Ethyl ester biodiesel has been produced from a non-edible Jatropha curcas oil. Oil was extracted from the plant seed using n-hexane at 60°C and pretreated by alkaline refining process to reduce the free fatty acid level to less than 1%. Base-catalysed transesterification reaction with absolute ethanol using potassium hydroxide catalyst was adopted for the conversion. Various physicochemical properties of the refined Jatropha curcas oil were investigated. The ethyl ester biodiesel produced was characterised for its fuel properties such as specific gravity at 15°C, flash point, pour point, kinematic viscosity, cetane number, iodine value and higher heating value using American Society for Testing and Materials Standard Methods. The crude and refined Jatropha curcas oil yields were 58.16% and 52.5%. The physicochemical analysis revealed FFA, saponification value and peroxide value of refined Jatropha curcas oil to be 0.58 mg KOH/g, 159.9 and 1.92 m E/kg respectively. The fatty acid composition obtained from gas chromatography (GC) revealed that the oil contained 44.85% oleic acid as the dominant fatty acid, while Margaric 0.01% and Behenic 0.02% the least. The biodiesel yield was 57.6%, and its measured fuel properties conformed with ASTM 6751 and EN 14214 standards.
The most desired properties of materials, products and industrial processes are sustainability, eco-efficiency and industrial ecology. Achieving a sustainable, resource-efficient and low-carbon economy is one of the key fundamental challenges in the 21st century [
Vegetable oils have long been in use as a substitute for diesel fuel as far back as 1930 [
Jatropha curcas is a hardy plant that has the potential to grow under both arid and semi-arid conditions [
This work provides technical data that can assist Nigeria in reaching informed decisions on industrial exploitation of local Jatropha seed for biodiesel production. It aimed at studying the physicochemical properties of Jatropha curcas seed oil sourced locally in Nigeria, to synthesise its ethyl ester biodiesel via base-catalysed transesterification process and to investigate the regulated and unregulated properties of the biodiesel thereof using standard techniques. This research provides a sustainable strategy, a viable alternative and renewable source for energy generation against over-dependence on fossil fuel that contributes to national energy security concern and environmental degradation.
All reagents (n-hexane, absolute ethanol and sodium sulphate) used were of analytical grade. All analyses were conducted according to standard test methods. The flash point was determined using a Pensky-Martens Closed Flash Tester (K-16270) by Kehler Instrument Company. A 6200 Automatic Isoperibol Oxygen Bomb Calorimeter was used to determine the higher heating value of the biodiesel. ASTM D613 was used to determine cetane number [
Jatropha curcas seeds were collected from Ado-Ekiti and Igbara Odo, both towns in Ekiti State, Nigeria. The seeds were identified according to the flora of West Africa in the Department of Plant Science and Biotechnology, Ekiti State University, Ado-Ekiti, Ekiti State. The seed shells were cracked to remove the seed (endosperms), air dried and later oven dried at 60˚C to constant weight. The dried seeds were crushed into cake with mortar and pestle before extracting the oil by Soxhlet extraction using n-hexane at 60˚C. The extracted oil was refined by alkaline refining process as follows: 0.16 g of 18 M NaOH was added to 30 g of oil and agitated for 30 min. The mixture was heated to 75˚C and centrifuged. The physicochemical analyses conducted on the oil include acid value, % FFA as oleic acid, peroxide value, saponification value and specific gravity at 15˚C. These analyses were conducted according to the methods described by the Association of Official Analytical Chemists [
Base-catalysed transesterification was adopted for this process. Ethanol was dried over anhydrous sodium sulphate prior to use. Potassium ethoxide was prepared by dissolving 0.37 g KOH (catalyst) in 16.6 ml absolute ethanol in a 250 ml beaker. The potassium ethoxide was gently introduced into 200 ml refined oil in a 1 L round bottom flask. The mixture was stirred and refluxed at 70˚C for 30 min. This was later transferred into a separating funnel and allowed to stand for 1 h in order to separate the mixture into layers. The lower layer was run off while the upper layer ran into a round bottom flask and refluxed again at 70˚C at 30 min with another potassium ethoxide catalyst. The ethyl ester was washed with 20 ml distilled water five times, drained into a beaker and dried over anhydrous sodium sulphate. The fatty acid ethyl ester was analysed for its fuel properties (specific gravity, flash point, pour point, kinetic viscosity, cetane number, iodine value and higher heating value) and tested according to India, ASTM 6751 and EN 41214 Biodiesel Standards.
Agilent 6890 Gas chromatograph System equipped with HP INNOWAX (30 m × 0.25 mm × 0.25 µm) and Agilent ChemStation software was used for the analysis using the following conditions: split injection (split ratio: 20:1), carrier gas: nitrogen, inlet temperature: 250˚C; oven programme: initial temperature at 60˚C, ramped at 12˚C/min for 20 min and then maintained for 2 min, ramped again at 15˚C/min for 3 min and then maintained for 8 min, detector: FID, detector temperature: 320˚C, hydrogen pressure: 22 psi, compressed air: 35 psi. The fatty acid was determined as ethyl ester. The ethyl ester was prepared following a standard procedure for GC analysis as follows: 20 mg of the oil was mixed with 2 cm3 of toluene Then 2 cm3 of 1.5% sulphuric acid in ethanol was added. The mixture was stirred and incubated at 55˚C overnight. 4 cm3 saturated solution of sodium chloride was added and vortexed. 2 cm3 HPLC grade hexane was added followed by addition of 3 cm3 of 2% NaHCO3. The mixture was also vortexed, and 180 µl of the upper phase was taken for GC analysis.
Results of physicochemical analyses carried out on the oil as shown in
Properties | Acid Value (mg KOH/g) | Saponification Value (mg KOH/g) | Peroxide Value (mE/kg) | % FFA as Oleic Acid | % Refined Oil Yield | Specific gravity |
---|---|---|---|---|---|---|
Jatropha oila | 1.16 | 159.9 | 1.92 | 0.58 | 52.5 | 0.882 |
Jatropha oilb | - | 193.55 | 1.93 | 2.23 | - | 0.903 |
Jatropha oilc | 35.8 | 193 | - | - | - | 0.895 |
aResult of this study, Crude Oil Yield = 58.16%; b [
yield of the oil is an important parameter that can determine its cost for biodiesel production. The oil content of Jatropha curcas seed (58.16%) was found to be higher than 47.25% and 49.1% reported by Akintayo and Martin et al. respectively [
Acid value is a measure of the acidic component in an oil sample. It is determined as the mass in mg of KOH required to neutralise the free fatty acid components in one gram of sample and is used to monitor oil degradation during storage. This was carried out by titration according to ASTM D664. The experimental result revealed a very high acid value of the extracted oil of 4.56 mg KOH/g. This high value explains the reason why the oil was subjected to alkaline refining prior to the production of biodiesel. Due to the chosen strength of potassium hydroxide used for refining (i.e. to neutralise some of the free fatty acids), the acid value of Jatropha curcas oil was reduced to 1.16 mg KOH/g and the % FFA (as oleic acid) reported as 0.58, values appropriate to complete the reaction with base catalysts. About 74.6% reduction was achieved for 1 h after refining. Jatropha curcas oil with FFA level of <1% has been reported to give a high yield of biodiesel [
Saponification value is a measure of the mean molecular weight of the fatty acid present in an oil sample. Result obtained for oil under investigation revealed a saponification value of 159.9, which was lower than 193 obtained by [
Peroxide value is an indicator of the deterioration of oil due to oxidation at double bond of an unsaturated fatty acid; rancidity. The peroxide value for refined Jatropha curcas oil was 1.92 mE/kg which is 0.05% lesser than 1.93 mE/kg obtained by [
The result of measured fuel analyses for biodiesel produced is shown in
A yield of 57.6% was obtained, and its specific gravity (15˚C) was determined to be 0.882.
Flash point is the lowest temperature at which fuel begins to evolve vapour in sufficient quantity to form an explosive or inflammable mixture with air. It measures the response of fuels to heat and assesses their flammability hazard levels and safety conditions. It has been reported that residual alcohol can reduce flash point of biodiesel [
PROPERTIES | METHOD | JATROPHAd BIODIESEL | EN 14214 | ASTM D6751 | IBSe |
---|---|---|---|---|---|
Pour point (˚C) | ASTM D97 | −6 | −15 - −16 | - | - |
Flash point (˚C) | ASTM D93 | 215 | 101 (min) | 130 (min) | 120 (min) |
Kinematic viscosity @40˚C (mm2/sec) | ASTM D445 | 5.01 | 3.5 - 5.0 | 1.9 - 6.0 | 2.5 - 6.0 |
Heating value (MJ/kg) | ASTM D240 | 42.77 | - | - | - |
Cetane number | ASTM D613 | 49.77 | 51 (min) | 47 (min) | 51 (min) |
Iodine value (g I2/100 g) | AOCS, 1997b | 99.20 | 120 (max) | - | - |
Specific gravity @15˚C | - | 0.86 | 0.88 - 0.9 | - | - |
dResult of this study; eIBS: India Biodiesel Standard.
using flash point. High flash point makes biodiesel safer for storage, handling and transportation [
The pour point is the lowest temperature at which fuel start to flow. It is used to measure the cold flow operability of fuel. The cold property is one of the most critical obstacles against the widespread of fuel usage. Pour point is mostly related to saturation of biodiesel [
Viscosity is a significant internal property of a fluid which indicates the degree of resistance to flow [
Cetane number is an indicator for measuring the ignition performance of fuel in a combustion engine. The cetane number of Jatropha curcas (ethyl ester) biodiesel was 49.77. This met ASTM D6751 standard of 47 but lower than the minimum of 51 recommended by EN 14214 and India Biodiesel specification (IBS).
Iodine value is a measure of the unsaturation of oils. High iodine value indicates high unsaturation of oils [
Heating value is an important parameter that measures the capacity of fuel to generate heat. It can be used to adjudge the suitability of biodiesel as an alternative to diesel fuel. The heating values of biodiesel are usually lower than that of diesel fuel―5 MJ/kg [
Results of the fatty acid composition of the ethyl ester of Jatropha curcas oil is shown in
FATTY ACID | FORMULA | STRUCTUREf | SYSTEMATIC NAME | Wt (%) |
---|---|---|---|---|
Myristic | C14H28O2 | 14:0 | Tetradecanoic | 0.051 |
Palmitic | C16H32O2 | 16:0 | Hexadecanoic | 13.07 |
Palmitoleic | C16H30O2 | 16:1 | cis-9-Hexadecenoic | 0.003 |
Margaric | C17H34O2 | 17:0 | Heptadecanoic | 0.01 |
Stearic | C18H36O2 | 18:0 | Octadecanoic | 6.30 |
Oleic | C18H34O2 | 18:1 | cis-9-octadecenoic | 44.85 |
Linoleic | C18H32O2 | 18:2 | cis-9-,cis-12-octadecedianioc | 34.87 |
Linolenic | C18H30O2 | 18:3 | cis-6-,cis-9-,cis-12-octadecatrienoic | 0.50 |
Arachidic | C20H40O2 | 20:0 | Eicosanoic | 0.03 |
Arachidonic | C20H32O2 | 20:4 | Cis-6-,cis-9-,cis-15-,Docosatetranoic | 0.20 |
Behenic | C22H44O2 | 22:0 | Docosanoic | 0.02 |
Erucic | C22H42O2 | 22:1 | cis-9-Docosenoic | 0.028 |
Lignoceric | C24H48O2 | 24:0 | Tetracosanoic | 0.05 |
Capric | C10H20O2 | 10:0 | Decanoic | - |
Lauric | C12H24O2 | 12:0 | Dodecanoic | - |
Caprylic | C8H16O2 | 8:0 | Octanoic | - |
fxx: y indicates xx carbons in the fatty acids with y double bonds. Total saturated fatty acids = 19.53%. Total unsaturated fatty acids = 80.45%.
atoms. The total unsaturated fatty acids consisting of oleic, palmitoleic, linoleic, linolenic, arachidonic and erucic acids made up 80.45%, which is relatively higher than 78.5% obtained by Lau [
The utilisation of non-edible Jatropha curcas seed oil for biodiesel production is sustainable. Biodiesel from refined jatropha oil can serve as a smart alternative to diesel fuel, which is non-renewable. The measured fuel properties of Jatropha curcas biodiesel compared favourably with those worked upon by other researchers and met both ASTM D6751 and EN 14214 standards as well as the India biodiesel specification (IBS). The pre-treatment of the extracted oil via alkaline refining process helped to reduce the free fatty acid content, which in turn enhanced the quality of the biodiesel produced thereof. The use of simple transesterification process using potassium hydroxide (base-catalyst) has proven to be an effective conversion route to obtain biodiesel from Jatropha curcas oil. The presence of high molecular fatty acids in the biodiesel can significantly affect fuel properties of the fuel. Although the biodiesel has comparatively compatible fuel properties with conventional diesel fuel, it was found to be less volatile than diesel fuel. But better still, the biodiesel produced from refined Jatropha curcas seed oil can be used as fuel blend in diesel engine. However, there is a need to evaluate the suitability of biodiesel as a blend in different diesel fuels and the blend proportion with optimum efficiency.
The authors declare no conflicts of interest regarding the publication of this paper.
Azeez, A.M., Fasakin, A.O. and Orege, J.I. (2019) Production, Characterisation and Fatty Acid Composition of Jatropha curcas Biodiesel as a Viable Alternative to Conventional Diesel Fuel in Nigeria. Green and Sustainable Chemistry, 9, 1-10. https://doi.org/10.4236/gsc.2019.91001