmental pollution demands
use of renewable energy sources for a more sustainable energy solution. Vast
scope exists for exploitation of castor, palm kernel and groundnut oils as
bioenergy crops (although there are still some technological challenges to
overcome especially for castor oil biodiesel).
The following conclusions could be drawn from the present study:
i. Biodiesels has been produced in a batch reactor using alkali-catalyzed
method.
ii. In order to obtain biodiesel, transesterification process has been
studied. Transesterification time controls the yield of product while
purification is fundamental in order to fulfill the characteristics of
propyl esters (biodiesel) as fuel.
iii. Temperature has noticeable effect on the transesterification process.
iv. Specific gravity of the biodiesel samples were found to be higher than
that of petrodiesel and that specific gravity of biodiesel samples were
temperature dependent. Also, specific gravities of castor oil biodiesel
blend (B10 and B20) were lower than that of unblended biodiesel.
v. Calorific values of the biodiesel samples were lower than that of
petrodiesel combusted under the same conditions of experiment.
vi. Biodiesel yield increases with reaction time up to 60 minutes.
vii. The viscosities of biodiesel samples decrease as temperature increases.
Both palm kernel and groundnut oils biodiesel conforms to kinematic
viscosities ASTM D6751 and EN 14214 specification standards.
viii. Castor oil biodiesel has the highest storage stability.
86
ix. The infrared analysis produces primary absorbances that give
fundamental knowledge of the type of the chemical group present in
the biodiesels.
Lastly, relying on fossil fuel alone is no longer realistic due to global
depletion of the non-renewable energy sources, its attendant negative
environmental impact. The race for energy security in the face of imminent
oil shortage is already gathering momentum. Countries in Asia, Europe,
South American and many US state governments are not waiting for their
fossil fuel to dry up completely before searching for alternative, and only
countries that don’t value their own security and that of their citizens would
stand aloof.
5.2 RECOMMENDATION
High viscosity limits the widespread use of castor oil as alternative to
be used in diesel engine as this report showed that castor oil biodiesel
viscosity exceeds both European/American and all other specification
standards. Likewise, in castor seed, research effort should be proposed for
reduction of the toxic protein ricin and conversion of ricinoleic acid rich
castor oil to oleic rich oil.
In future, a lot of work can be done to reduce the cost of biodiesel if
we consider non-edible oils, used frying oils instead of edible oils. Non
edible oils such as Neem, Karanja, Jatropha etc are easily available in
Nigeria and very cheap compared to edible oils. With the mushrooming of
fast food centres and restaurants in Nigeria, it is expected that considerable
amount of used frying oils will be discarded. This can be used for making
biodiesel.
All potential feedstocks for biofuel (biodiesel) production are in
abundance in the country (Nigeria). Nigeria, with her expansive arable land
mass, can be one of the world’s leading exporters of biodiesel, if the
87
government puts a premium on energy security like many countries (such as
US and some European countries) are now doing. However, there are fears
that since biodiesel relies on primary agricultural products, a substantial
growth in the biodiesel industry could make the prices of vegetable oil
unaffordable to the common man. Hence, our approach to renewable energy
sources should be gradual.
Lastly, government should provide funding, enabling environment and
an enticing package of incentives. This involves providing comprehensive
policy support and funding for research in the area of renewable energy
source (biofuels).
88
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APPENDIX I
SAPONIFICATION VALUES (S.V)
These values were calculated from our expression in the procedure
S.V = (b – a) x 28.05
Weight (in g) of sample
For example,
GNO biodiesel = 28.05 (24.00 – 17.58)
1
= 180.08mg KOH/g
IODINE VALUES (I.V)
The iodine values were calculated from the expression as outlines in
the procedure.
I.V = (b – a) x 1.269
Weight (in g) of sample
For example,
Crude PKO = (49.00 – 39.00) x 1.269
1
= 10 x 1.269
= 12.69g of iodine/g
ACID VALUES (A.V)
The acid values were estimated from the expression in the procedure.
AV = Titration (ml) x 5.61
Weight of sample used
For example,
Refined GNO = 0.28 X 5.61
1
= 1.57mg NaOH/g
98
PEROXIDE VALUE (P.V):
Peroxide value were calculated using the formula
Peroxide value (P.V) = T x M x 1000
Sample weight (g) mmol peroxide/kg sample
where T – titre value of Na2S2O3
M – Molarity of Na2S2O3
For example, castor oil biodiesel
Initial burette reading = 38.50
Final burette = 38.20
P.V = (38.50 – 38.20) x 0.1 x 1000
1
= 30 mmol peroxide/kg sample
Viscosities:
Dynamic viscosity (cP) = 102Mf.Ir
Kinematic viscosity (mm2/s) = 10
2Mf.Ir/p (g/cm
3)
where Mf - Multiplication factor, peculiar for each cylinder
Ir – Instrument reading (Poise)
For example CSO kinematic viscosity is calculated as
Dynamic viscosity µ (cP) = 102 (0.0087) 39.5
Kinematic viscosity V (mm2/s) = µ (Dynamic viscosity)
ρ (sample density)
= 102 (0.0087) (39.5)
0.96
= 35.78 mm2/s
SPECIFIC GRAVITY (S.G)
S.G were calculated from the expression
S.G = W2 – Wb
W1 – Wb
where W2 = weight of density bottle + sample
W1 = weight of density bottle + water
99
For example, S.G of Petrodiesel;
Volume of density bottle = 25ml
weight of Density bottle = 24.18g
weight of Density bottle + water = 49.07g
weight of Density bottle + Petrodiesel = 45.07g
S.G of Petrodiesel = 45.07 – 24.18 = 20.89
49.23 – 24.18 25.85
= 0.83
CALORIFIC/COMBUSTION VALUES:
Calorific values were calculated from the expression
W = E∆T – Φ – V
m
where E = Benzoic acid standard = 13,039.308 cal/g
∆T = Temperature difference = (Tf – To)
W = Calorific value of the sample (calorie/g)
m = weight of the sample (g)
Φ = 2.3L (where L = Length of the unburnt wire)
V = titre value of the Na2CO3 solution
The combustion value were converted to Joules, 1 calorie = 4.148 Joules
For example, the calorific value of PKO biodiesel in Table 4.6 was
obtained thus:
W = 13.039.308 (0.75) – 16.21 – 5.32 cal/g
1.048
= 38.62 MJ/kg
100
APPENDIX II
Percentage (%) yield of the oil = Weight of extracted oil x 100%
Weight of oil seeds
The percentage weight per volume (% wt/v) of the catalyst was
calculated based on the formula.
% wt/v = weight of catalyst x 100%
volume of oil
and that of percentage yield of biodiesel
% yield of biodiesel = Volume of (CSO, PKO, GNO biodiesel) x 100%
Volume of oil
% loss on pretreatment = Weight of unrefined oil – Weight of refined oil x 100%
Weight of unrefined oil
Conversion of oils
The conversions of oils used in Table 4.7 were based on the
stoichiometric balance, that 100cm3 of oil gives approximately 100cm
3 of
methyl esters.
For example
The conversion of CSO is calculated as
89.50 = 0.895
100
= 85.5%
Average Fatty Acids Compositions
Oil sample CSO PKO GNO Relative Molecular Mass
of Fatty Acids
Capric _ 3.5 _ 172
Caprylic _ 4.0 _ 144
Lauric _ 48.0 _ 200
Myristic _ 16.0 _ 228
Palmitic 0.5 8.0 11.6 256
Stearic 0.5 3.0 3.1 284
Oleic 2.0 15.0 48.5 282
Linolenic 1.0 _ 31.4 278
Linoleic 1.0 2.0 _ 278
Ricinoleic 95.0 - - 155
Dihydroxystearic 0.3 - - 302
101
PALM KERNEL OIL
Relative molecular mass (RMM)
RMM = MA x Abundance (%) + MB x Abundance (%) + …
100 100
Capric = CH3(CH2)8COOH
= 12 + 3 + (12 + 2)8 + 12 + 32 + 1
= 15 + 112 + 12 + 33 = 172
Lauric = CH3(CH2)10COOH
= 15 + (12 + 2)10 + 12 + 32 + 1
= 15 + 140 + 12 + 33 = 200
Myristic = CH3(CH2)12COOH
= 15 + 168 + 12 + 32 + 1 = 228
Palmitic = CH3(CH2)14COOH
= 15 + 196 + 12 + 33 = 256
Stearic = CH3(CH2)16COOH
= 15 + (12 + 2)16 + 12 + 32 + 2
= 15 + 224 + 12 + 33 = 284
Oleic acid = CH3(CH2)7CH=CH(CH2)7COOH
= 15 + (12 + 2)7 + 12 + 1 + 12 + 1(12 + 2)7 + 12 + 32 + 2
= 282
Linoleic acid = CH3(CH2)4CH=CHCH2COOH
= CH(CH2)7COOH
= 15+(12 + 2)4+12+1+12+1+14+13+13+(14)7+12+32+1
= 278
RMM =
172 x 4 + 200 x 48 + 228 x16 +256 x 8 +284 x 3 + 282 x 15 + 278 x 2
100 100 100 100 100 100 100
= 6.88 + 96 + 36.48 + 20.48 + 8.52 + 42.30 + 5.56
RMM = 216.22
102
Equation
3 fatty acid + CH2OH Triglyceride + 3H2O
CHOH
CH2OH
3 x 216.26 + 92 = X + 54
740.66 = X + 54
= 686.66 MM of Triglyceride
MM = Molecular mass
Now, for biodiesel preparation
The equation for biodiesel is
Triglyceride + 1-Propanol Alkylesters + glycerol
683.21 + 180
Palm kernel oil
Density = mass/volume
0.9168 = 686.66/vol
Volume = 686.66
0.9168
Volume = 748.97ml or cm3
For alcohol (1-propanol)
0.8 = 180/volume
volume = 180/0.8
= 225ml
748.97 : 225
For every 100ml of oil 100 : X
Therefore by cross multiplication
X = 22500 = 30.04 ≈ 30.00
748.97
103
for 1 : 6 oil-propanol basis
oil Propanol
100 30ml x 2 = 60ml
1 : 6
CASTOR OIL
1. Ricinoleic acid
CH3(CH2)5CHOHCH2CH=CH
12+3+(12+2)5+12+1+16+1+12+2+12+1+12+1
85 + 30 + 27 + 13 = 155
2. Oleic acid
CH3(CH2)7CH=CH(CH2)7COOH
12+3+(12+2)7+12+1+12+1+(12+2)7+12+32+1
15 + 98 + 13 + 13 + 98 + 12 + 33 = 282
3. Linoleic acid
CH3(CH2)4CH=CHCH2CH=CH(CH2)7COOH
2800
4. Linoleic acid: 278
5. Stearic acid: 284
6. Palmitic acid: 256
7. Dihydrostearic acid: 302
8. Others: 1
Relative molecular mass
155 x 95 + 282 x 6 + 280 x 6 +280 x 8 +278 x 1 + 284 x 1 + 256 x 1 +
100 100 100 100 100 100 100
302 x 0.5 = 147.25 + 16.92 + 14 + 2.78 + 2.84 + 2.56 + 1.51 = 187.86
100
Density of CSO = 46.20/50 = 0.9240 gcm –3
104
Castor oil relative molecular mass
3 fatty acid + CH2OH Triglyceride + 3H2O
CHOH
CH2OH
3 x 181.86 + 92 X + 54
563.58 + 92 X + 54
X = 693.58 MM of Triglyceride
MM = Molecular mass
Now, for biodiesel production
Triglyceride + Propanol Alkylesters + glycerol
For castor
Density = mass of Triglyceride/ volume
0.9240 = 693.58/volume
volume = 693.58/0.9240
= 750.12ml or cm3
For Alcohol (1-propanol)
0.812 = 180/Volume
Volume = 180/0.812
Volume = 221.67
750.12ml : 225
For every 100ml, 100 : X
X = 22500 = 29.99 ≈ 30ml or cm3
750.12
for 1 : 6 oil-propanol basis
oil Propanol
100 30ml x 2 = 60ml
1 : 6
For every 100ml of oil, 60ml of 1-propanol is required
105
Groundnut Oil
Palmitic: CH3(CH2)14COOH
256
Stearic: CH3(CH2)16COOH
284
Oleic: CH3(CH2)7CH=CH3(CH2)7COOH
282
Linolenic: CH3CH2CH=CHCH2CH=CHCH2CH=CH(CH2)7COOH
278
Relative molecular mass =
256 x 11.6 + 284 x 3.1 + 282 x 48.5 +278 x 31.4
100 100 100 100
= 29.696 + 8.804 + 136.77 + 87.292
Equation
3 fatty acid + CH2OH Triglyceride + 3H2O
CHOH
CH2OH
3 x 262.562 92 X + 54
X = 825.68 MM of Triglyceride
MM = Molecular mass
Density = mass/volume
0.927 = 825.68
Volume
Volume = 825.68
0.927
= 890.70ml or cm3
106
For alcohol (1-Propanol)
0.8 = 180/Volume
Volume = 225ml
890.70 : 225
For every 100ml, 100 : X
X = 22500/890.70
X = 25.26
Oil : Propanol
100 : 25ml x 2 = 50ml
1 : 3x2
1 : 6
Oil Alcohol ratio
This implies that for every 100ml of oil, 50ml of 1-propanol is required
Mobile phase = Acetonitrile : Acetone (59:41)
Flow rate = 1.0 ml/min
Detector = 2.15µm (UV)
Column = C8 (4.2 x 100mm, 3.5µ)
Amount injected = 20 µl (microlitre)
Standard concentration of fatty acid (%)
Lauric = 0.15
Palmitic = 0.25
Oleic = 0.63
Myristic = 0.17
Stearic = 0.07
Linoleic = 0.63
Arachidic = 0.19
107
Calculation of the relative molecular weight of triglycerides and
oil/alcohol molar ratio
Table 1
Sample CSO PKO GNO
Av. Molar wt of fatty acid 187.86 216.22 262.56
Density (cm3) 0.924 0.917 0.927
Relative molecular weight of
TG
693.58 686.66 825.68
Oil/Alcohol molar 1:6 ratio
for every 100ml of oil
60 60 50
Table 2
Samples CSO PKO GNO 1-Propanol
Average molar weight of
fatty acids
187.86 216.22 262.56
Density (cm3) 0.924 0.917 0.927
Relative molecular
weight of Triglycerides
693.58 686.66 825.68
Molar volume (m/s)
cm3/mol
750.63 748.81 890.70
Table 3
Samples
CSO PKO GNO
Molar volume (cm3/mol) 750.63 748.81 890.70
Molar reaction volume
(cm3)
750.63 748.81 890.70
Oil/Alcohol ratio for 100
cm3 of oil at
30 30 25
Oil/Alcohol molar ratio
at 1:6
for every 100 cm3 of oil
at 6:1
60 60 50
Density of 1-propanol = 0.812kg/m3
108
Table B2
Transesterification Process Parameters for Optimal Catalyst Weight Test of
Biodiesel at 1:3 Oil/Alcohol Molar Ratio
Experimental conditions Values for all the experiment
Castor, palm kernel and
groundnut oils quantity (cm3)
50.0
1-propanol quantity (cm3) 15.0 for CSO and PKO and 12.5 for GNO
Reaction Temperature (oC) 55
Weight of catalyst (NaOH)g Varies with reaction batches 1 – 8
Transesterification duration
(minutes)
60.0
Table B3
Alkali-catalyzed Batch Production of Biodiesel Parameter at 1:6 Oil/Alcohol
Molar Ratio
Experimental conditions Values for all the experiment
Castor, palm kernel and
groundnut oils quantity (cm3)
100.0
1-propanol quantity (cm3) 60.0 for CSO and PKO and 5.0 for GNO
Reaction Temperature (oC) 65
Weight of catalyst (NaOH)g 0.50 for CSO and PKO, 0.40 for GNO
Transesterification duration
(mins)
60
109
Table B4
Kinetics Studies Parameters for Biodiesel Production at 1:6 Oil/Alcohol
Molar Ratio
Experimental conditions Values for all the experiment
Castor, palm kernel and
groundnut oils quantity (cm3)
50.0
1-propanol quantity (cm3) 30.0 for CSO and PKO and 25.0 for GNO
Reaction Temperature (oC) Varies (30 – 75)
Weight of catalyst (NaOH)g 0.50 for CSO and PKO, 0.40 for GNO
Transesterification duration (min) Varies with experimental batches 1 - 4
110
APPENDIX III
Kinetic Studies Result at Various Temperatures
at 30oC
Time
(min)
Volume of biodiesel
(cm3)
Conversion of oils % Conversion
CSO PKO GNO CSO PKO GNO CSO PKO GNO
5 3.6 3.9 3.2 0.42 0.46 0.38 42.0 46.0 38.0
10 4.2 5.6 4.8 0.49 0.66 0.57 49.0 66.0 57.0
20 5.6 6.4 6.0 0.66 0.75 0.71 66.0 75.0 71.0
60 7.6 7.9 7.8 0.89 0.93 0.93 89.0 93.0 93.0
at 45oC
Time
(min)
Volume of biodiesel
(cm3)
Conversion of oils % Conversion
CSO PKO GNO CSO PKO GNO CSO PKO GNO
5 3.8 4.0 3.5 0.44 0.47 0.42 44.0 47.0 42.0
10 4.5 5.8 5.1 0.53 0.68 0.61 53.0 68.0 61.0
20 5.9 6.7 6.2 0.69 0.79 0.74 69.0 79.0 74.0
60 7.6 8.1 8.0 0.92 0.95 0.95 92.0 95.0 95.0
at 60oC
Time
(min)
Volume of biodiesel
(cm3)
Conversion of oils % Conversion
CSO PKO GNO CSO PKO GNO CSO PKO GNO
5 4.1 4.2 3.8 0.48 0.49 0.45 48.0 49.0 45.0
10 4.7 6.1 5.4 0.55 0.72 0.64 55.0 72.0 64.0
20 6.3 6.9 6.4 0.74 0.81 0.76 74.0 81.0 76.0
60 8.1 8.0 8.0 0.95 0.94 0.95 95.0 94.0 95.0
at 75oC
Time
(min)
Volume of biodiesel
(cm3)
Conversion of oils % Conversion
CSO PKO GNO CSO PKO GNO CSO PKO GNO
5 4.2 4.4 3.9 0.49 0.52 0.46 49.0 52.0 46.0
10 4.9 6.2 5.7 0.58 0.73 0.68 58.0 73.0 68.0
20 6.4 7.1 6.5 0.75 0.84 0.77 75.0 84.0 77.0
60 8.2 8.2 8.3 0.92 0.96 0.99 96.0 96.0 99.0
111
Infrared Spectra for Castor Seed Oil
111
112
Infrared Spectra for Palm Kernel Oil
112
113
Infrared Spectra for Groundnut Oil
113
114
APPENDIX IV
Table D1
Result of the Optimal Catalyst Weight Test for Maximum Biodiesel Yield at 1:3 Oil/Alcohol Ratio
The biodiesel yield obtained for the various catalyst weights are as shown below.
Volume of
oil (cm3)
Volume of C3H2OH
(cm3)
CSO, PKO,
GNO wt of
catalyst (g)
% (wt/v) of
catalyst
Vol. of Biodiesel % yield of Biodiesel
CSO PKO GNO CSO PKO GNO
50 15.00 for CSO &
PKO and 12.50 GNO
0.05 0.10 4.1 7.0 1.5 8.2 14.0 3.0
50 15.00 for CSO &
PKO and 12.50 GNO
0.10 0.20 6.0 18.0 19.5 12.0 36.0 39.0
50 15.00 for CSO &
PKO and 12.50 GNO
0.15 0.30 19.0 33.0 35.0 36.0 64.0 70.0
50 15.00 for CSO &
PKO and 12.50 GNO
0.20 0.40 30.0 38.0 39.6 60.0 76.0 79.0
50 15.00 for CSO &
PKO and 12.50 GNO
0.25 0.50 33.0 39.5 34.0 66.0 79.0 68.0
50 15.00 for CSO &
PKO and 12.50 GNO
0.30 0.60 12.5 37.5 38.5 65.0 75.0 57.0
50 15.00 for CSO &
PKO and 12.50 GNO
0.35 0.70 31.5 36.0 25.0 62.5 72.0 50.0
50 15.00 for CSO &
PKO and 12.50 GNO
0.40 0.80 29.5 25.0 15.0 59.0 50 30.0
114
