ABSTRACT
In this study, waste soya oil was transesterified with methanol in the presence of sodium hydroxide (NaOH) as catalyst among other process conditions to produce biodiesel. Waste soya oil was collected, and characterized to determine its density, refractive index, moisture content, saponification value, viscosity, acid value, peroxide value and iodine value, while those for the biodiesel produced through transesterification were density, cloud and pour points, flash and fire points, anisidine point, API gravity and cetane value. The effects of the process parameters (catalyst concentration, reaction time, reaction temperature, methanol/sample ratio and agitation speed) were studied individually and in matrix form to establish synergistic interactions. Process optimal conditions that gave the maximum yield of 94.70% were: catalyst concentration of 1%, reaction time of 60 minutes, reaction temperature at 70oC, methanol/sample ratio of 6:1, and agitation speed of 300rpm. Other set of conditions that caused the lowest biodiesel yield of 66.20% produced were catalyst concentration of 0.25% at reaction time of 30 minutes, under the reaction temperature of 50oC with methanol to sample ratio of 2:1, and agitation speed of 150rpm. The physiochemical properties of the yield investigated to ascertain their adherence with the ASTM and EN standards for biodiesel production revealed that the developed biodiesel properties conformed within the standard recommendations. NaOH was proven to be efficient as the catalyst for converting the waste used soya oil to biodiesel. From the established results, Cetane index of 74.12, kinematic viscosity of 4.43mm2/s, density of 876.6kg/m3, flash point of 142oC, fire point of 150oC, cloud point of 8.5oC and moistuure content of 0.04% were respectively obtained. All these values fell within the recommended ASTM and EN standards. The use of surface and contour plots for the process parameters explained the synergistic yield during the optimization process. The gas chromatography mass spectrometry (GCMS) analysis carried out to evaluate the quality of the sample with respect to deterioration, gave an ester percentage of 99.8% for the bio-oil which was within the minimum standard range of not less than 96.5% recommended. From the GCMS profiling of the waste bio-oil, it was established that the most prevalent fatty acids identified among other 13 distinct compounds were palmitic, oleic and stearic acids with percentage concentrations of 36.73, 32.39 and 8.84% respectively. Consequently, prominent among other 16 distinct esters found in the biodiesel sample with regards to their percentage concentrations were most prevalently methyl hexadecanoate (22.98%), methyloctadecanoate (16.89%), methyl tridecanoate (16.68%), methyl myristate (9.67%), methyl 15-methylhexadecanoate (5.97%), methyl octanoate (4.49%) and methyl caprylate (3.90%), with exogenous substances identified in the sample to include cyclododecane epoxide, methyl triacontanoate and methyl heptacosanoate.
TABLE OF CONTENTS
Cover Page i
Title Page ii
Declaration iii
Dedication iv
Certification v
Acknowledgements vi
Table of Contents vii
List of Tables x
List of Figures xi
List of Plate xii
Abstract xiii
CHAPTER 1: INTRODUCTION
1.1 Background of Study 1
1.2 Statement of Problem 2
1.3 Aim and Objectives of Study 3
1.4 Scope of Study 3
1.5 Justification of the Study 3
CHAPTER 2: LITERATURE REVIEW
2.1 Conventional Biodiesel Production 5
2.2 Biodiesel Stability 10
2.3 Experimental Setup Output 12
2.4 Production of Biodiesel using Pure Soya bean Cooking Oil (PSCO) and Waste Soya bean Cooking Oil (WSCO) 19
CHAPTER 3: MATERIALS AND METHODS
3.1 Materials 21
3.2 Methods 21
3.2.1 Sample Collection and Preparation 21
3.2.2 Oil Characterization 21
3.2.3 Determination of Bio-oil Yield for Transesterification 26
3.2.4 Method for Gas Chromatography-Mass Spectrometry (GC-MS) Oil Analysis 26
3.2.5 Biodiesel Production (Transesterification) 27
3.2.6 Biodiesel Production by Wet Washing Method 28
3.2.7 Biodiesel Characterization 29
3.3 Effects of Process Parameters 31
3.3.1 Effect of Catalyst Concentration 31
3.3.2 Effect of Reaction Time 32
3.3.3 Effect of Reaction Temperature 32
3.3.4 Effect of Methanol/Sample Molal Ratio 32
3.3.5 Effect of Agitation Speed 32
3.3.6 Optimal Conditions for the Biodiesel Production Yield 33
3.4 Design of Experiment for Biodiesel Production 33
3.4.1 Fractional Factorial Design of Experiment for Biodiesel Production 33
3.4.2 Matrix Design Equation in Terms of Coded Factors for the Effects of the Process Parameters on Biodiesel Produced from Used Soya Oil using Response Surface Method (RSM) 34
CHAPTER 4: RESULTS AND DISCUSSION
4.1 Characterization Test Results of the Used Soya Oil 37
4.2 Effects of Process Parameters Results on Biodiesel Yield 38
4.3 Characterization Test Results of the Biodiesel Produced 43
4.4 Results from the Experimental Matrix using the Fractional Factorial Design 45
4.4.1 Combined Effects of Factors for Biodiesel Production from Waste Soya Oil 45
4.4.2 Analysis of Variance (ANOVA) for Quadratic Model 45
4.4.3 Fit Statistics 47
4.5 Optimal Effects of Process Parameters on Biodiesel Yield 49
4.5.1 Predicted and Experimental or Actual Values 50
4.5.2 Contour and 3-Dimensional (3D) Plots Interaction of the Process Parameters 50
4.5.3 Contour and 3-Dimensional (3D) Plots Interactions between Exposure Time and Other Process Parameters 55
4.5.4 Contour and 3-Dimensional (3D) Plots Interactions between Exposure Temperature and Other Process Parameters 58
4.5.5 Contour and 3-Dimensional (3D) Plots Interactions between Exposure Time and Agitation Speed 61
4.6 Gas Chromatography Mass Spectrometry (GCMS) Analysis Test Results of the Waste Used Soya Bio-Oil and the Developed Biodiesel Samples 62
CHAPTER 5: CONCLUSION AND RECOMMENDATIONS
5.1 Conclusion 66
5.1.1 Contribution to Knowledge 66
5.2 Recommendations 67
References 68
Appendices 73
LIST OF TABLES
3.1 Study range of each factor in actual and coded forms 34
3.2 Experimental design matrix for biodiesel production from waste soya oil using sodium hydroxide as catalyst 36
4.1 Characterization test results of waste soya oil for biodiesel production 37
4.2 Physiochemical properties test results of the synthesized biodiesel 43
4.3 Actual table for combined effects of factors for biodiesel production from waste soya oil using sodium hydroxide as catalyst 46
4.4 ANOVA for quadratic model (Response 1: biodiesel yield) 47
4.5 Fit Statistics 48
4.6 Coefficients in terms of coded factors 49
4.7 Results of gas chromatographic analysis of the waste used soya bio-oil 64
4.8 Results of gas chromatographic analysis of biodiesel developed from the waste used soya bio-oil 65
LIST OF FIGURES
4.1 Biodiesel yield against catalyst concentration for biodiesel produced using waste soya oil 38
4.2 Biodiesel yield against reaction time for biodiesel produced using waste soya oil 39
4.3 Biodiesel yield against reaction temperature for biodiesel produced using waste soya oil 40
4.4 Biodiesel yield against methanol/oil molal ratio for biodiesel produced using waste soya oil 41
4.5 Biodiesel yield against agitation speed for biodiesel produced using waste soya oil 42
4.6 Predicted versus actual plot 50
4.7 Contour plot interaction for molal ratio and catalyst concentration 51
4.8 3D plot interaction for molal ratio and catalyst concentration 51
4.9 Contour plot interaction for molal ratio and reaction temperature 52
4.10 3D plot interaction for molal ratio and reaction temperature 52
4.11 Contour plot interaction for molal ratio and reaction time 53
4.12 3D plot interaction for molal ratio and reaction time 53
4.13 Contour plot interaction for molal ratio and agitation speed 54
4.14 3D plot interaction for molal ratio and agitation speed 54
4.15 Contour plot interaction for catalyst concentration and reaction temperature 55
4.16 3D plot interaction for catalyst concentration and reaction temperature 56
4.17 Contour plot interaction for catalyst concentration and reaction time 56
4.18 3D plot interaction for catalyst concentration and reaction time 57
4.19 Contour plot interaction for catalyst concentration and agitation speed 57
4.20 3D plot interaction for catalyst concentration and agitation speed 58
4.21 Contour plot interaction for reaction temperature and reaction time 59
4.22 3D plot interaction for reaction temperature and reaction time 59
4.23 Contour plot interaction for reaction temperature and agitation speed 60
4.24 3D plot interaction for reaction temperature and agitation speed 60
4.25 Contour plot interaction for reaction time and agitation speed 61
4.26 3D plot interaction for reaction time and agitation speed 62
4.27 Chromatogram of the gas chromatographic analysis of the used soya bio-oil 63
4.28 Chromatogram of the gas chromatographic analysis of the biodiesel developed from the used soya bio-oil 63
LIST OF PLATE
1.1 Biodiesel production (transesterification) 29
CHAPTER 1
INTRODUCTION
1.1 BACKGROUND OF STUDY
Environmental issues are the driving forces for the development of alternative energy sources, since the burning of fossil fuels causes various environmental problems including global warming, air pollution, acid precipitation, ozone depletion, forest destruction, and emission of radioactive substances (Dincer, 2000). The alternative energy source of fossil fuels includes hydro, wind, solar, geothermal, hydrogen, nuclear, and biomass (Demirbas, 2005). Among these alternative energy sources, biofuels derived from biomass are considered as the most promising alternative fuel sources because they are renewable and environmental friendly.
Biomass and agricultural derived materials have been used as alternative energy sources and the use of biodiesel as fuel is a promising potential being a market that grows rapidly (Harten, 2003; Hossain and Boyce, 2009). This is due to its great contribution to the environment and to its role as a strategic source of renewable energy in substitution to diesel oil and other petroleum-based fuels (Monyem et al., 2001; Hossain and Boyce, 2009).
Biodiesel produced from seed oils via transesterification reaction has turned out to be an increasingly possible proposal as a substitute for automotive gas oil (AGO) due to features such as high flash point, excellent lubricity, and high cetane number, in addition to economic and environmental advantages (Demirbas, 2005).
Generally, biodiesel is produced by means of transesterification. Transesterification is the reaction of a lipid with an alcohol to form esters and a byproduct, glycerol. It is, in principle, the action of one alcohol displacing another from an ester, referred to as alcoholysis (cleavage by an alcohol). The reaction is reversible, and thus an excess of alcohol is usually used to force the equilibrium to the product side. The stoichiometry for the reaction is 3:1 alcohol to lipids. However, in practice this is usually increased to 6:1 to raise the product yield. Transesterification consists of a sequence of three consecutive reversible reactions. The first step is the conversion of triglycerides to diglycerides, followed by the conversion of diglycerides to monoglycerides, and finally monoglycerides into glycerol, yielding one ester molecule from each glyceride at each step. The reactions are reversible, although the equilibrium lies towards the production of fatty acid esters and glycerol (Meher et al., 2006 and Van-Gerpen, 2005).
Biodiesel, described as a fuel comprised of mono-alkyl esters of long chain fatty acids derived from vegetable oils or animal fats is oxygenated, essentially free of sulphur and biodegradable (Carlson et al., 2004). It has also been widely reported to be characterized with reduced exhaust emissions, reduced toxicity and improved lubricity, higher flash point, lower vapour pressure and positive energy balance (Knothe and Steidly, 2005; Best, 2006). It can be used in the pure form, or blend in any amount with diesel fuel for use in compression ignition engines (Krahl et al., 2005).
1.2 STATEMENT OF PROBLEM
In recent decades, there have been a growing concern on increasing energy crisis and environmental pollution as world population gradually increases. Sources of pollutants to the environment include automotive exhaust fumes which increases lead and carbon monoxide concentration in the environment following incomplete combustion of fossil fuel. These substances endanger humane health and the environment (carbon monoxide interferes with ozone layer) at large. Also humane domestic waste such waste fry vegetable oil is harmful when discharged to the environment. If found in aquatic fresh water, they envelop the water body, thus prevents the circulation or dissolution of oxygen into the water body hence disrupt the quality of aquatic life. It is therefore necessary to device safe technologies that utilises waste materials harmful to the environmental towards enhancement of humane and environmental well being.
1.3 AIM AND OBJECTIVES OF STUDY
This study aims at investigating the effects of process parameters and optimization of biodiesel production from waste cooking soya oil using sodium hydroxide as catalyst. The specific objectives are to:
i. characterize waste soya oil to determine its specific gravity, moisture content, refractive index, acid value, saponification value, peroxide value, iodine value and kinematic viscosity.
ii. study the effects of the process parameters such as catalyst concentration, reaction time, stirring speed, temperature and methanol / sample molal ratio on biodiesel production; and
iii. establish optimized condition for biodiesel production.
1.4 SCOPE OF STUDY
The scope of this study includes:
i. Extraction and characterization of the bio-oil from the waste cooking oil.
ii. Production and characterization of the biodiesel from the extracted bio-oil samples
iii. Optimization of the process parameters for optimum biodiesel production.
1.5 JUSTIFICATION OF THE STUDY
Biodiesels produced from recycled used soya oil are economically viable. As alternative resource to petroleum-based counterpart, it is readily available. The waste used soya oils discarded when converted to biodiesel would decongest the environment and make the energy produced clean and green. This protects the environment from toxic and hazardous chemicals generated as by-product of fossil fuels. It also saves the foreign exchange that would have been expended in importing refined base products, thus enhancing national development and gross domestic product (GDP), as well as reducing greenhouse gaseous emissions.
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