- Email: [email protected]
Study on Production Process of Biodiesel from Rubber Seed (Hevea Brasiliensis) by in Situ (Trans)Esterification Method with Acid Catalyst
Available online at www.sciencedirect.com
Energy Procedia 32 (2013) 64 – 73
International Conference on Sustainable Energy Engineering and Application [ICSEEA 2012]
Study on production process of biodiesel from rubber seed (hevea brasiliensis) by in situ (trans)esterification method with acid catalyst Widayata,b,*, Agam Duma Kalista Wibowoa, Hadiyantoa,b a
Chemical Engineering, Diponegoro University Jl. H. Prof. Sudarto, SH, Semarang, Indonesia 50275 b C-Biore : Center Biomass and Renewable Energy
Abstract Biodiesel is fatty acid methyl or ethyl esters made from vegetable oils (edible and non edible) or animal fats. The objective of this research was to produce biodiesel from rubber seed by in situ method with acid catalyst with a goal for obtaining environmentally friendly alternative fuels from non edible raw material. This research focuses on influence of reaction time, concentration of acid catalyst and ratio raw material to methanol. The first stage was carried out in order to get reaction time based on the density and viscosity of mixture produced. In this process H2SO4 0.5% (v/v) was used as catalyst and ratio of raw material to methanol (1:2). The experiments were conducted by investigating the catalyst concentration in range 0.1-1%(v/v) and ratio of raw material to methanol in range 1:1.5-1:3. The research method included, the preparation of samples, biodiesel production, biodiesel separation, and biodiesel characterization i.e density, viscosity, GC analysis, acid value and Iodine number. The results shows that the operation time for biodiesel production by in situ method with acid catalyst was 120 minutes and the yield of Fatty Acid Methyl Ester (FAME) obtained was at 91,05%.
2012.The Published Elsevierby Ltd. © 2013 Authors.byPublished Elsevier Ltd. Selectionand and/or peer-review responsibility Research Centre Electrical Power Selection peer-review underunder responsibility of theof Research Centre forfor Electrical Power and and Mechatronics,Indonesian IndonesianInstitute Institute Sciences Mechatronics, ofof Sciences. Keywords: Biodiesel; rubber seed; in situ; (trans)esterification; Fatty Acid Methyl Ester (FAME).
* Corresponding author. Tel.: +62 24 7460058; fax: +62 24 76480675. E-mail address: [email protected].
1876-6102 © 2013 The Authors. Published by Elsevier Ltd. Selection and peer-review under responsibility of the Research Centre for Electrical Power and Mechatronics, Indonesian Institute of Sciences. doi:10.1016/j.egypro.2013.05.009
Widayat et al. / Energy Procedia 32 (2013) 64 – 73
1. Introductiom Currently, fuel oil is the source of energy with the largest consumption in Indonesia when compared to other energy sources. Oil consumption in Indonesia reaches 363.52 million BOE (Barrels of Oil Equivalent) or approximately 36,41% of the total consumption of energy amounted to 998.53 million BOE [1]. The magnitude of the oil consumption is inversely proportional to the petroleum reserves in Indonesia which decrease from year to year. In 2011 the total remaining oil reserves 7.73 billion barrels, decrease 0.3% from 2010 [1]. To reduce dependence on petroleum and meet the requirements of the global environment, the only way is by the development of eco-friendly alternative fuels. One of the alternative energy is biodiesel. Biodiesel is a methyl or ethyl esters of fatty acid made from vegetable oils (edible and non edible) or animal fats. Biodiesel can be produced from various raw material. Raw material include the most common vegetable oils (e.g., soybean, cottonseed, coconut, nuts, canola/rapeseed, sunflower, safflower, coconut, castor), animal and used frying oil [2]. Indonesia is a country with a largest rubber plantation area of the world with vast acreage totalled 3.4 million hectares, with rubber production reached 2.6 million tons in 2009 [3]. With regard to rubber plant, rubber seed are not much utilized, whereas oil content is high enough for about 40-50% [4]. Utilization of rubber seed as raw material of biodiesel production is highly potential in Indonesia. Currently, most biodiesel is produced from Crude Palm Oil (CPO) using methanol and base catalyst. CPO is an edible so the use of it for biodiesel production may be a contradiction with human needs. Furthermore an alternative raw material that does not collide is non edible oil such as rubber seed etc. Biodiesel production employs esterification or/and transesterification reaction. Esterification is reaction between alcohol and carboxylic acid (free fatty acid). Transesterification is a reaction between triglyceride and alcohol to produce fatty acid methyl ester (FAME) and glycerol. Transesterification reaction is presented in Figure 1. Biodiesel production process can be done by using a homogenous acid catalyst process [5], supercritical process [6], enzymatic process [7], heterogeneous acid catalyst [8] and sonochemical [9]. To obtain the vegetable oil by conventional method, the seed is pressed by mechanical process or extraction with chemical solvent. The oil further pretreated by degumming process. Of course this process of course requires a lot of manufacturing cost. The biodiesel production from rubber seed oil used two stages method of esterification reaction followed by transesterification reaction [4,10]. This process still has the same drawbacks that is the pretreatment process of the oil. To solve this drawbacks, the (trans)esterification process by in situ method will be one of the possible alternatives.
Fig. 1. Transesterification reaction of biodiesel production
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Fig. 2. Experiment tool sets
Biodiesel production process can reduce the cost if using in situ (trans)esterification. In this process, costs for solvent extraction and oil purification can be reduced. So, biodiesel production becomes simpler [11]. In situ (Trans)esterification, is a method to produce biodiesel that raw material (seed) is directly contacted with alcohol/methanol assisted with acid/alkaline catalyst. In the process either with an acid or alkaline catalyst, molar ratio of methanol/oil is much higher than the value calculated based on the stoichiometry, for instance, 532:1 [12], 300:1 [13] and 543:1 [14]. Excess methanol will play the role as the solvent extraction [12]. In situ transesterification was introduced by Harrington & Evans [12]. They used sunflower seed as a raw material. Marinkovic et.al. [13] did experiments from sunflower seed with the same process. Haas et al., [14] did in situ process from soybeans. Ozgul and Selma [15, 16] did in situ esterification with rice bran as raw material and ethanol and methanol as solvent and Ginting et.al., [17] also did in situ transesterification from castor seed (Jatropha curcas). The objectives of this research are to produce biodiesel from rubber seed with in situ method which has not been done by previous researchers and to study the influences of reaction time, ratio methanol to rubber seed and concentration of acid catalyst. 2. Methodology 2.1. Material The rubber seed was obtained from rubber plantation in Kendal, Indonesia. Methanol used was of technical grade and, H2SO4 as catalyst used was of analytical grade (Merck, Germany). 2.2. Experimental procedure Rubber seed sample were peeled. The seed kernels was macerated, blended and dried in an oven at 55°C for 2 hours. One hundred grams of samples were introduced into flask equipped with mixer (see Fig. 2). Aqueous methanol and H2SO4 were added and then heated and mixed. The solution was heated to 60oC at atmospheric pressure. The in situ process (extraction-reaction process) was done for 120 minutes. The product was filtered and methanol was separated with distillation. Biodiesel product was analyzed for weight, viscosity, density and concentration. Concentration of methyl ester in biodiesel product was analyzed by GC. The experiment was divided into three stages. The first stage (preliminary study) was carried out to obtain reaction time for in situ processing. In this step, response variable was analyzed on density and
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viscosity. The experiment was done at H2SO4 0,5% (v/v) and ratio of raw material to methanol (1:2) and every 15 minutes was analyzed until constants condition. In the second stage, the experiment was investigated with catalyst concentration of H2SO4 about 0.1; 0.25; 0.5; 0.75 and 1% (v/v). The experiment was done in variable ratio of raw material to methanol (1:2) and 120 minutes reaction time. In the third stage, the experiment was conducted about effect of ratio of raw material to methanol i.e; 1:1.5; 1:1.75; 1:2; 1:2.5 and 1:3 (w:v). Weight of product was used to calculate the biodiesel yield. Yield of FAME was calculated using this equation (1) [17,18] : Yield of FAME=
actual weightof biodiesel( g ) x 100% theoretical weightof biodiesel( g )
(1)
3. Results and discussion 3.1. Preliminary study Figure 3 is graph of density and kinematic viscosity versus reaction time. Density and viscosity are physical properties that depend on the composition in solution. The (trans)esterification reaction produced methyl ester and glycerol. So, the in situ process could obtain methyl ester, glycerol, and vegetable oil as products. Figure 3 shows that increasing of time is followed by increasing the density and viscosity of product reaction. The product has constant density and kinematic viscosity at 120 minutes. It shows that biodiesel production and oil extraction have been completed. Thus from this stage it was obtained that 120 minutes was an optimum reaction time, which would be used as a reference time for the second and third stages. 3.2. Effect of catalyst concentration In this stage, the experiment was to study the influence of catalyst concentration. Concentration of H2SO4 was varied in range 0.1-1% (v/v). The results of these experiments is presented at Figure 4 & 5. Maximum yield of oil was obtained at H2SO4 0.25% (v/v) with value 21.54% and the lowest at H2SO4 0.5% (v/v) with 13.21%. According to Ramadhas et al., [4] and Ketaren, [19], rubber seed contain 4050% of the oil. When compared with the results of this study were too small. This is because of the low quality of rubber seed and it was likely that the oil contained therein was small. Rubber seed will quickly rots if the skin already peeled, but this can be avoid with dry it quickly which make them to be more durable and can be stored in a long time. As mentioned by Ramadhas., et al. [4] from physical appearance the higher catalyst concentration, the darker also biodiesel produced. Therefore the addition of a suitable catalyst concentration is important to the physical appearance of biodiesel. Figure 4 is a graph on the effect of catalyst concentration (H2SO4) to density and kinematic viscosity of biodiesel. The density of biodiesel was obtained the lowest value on H2SO4 0.25% (v/v) at 0.89 g/mL, and the highest on H2SO4 0.5% (v/v) at 0.96 g/mL. The density of biodiesel according to SNI 04-7182-2006 is 0.85-0.90 g/mL. The density values obtained in this experiment were slightly different from biodiesel standard. That because there were no washing and neutralization process to the biodiesel product so the impurities were still present in the product. The product was the result of the extraction-reaction, so there were still other products besides biodiesel such as resin. The biodiesel product that obtained with H2SO4 0.25% (v/v) is 0.89 g/mL which meets with biodiesel standard.
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Fig. 3. Graph of time versus viscosity and density of biodiesel
Fig. 4. Effect of catalyst concentration (%) on density & kinematic viscosity of biodiesel
The density of fuel has some effect on the breakup of the fuel injected into the cylinder. In addition, more fuel is injected by mass as the fuel density increases [20]. The injected fuel amount, injection timing and injection spray pattern are directly affected by these parameters [21]. With increasing density, the diameter of the fuel droplets increases. Since the inertia of the big droplets is big, their penetrations in the combustion chamber will be higher, as well [22]. When a fuel with lower density and viscosity is injected, improved atomization and better mixture formation can be attained [20]. Another parameter which quite important is viscosity. The viscosity of an engine fuel is one of the most critical fuel features. It plays a dominant role in the fuel spray, mixture formation and combustion process. The high viscosity interferes with the injection process and leads to insufficient fuel atomization. Moreover, the mean diameter of the fuel droplets from the injector and their penetration increases with increasing fuel viscosity [22]. The inefficient mixing of fuel with air contributes to incomplete combustion in the engine. In addition to all these, high viscosity can cause early injection due to high line pressure, which moves the combustion of the fuel closer to top dead center, increasing the maximum pressure and temperature in the combustion chamber [21, 22].
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Fig. 5. Effect of catalyst concentration to yield of FAME
The viscosity of any fuel is related to its chemical structure. The viscosity increases with the increase in the chain length and decreases with the increase in the number of double bonds (unsaturation level) [23, 24, 25]. The kinematic viscosity increases with increasing concentrations of H2SO4 up to 0.75% (v/v) (as shown in Figure 4) become the highest viscosity 1.58 mm2/s whereas the lowest viscosity 1.2 mm2/s at H2SO4 0.1% (v/v). Overall value of biodiesel viscosity (40oC) is still below the standard value of the SNI 04-7182-2006 with range at 2.3-6.0 mm2/s. It means they are more dilute than biodiesel standard and even the values are closer with a diesel fuel standard viscosity 1.6-5.8 mm2/s range at SNI, so that this becomes no problem. In spite of, low viscosity causes rapid wear of engine parts such as injection pump and fuel injector as expressed by Chigier [26], the viscosity of methyl ester from rubber seed oil is lower at higher temperatures and almost equal to the diesel fuel, this helps the combustion as air entrainment increases, as spray cone angle increases due to reduction in viscosity [27]. Figure 5 shows that variation of H2SO4 concentration and affects on yield of FAME. The highest yield of FAME was obtained when in situ process did in H2SO4 0.25% (v/v) with value of yield of FAME is 53.61%. With increasing the concentration of catalyst after 0.25% (v/v), it will not increase the yield of FAME and tend to decrease. Beside that, the yield of FAME wasn’t high because at the second stages was used ratio of raw material to methanol (1:2). So, methanol used for solvent and reactant was too little when compared with experiments that did by the other researcher [12,13,14]. It was supposed that lower efficiency of methanol extraction and (trans)esterification reaction of the oil into biodiesel. By increasing the ratio of raw material to methanol (1:3) at the third stage, it was obtained maximum yield of FAME 91.05% as shown in Figure 7. 3.3. Effect of ratio of raw material to methanol The effect of ratio of raw material to methanol is presented in Figure 6 and 7. Increasing the ratio of raw material to methanol caused reduction of the biodiesel density. Density of biodiesel was obtained the highest value off 0.90 g/mL at ratio 1:1.5 and the lowest value 0.87 g/mL at ratio 1:3. When compared with biodiesel standard SNI 04-7182-2006, density of biodiesel is 0.85-0.90 g/mL, then the overall value that meets to the standard value are at ratio 1:2 until 1:3. That means the density of biodiesel will meet to the standard if the methanol is given in excess. The kinematic viscosity of biodiesel tends to be constant at ratio 1:1.5 until 1:2 from 1.33 mm2/s to 1.35 mm2/s but at ratio 1:2.5, the value increase to 1.60 mm2/s which meet to diesel fuel standard kinematic viscosity range at 1.6-5.8 mm2/s on SNI 04-7182-2006. At ratio 1:3, the viscosity was obtained at 1.49 mm2/s which is not too far away from diesel fuel standard on SNI.
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Fig. 6. Effect of ratio of raw material to methanol on density & kinematic viscosity of biodiesel
Fig. 7. Effect of ratio of raw material to methanol on yield of FAME
As expressed by Özgül-Yücel and Türkay [16], the role of methanol in the in situ process is very important because the methanol has a dual role : as a solvent for oil extraction as well as reactant, so the addition should be in excess. Figure 7 shows that yield of FAME increases significantly at ratio 1:2.5 and 1:3 by 90.76% and 91.05%, respectively. The amount of methanol, however, should not be too exaggerated, as expressed by Ramadhas., et al [4], methanol on ester layers can lower the flash point of biodiesel. Therefore the purification process and removal of methanol with distillation should be perfect. Distillation process should be concerned (±1 hour) because if it is too long causing a condensed biodiesel and difficult to pour it at room temperature. The acid number (acid value) is the mass of potassium hydroxide (KOH) in milligram that is required to neutralize one gram of chemical substance. The acid value is a measurement of the amount of carboxylic acid groups in chemical compound, such as fatty acids. The acid value on biodiesel was still quite high with the lowest value 48.42 mg KOH/g biodiesel at H2SO4 1% (v/v) and the highest value 66.33 mg KOH/g biodiesel at H2SO4 0.75% (v/v) as shown in Figure 8. Figure 9 shows that acid value increases starting from ratio of raw material to methanol (1:1.75) until (1:3). This data shows that there are still a lot of free fatty acid that has not been converted into methyl ester. Free fatty acid is obtained from the extraction process, thus the extraction process is more dominant when compared to the (trans)esterification reaction. Figure 9 shows that the more methanol is added, the more the oil/free fatty acid is extracted. Because of this, the acid value increases also. High acid value not only will make
Widayat et al. / Energy Procedia 32 (2013) 64 – 73
deposits in the fuel system but also decrease the components quality in the fuel system [28]. So, to increase the quality of biodiesel or to decrease the acid value, the in situ process must be preceded by esterification followed by transesterification reaction with acid and alkaline catalyst respectively. The Iodine number is the mass of Iodine in gram that is consumed by 100 grams of a chemical substance. Iodine number is often used to determine the amount of unsaturated fatty acid. The unsaturated fatty acid is in the form of double bonds, which can react with iodine compounds. The higher the Iodine number, the more C=C bonds are present in the fat/oil [29]. The Iodine number was relatively stable at both either the variation of catalyst concentration and the ratio of raw material to methanol especially on each optimum condition. At H2SO4 0.25% (v/v) had an Iodine number 26.5 g I2/100 g biodiesel and at ratio 1:3 had an Iodine number 26,46 g I2/100 g biodiesel which means the unsaturated of biodiesel was relatively small and quite well and all of the Iodine numbers at all variations were still below the SNI 047182-2006 biodiesel standard with the maximum value at 115 g I2/100 g biodiesel.
Fig. 8. Effect of catalyst concentration to acid value & Iodine number.
Fig. 9. Effect of ratio of raw material to methanol on acid value & Iodine number.
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Fig. 10. GC chromatogram of biodiesel on H2SO4 0.25% (v/v).
Chromatogram of Fatty Acid Methyl Ester (FAME) was detected at 8-11 retention time minutes and it was meet with the biodiesel standard chromatogram with FAME at 6-14 retention time minutes. When compared to standard, the expected results of biodiesel analysis with GC, 8.77 minutes was methyl stearic (C18:0), 9.23 minutes was methyl oleic (C18:1), 10,28 minutes was methyl linoleic (C18:2), 11,27 minutes was methyl nonadecanoic (C19:0) and 11.99 minutes was methyl arachidic (C20:0). Although all of the peak weren’t obvious, but it shows that the FAME was indeed formed in biodiesel sample and the oil/triglyceride wasn’t detected again. 4. Conclusion Biodiesel production from rubber seed by in situ method takes 120 minutes at 60oC with maximum yield of FAME 53.61% at H2SO4 0.25% (v/v) and maximum yield of FAME 91.05% at ratio of raw material to methanol (1:3). Based on the results, ratio of raw material to methanol is quite important to increase yield of FAME significantly. Acknowledgement This research was supported by research grant of postgraduates from Directorate General of Higher Education, Ministry of National Education, Indonesia. Authors was thank to Department of Chemical Engineering Polytechnic Malang for Gas Chromatography analysis. References [1] Syahrial, Ego., Adam, Rinaldi., Suharyati, Ajiwihanto, Nunung., Indarwati, R.R. Fifi., Kurniawan, Feri., Kurniawan, Agung. dan Suzanti, Vony Mela. Handbook of Energy & Economic Statistics of Indonesia. 8th ed. Jakarta: Kementrian ESDM; 2011. [2] Knothe, Gerpen, Jon Van., Krahl, Jürgen. The Biodiesel Handbook, 9-10, Champaign, Illinois USA: AOCS Press; 2005. [3] Parhusip, Adhy Basar. Potret Karet Alam Indonesia. Economic Review. 2008. [4] Ramadhas, A.S., Jayaraj, S., Muraleedharan, C. Biodiesel production from high FFA rubber seed oil, Elsevier Ltd, 00162361/$, 335-339. 2005. [5] Furukawa, S., Uehara, Y., Yamasaki, H. Variables affecting the reactivity of acid-catalyzed transesterification of vegetable oil with methanol. Bioresour. Technol. 2010; 101:3325–3332.
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[6] Deshpande, A., Anitescu, G., Rice, P.A., Tavlarides, L.L. Supercritical biodiesel production and power cogeneration: Technical and economic feasibilities. Bioresour. Technol. 2010; 101:1834–1843. [7] Sotoft, L.F., Rong, B., Christensen, K.V., Norddahl, B. Process simulation and economical evaluation of enzymatic biodiesel production plant. Bioresour. Technol. 2010; 101:5266–5274. [8] Jitputti, J., Kitiyanan, B., Rangsunvigit, P., Bunyakiat, K., Attanatho, L., Jenvanitpanjakul, P. Transesterification of crude palm kernel oil and crude coconut oil by different solid catalysts. Chem. Eng. J. 2006; 116:61–66. [9] Ragavan, S. Nivetha & Roy, D. Vetha. Transesterification of rubber seed oil by sonication technique for the production of methyl esters, Springer-Verlag, DOI 10.1007/s13399-011-0012-4. 2011. [10] Georgogiannia, K.G., Kontominas M.G., Pomonis P.J., Avlonitis D., Gergis V. Conventional and in situ transesterification of sunflower seed oil for the production of biodiesel, Elsevier B.V, 0378-3820/$, 504. 2007. [11] Hincapié, Gina., Mondragón, Fanor., López Diana. Conventional and in situ transesterification of castor seed oil for biodiesel production, Elsevier Ltd, 0016-2361/$ , 1619. 2011. [12] Harrington, Kevin J and D'arcy-Evans, Catherine. Comparison of Conventional and in situ Methods of Transesterification of Seed Oil from a Series of Sunflower Cultivars, JAOCS, 1985;62. [13] Marinkovic, S. Siler and Tomasevic, A. Transesterification of sunflower oil in situ, Elsevier Science Ltd, Fuel. 1998; 77. [14] Haas, Michael., Karen M, Scott., William N. Marmer, and Foglia,Thomas A. In situ Alkaline Transesterification: An Effective Method for the Production of Fatty Acid Esters from Vegetable Oils, JAOCS, 2004; 81:83. [15] Ozgul, Sevil and Turkay, Selma. In situ Esterification of Rice Bran Oil with Methanol and Ethanol. JAOCS, 1993; 70. [16] Özgül, Sevil -Yücel and Türkay, Selma. Variables Affecting the Yields of Methyl Esters Derived from in situ Esterification of Rice Bran Oil, JAOCS, 2002; 79. [17] Ginting, M. Surya Abadi., Azizan, M. Tazli., Yusup, Suzana. Alkaline in situ ethanolysis of Jatropha curcas. 0016-2361/$ Elsevier Ltd. 2011. [18] Yang, Ru., Su, Mengxing., Zhang, Jianchun., Jin, Fuqiang., Zha, Chunhong., Li, Min & Hao, Xinmin. Biodiesel production from rubber seed oil using poly (sodium acrylate) supporting NaOH as a water-resistant catalyst, Elsevier Ltd. 0960-8524/$, 2665. 2010. [19] Ketaren, S. Pengantar Teknologi Minyak dan Lemak Pangan. Jakarta: Universitas Indonesia (UI-Press); 1986. [20] Canakci, M & Sanli, H. Biodiesel production from various feedstocks and their effects on the fuel properties. J Ind Microbiol Biotechnol. 2008; 35:431–441. [21] Lee S, Tanaka D, Kusaka J, Daisho Y. Effects of diesel fuel characteristics on spray and combustion in a diesel engine. JSAE. 2002; 23:407–414. [22] Choi CY, Reitz RD. A numerical analysis of the emissions characteristics of biodiesel blended fuels. J Eng Gas Turbines Power. 1999; 121:31–37. [23] Goering CE, Schwab AW, Daugherty MJ, Pryde EH, Heakin AJ. Fuel properties of eleven vegetable oils. Trans ASAE. 1982; 25:1472–1477. [24] Graboski MS, McCormick RL. Combustion of fat and vegetable oil derived fuels in diesel engines. Prog Energy Combust Sci. 1998; 24:125–164. [25] Knothe G. Dependence of biodiesel fuel properties on the structure of fatty acid alkyl esters. Fuel Process Technol. 2005; 86:1059–1070. [26] Chigier, Norman. Energy, combustion, environment. England: McGraw Hill Publishers; 1983. [27] Satyanarayana, M, & Muraleedharan, C. A comparative study of vegetable oil methyl esters (biodiesels). 0360-5442/$ doi:10.1016/j.energy.2010.09.050. Elsevier Ltd. 2010. [28] Weiksner, J.M., Crump, S.L & White, T.L. Understanding biodiesel fuel quality and performance. U.S. Department of Commerce. Springfield. [29] Alfred Thomas. Fats and Fatty Oils. Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. DOI:10.1002/14356007.a10_173. 2002.
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Energy Procedia 32 (2013) 64 – 73
International Conference on Sustainable Energy Engineering and Application [ICSEEA 2012]
Study on production process of biodiesel from rubber seed (hevea brasiliensis) by in situ (trans)esterification method with acid catalyst Widayata,b,*, Agam Duma Kalista Wibowoa, Hadiyantoa,b a
Chemical Engineering, Diponegoro University Jl. H. Prof. Sudarto, SH, Semarang, Indonesia 50275 b C-Biore : Center Biomass and Renewable Energy
Abstract Biodiesel is fatty acid methyl or ethyl esters made from vegetable oils (edible and non edible) or animal fats. The objective of this research was to produce biodiesel from rubber seed by in situ method with acid catalyst with a goal for obtaining environmentally friendly alternative fuels from non edible raw material. This research focuses on influence of reaction time, concentration of acid catalyst and ratio raw material to methanol. The first stage was carried out in order to get reaction time based on the density and viscosity of mixture produced. In this process H2SO4 0.5% (v/v) was used as catalyst and ratio of raw material to methanol (1:2). The experiments were conducted by investigating the catalyst concentration in range 0.1-1%(v/v) and ratio of raw material to methanol in range 1:1.5-1:3. The research method included, the preparation of samples, biodiesel production, biodiesel separation, and biodiesel characterization i.e density, viscosity, GC analysis, acid value and Iodine number. The results shows that the operation time for biodiesel production by in situ method with acid catalyst was 120 minutes and the yield of Fatty Acid Methyl Ester (FAME) obtained was at 91,05%.
2012.The Published Elsevierby Ltd. © 2013 Authors.byPublished Elsevier Ltd. Selectionand and/or peer-review responsibility Research Centre Electrical Power Selection peer-review underunder responsibility of theof Research Centre forfor Electrical Power and and Mechatronics,Indonesian IndonesianInstitute Institute Sciences Mechatronics, ofof Sciences. Keywords: Biodiesel; rubber seed; in situ; (trans)esterification; Fatty Acid Methyl Ester (FAME).
* Corresponding author. Tel.: +62 24 7460058; fax: +62 24 76480675. E-mail address: [email protected].
1876-6102 © 2013 The Authors. Published by Elsevier Ltd. Selection and peer-review under responsibility of the Research Centre for Electrical Power and Mechatronics, Indonesian Institute of Sciences. doi:10.1016/j.egypro.2013.05.009
Widayat et al. / Energy Procedia 32 (2013) 64 – 73
1. Introductiom Currently, fuel oil is the source of energy with the largest consumption in Indonesia when compared to other energy sources. Oil consumption in Indonesia reaches 363.52 million BOE (Barrels of Oil Equivalent) or approximately 36,41% of the total consumption of energy amounted to 998.53 million BOE [1]. The magnitude of the oil consumption is inversely proportional to the petroleum reserves in Indonesia which decrease from year to year. In 2011 the total remaining oil reserves 7.73 billion barrels, decrease 0.3% from 2010 [1]. To reduce dependence on petroleum and meet the requirements of the global environment, the only way is by the development of eco-friendly alternative fuels. One of the alternative energy is biodiesel. Biodiesel is a methyl or ethyl esters of fatty acid made from vegetable oils (edible and non edible) or animal fats. Biodiesel can be produced from various raw material. Raw material include the most common vegetable oils (e.g., soybean, cottonseed, coconut, nuts, canola/rapeseed, sunflower, safflower, coconut, castor), animal and used frying oil [2]. Indonesia is a country with a largest rubber plantation area of the world with vast acreage totalled 3.4 million hectares, with rubber production reached 2.6 million tons in 2009 [3]. With regard to rubber plant, rubber seed are not much utilized, whereas oil content is high enough for about 40-50% [4]. Utilization of rubber seed as raw material of biodiesel production is highly potential in Indonesia. Currently, most biodiesel is produced from Crude Palm Oil (CPO) using methanol and base catalyst. CPO is an edible so the use of it for biodiesel production may be a contradiction with human needs. Furthermore an alternative raw material that does not collide is non edible oil such as rubber seed etc. Biodiesel production employs esterification or/and transesterification reaction. Esterification is reaction between alcohol and carboxylic acid (free fatty acid). Transesterification is a reaction between triglyceride and alcohol to produce fatty acid methyl ester (FAME) and glycerol. Transesterification reaction is presented in Figure 1. Biodiesel production process can be done by using a homogenous acid catalyst process [5], supercritical process [6], enzymatic process [7], heterogeneous acid catalyst [8] and sonochemical [9]. To obtain the vegetable oil by conventional method, the seed is pressed by mechanical process or extraction with chemical solvent. The oil further pretreated by degumming process. Of course this process of course requires a lot of manufacturing cost. The biodiesel production from rubber seed oil used two stages method of esterification reaction followed by transesterification reaction [4,10]. This process still has the same drawbacks that is the pretreatment process of the oil. To solve this drawbacks, the (trans)esterification process by in situ method will be one of the possible alternatives.
Fig. 1. Transesterification reaction of biodiesel production
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Fig. 2. Experiment tool sets
Biodiesel production process can reduce the cost if using in situ (trans)esterification. In this process, costs for solvent extraction and oil purification can be reduced. So, biodiesel production becomes simpler [11]. In situ (Trans)esterification, is a method to produce biodiesel that raw material (seed) is directly contacted with alcohol/methanol assisted with acid/alkaline catalyst. In the process either with an acid or alkaline catalyst, molar ratio of methanol/oil is much higher than the value calculated based on the stoichiometry, for instance, 532:1 [12], 300:1 [13] and 543:1 [14]. Excess methanol will play the role as the solvent extraction [12]. In situ transesterification was introduced by Harrington & Evans [12]. They used sunflower seed as a raw material. Marinkovic et.al. [13] did experiments from sunflower seed with the same process. Haas et al., [14] did in situ process from soybeans. Ozgul and Selma [15, 16] did in situ esterification with rice bran as raw material and ethanol and methanol as solvent and Ginting et.al., [17] also did in situ transesterification from castor seed (Jatropha curcas). The objectives of this research are to produce biodiesel from rubber seed with in situ method which has not been done by previous researchers and to study the influences of reaction time, ratio methanol to rubber seed and concentration of acid catalyst. 2. Methodology 2.1. Material The rubber seed was obtained from rubber plantation in Kendal, Indonesia. Methanol used was of technical grade and, H2SO4 as catalyst used was of analytical grade (Merck, Germany). 2.2. Experimental procedure Rubber seed sample were peeled. The seed kernels was macerated, blended and dried in an oven at 55°C for 2 hours. One hundred grams of samples were introduced into flask equipped with mixer (see Fig. 2). Aqueous methanol and H2SO4 were added and then heated and mixed. The solution was heated to 60oC at atmospheric pressure. The in situ process (extraction-reaction process) was done for 120 minutes. The product was filtered and methanol was separated with distillation. Biodiesel product was analyzed for weight, viscosity, density and concentration. Concentration of methyl ester in biodiesel product was analyzed by GC. The experiment was divided into three stages. The first stage (preliminary study) was carried out to obtain reaction time for in situ processing. In this step, response variable was analyzed on density and
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viscosity. The experiment was done at H2SO4 0,5% (v/v) and ratio of raw material to methanol (1:2) and every 15 minutes was analyzed until constants condition. In the second stage, the experiment was investigated with catalyst concentration of H2SO4 about 0.1; 0.25; 0.5; 0.75 and 1% (v/v). The experiment was done in variable ratio of raw material to methanol (1:2) and 120 minutes reaction time. In the third stage, the experiment was conducted about effect of ratio of raw material to methanol i.e; 1:1.5; 1:1.75; 1:2; 1:2.5 and 1:3 (w:v). Weight of product was used to calculate the biodiesel yield. Yield of FAME was calculated using this equation (1) [17,18] : Yield of FAME=
actual weightof biodiesel( g ) x 100% theoretical weightof biodiesel( g )
(1)
3. Results and discussion 3.1. Preliminary study Figure 3 is graph of density and kinematic viscosity versus reaction time. Density and viscosity are physical properties that depend on the composition in solution. The (trans)esterification reaction produced methyl ester and glycerol. So, the in situ process could obtain methyl ester, glycerol, and vegetable oil as products. Figure 3 shows that increasing of time is followed by increasing the density and viscosity of product reaction. The product has constant density and kinematic viscosity at 120 minutes. It shows that biodiesel production and oil extraction have been completed. Thus from this stage it was obtained that 120 minutes was an optimum reaction time, which would be used as a reference time for the second and third stages. 3.2. Effect of catalyst concentration In this stage, the experiment was to study the influence of catalyst concentration. Concentration of H2SO4 was varied in range 0.1-1% (v/v). The results of these experiments is presented at Figure 4 & 5. Maximum yield of oil was obtained at H2SO4 0.25% (v/v) with value 21.54% and the lowest at H2SO4 0.5% (v/v) with 13.21%. According to Ramadhas et al., [4] and Ketaren, [19], rubber seed contain 4050% of the oil. When compared with the results of this study were too small. This is because of the low quality of rubber seed and it was likely that the oil contained therein was small. Rubber seed will quickly rots if the skin already peeled, but this can be avoid with dry it quickly which make them to be more durable and can be stored in a long time. As mentioned by Ramadhas., et al. [4] from physical appearance the higher catalyst concentration, the darker also biodiesel produced. Therefore the addition of a suitable catalyst concentration is important to the physical appearance of biodiesel. Figure 4 is a graph on the effect of catalyst concentration (H2SO4) to density and kinematic viscosity of biodiesel. The density of biodiesel was obtained the lowest value on H2SO4 0.25% (v/v) at 0.89 g/mL, and the highest on H2SO4 0.5% (v/v) at 0.96 g/mL. The density of biodiesel according to SNI 04-7182-2006 is 0.85-0.90 g/mL. The density values obtained in this experiment were slightly different from biodiesel standard. That because there were no washing and neutralization process to the biodiesel product so the impurities were still present in the product. The product was the result of the extraction-reaction, so there were still other products besides biodiesel such as resin. The biodiesel product that obtained with H2SO4 0.25% (v/v) is 0.89 g/mL which meets with biodiesel standard.
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Fig. 3. Graph of time versus viscosity and density of biodiesel
Fig. 4. Effect of catalyst concentration (%) on density & kinematic viscosity of biodiesel
The density of fuel has some effect on the breakup of the fuel injected into the cylinder. In addition, more fuel is injected by mass as the fuel density increases [20]. The injected fuel amount, injection timing and injection spray pattern are directly affected by these parameters [21]. With increasing density, the diameter of the fuel droplets increases. Since the inertia of the big droplets is big, their penetrations in the combustion chamber will be higher, as well [22]. When a fuel with lower density and viscosity is injected, improved atomization and better mixture formation can be attained [20]. Another parameter which quite important is viscosity. The viscosity of an engine fuel is one of the most critical fuel features. It plays a dominant role in the fuel spray, mixture formation and combustion process. The high viscosity interferes with the injection process and leads to insufficient fuel atomization. Moreover, the mean diameter of the fuel droplets from the injector and their penetration increases with increasing fuel viscosity [22]. The inefficient mixing of fuel with air contributes to incomplete combustion in the engine. In addition to all these, high viscosity can cause early injection due to high line pressure, which moves the combustion of the fuel closer to top dead center, increasing the maximum pressure and temperature in the combustion chamber [21, 22].
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Fig. 5. Effect of catalyst concentration to yield of FAME
The viscosity of any fuel is related to its chemical structure. The viscosity increases with the increase in the chain length and decreases with the increase in the number of double bonds (unsaturation level) [23, 24, 25]. The kinematic viscosity increases with increasing concentrations of H2SO4 up to 0.75% (v/v) (as shown in Figure 4) become the highest viscosity 1.58 mm2/s whereas the lowest viscosity 1.2 mm2/s at H2SO4 0.1% (v/v). Overall value of biodiesel viscosity (40oC) is still below the standard value of the SNI 04-7182-2006 with range at 2.3-6.0 mm2/s. It means they are more dilute than biodiesel standard and even the values are closer with a diesel fuel standard viscosity 1.6-5.8 mm2/s range at SNI, so that this becomes no problem. In spite of, low viscosity causes rapid wear of engine parts such as injection pump and fuel injector as expressed by Chigier [26], the viscosity of methyl ester from rubber seed oil is lower at higher temperatures and almost equal to the diesel fuel, this helps the combustion as air entrainment increases, as spray cone angle increases due to reduction in viscosity [27]. Figure 5 shows that variation of H2SO4 concentration and affects on yield of FAME. The highest yield of FAME was obtained when in situ process did in H2SO4 0.25% (v/v) with value of yield of FAME is 53.61%. With increasing the concentration of catalyst after 0.25% (v/v), it will not increase the yield of FAME and tend to decrease. Beside that, the yield of FAME wasn’t high because at the second stages was used ratio of raw material to methanol (1:2). So, methanol used for solvent and reactant was too little when compared with experiments that did by the other researcher [12,13,14]. It was supposed that lower efficiency of methanol extraction and (trans)esterification reaction of the oil into biodiesel. By increasing the ratio of raw material to methanol (1:3) at the third stage, it was obtained maximum yield of FAME 91.05% as shown in Figure 7. 3.3. Effect of ratio of raw material to methanol The effect of ratio of raw material to methanol is presented in Figure 6 and 7. Increasing the ratio of raw material to methanol caused reduction of the biodiesel density. Density of biodiesel was obtained the highest value off 0.90 g/mL at ratio 1:1.5 and the lowest value 0.87 g/mL at ratio 1:3. When compared with biodiesel standard SNI 04-7182-2006, density of biodiesel is 0.85-0.90 g/mL, then the overall value that meets to the standard value are at ratio 1:2 until 1:3. That means the density of biodiesel will meet to the standard if the methanol is given in excess. The kinematic viscosity of biodiesel tends to be constant at ratio 1:1.5 until 1:2 from 1.33 mm2/s to 1.35 mm2/s but at ratio 1:2.5, the value increase to 1.60 mm2/s which meet to diesel fuel standard kinematic viscosity range at 1.6-5.8 mm2/s on SNI 04-7182-2006. At ratio 1:3, the viscosity was obtained at 1.49 mm2/s which is not too far away from diesel fuel standard on SNI.
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Fig. 6. Effect of ratio of raw material to methanol on density & kinematic viscosity of biodiesel
Fig. 7. Effect of ratio of raw material to methanol on yield of FAME
As expressed by Özgül-Yücel and Türkay [16], the role of methanol in the in situ process is very important because the methanol has a dual role : as a solvent for oil extraction as well as reactant, so the addition should be in excess. Figure 7 shows that yield of FAME increases significantly at ratio 1:2.5 and 1:3 by 90.76% and 91.05%, respectively. The amount of methanol, however, should not be too exaggerated, as expressed by Ramadhas., et al [4], methanol on ester layers can lower the flash point of biodiesel. Therefore the purification process and removal of methanol with distillation should be perfect. Distillation process should be concerned (±1 hour) because if it is too long causing a condensed biodiesel and difficult to pour it at room temperature. The acid number (acid value) is the mass of potassium hydroxide (KOH) in milligram that is required to neutralize one gram of chemical substance. The acid value is a measurement of the amount of carboxylic acid groups in chemical compound, such as fatty acids. The acid value on biodiesel was still quite high with the lowest value 48.42 mg KOH/g biodiesel at H2SO4 1% (v/v) and the highest value 66.33 mg KOH/g biodiesel at H2SO4 0.75% (v/v) as shown in Figure 8. Figure 9 shows that acid value increases starting from ratio of raw material to methanol (1:1.75) until (1:3). This data shows that there are still a lot of free fatty acid that has not been converted into methyl ester. Free fatty acid is obtained from the extraction process, thus the extraction process is more dominant when compared to the (trans)esterification reaction. Figure 9 shows that the more methanol is added, the more the oil/free fatty acid is extracted. Because of this, the acid value increases also. High acid value not only will make
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deposits in the fuel system but also decrease the components quality in the fuel system [28]. So, to increase the quality of biodiesel or to decrease the acid value, the in situ process must be preceded by esterification followed by transesterification reaction with acid and alkaline catalyst respectively. The Iodine number is the mass of Iodine in gram that is consumed by 100 grams of a chemical substance. Iodine number is often used to determine the amount of unsaturated fatty acid. The unsaturated fatty acid is in the form of double bonds, which can react with iodine compounds. The higher the Iodine number, the more C=C bonds are present in the fat/oil [29]. The Iodine number was relatively stable at both either the variation of catalyst concentration and the ratio of raw material to methanol especially on each optimum condition. At H2SO4 0.25% (v/v) had an Iodine number 26.5 g I2/100 g biodiesel and at ratio 1:3 had an Iodine number 26,46 g I2/100 g biodiesel which means the unsaturated of biodiesel was relatively small and quite well and all of the Iodine numbers at all variations were still below the SNI 047182-2006 biodiesel standard with the maximum value at 115 g I2/100 g biodiesel.
Fig. 8. Effect of catalyst concentration to acid value & Iodine number.
Fig. 9. Effect of ratio of raw material to methanol on acid value & Iodine number.
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Fig. 10. GC chromatogram of biodiesel on H2SO4 0.25% (v/v).
Chromatogram of Fatty Acid Methyl Ester (FAME) was detected at 8-11 retention time minutes and it was meet with the biodiesel standard chromatogram with FAME at 6-14 retention time minutes. When compared to standard, the expected results of biodiesel analysis with GC, 8.77 minutes was methyl stearic (C18:0), 9.23 minutes was methyl oleic (C18:1), 10,28 minutes was methyl linoleic (C18:2), 11,27 minutes was methyl nonadecanoic (C19:0) and 11.99 minutes was methyl arachidic (C20:0). Although all of the peak weren’t obvious, but it shows that the FAME was indeed formed in biodiesel sample and the oil/triglyceride wasn’t detected again. 4. Conclusion Biodiesel production from rubber seed by in situ method takes 120 minutes at 60oC with maximum yield of FAME 53.61% at H2SO4 0.25% (v/v) and maximum yield of FAME 91.05% at ratio of raw material to methanol (1:3). Based on the results, ratio of raw material to methanol is quite important to increase yield of FAME significantly. Acknowledgement This research was supported by research grant of postgraduates from Directorate General of Higher Education, Ministry of National Education, Indonesia. Authors was thank to Department of Chemical Engineering Polytechnic Malang for Gas Chromatography analysis. References [1] Syahrial, Ego., Adam, Rinaldi., Suharyati, Ajiwihanto, Nunung., Indarwati, R.R. Fifi., Kurniawan, Feri., Kurniawan, Agung. dan Suzanti, Vony Mela. Handbook of Energy & Economic Statistics of Indonesia. 8th ed. Jakarta: Kementrian ESDM; 2011. [2] Knothe, Gerpen, Jon Van., Krahl, Jürgen. The Biodiesel Handbook, 9-10, Champaign, Illinois USA: AOCS Press; 2005. [3] Parhusip, Adhy Basar. Potret Karet Alam Indonesia. Economic Review. 2008. [4] Ramadhas, A.S., Jayaraj, S., Muraleedharan, C. Biodiesel production from high FFA rubber seed oil, Elsevier Ltd, 00162361/$, 335-339. 2005. [5] Furukawa, S., Uehara, Y., Yamasaki, H. Variables affecting the reactivity of acid-catalyzed transesterification of vegetable oil with methanol. Bioresour. Technol. 2010; 101:3325–3332.
Widayat et al. / Energy Procedia 32 (2013) 64 – 73
[6] Deshpande, A., Anitescu, G., Rice, P.A., Tavlarides, L.L. Supercritical biodiesel production and power cogeneration: Technical and economic feasibilities. Bioresour. Technol. 2010; 101:1834–1843. [7] Sotoft, L.F., Rong, B., Christensen, K.V., Norddahl, B. Process simulation and economical evaluation of enzymatic biodiesel production plant. Bioresour. Technol. 2010; 101:5266–5274. [8] Jitputti, J., Kitiyanan, B., Rangsunvigit, P., Bunyakiat, K., Attanatho, L., Jenvanitpanjakul, P. Transesterification of crude palm kernel oil and crude coconut oil by different solid catalysts. Chem. Eng. J. 2006; 116:61–66. [9] Ragavan, S. Nivetha & Roy, D. Vetha. Transesterification of rubber seed oil by sonication technique for the production of methyl esters, Springer-Verlag, DOI 10.1007/s13399-011-0012-4. 2011. [10] Georgogiannia, K.G., Kontominas M.G., Pomonis P.J., Avlonitis D., Gergis V. Conventional and in situ transesterification of sunflower seed oil for the production of biodiesel, Elsevier B.V, 0378-3820/$, 504. 2007. [11] Hincapié, Gina., Mondragón, Fanor., López Diana. Conventional and in situ transesterification of castor seed oil for biodiesel production, Elsevier Ltd, 0016-2361/$ , 1619. 2011. [12] Harrington, Kevin J and D'arcy-Evans, Catherine. Comparison of Conventional and in situ Methods of Transesterification of Seed Oil from a Series of Sunflower Cultivars, JAOCS, 1985;62. [13] Marinkovic, S. Siler and Tomasevic, A. Transesterification of sunflower oil in situ, Elsevier Science Ltd, Fuel. 1998; 77. [14] Haas, Michael., Karen M, Scott., William N. Marmer, and Foglia,Thomas A. In situ Alkaline Transesterification: An Effective Method for the Production of Fatty Acid Esters from Vegetable Oils, JAOCS, 2004; 81:83. [15] Ozgul, Sevil and Turkay, Selma. In situ Esterification of Rice Bran Oil with Methanol and Ethanol. JAOCS, 1993; 70. [16] Özgül, Sevil -Yücel and Türkay, Selma. Variables Affecting the Yields of Methyl Esters Derived from in situ Esterification of Rice Bran Oil, JAOCS, 2002; 79. [17] Ginting, M. Surya Abadi., Azizan, M. Tazli., Yusup, Suzana. Alkaline in situ ethanolysis of Jatropha curcas. 0016-2361/$ Elsevier Ltd. 2011. [18] Yang, Ru., Su, Mengxing., Zhang, Jianchun., Jin, Fuqiang., Zha, Chunhong., Li, Min & Hao, Xinmin. Biodiesel production from rubber seed oil using poly (sodium acrylate) supporting NaOH as a water-resistant catalyst, Elsevier Ltd. 0960-8524/$, 2665. 2010. [19] Ketaren, S. Pengantar Teknologi Minyak dan Lemak Pangan. Jakarta: Universitas Indonesia (UI-Press); 1986. [20] Canakci, M & Sanli, H. Biodiesel production from various feedstocks and their effects on the fuel properties. J Ind Microbiol Biotechnol. 2008; 35:431–441. [21] Lee S, Tanaka D, Kusaka J, Daisho Y. Effects of diesel fuel characteristics on spray and combustion in a diesel engine. JSAE. 2002; 23:407–414. [22] Choi CY, Reitz RD. A numerical analysis of the emissions characteristics of biodiesel blended fuels. J Eng Gas Turbines Power. 1999; 121:31–37. [23] Goering CE, Schwab AW, Daugherty MJ, Pryde EH, Heakin AJ. Fuel properties of eleven vegetable oils. Trans ASAE. 1982; 25:1472–1477. [24] Graboski MS, McCormick RL. Combustion of fat and vegetable oil derived fuels in diesel engines. Prog Energy Combust Sci. 1998; 24:125–164. [25] Knothe G. Dependence of biodiesel fuel properties on the structure of fatty acid alkyl esters. Fuel Process Technol. 2005; 86:1059–1070. [26] Chigier, Norman. Energy, combustion, environment. England: McGraw Hill Publishers; 1983. [27] Satyanarayana, M, & Muraleedharan, C. A comparative study of vegetable oil methyl esters (biodiesels). 0360-5442/$ doi:10.1016/j.energy.2010.09.050. Elsevier Ltd. 2010. [28] Weiksner, J.M., Crump, S.L & White, T.L. Understanding biodiesel fuel quality and performance. U.S. Department of Commerce. Springfield. [29] Alfred Thomas. Fats and Fatty Oils. Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. DOI:10.1002/14356007.a10_173. 2002.
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