Study of an Effective Technique for the Production of Biodiesel from Jatropha Oil

Transcription

1 Journal of Emerging Trends in Engineering and Applied Sciences (JETEAS) 2 (1): Scholarlink Research Institute Journals, 2011 (ISSN: ) jeteas.scholarlinkresearch.org Journal of Emerging Trends in Engineering and Applied Sciences (JETEAS) 2 (1): (ISSN: ) Study of an Effective Technique for the Production of Biodiesel from Jatropha Oil 1 S.J. Ojolo, 2 B.S. Ogunsina, 1 A.O. Adelaja, 1 M. Ogbonnaya 1 Mechanical Engineering Department, University of Lagos, Lagos Nigeria 2 Agricultural Engineering Department, Obafemi Awolowo University, Ile-Ife. Nigeria Corresponding Author: S.J. Ojolo Abstract This paper presents biodiesel production from non-edible jatropha oil by transesterification process on a bench scale using sodium hydroxide ( aoh) as catalyst for the methanolysis of the jatropha oil. This study evaluated the effect of the concentration of the basic catalyst on the biodiesel yield. The biodiesel was evaluated for fuel properties and compared with the American Society for Testing and Material (ASTM) specification for biodiesel according to its physical, chemical and mechanical properties such as viscosity, flash point, density, sulphur content. The results show that the properties of the biodiesel produced was found to be within the limit of the ASTM specifications for biodiesel. At a catalyst concentration of 0.8%, reaction temperature of 65%, reaction time of 1 hour and methanol to oil molar ratio 5:1, the amount of biodiesel produced was 95.5%. Keywords: jatropha, biodiesel, trans-esterification, methanolysis, ASTM I TRODUCTIO In the context of growing interest for renewable energy sources, biodiesel energy production derived from vegetable oil, animal fat, and used waste cooking oil including triglycerides is proposed as an alternative to petroleum based fuel to reduce greenhouse gas emission, pollution and man s total dependence on petroleum fuel. Bio-diesel is the most valuable form of renewable energy. It is environmentally friendly and ideal for heavily polluted cities and is as biodegradable as salt. Research has found that it produces 80% less carbon dioxide, 100% less sulfur dioxide emissions and has 90% reduction in cancer risk (Tiwari et. al., 2007). With the increasing population, today over 90% of the world entire population depends on petroleum or fossil fuel as the only source of energy. With recent finding, it has been made known that there is gradual depletion of oil and gas reserve that it will get to a time when there will not be enough energy from fossil fuel to serve the world at large. Since the petroleum crises in 1970s, the rapidly increasing prices and uncertainties concerning petroleum availability, a growing concern of the environment and the effect of greenhouse gases during the last decades, has revived more and more interests in the use of renewable energy as a substitute of fossil fuel (Wang et. al., 2006). Biodiesel is a substitute for or an additive to diesel fuel produced from renewable sources such as vegetable oils, animal fats, and recycled cooking oils which is derived from the oils and fats of plants and animals such as sunflower, canola or Jatropha (Barn Wall and Sharma, 2005). Biodiesel is most commonly used as a blend with petroleum diesel. At concentration of 6% to 20% biodiesel blends, it can be used in many applications 79 that use diesel without modification of the engine (Zhang et al., 2003). Vegetable oils can be used directly as diesel engine fuels, but this requires engine modification because some of their properties are less advantageous for this application. Two major problems are their very high viscosity and poor thermal and hydrolytic stability. They also have less favorable ignition qualities (Reffy and Raju, 2009). Due to these undesirable properties of the oil, there is a need to pass the oil through a process of transesterification. Transesterification transform the large branched molecule structure of the oils into smaller, straight chained molecules similar to the standard diesel hydrocarbons (Morrision and Boyd, 2005). Transesterification is the process of exchanging the organic group R" of an ester with the organic group R' of an alcohol. These reactions are often catalyzed by the addition of an acid or base. Transesterification is common and well-established chemical reaction in which alcohol reacts with triglycerides of fatty acids (vegetable oil) in the presence of catalyst (Reddy and Ramesh, 2005). The transesterification reaction scheme is shown below Figure 1 Transesterification Reaction Scheme

2 Biodiesel is made by chemically reacting vegetable oil or animal fat or a combination of oils and fats with alcohol, usually nearly pure methanol, denatured ethanol or ethanol. The mixture is then combined with a catalyst: an alkaline chemical such as potassium hydroxide or sodium hydroxide, also known as lye. The oil is chemically acidic. The combination of the alcohol and catalyst, also known commonly as methoxide, is chemically a base. This chemical reaction breaks the fat molecules in the oils into an ester, which is the biodiesel fuel, and glycerol (Krishnakumar and Venkachalapathy, 2007). This reaction is called transesterification. Since transesterification reaction is an equilibrium reaction, where more amount of alcohol is required to shift the reaction equilibrium to right side and produced more esters as proposed product (Dorado et al., 2004). Methanol and ethanol are used most frequently; especially methanol is preferred because of its low cost and its physical and chemical advantages (polar and shortest chain alcohol). It can quickly react with triglycerides and NaOH gets easily dissolved in it. Ethyl ester and methyl ester almost has same heat content. Viscosity of ethyl ester is slightly higher and pour point is slightly lower than those of methyl ester (Tiwari et al., 1985). The catalyst may be acidic (e.g. Sulphuric acid, hydrogen Chloride, Boron trifluoride etc) or alkaline (e.g. Metal alkoxide, alkaline hydroxide etc) with the alkaline catalyst given faster reaction (Meher, 2006). In the transesterification process, the common based catalyst that is used is the sodium hydroxide (NaOH) and the potassium Hydroxide (KOH). The catalyst is to increase the rate of the reaction. The catalyst concentration increase influences the ester yield in a positive manner up to 0.92% NaOH for jatropha oil after that the ester yield decreases (Krishnakumar et al., 2008). If the catalyst used exceeded 1.3% oil, the reaction solidified causing the formation of soap (Meher, 2006). The reaction temperature increase influence the reaction in a positive manner and the ester yield slightly decreases above 50 C reaction temperature (Tiwari et al., 1985). Other researchers found better result above 50 0 C. As the reaction time increases the conversion rate also increases. The reaction starts very fast and almost 80% of conversion takes place in first 5 minutes and after 1 hour almost 93-98% conversion of triglycerides into ester takes place (Reddy and Ramesh, 2005). The effect of reaction time was studied from 45 minutes to 120 minutes on the methyl ester (biodiesel) yield. It was found that ester yield increased as the reaction time increases. However if the reaction time is increased beyond 1 hour, the increase in the yield of ester is small (Krishnakumar et al., 2008). One of the important parameters affecting the yield of the ester is the molar ratio of alcohol to vegetable oil employed. The yield of alkyl ester increased when the molar ratio of oil to alcohol was increased (Demibras, 2008). The stoichiometric requirement for transesterification was 3:1 to yield 3 mole of ester and 1 mole of glycerin (Ramadhas et al., 2004). For optimum amount of biodiesel production 6:1 molar ratio is taking during alkaline esterification (Velkovic et al., 2006). When the biodiesel displaces petroleum, it significantly reduces green house gas (GHG) emission. By some estimate, GHG emission (including carbon dioxide (CO 2 ), methane, Nitrogen oxide (NO x ) are reduced by 41% if biodiesel is produced from crops harvested from fields that are already in production (Morrision and Boyd, 2005). At a very low concentration, biodiesel improves fuel lubricity and raises the cetane number of the fuel. Diesel engine depends on the lubricity of the fuel to keep moving parts, especially fuel pumps, from wearing prematurely. Biodiesel can impart adequate lubricity to diesel fuels at blends level as low as 1% (Krishnakumar and Venkachalapathy, 2007). Jatropha belongs to the family Euphorbiaceae. The word Jatropha is derived from two Greek words Jatros meaning doctor and trophe, which means nutrition. Jatropha curcas is a drought-resistant perennial shrub or a small tree. It grows wild in tropical and sub-tropical climatic regions and can be successfully grown in problematic soils and arid regions. It can produce seed for fifty years. Jatropha curcas has a wide range of uses and promise various significant benefits to human and industry. Extracts from this plant have been shown to have anti tumor activity, the leaves can be used as remedy for malaria and the seed can be used in the treatment of constipation and the sap was found to be effective in accelerating wound healing (Barn Wall and Sharma, 2005). However, this plant can be used as an ornamental plant, raw material for dye, potential feedstock, pesticides, soil enrichment manure and more importantly as an alternative for biodiesel production. Jatropha produces seeds with oil content of about 33 to 37%. The oil can be combusted as fuel without being refined. It burns with clear smoke-free flame. The methods that are used for the extraction of the oil are oil presses, oil expeller, traditional method and the modern concept, which involves using the method of ultrasonication. The production of this biodiesel from non edible oil will in return reduce the overall dependence on petroleum diesel, thereby saving the environment from hazards. Several research work have been carried out using vegetable oil and animal fats in the production of biodiesel, this have become a great concern because they compete with food material. The use of jatropha oil in the production of biodiesel is justified since this oil is non edible and it can be used in the production of biodiesel which in the long run will reduce the consumption and demand for petroleum products. This work is very significant because it will provide 80

3 an alternative to diesel fuel using vegetable oil from jatropha seeds. Biodiesel from jatropha oil is becoming popular in Nigeria. Therefore, it is very important to study the effective technique of producing biodiesel from jatropha oil. This work also provides data for further works on biodiesel from jatropha oil in Nigeria. The objectives of this work are to produce biodiesel from the Jatropha oil through the process of transesterification and to determine the physical, chemical and mechanical properties of the biodiesel produced and also to compare the properties of the biodiesel with ASTM D, 6751 of biodiesel and ASTM D, of petroleum diesel. MATERIALS A D METHODS Reaction Raw Material The jatropha oil used was obtained from the Biodiesel Nigeria Limited. The alcohol used was methanol (CH 3 OH) 99% and pure Sodium Hydroxide (NaOH) as catalyst which must be dried and it is commercially available reagent grade. The materials for the titration include Isopropyl alcohol 99%, pure distilled water, and Phenolphthalein solution (not more than a year and kept protected from strong light). Vinegar and water were used for the washing of the products of the experiment. The oil is filtered to remove solid particles. The oil is warmed up a bit to about 35 0 C to allow it run freely. A cartilage filter is used. The oil is heated to C and it is held there to allow any water to boil off. Any trace of water will slow down the reaction and cause saponification (soap formation). METHODS Basic Titration The essence of the titration process is to get the number of gram of NaOH that will be used per liter of oil in the transesterification process. This will give a rough guide on the amount of catalyst that will give an optimum yield. Dissolve 1 gram of NaOH in 1 liter of distilled water (0.1 NaOH) solution. Phenolphthalein solution is used to get the end point. In a smaller beaker, 1ml of jatropha oil is dissolved in 10ml of pure isopropyl alcohol. The beaker is warmed gently by standing it in some hot water, stir until all the oil dissolves in the alcohol and the mixture turns clear. 2 drops of phenolphthalein solution is added. Using a burette, 0.1% NaOH solution is added drop by drop to the oil alcohol phenolphthalein solution, stirring all the time, until the solution stays pink for 10 seconds. The number of mls of 0.1% NaOH solution used added to 5.0 will give the number of NaOH to be used per liter of oil (Tiwari et al., 2008). Test Batches For the production of biodiesel, a test batch was carried out to try out the amount of NaOH that is best used for the optimum yield of biodiesel. Based on the titration value, the catalyst was varied between 0.6g and 1.2g for 100g of oil. Preparing of Sodium Methoxide The amount of methanol used is 20% of the jatropha oil by mass according to the molar ratio of oil to methanol which is 6:1. This is calculated using their molar mass. The 20g of methanol is mixed with the 0.8g of NaOH in a separate vessel and was poured into a round bottom flask while stirring continuously until all the NaOH dissolves in the methanol, creating sodium methoxide in an exothermic reaction. During this process caution is taken to treat sodium methoxide with extreme care. A splash of the mixture on your skin is likely to burn the skin thereby killing the nerves if it is not washed immediately with a lot of water. Heating and Mixing The jatropha oil is heated to 65 0 C in the oven and it is stirred at interval to allow for uniform distribution of heat and prevent temperature gradient. The jatropha oil is poured in a flat bottom flask and placed on an electric mixer and a magnetic stirrer is used to stir. Too much agitation should be avoided since it can cause splashing, bubbles through vortexing, and reduce mix efficiency. The sodium methoxide is added into the oil and it is mixed for an hour. The transesterification process separates the methyl esters from the glycerin. The CH 3 O of the methanol then caps off the ester chains and OH from the NaOH stabilizes the glycerin. Settling and Separation The solution is poured into a separating funnel and is allowed to separate for 12 hours or more. The methyl ester (biodiesel) will be floating on top while the denser glycerine will be at the bottom of separating funnel. The bottom layer consists of glycerin, excess alcohol, catalyst, impurities, and traces of unreacted oil. The tap of the funnel is open to carefully separate the glycerine from the biodiesel. If the glycerine congeals in the funnel, it is reheated just enough to liquefy the glycerine again. Washing and Drying For washing and purification of methyl ester, it was mixed, washed with warm distilled water to remove the unreacted alcohol, oil and catalyst. It is allowed to settle under gravity for 24 hours. Before washing the biodiesel for the first time, a small amount of dilute acetic acid is added bore adding the water. This is to bring the PH of the solution closer to neutral because it neutralizes and drop out any NaOH suspended in the biodiesel. Two layers were formed, the upper layer was the biodiesel and the lower layer was made of water and impurities. This process was repeated until the lower phase had a ph value that was similar to that of distilled water, thus indicating that only 81

4 water was present and the catalyst is removed completely in the washing. It was found that during washing some ester was lost due to emulsion formation. The separated biodiesel is taken for characterization. The block diagram for the production of biodiesel is shown in Figure 2. Jatropha Filtering Methyl Washing BIODIESEL NaOH transesterification Phase separation mixing Glycerin Figure 2: Schematic Diagram for Biodiesel Production Determination of Physical and Chemical Properties of Biodiesel The appearance was determined using the visual test method. The colour was determined using the ASTM, D method. The total acidity was determined using the ASTM, D method. The flash point was determined by ASTM, D 93 method. The specific gravity was determined by ASTM, D 1293 method. The kinematic viscosity was determined by ASTM, D. The sulphur content was determined using Acq method sulphur M. The Polyaromatic hydrocarbon (PAH) was determined using Acq method PAH. M. The water content was determined with ASTM, D method. The sulfated Ash was determined with ASTM, D method. Conditions for Determination of Physical and Chemical Properties Pressure: atmospheric pressure Temperature: temperature of the laboratory at 37 0 C Condition for PAH Column HP 5ms 30m length D (mm) initial diameter 0.25(µm) Temperature Initial = 100 hold at 4 to 320 at the rate of 6 0 C/min to hold for 9 mins. Pressure 1.8 Psi Flow Velocity 40cm/sec Final run time mins Syringe size 10µl Injection volume 1µl Heating 250 GL system 7890A Injector 7683B series Detector 5975C VL MSD Condition for sulphur Colum HP 5ms 30m length D (mm) initial diameter 0.25(µm) Temperature initial temperature 60 0 C for 2mm rate 20 0 C/min to C and hold 4 mins. Pressure 10 Psi Flow 20ml/mins at 60 0 C Velocity 40cm/sec Final run time mins Syringe size 10µl Injection volume 1µl Heating 250 GL system 7890A Injector 7683B series Detector 5975C VL MS RESULTS A D DISCUSSIO Results of physical and chemical properties of jatropha oil The chemical and physical properties of jatropha oil were determined, the results of density, kinematic viscosity, flash point was determined and is shown in Table 1.s Table 1: Chemical and Physical Properties of Jatropha Oil Property Jatropha oil Density at 30 0 C (kg/m 3 ) Kinematic Viscosity at 30 0 C (mm 2 /s) Flash point ( 0 C) 216 From the result it is seen that the viscosity of the jatropha oil is very high and because of this it is not suitable for use in a compression ignition engine. Due to this, there is a need to reduce the viscosity. This can only be done through the process of transesterification. 82

5 Table 1: Chemical and Physical Properties of Jatropha Oil Property Jatropha oil Density at 30 0 C (kg/m 3 ) Kinematic Viscosity at 30 0 C (mm 2 /s) Flash point ( 0 C) 216 From the result it is seen that the viscosity of the jatropha oil is very high and because of this it is not suitable for use in a compression ignition engine. Due to this, there is a need to reduce the viscosity. This can only be done through the process of transesterification. Titration Result The rough idea of the amount catalyst to be used for the trans-esterification process for optimum yield was determine by the process of titration and the result is shown in Table 2. Table 2: Titration Values Sample number Initial volume of 0.1% NaOH (ml) Final volume of 0.1% NaOH (ml) Volume of 0.1% NaOH used (ml) Average 7.2 Note: 100g of oil is equivalent to 125ml of oil in volume. The number of sodium hydroxide required per liter of oil is given as 7.2g. If 7.2g of NaOH is used for 1000ml of oil, therefore 0.9g will be used for 125ml of oil. Since the amount of catalyst to be used varies with oil, a rough idea of the amount to be used was determined and according to the result, one can take a range of 0.6g to 1.2g to determine the amount of catalyst that can be used to obtain optimum yield of biodiesel. Required mass NaOH/oil (g/l) Yield Percentage of Biodiesel from Jatropha Oil with Varying Amount Of Catalyst The effect of NaOH concentration was studied in the range of % (weight of NaOH/weight of oil), whiles the other parameters such as reaction temperature, reaction time, molar ratio of oil to methanol, were kept constant. The catalyst concentration increase influences the ester yield in a positive manner up to 0.80% NaOH for jatropha oil after that it decreases. This can be seen in Table 3. Table 3: Yield Percentage of Biodiesel with Varying Amount of Catalyst Sample Catalyst Oil Methanol Reaction time (hr) Reaction Temp.( 0 C) Biodiesel (%) Glycerin (%) of Yield percentage of biodiesel from jatropha oil The amount of catalyst for optimum yield is 0.8g. Various samples were carried out to get the average. The result is given in Table 4. Table 4: Yield Percentage of Biodiesel Sample Catalyst Oil Methanol Reaction time (hr) Reaction Temp.( 0 C) Biodiesel (%) Average Glycerin (%)

6 From the result it is seen that the average yield of biodiesel with 0.8% NaOH is 95.55%. Qualitative and Quantitative Analysis of Biodiesel Quantitative and qualitative analysis of the reaction mixture was conducted using gas chromatography (GC). It is a procedure used in determining the composition of a mixture of methyl esters. The result of the gas chromatography is shown below in Fig. 4. Abundance According to the search report of the gas TIC: [BSB1] a.D\data.ms chromatography, the composition of the biodiesel and their percentage area is shown in Appendix 1. It can be seen that at the retention time (RT) of minute the major methyl ester found at this point is Hexadeconic acid which is in the family of methyl ester Sulphur Content Analysis The sulphur content of biodiesel was analyzed using the gas chromatography and the result is shown in figure 3 and Appendix 2. The result shows that biodiesel contains no sulphur present in the composition of biodiesel. This shows that biodiesel is an environmental friendly biofuel Time--> Figure 3: Gas Chromatography of Biodiesel Table 5: Physical, Chemical and Mechanical Properties of Biodiesel Property Unit Jatropha biodiesel ASTM D 6751 standard for biodiesel ASTM D 975 standard for diesel fuel Density at 30 0 C Kg/m Report Dynamic viscosity Mpa. S Kinematic viscosity at 40 0 C mm 2 /s Flash point 0 C min Water content % max 0.5 max Sulfated Ash % Nil max 0.01 max Sulphur content Ppm Nil 0.05 max 0.05 max Total acidity % max 0.5 Colour Appearance Clear and bright Clear and bright Clear and bright Abundance TIC: D\data.ms Results of Physical, Chemical and Mechanical Properties of Biodiesel from Jatropha Oil The physical and chemical properties of biodiesel from jatropha oil were studied and the properties measured were compared with the ASTM specification and the results are presented in Table 5. Time--> Figure 4: Gas Chromatograph showings Sulphur Content 84 The flash point of biodiesel fuel from jatropha oil is very high compared to diesel fuel and this makes it safer to handle and store. Considering the kinematic viscosity, the decrease in kinematic viscosity from 42.26mm 2 /sec to 4.73mm 2 /s is the important fuel property of the trans-esterified jatropha oil. It indicates that the flow capability of the jatropha oil has increased to a large extent by trans-esterification. The increase in the fuel ability to flow would induce complete burning of the fuel without any delay in ignition. The density of biodiesel was 865kg/m 3 and it was reduced to a significant extent when compared with the density of jatropha oil. Comparing the result

7 gotten with that of ASTM D standard for biodiesel and ASTM D standard for diesel fuel, it falls within the acceptable range. CO CLUSIO A D RECOMME DATIO Conclusion In this work, trans-esterification reaction was carried out using the non edible jatropha oil and alkali methoxide. The quantity of catalyst for optimal biodiesel yield of 95.5% was 0.8g at a reaction time of 1 hour, reaction temperature of 65 o C and molar ratio of oil to methanol as 5:1. The biodiesel produced was analyzed for its physical, chemical and mechanical properties and compared with the properties of petroleum based diesel. Biodiesel from jatropha oil has compatible properties as conventional diesel, thus can be used as blends or direct fuel in compression ignition engine. Viscosity of a fuel is an important property to consider in a fuel and a high viscosity fuel is not suitable for an engine. The viscosity of the jatropha oil reduces substantially after trans-esterification and falls within the ASTM D, 6751 for biodiesel and when compared with ASTM D for petroleum diesel, it falls within the range. Table 6: Standards used in the experiments Test method Standard specification of Diesel ASTM D ASTM D ASTM D ASTM D92 50 ASTM D 0.5max ASTM D 0.01 Gas Chromatography 1.2% 0r less ASTM D 0.5 ASTM D 4 or less Visual Clear and bright Source: (Tiwari et al., 2007; Krishnakumar et al., 2008) Table 6 shows the standards used as basis for comparison in all the experiments. Biodiesel properties like density, viscosity, flash point, water content are within the ASTM norms. Biodiesel produced from jatropha oil is a clean fuel since it contains no sulfur; therefore it is environmental and human friendly and the CO 2 produced during combustion is used by the plant thereby reducing green house effect. The use of jatropha oil as a source of biodiesel could offer opportunity for generation of rural employment and improving the environment. Finally, it is concluded that the biodiesel from jatropha oil could be recommended as a fuel to be used in compression ignition engine, if tested in an engine and the engine performance provides a satisfactory result. RECOMME DATIO Further work is required to fully optimize the overall trans-esterification process to get a 100 percentage yield of biodiesel from the oil including modeling of the reaction. The production of biodiesel operation is carried out in various units. Further work need to be done to develop a unit operation which will involve an automated reactor that will carry out all the processes of biodiesel production in just a unit plant. It is also recommended that the biodiesel be used in a compression ignition engine, to obtain a satisfactory result which will establish the fact even further that it is an alternative to petroleum diesel. REFERE CES Barn Wall, B. K., Sharma, M. P., Prospects of Biodiesel Production from Vegetable Oils in India, Renewable & Sustainable Energy Review no , Pp Demirbas, A. Biodiesel: A realistic fuel alternative for diesel engine. London: Springer 2008 Dorado, M. P., Ballesteros, E., Lopez, F. J., Mittelbach, M. Optimization of alkali-catalyzed trans-esterification of brassica oil for biodiesel production Energy Fuel, 18 (1) 2004, Pp Krishnakumar, J., Venkatachalapathy, V. S. K.. Comparative Analysis of Mineral Diesel, Vegetable Oil and their Blends. Proceedings, National Conference Organized by the Department of Mechanical Engineering, Kumaraguru College of Technology, Coimbatore, India, Vol Krishnakumar, J., Venkatachalapathy, V.S.K., and Elancheliyan, S.. Technical Aspects of Biodiesel Production from vegetable oil. Thermal science, vol. 12, 2008, Pp Meher, L. C., Sagar, D. V., Naik, S. N.. Technical aspects of biodiesel production by transesrerification: A review. Renew Sust. Energ. Rev., 10 (3), 2006, Pp Morrison. R. T., Boyd, R. N.. Organic Chemistry, 6th ed., Prentice Hall Ltd., New Delhi, 2005, pp Ramadhas, A.S., Jayara, S., Muraleedharaun, C. Use of Vegetable oils as I.C engine fuels: A Review. Renew Energy 29, 2004, Pp Reddy, J.N. and Ramesh, AParametric study for improving the performance of a jatropha oil fuelled compression ignition engine. Renewable Energy, 31, 2005, Pp

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