TRANSESTERIFICATION OF KARANJA (PONGAMIA PINNATA) OIL FOR THE PRODUCTION OF BIODIESEL
BY
LEKHA CHARAN MEHER
Centre for Rural Development and Technology Submitted
in the fulfillment of the requirement of the degree of Doctor of Philosophy to the
INDIAN INSTITUTE OF TECHNOLOGY, DELHI
HAUZ KHAS, NEW DELHI — 110016 INDIA
To my parents
CERTIFICATE
This is to certify that the thesis entitled, "TRANSESTER1FICATION OF KARANJA (PONGAMIA PINNATA) OIL FOR THE PRODUCTION OF BIODIESEL" being
submitted by Mr. Lekha Charan Meher to the Indian Institute of Technology, Delhi for the award of Doctor of Philosophy is a record of bonafide research work carried out by him under my guidance and supervision in confirmatory with the rules and regulations of Indian Institute of Technology, Delhi
The research report and results presented in this thesis have not been submitted, in part or in full, to any other university or institute for the award of any degree or diploma.
(Dr. S. N. Naik) Associate Professor
Centre for Rural Development and Technology Indian Institute of Technology, Delhi
New Delhi -110016, India.
ACKNOWLEDGEMENT
Gratitude can seldom be expressed in words.
Beginning with the formulation of research problem, till date, I have been especially privileged one to receive guidance from my supervisor Dr. S. N.
Naik whose academic excellence and constant encouragement steered me through the work all the way and all the time. I would extend the opportunity to express my deep sense of gratitude for his motivational urge, valuable analysis, criticism and personal affection which installed in me immense confidence to continue my research right from the beginning of my research work till the accomplishment of the goal.
I am extremely grateful to Prof. A. K. Dalai, University of Saskatchewan, for the valuable guidance, suggestion and affection, especially inviting as visiting scholar and providing financial assistance during my research work carried out at University of Saskatchewan, Saskatoon, Canada. I thank Dr. R. N.
Ram, External SRC member, Dr. K. L. Patel, External expert for CSIR JRF- SRF assessment committee, Prof. A. K. Gupta, Dept. of Chemical Engineering
and Prof. L. M. Das, Center for Energy Studies for their helpful discussion and suggestions.
I am indebted to my friends Mangesh, Rajesh for the help as well as valuable discussions and suggestions provided during my research. I acknowledge the co-operations from Dr. N. N. Bakhshi, Dr. Das and Dr. Pail of University of Saskatchewan. I express my sincere appreciation to all the members of CRDT as well as Catalysis and Chemical Reaction Engineering Laboratories, University of Saskatchewan for all the co-operation and support.
I am grateful to Prof. Santosh Satya, Prof. R. C. Maheshwari, Prof. Rajendra Prasad, Prof. P. Vasudaven, Dr. Satyawati Sharma, Dr. V. K. Vijay, Dr. V. M.
Chariar, Dr. A. Malik, laboratory and office staff of the Centre for providing laboratory facilities and timely requirements for my research work.
I feel pleased to acknowledge the love, affection and support received from Mr. and Mrs. Madhumita Patel, Mr. and Mrs. Vidya Sagar Swamy, Mr. and Mrs. Chudamani Naik, Srikant Pradhan, Ajaya Dash, Gaja, Geeta, Richa, Jade ja, Prashant, Malaya, Mamun and Mrs. Jyoti Manjari Naik.
When one owes so many, it is almost impossible and even invidious to single out names. However, I am indebted to my friends Amanda, Ashis, Chandrakant, Ganesh Prabhu, Lalit, Mohini, Nidhi, Parag, Prabhat, Priyabrat, Rama, Rekha, Sabyasachi, Sashtri, Satya, Tapan, Titipong, for their constant encouragement and wholehearted support without which it would have been difficult to finish this task. I would like to thank M. T. Wallentiny, Rechard Blondin and Dragon Cekic of University of Saskatchewan and G. P. Singh and Attar Singh of Centre of Energy Studies for their assistance during my research work in the laboratory.
I express gratitude to Council of Scientific and Industrial Research (CSIR), New Delhi, India for providing me financial assistance in the form of Junior Research Fellow/Senior Research Fellow.
Lastly, I am ever indebted to my parents and sisters whose blessings, love and moral support encouraged me throughout my academic pursuits.
fre,A114/
(Lekha Charan Meher)
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ABSTRACT
The increased industrialization and the growing transport sectors in the developing countries face major challenges of the energy demand as well as the increased environmental concerns. The rising demand of fuel and limited availability of mineral oil provide incentives for the development of alternative fuels from renewable sources with less environmental impacts. One of the possible alternatives to the petroleum based fuels is the use of fuels derived from plant origins. Biodiesel is fatty acid alkyl esters derived from lipid feedstock such as vegetable oils and animal fats that can be used as diesel fuel substitute or extender. The conventional route of biodiesel preparation use alkali catalyst for transesterification of low free fatty acid oils with methanol or ethanol. Most of the research work has been done on the preparation of biodiesel from edible grade vegetable oils such as rapeseed, palm, soybean, sunflower etc. Since India is one of the largest importers of vegetable oil for food purpose, the use of edible oils for biodiesel production seems to be insignificant. India produces wide range of non-edible oilseeds like karanja (Pongamia pinnata), jatropha (Jatropha curcas), neem (Azadirachta indica), simarouba (Simarouba glauca), etc. Among these, karanja is one of the tree-borne plant having annual oilseed production potential of 2 lakh tons. The present study investigated the scope of karanja oil as an inexpensive feedstock for biodiesel production.
Fatty acid methyl/ethyl esters (biodiesel) were prepared by transesterification of karanja oil with methanol/ethanol catalyzed by a homogeneous alkali. The process conditions for transesterification of karanja oil with methanol and ethanol were optimized which
resulted 97-98% and 95% methyl and ethyl esters respectively. The initial rate of methyl ester formation was correlated with the process variables such as catalyst concentration, alcohol to oil molar ration, reaction temperature and rate of stirring.
The non-edible oils of Indian origin are often contaminated with high free fatty acids (FFA), which is problematic for alkali catalyzed transesterification. The acid value of karanja oil ranged from 0.6 to 11.5 mg KOH/g. The influence of FFA (0.3 to 5.8% w/w of oil) on karanja oil transesterification was studied. As the FFA level goes on increasing, the yield of methyl esters sharply decreases due to the predominating saponification reaction. In order to utilize the high FFA content oil, two-step process i.e. acid catalyzed esterification followed by alkali catalyzed transesterification was carried out for methanolysis to obtain methyl esters. Oil having 20% of FFA can be pretreated to reduce its acid value significantly, which will be suitable for alkali catalyzed second step. The overall yield of methyl esters was nearly same i.e. 96.7-97% from karanja oil containing FFA up to 20%.
The chemical kinetics of alkali catalyzed transesterification of karanja oil with methanol was studied. The reactants form two immiscible layers due to the differences in the polarities of methanol and oil and the reaction is mass transfer controlled and the reaction is initiated by vigorous mixing. The formation of methyl esters act as co-solvent since it is soluble in methanol and oil. As the reaction proceeds, a lower glycerol rich phase is separated from the ester-rich phase. The catalyst remains in the glycerol phase and again the reaction is mass transfer controlled. The reactions were studied at a
reaction temperature of 60°C and catalyst concentration 0.29-2.11% KOH (wt. of oil), methanol to oil molar ratio 1:1 to 6:1 with stirring at 600 rpm considering saponification of glycerides as competitive irreversible reaction.
The soluble alkali catalysts cause side reaction such as saponification during biodiesel preparation from high FFA oils. Pre-treatment of high FFA oil is required before alkali catalyzed transesterification, which adds extra cost to biodiesel. Solid catalysts have the advantage of less possibility of saponification, easy separation of the products which do not need washing of biodiesel and the catalyst can be re-used. Solid basic catalysts such as Ba(OH)2, alkali metal (Li, Na, K) doped CaO and K2CO3/A1203 have been used for biodiesel preparation from high free fatty acid karanja oil. The alkali metal doped catalysts are effective for transesterification of oil containing 5.8% FFA.
Transesterification of karanja oil with methanol and ethanol catalyzed by Thermomyces lanuginosus (TL IM) and Rhizomucor miehei (RM IM) were studied in liquid CO2 medium. The reaction proceeds slowly as compared to the conventional alkali catalyzed route, but faster as compared to enzymatic transesterification in solvent free medium. The ethanolysis of karanja oil catalyzed TL IM resulted 72% ethyl esters in 5 h when the reaction was conducted in liquid carbon dioxide medium. Using the silica gel 5% (w/w of oil) in the reaction medium promotes the acyl-migration during the ethanolysis of karanja oil where the yield of ethyl esters is improved up to 75.2%. The influence of FFA (up to 20% w/w of oil) on TL IM catalyzed ethanolysis of karanja oil was studied, where FFA has no negative influence on the yield of ethyl ester. The reusability of lipozyme TL
IM was studied for karanja oil ethanolysis, the catalytic activity remained intact after five time reuse.
The fuel qualities of biodiesel prepared by alkali catalyzed route were evaluated and compared with the IS 15607:2005 biodiesel specification. The karanja methyl and ethyl esters have the fuel characteristics: acid value (mg KOH/g) 0.5, 0.5; cloud point (C) 19, 23; pour point (C) 6, 15; flash point (C) 174, 148; density (g/cc @15°C) 0.88, 0.88;
viscosity (cSt) 4.77, 5.56; heating value (MJ/kg) 40.8, 40.7, respectively. The cloud point and pour point of karanja based biodiesel are slightly higher which is problematic for cold climate when pure biodiesel is to be used in engines, but in Indian climate this problem doesn't arise. When blended with diesel, the pour point is lowered to a considerable extent i.e. 0 and -3°C for B20 blends (20% esters in diesel) of karanja methyl and ethyl esters respectively. The fuel qualities of karanja based biodiesel are in accordance with the IS 15607 biodiesel specification.
The storage stabilities of karanja methyl and ethyl esters were evaluated. In the recent Indian as well as European specifications of biodiesel, a minimum value of 6 h induction period at 110°C measured with a Rancimat instrument is specified. The Rancimat induction periods of karanja methyl and ethyl esters are less than 6h. In order to satisfy the IS 15607 and EN 14214 norms, the effects of commercial synthetic antioxidants were studied on the induction period of karanja based biodiesel. Pyrogallol when added as an antioxidant (50 ppm), increases the induction period of both methyl and ethyl esters up to 12 h satisfying the specification for oxidation stability.
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The raw material i.e. karanja oil contains some unsaponifiable matters such as karanjin and pongamol. These components get separated from biodiesel after completion of the reaction and do not need any extra steps for their separation from biodiesel. Also these components contaminate the by-product glycerol.
The crude glycerol obtained as byproduct of karanja oil transesterification contains excess methanol, alkali catalyst, soap, unreacted partial glycerides, unsaponifiable matters, methyl esters and water. The crude glycerol layer obtained as byproduct contains 45-47% glycerol and the used excess alcohol. The purification of crude glycerol was carried out where the purity is improved to 90-91% that can be used as industrial grade glycerol.
CONTENTS
Acknowledgement Abstract
List of Figures List of Tables List of Schemes Notations
Chapter I: Introduction 1.1 Background
1.1.1 Environmental concerns using petroleum based fuels 1.1.2 Need of alternative and renewable fuel
1.1.3 Biodiesel
1.1.4 Advantages of biodiesel
1.1.5 Chemical modification of vegetable oil to biodiesel 1.1.6 Feedstock for biodiesel in India
1.1.7 Karanja seeds as feedstock for biodiesel 1.1.8 Literature survey
1.2 Knowledge gaps
1.3 Scope of the present work 1.4 Objectives
Chapter II: Materials and Methods
2.1 Extraction and characterization of oil
2.1.1 Extraction of oil from karanja seed kernel 2.1.2 Physico-chemical properties of karanja oil 2.1.3 Neutralization of high FFA karanja oil
2.1.4 Analysis of fatty acid profiles of karanja oil by GC-MS 2.1.5 Analysis of fatty acid composition of karanja oil by GC 2.1.6 Calculation of average molecular weight of karanja oil
Page no.
i iv ix xii xiii xiv
1 2 3 4 5 6 11 13 15 15 16 16
17 17 18 18 19 20 20
triglycerides
2.2 Separation and Characterization of lipid associates 24 2.2.1 Separation of lipid associates from karanja oil 24
2.2.2 Purification of the components 24
2.2.3 Identification of the major lipid associates 25 2.2.4 Quantification of karanjin and pongamol by RP-HPLC 26 2.3 Experimental set up and procedure for transesterification 30 2.3.1 Designing of the transesterification reactor 30 2.3.2 Experimental set up for Parr reactor 31 2.3.3 Reactor for subcritical CO2 mediated enzymatic alcoholysis 32 2.4 Analytical monitoring of the reaction and analysis of biodiesel 34
2.4.1 Monitoring the reaction by TLC 34
2.4.2 Simultaneous analysis of TG, DG, MG, esters, and glycerol by 35 GPC
2.4.3 Quantification of methyl/ethyl esters in Biodiesel by RP-HPLC: 36 One of the latest analytical method
2.4.4 Quantification of methyl/ethyl esters by I HNMR 39
2.4.4.1 Methyl esters quantification 39
2.4.4.2 Ethyl esters quantification 40
Chapter III: Homogeneous Alkali Catalyzed Transesterification of Karanja Oil
3.1 Preparation of karanja methyl esters 44
3.1.1 Process optimization 45
3.1.1.1 Influence of catalyst concentration 45 3.1.1.2 Influence of methanol/oil molar ratio 47 3.1.1.3 Influence of reaction temperature 48 3.1.1.4 Influence of mixing intensity 49 3.1.1.5 Effect of reaction variables on the rate of formation of 50
3.1.3 Two-step process for biodiesel preparation from high FFA 56 karanja oil
3.1.3.1 Acid catalyzed pretreatment 57
3.1.3.2 Alkali catalyzed transesterification 58 3.1.3.3 Influence of FFA on dual step process for preparation of 59
methyl esters
3.2 Preparation of karanja ethyl esters 60
3.2.1 Reaction conditions for ethanolysis of karanja oil 60 3.2.2 Effect of FFA and water on ethanolysis 62 3.2.3 Two-step process for preparation of ethyl esters from high FFA 64
karanja oil
3.3 Purification of biodiesel 65
3.4 Separation of unsaponifiable matters from transesterified products 65
3.5 Purification of glycerol 66
3.5.1 Phosphoric acid treatment 68
3.5.2 Separation of methyl esters from crude glycerol layer 69 3.5.3 Separation of partial glycerides and unsaponifiable matters 69
3.5.4 Activated charcoal treatment 69
Chapter IV: Chemical Kinetics of Transesterification
4.1 Introduction 70
4.2 Chemistry of triglyceride transesterification 72
4.2.1 Proposed assumptions 73
4.2.2 Proposed model 74
4.3.3 Final state of the reaction 79
4.3 Procedure for transesterification of karanja oil 82
4.3.1 Initial reaction conditions 82
4.3.2 Experimental procedure 83
4.3.3 Analysis of the transesteification product 84
4.4 Results and discussion 85
4.4.1 Composition of the reaction mixture vs. time 85
4.4.2 Equilibrium constants 89 4.4.3 Limitation of kinetics study of triglyceride transesterification 90
Chapter V: Preparation of Biodiesel by Heterogeneous Catalysts
5.1 Solid basic catalysts 93
5.1.1 Catalyst preparation 95
5.1.2 Catalyst characterization 96
5.1.2.1 Basicity study by CO2-TPD 96
5.1.2.2 BET surface area analysis 97
5.1.2.3 X-ray diffraction study 99
5.1.2.4 Catalytic activities of M/CaO 101 5.1.3 Transesterification of karanja oil using M/CaO catalyst 102 5.1.3.1 Effect of catalyst concentration 102 5.1.3.2 Effect of reaction temperature 103 5.1.3.3 Effect of Me0H/oil molar ratio 104
5.1.3.4 Effect of free fatty acids 106
5.1.3.5 Effect of alkali metal on the activity of the catalyst 108
5.1.3.6 Re-use of Li/CaO catalyst 110
5.1.4 Fuel quality of methyl esters prepared by M/CaO catalysts 110 5.1.5 K2CO3/Alumina catalyzed karanja oil transesterification 111 5.1.6 Ba(OH)2 catalyzed karanja oil transesterification 112 5.2 Enzymes as catalyst for esterification and transesterification 113 5.2.1 Lipase catalyzed biodiesel production 114 5.2.2 Enzymatic transesterification in solvent free medium 116 5.2.3 Enzymatic transesterification in liquid carbon dioxide medium 118
5.2.3.1 Effect of type of alcohols 120
Chapter VI: Fuel Characteristics of Biodiesel Produced from Karanja Oil
6.1 Specification and quality standards of biodiesel 127 6.2 Fuel properties of karanj a based biodiesel 128
6.2.1 Density/specific gravity 128
6.2.2 Cetane index/cetane number 129
6.2.3 Viscosity 130
6.2.4 Flash point 131
6.2.5 Cold filter plugging point 132
6.2.6 Cloud point and pour point 132
6.2.7 Stability of biodiesel 133
6.2.8 Iodine number and polyunsaturated methyl/ethyl esters 139
6.2.9 Water content 139
6.2.10 Heat of combustion 140
6.2.11 Acid value/neutralization number 140 6.2.12 Distillation characteristics of karanja methyl/ethyl esters 141
6.2.13 Free and total glycerol 142
6.2.14 Ester content 143
6.2.15 Conradson carbon residue 144
6.2.16 Sulfur content 144
6.2.17 Phosphorus content 144
6.2.18 Sulfated ash 145
6.2.19 Copper strip corrosion 145
6.2.20 Methanol/ethanol content 145
Chapter VII: Summary, Conclusions and Future Scope 147
Bibliography 156
Biodata
