Lfc/DOM/a/120 fx 
E F F E C T O F ULTRASOUND M I X I N G ON 
E S T E R I F I C A T I O N O F FFA IN R U B B E R SEED O I L 
Madusanka Nishan Dayananda Mal l iyawadu 
(07/8203) 
Dissertation submitted in partial fulfillment of the requirement for the 
Degree of Master of Science in Sustainable Process Development 
Department o f Chemical & Process Engineering 
University o f Moratuwa 
Sri Lanka 
November 2011 
University of Moratuwa 
102521 
/0252/ 
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CD -RO*o 
102521 
DECLARATION 
I declare that this is my own work and this dissertation does not incorporate without 
acknowledgement any material previously submitted for a Degree or Diploma in any 
University or other institute of higher learning and tQ the.best of my knowledge and 
belief it does not contain ariy material previously published or written by another 
person except where the acknowledgement is made in the text. 
J ^ i ^ U _ _ _ _ . . 3 / 1 1 / a ° U 
M.N.D.Malliyawadu Date 
I hereby grant the University of Moratuwa the right to archive and to make available 
my thesis or dissertation in whole or part in the University Libraries in all forms of 
media, subject to the provisions of the current copyright act of Sri Lanka. I retrain all 
proprietary rights, such as patent rights. I also retain the right to use in future works 
(such as articles or books) all or part of this thesis or dissertation. 
M.N.D.Malliyawadu Date 
I have supervised and accepted this dissertation for the award of the degree. 
Supervisor 
Dr. SHP Gunawardena 
ABSTRACT 
There is an increasing demand for biodiesel, because of its environmental friendly nature and 
especially due to the depletion of petroleum reserves. Currently, most of the biodiesel is 
produced from edible oils under base catalyzed transesterification. However, large amount of 
non edible oils are underutilized and can be converted to biodiesel. The difficulty with base 
catalyzed transesterification of non edible oil is its higher content of free fatty acids. These 
free fatty acids react with base catalyst to produce soap and which prevent the separation of 
ester from the glycerin. 
The reduction of free fatty acid content of rubber seed oil under catalyzed esterification with 
ultrasonic mixing (20 kHz, 500 W) was investigated in this study and compared with 
mechanical agitation. Batch esterification of rubber seed oil was carried out using 2.5:1 
(w/w) methanol/ FFA and 0.05:1 (w/w) H2S04/FFA and effect of ultrasound frequency, 
reaction temperature and reaction time were studied. With the increase of ultrasonic 
amplitude, mixing intensity was increased and as a result, maximum FFA% reduction of 
88.9 observed at the amplitude of 75% and at a temperature of 55°C. When the esterification 
reaction carried out at elevated temperatures, it shows a greater reduction of FFA% under 
ultrasonic and mechanical mixing. However, optimum result was gained under mechanical 
mixing at the temperature of 55°C and at a reaction time of 30 min and the final FFA% of 
rubber seed oil was 2.75. At the same reaction conditions, acid esterification of rubber seed 
oil under ultrasonic mixing achieved a FFA% of 3.31. 
Keywords: Biodiesel, FFA, esterification, ultrasonic mixing, 
ii 
ACKNOWLEDGEMENT 
It is a great pleasure to express gratitude to those who were behind me in completing 
my research successfully. First, I would like to offer grateful thanks to the 
supervisors Dr. (Mrs.) SHP Gunawardena and Dr. (Mrs) FM Ismail, Senior 
Lecturers, Department of Chemical & Process Engineering, University of Moratuwa 
who's guided and supervised me throughout the research beyond my perspectives. 
Then my sincere thanks are due to Dr. PG Rathnasiri and Dr. BAJK Premachandra, 
Senior Lecturers, Department of Chemical & Process Engineering, University of 
Moratuwa for their valuable comments, suggestions and the encouragement given. 
I must specially thank Dr. ADUS Amarasinghe, Head of the Department, 
Department of Chemical & Process Engineering and all other lecturers of the 
Department of Chemical & Process Engineering, University of Moratuwa for the 
help given in various aspects. 
All the staff of Chemistry, Food & Microbiology, Latex Technology and Energy 
Engineering laboratories; specially Mr. Masakorala, Mr.Lalith and Ms. Amali 
Wahalathanthri, are gratefully acknowledged for their support given in various 
occasions. 
Finally I would like to thank all the colleagues of the PG Division of the Department 
of Chemical & Process Engineering and my family, for the help and cooperation 
given. 
iii 
TABLE OF CONTENTS 
DECLARATION i 
ACKNOWLEDGEMENT iii 
TABLE OF CONTENTS iv 
LIST OF FIGURES vii 
LIST OF TABLES ix 
LIST OF ABBREVIATIONS x 
CHAPTER 1. INTRODUCTION 1 
CHAPTER 2. LITERATURE REVIEW 6 
2.1 Biodiesel 6 
2.2 Feedstock 7 
2.3 Process Technologies of Biodiesel production 9 
2.3.1 Direct use 9 
2.3.2 Micro emulsion 10 
2.3.3 Pyrolysis 10 
2.3.4 Transesterification 10 
2.3.4.1 Homogeneous alkali catalyzed transesterification 11 
2.3.4.2 Homogeneous acid catalyzed transesterification 14 
2.3.4.3 Dual step transesterification 16 
2.3.4.4 Heterogeneous acid and base catalyzed transesterification.... 18 
2.3.4.5 Enzymatic transesterification 20 
2.3.4.6 Supercritical alcohol transesterification 20 
2.3.4.7 Microwave assisted transesterification 21 
2.3.4.8 Ultrasound assisted transesterification 22 
2.3.5 Process variables of biodiesel production 25 
iv 
2.3.5.1 Effect of alcohol/oil molar ratio 25 
2.3.5.2 Catalyst type and concentration 26 
2.3.5.3 Effect of reaction time and temperature 26 
2.3.6 Downstream processing of biodiesel 27 
2.3.6.1 Separation of biodiesel 27 
2.3.6.2 Purification of biodiesel 28 
2.3.6.3 Alcohol recovery 28 
2.3.6.4 Washing of biodiesel 28 
2.3.6.5 Drying of biodiesel 28 
2.3.6.6 Distillation of biodiesel 29 
2.4 Analysis of Biodiesel 29 
2.4.1 Thin layer chromatography 29 
2.4.2 Gas chromatography 29 
2.4.3 High performance liquid chromatography 30 
2.5 Stability of Biodiesel 30 
2.6 Emission from Biodiesel and Diesel 30 
CHAPTER 3. METHODOLOGY 32 
3.1 Materials & Chemicals 32 
3.2 Equipments 32 
3.3 FFA Value of Test Samples 32 
3.4 Dynamic Viscosity of RSO 33 
3.5 Acid Catalyzed Esterification by Mechanical Agitation 33 
3.5.1 Effect of temperature on esterification reaction 34 
3.6 Acid Catalyzed Esterification by Ultrasonic Irradiation 34 
3.6.1 Effect of temperature on esterification reaction 35 
v 
3.6.2 Effect of reaction time on esterification reaction 35 
3.6.3 Effect of ultrasonic amplitude on esterification reaction 35 
CHAPTER 4. RESULTS AND DISCUSSION 36 
4.1 Properties of RSO 36 
4.2 FFA Conversion under Mechanical Agitation 36 
4.3 FFA Conversion under Ultrasonic Irradiation 38 
4.3.1 Effect of amplitude on acid value reduction 38 
4.3.2 Effect of Temperature on acid value reduction 40 
4.4 Comparison of Ultrasonic Irradiation and Mechanical Agitation 41 
CHAPTER 5. CONCLUSIONS AND RECOMMENDATIONS 44 
CHAPTER 6. REFERENCES 45 
vi 
LIST OF FIGURES 
Figure 1-1 : World energy consumption by source in 2007 : 1 
Figure 1 -2 : Crude oil imports to Sri Lanka 4 
Figure 1-3 : Crude oil price variation 4 
Figure 2-1 : General equation for trans-esterification of triglycerides 11 
Figure 2-2 : Reaction steps for trans-esterification of triglycerides 11 
Figure 2-3 : Mechanism of alkali catalyzed transesterification 12 
Figure 2-4 : Free fatty acid reaction with base catalyst 13 
Figure 2-5 : Effect of FFA on the yield of methyl ester during transesterification... 13 
Figure 2-6 : Mechanism of acid catalyzed transesterification 15 
Figure 2-7 : Acid catalyzed esterification reaction 15 
Figure 2-8 : Mechanism of acid catalyzed esterification 16 
Figure 2-9 : Acid value variation with time in esterification reaction 17 
Figure 2-10 : Variations of the reaction mixture composition (mole %) with time .. 18 
Figure 2 -11 : Cavitation bubble formation and disruption under ultrasonic irradiation 
23 
Figure 2-12 : Droplet sizes created by ultrasound and mechanical mixing 24 
Figure 2-13 : Process flow schematic for biodiesel production 27 
Figure 3-1 : mechanical mixing of rubber seed oil 33 
Figure 3-2 : ultrasonic mixing of rubber seed oil 34 
Figure 4-1 : Rubber seed oil Acid value with reaction time 37 
Figure 4-2: Variation of Acid value with the amplitude of ultrasonic wave 38 
Figure 4-3 : Acid value reduction in different ultrasonic wave amplitudes (without 
temperature control) 39 
vii 
Figure 4-4 : Variation of Acid value of oil with different temperatures (amplitude of 
60%) 41 
Figure 4-5 : Comparison of ultrasonic irradiation and mechanical mixing 42 
viii 
LIST OF TABLES 
Table 2-1 : ASTM D 6751 Biodiesel Specifications 6 
Table 2-2 : Fatty acid composition and physical properties of oils 7 
Table 2-3 : Alkali catalyst for transesterification 14 
Table 2-4 : acid catalyst for transesterification 16 
Table 2-5 : Heterogeneous catalyst for transesterification 19 
Table 2-6 : Emission comparison of biodiesel and diesel 31 
Table 4-1 : Rubber seed oil Acid value reduction with reaction time 37 
Table 4-2 : Acid value reduction in different ultrasonic wave amplitude 39 
Table 4-3 : Acid value reduction in different ultrasonic wave amplitudes (without 
temperature control) 40 
Table 4-4 : Variation of acid value of oil with different temperatures (amplitude of 
60%) 40 
Table 4-5 : Comparison of ultrasonic irradiation and mechanical mixing 43 
ix 
LIST OF ABBREVIATIONS 
Abbreviation Description 
ASTM D 6751 American Society for Testing and Materials 
Btu British thermal unit 
B100 Pure Biodiesel 
DG Diglycerides 
FAEE Fatty Acid Ethyl Ester 
FFA Free Fatty Acids 
FAME Fatty Acid Methyl Ester 
MG Monoglycerides 
RSO Rubber Seed Oil 
TG Triglycerides 
WEO Waste Edible Oil