ABSTRACT
Waste materials (carbide slurry and waste cooking oil) were explored in esterification and trans- esterification reactions as a viable alternative to conventional resources in lowering the cost of biodiesel production. Physicochemical study suggested esterification pretreatment for the waste cooking oils (WCO), having 3.6% moisture and sediment content and acid value of 3.8 mgKOH/g. Calcium Oxide catalyst was prepared from carbide slurry by thermal activation. The Fourier transformed infrared spectroscopy (FTIR), Atomic absorption spectroscopy (AAS) and Scanning electron microscope (SEM) techniques showed that the prepared calcium oxide had improved basic sites, calcium content and surface morphology respectively. Alkali supported on calcium oxide catalyst was then prepared by wet-impregnation method. The optimization of the esterification process for waste cooking oil was carried out using AlCl3 and H2SO4 catalysts. Using a two level, three factorial (23) experimental design, eight experiments were carried out at varying conditions of catalyst loading, reaction time and methanol- oil molar ratio. Response surface plot were used to show the interaction of the factors as they affect the percentage free fatty acid reduction. Free fatty acid reduction above 90% was achieved with both catalysts. Transesterification was then carried out with the esterified oils using prepared NaOH/CaO catalyst to synthesize the biodiesel. The quality and yield of the produced biodiesel was compared with those of aluminum chloride (AlCl3) and alkali (NaOH) catalysts. The percentage yields of prepared biodiesels were 90.2±0.57 for AlCl3, 89.7±0.16 for NaOH and 92.22±0.31 for NaOH/CaO catalyzed transesterification reactions. Fuel properties such as cetane number, cloud and pour points etc. showed trend with levels of saturation in transesterified oils. The fatty acid profile showed C16:0, C14:0, C18:0, C18:1, and C18:2. (Palmitic acid, myristic acid, stearic acid, oleic acid, and linoleic acid) to be the major fatty acids among the biodiesel samples. The reusability of the NaOH/CaO catalyst was studied and found to give an appreciable yield of 74.5 % on the fourth reaction cycle, making it a durable catalyst for biodiesel production.
TABLE OF CONTENTS
Cover Page i
Title Page ii
Declaration iii
Certification iv
Dedication v
Acknowledgement vi
Abstract vii
Table of Content viii
List of Tables xiv
List of Figures xv
List of Plates xvi
List of Appendices xvii
List of Abbreviations xviii
CHAPTER ONE 1
1.0 Introduction 1
1.1 Biodiesel 1
1.2 Feedstock for Biodisel Production 2
1.3 Catalysts in Biodiesel Production 2
1.4 Statement of Problem 3
1.5 Justification of Research 3
1.6 Aim and Objectives 4
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CHAPTER TWO 6
2.0 Literature Review 6
2.1 Background and History of Biodiesel 6
2.2 Biodiesel Feedstock 6
2.3 Chemistry of Waste Cooking Oil 7
2.4 Advantages and Disadvantages of Biodiesel 8
2.5 Parameters Affecting the Yield of Biodiesel 8
2.5.1 Reaction Temperature 8
2.5.2 Reaction Time 8
2.5.3 Alcohol to Oil Ratio 9
2.5.4 Catalyst Type and Concentration 9
2.5.5 The Effect of Free Fatty Acids 10
2.6 Esterification10
2.6.1 The Esterification of waste cooking Oil (WCO) 11
2.7 Transesterification11
2.8 Processes for Biodiesel Preparation 14
2.9 Catalyst for Biodisel Production 14
2.9.1 Homogeneous Catalyst 15
2.9.2 Heterogeneous catalyst 15
2.10.1 Calcium Oxide Catalyst 18
2.10.2 Aluminium chloride catalyst 20
2.11 Optimization of Biodiesel Production 21
2.12 Characterisation of Biodiesel 22
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CHAPTER THREE 22
3.0 Materials and Method 23
3.1 Sample Collection 23
3.2 Sample Pretreatment 24
3.3 Determination of Physicochemical properties 25
3.4.1 Acid value 25
3.4.2 Saponification value of waste cooking oil 25
3.4.3 Density 26
3.4.4 Viscosity 26
3.4.5 Iodine value 27
3.4.5 Sediment and water content 27
3.5 Fatty Acid Methyl Ester (FAME) Profile 28
3.6 Determination of Functional groups 29
3.7 Pretreatment and Preparation of Alkali Supported on Calcium Oxide (NaOH/CaO) Catalyst 29
3.8.1 Determination of Calcium Content of Calcined Carbide Slurrry 30
3.8.2 Determination of functional groups on prepared calcium oxide (CaO) 30
3.8.3 Determination of size and morphology of carbide slurry and calcium oxide 30
3.9 Optimization of Esterification of Waste Cooking Oil (WCO) 31
3.9.1 Esterification using 0.5 M sulphuric acid catalyst 31
3.9.1 Esterification using aluminum chloride catalyst 32
3.10 Transesterification of Esterified Waste Cooking Oil (WCO) 32
3.11 Determination of Physicochemical and Fuel Properties of Biodiesel 33
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3.11.1 Cetane number 34
3.11.2 Cloud point and Pour point 34
3.11.3 Flash point 34
3.12 Fatty Acid Profile 34
3.13 Determination of Functional groups 35
3.14 Reusability of NaOH/CaO Catalyst 35
3.15 Statistical Analysis 35
CHAPTER FOUR 36
4.0 RESULTS 36
4.1 Physicochemical Analysis, Gas Chromatography-Mass Spectrometry and Fourier Transformed Infrared Spectroscopy for Waste Cooking Oil 36
4.2 Properties of Carbide Slurry and NaOH/CaO Catalyst 36
4.2.1 Functional group analysis of carbide slurry and NaOH/CaO catalyst 36
4.3 Optimization of Esterification of Waste Cooking Oil 44
4.3.1 Experimental design, response surface plot and main effects for sulphuric acid esterification of waste cooking oil 44
4.3.2 Experimental design, response surface plot and main effects for aluminium chloride esterification of waste cooking oil 50
4.4 Physicochemical Properties, Gas Chromatography and Fourier Transformed Infrared Spectroscopy of fatty acid methyl esters (FAME) 56
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CHAPTER FIVE 63
5.0 Discussion 63
5.1 Properties of Waste Cooking Oil 63
5.1.1 Physicochemical properties 63
5.1.2 Fatty acid profile 63
5.1.3 Determination of functional groups 64
5.2 Properties of Carbide slurry and Prepared Calcium Oxide 64
5.2.1 Determination of functional groups 64
5.2.2 Scanning electron microscopy (SEM) studies 65
5.3 Optimization of Esterification of waste Cooking Oil 66
5.4 Yield of Biodiesel 68
5.5 Physicochemical Properties of Biodiesels 68
5.5.1 Acid value 68
5.5.2 Saponification value 69
5.5.3 Density 70
5.5.4 Cloud point and pour point 70
5.5.5 Cetane number 71
5.5.6 Viscosity 72
5.5.7 Iodine value 73
5.5.8 Flash point 73
5.5.9 Moisture and Sediment 74
5.6 Fatty acid Methyl Esters (FAME) Profile 75
5.7 Determination of Functional group 75
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5.4.5 Reusability of prepared NaOH/CaO catalyst 76
CHAPTER SIX 77
6.0 Summary, Conclusion and Recommendation 77
6.1 Summary and Conclusion 77
6.2 Recommendations 78
REFERENCE 79
APPENDICE 88
CHAPTER ONE
1.0 Introduction
1.1 Biodiesel
Industrialization processes have continued to grow globally in line with human population leading to the growing worldwide demand for petrochemical resources, coal and natural gases. This phenomenon has caused the depletion of fossil energy resources to increase exponentially with consequent environmental problems to the society (Abdullah et al., 2009). In the last decade, many fuel developers have shown interests in alternative renewable fuels to substitute or compliment petroleum-based fuels. An alternative fuel should be easily available, environment friendly and techno-economically competitive (Sharma et al., 2008).
Biodiesel is considered as a “direct-pour” alternative fuel to petroleum diesel, as it requires almost no modification to most modern diesel engines. Biodiesel can be produced locally and therefore reduces foreign oil dependence. It has been reported that biodiesel combustion can result in less air pollutants such as carbon monoxide, sulphur dioxide, particulate matter, hydrocarbons, but with slightly higher nitrogen oxides (Graboski 1998). Since the feedstock of biodiesel is mostly renewable, it significantly reduces carbon dioxide emission during its whole life cycle (Sheehan et al., 1998). According to the American Standard Testing Methods (ASTM),Biodiesel is defined as mono-alkyl esters of long chain fatty acids derived from vegetable oils or animal fats which conform to ASTM D6751 specifications for use in diesel engines.(Knothe, et al.,2007)As an alternative fuel, biodiesel can be used in neat form or mixed with petroleum-based diesel. Biodiesel as an alternative fuel has many merits. It is derived from a renewable resource, thereby relieving reliance on
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petroleum fuel imports. It is biodegradable and non-toxic. Compared to petroleum-based diesel and has a more favourable combustion emission.
1.2 Feedstock for Biodisel Production
Though biodiesel production has currently not been commercialized worldwide due to high cost of feed stock ( Yun and Mahiran, 2011; Canakci and Sanli, 2008), the cost of biodiesel can be reduced by low quality feed stock such as waste or used vegetable oils, non-edible oils, trapped greese and soap stock (by-product of vegetable oil refinery) which are cheaply available and can be regarded as attractive feedstock for biodiesel production. (Ali et al., 2002; Ali and Cuppett, 1995; Jian – xun, 2007; Sanli et al., 2008) Even though the cost of biodiesel production may be reduced, using such cheap feed stocks usually have the problem of high free fatty acid (FFA) in oil samples. These productions therefore, require a two-step process. FFA must first be converted to their methyl esters (biodiesel) via esterification using a catalyst preferably acid prior to transesterification with a homogeneous base catalyst. In the first step, FFA must be typically esterified to an acceptable level, (acid level less than one) in order to prevent soap formation and increase the biodiesel yield in the subsequent alkaline catalyzed transesterification. Usually catalysts are used to enhance such reactions.
1.3 Catalysts in Biodiesel Production
Esterification and transesterification of free fatty acids use catalysts to enhance the reaction rate. Catalysts that are commonly used in esterification include strong liquid mineral acids, heterogenous catalysts and enzymes e.t.c. Homogenous catalysts are widely used, but their reaction with free fatty acids affects the properties and yield of biodiesel. However heterogeneous catalysts have proved to be bettercompared to homogenous catalysts, due to their benefits not only in the purity of the secondary product glycerin, but also because it simplifies down streaming separation process, since it does not need much washing or
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neutralization. Particulate heterogeneous catalysts can be readily separated from the products following reactions allowing the catalyst to be reused, thereby generating less waste, and consuming less energy. Recycling and reactivating the catalyst have been studied and found to maintain efficiency for use in industries (Park, 2010). Researchers like, liu et al., 2010 and Ghiasi and malekzadeh, 2012 have introduced heterogeneous catalyst for their experiment, examples are CaO, SrO, BaO, and Ca(OCH3)2. However, homogeneous catalysts have been widely used in industries and they include KOH, NaOH, and CH3ONa (Lu et al., 2009). Alkali metal hydroxides or alkoxides can be used as transesterification catalysts. Hydroxides are cheaper than alkoxides, but must be used in higher concentrations to achieve good reaction (Freedman et al., 1984).
1.4 Statement of Problem
Globally, virgin oils are the major feedstock used for biodiesel production (Thamsiroj and murphy, 2009). This causes an imbalance in the utilization of energy sources and thus contributes to the higher cost of biodiesel feedstock (Mohammed and Ali, 2002). Also, the use of base catalyst, which is expensive, for esterification and transesterification leads to the production of soap as side reaction which, affects the quality of the biodiesel produced (Tat and van Gerpen, 2000). However, the difficulty in recovering homogenous alkali catalysts after transesterification also leads to higher cost of biodiesel production as large quantities of water and reagents are needed to purify the produced biodiesel (Dennis et al., 2010).
1.5 Justification of Research
Increasing uncertainty about global energy production and supply, environmental concerns due to the use of fossil fuels, and unsustainable nature of petroleum products gives reasons for the search for alternatives to fossil fuels. (MacLeana and Laveb, 2003;; Körbitz,1999). Biodiesel is one of the best substitutes for petrodiesel due to its advantage of
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environmentally friendly properties. (Helwani et al., 2009). Currently, more than 95% of the world biodiesel is produced from edible oil. However, continuous and large-scale production of biodiesel from edible oil has become an issue of great concern because of competition with food materials (Mustafa, 2011; Arjun et al., 2008). The most common methods for biodiesel preparation are homogenous base or acid catalyzed transesterification (Meheret al., 2006).These methods, however, come with a lot of disadvantagessuch as soap formation, reduced yields of biodiesel, high cost and also their inability to be recycled. (Sharma et al., 2008). In this sense, methods that permit minimizing the costs of the raw materials are of special interest. The use of waste cooking oil, instead of virgin oil, to produce biodiesel reduces the raw material cost because waste cooking oil is estimated to be about half the price of virgin oil (Zheng et al., 2006).The local production of heterogenous catalysts such as calcium oxide (CaO) to be used directly in biodiesel production or as solid support for other catalysts will help to reduce the overall cost of biodiesel production. This will significantly enhance the economic viability of biodiesel production in Nigeria, where this resourceabound.
1.6 Aim and Objectives
The aim of the study is to find a potential way to reduce the cost of biodiesel production by using waste cooking oil (WCO) as biodiesel feedstock as well as using calcium oxide derived from waste carbide slurry as support for the catalyst sodium hydroxide The objectives of this research include :
(i) Pretreatment of waste cooking oil (WCO)
(ii) Purification of calcium oxide catalyst (CaO) from waste carbide slurry.
(iii)Determination of physicochemical properties of waste cooking oil (WCO)
(iv) Determination of physicochemical properties of calcium oxide catalyst (CaO) from waste carbide slurry.
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(v) Esterification of waste cooking oil using aluminum chloride (AlCl3) and sulphuric acid (H2SO4) catalysts using different reaction conditions.
(vi) Transesterification of waste cooking oil using alkali supported on calcium oxide (NaOH/CaO), aluminum chloride (AlCl3), and alkali (NaOH) catalysts.
(vii) Determination of fuel properties of the biodiesel produced using NaOH/CaO, AlCl3and NaOH and comparing them with the standards.
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