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Effect of ethanol–palm kernel oil ratio on alkali-catalyzed biodiesel yield
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Fuel 87 (2008) 1529–1533 www.fuelfirst.com
Effect of ethanol–palm kernel oil ratio on alkali-catalyzed biodiesel yield O.J. Alamu a
a,*
, M.A. Waheed b, S.O. Jekayinfa
c
Department of Mechanical Engineering, Olabisi Onabanjo University, Ibogun Campus, P.O. Box 304, Ifo Post Office, Ogun State, Nigeria b Department of Mechanical Engineering, Ladoke Akintola University of Technology, Ogbomoso, Nigeria c Department of Agricultural Engineering, Ladoke Akintola University of Technology, Ogbomoso, Nigeria Received 11 June 2007; received in revised form 6 August 2007; accepted 20 August 2007 Available online 12 September 2007
Abstract The finite nature of fossil fuel necessitates consideration of alternative fuel from renewable sources. Palm kernel oil (PKO) has been identified as a renewable resource from which biodiesel can be produced. The effect of ethanol–PKO ratio on PKO biodiesel yield was studied with a view to obtaining optimal feedstock ratio. Experiments were conducted for ethanol–PKO ratios 0.1, 0.125, 0.15, 0.175, 0.2, 0.225 and 0.25 under transesterification conditions of 60 C temperature, 120 min reaction time and 1.0% KOH catalyst concentration. Results obtained gave 29.5%, 54%, 75%, 89%, 96%, 93.5% and 87.2% average PKO biodiesel yield for the respective feedstock ratios. This shows increase in biodiesel yield with ethanol–PKO ratio up to 0.2. Standard fuel test results of the PKO biodiesel are within biodiesel specifications. 2007 Elsevier Ltd. All rights reserved. Keywords: Ethanol; Palm kernel oil; Biodiesel yield; Transesterification
1. Introduction Depletion of fossil fuel deposits, threat of supply instability, rising petroleum prices and increasing threat to the environment from exhaust emissions informed the reactivation of worldwide interest in renewable biofuels [1–3]. The production of biofuel to replace oil and natural gas is in active development in major parts of the world and in nascent status in numerous others [4–6], focusing on the use of cheap organic matter in the efficient production of liquid and gas biofuels which yield high net energy gain. Modern biofuels are a promising long term renewable energy source which has potential to address both environmental impacts and security concerns posed by current dependence on petroleum based fuels [1,2,4]. One such biofuel is biodiesel, defined as the mono-alkyl esters of vegetable oils and animal fats [5,7,8].
*
Corresponding author. Tel.: +234 803 385 8298. E-mail address: [email protected] (O.J. Alamu).
0016-2361/$ - see front matter 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.fuel.2007.08.011
Biodiesel products have been reported as a very modern and technological area for researchers due to its environmental advantages [9]. It is renewable, biodegradable, non-toxic, and typically produces about 65% less net carbon monoxide, 90% less sulphur dioxide and 50% less unburnt hydrocarbon emission than petroleum-based diesel [7,10]. It has also been stated in the literature that most research on biodiesel aims at reducing pollutant emission [11]. Increasing the use of biofuel could also lead to improved economic development and poverty alleviation, especially in rural areas, since it attracts investment in new jobs and business opportunities for small- and medium-sized enterprises in the fields of production, transportation, trade and use [6]. Biodiesel can be used in its pure form (B100) or may be blended with petroleum diesel in modern diesel engines [12,13]. Vegetable oil remains the major feedstock for biodiesel production. Animal fat and waste cooking oil have also been used [14,15]. Soybean (US), rapeseed (Europe), oil palm (South-East Asia) and canola, to mention a few have been successfully used as renewable vegetable oil sources to
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O.J. Alamu et al. / Fuel 87 (2008) 1529–1533
generate biodiesel with superior qualities over the petroleum-based fuels [16–18]. Oil palm (Elaeis guineensis Jacq.) produces fruit which consist of a hard kernel inside a shell, which is surrounded by a fleshy mesocarp. The mesocarp contains about 49% palm oil while the kernel contains about 50% palm kernel oil. Palm kernel oil is yellowish in color. It contains mainly lauric acid (C12:0) and more than 80% saturated fatty acids. World producers of palm kernel include Malaysia, Indonesia, Nigeria, Cote d’ivore, Colombia, Thailand, Zaire and Equador [19]. A few published works on laboratory production and testing of PKO biodiesel as alternative fuel have produced promising results [2,20,21]. However, economic considerations on PKO biodiesel production have not been explored in the literature. A number of such studies have appeared in prints on Jatropha curcus oil (India) [22], Soybean (Brazil) [17,20], and Palm oil (Malaysia) [18]. In these studies, the authors have indicated feedstock proportions as one of the important process parameters upon which biodiesel yield depends. In this work, laboratory scale biodiesel production through transesterification of PKO with ethanol using potassium hydroxide (KOH) catalyst is reported. Fuel characterization results for the produced PKO biodiesel through ASTM standard fuel tests are also reported, while the effect of ethanol–PKO ratio on biodiesel yield is investigated with a view to identifying the reactant proportions corresponding to optimum process yield. 2. Methods 2.1. Experimental materials and procedures Local palm kernel oil was purchased at Ogijo, Ogun State, Nigeria. The PKO contains many lauric acids, its fatty acid profile is presented in Table 1. Ethanol and the potassium hydroxide (KOH) used were manufactured by Aldrich Chemicals Co. Ltd., England. The blender used was a dry and wet mill blender 462; product of Nakai, Japan. Other materials used include scales, measuring beakers, translucent white plastic container with bung and screw-on cap, funnels, 2-l PET bottles, duct tape and thermometer.
Table 1 Fatty acid profile of PKO Type of fatty acid
Percentage
Lauric (C12:0) Myristic (C14:0) Palmitic (C16:0) Capric (C10:0) Caprylic (C8:0) Stearic (C18:0) Oleic (C18:1) Linoleic (C18:2) Others (unknown)
48.2 16.2 8.4 3.4 3.3 2.5 15.3 2.3 0.4
Reaction parameters for the transesterification process including reaction temperature, reaction time, catalyst concentration and PKO quantity were held constant at 60 C, 120 min, 1.0% KOH (wt% PKO) and 100 g PKO, respectively. Ten grams of ethanol was measured and poured into a plastic container after which 1.0 g of KOH was carefully added. The bung and the screw on the cap were replaced tightly. The container was shook a few times by swirling round thoroughly for about 2 min until the KOH completely dissolved in the ethanol, forming potassium ethoxide. Hundred grams of PKO was measured out in a beaker, pre-heated to 60 C and poured into the blender. The prepared potassium ethoxide was carefully poured into the PKO; the blender lid was secured tightly and the blender was switched on. The mixture was left to blend for 120 min after which it was poured into a 2-l PET bottle for settling. The reaction mixture was allowed to stand overnight while phase separation occurred by gravity settling. The next day, the golden/pale PKO biodiesel at the top was carefully decanted into a PET bottle leaving the light brown glycerol at the base. Washing of the biodiesel was carried out as previously reported [2,21]. The procedure was replicated three times and average biodiesel yield as well as glycerol yield was recorded. ASTM standard fuel tests were subsequently carried out on the PKO biodiesel. Specific gravity and viscosity measurements were made following ASTM standards D1298 and D445, respectively. The biodiesel was analysed for pour point, cloud point and flash point following ASTM standards D97, D25100-8 and D-56, respectively. Boiling points (ASTM D86), sulphated ash (ASTM D847), gross and net heat of combustion were also measured. Detailed procedures and instrumentation for these tests have been described [21]. As a standard for comparison, similar fuel characterization tests were conducted for Philips low sulphur diesel fuel (No. 2 Diesel) purchased at Total Fuel Station, Ifo, Ogun State, Nigeria.
2.2. Effect of ethanol–PKO ratio on PKO biodiesel yield The molar requirement of ethanol was found to be 15.33% (wt% PKO) [2]. To investigate the effect of ethanol–PKO ratio on PKO biodiesel yield, using ethanol as the variable feedstock, experiments were conducted with 10%, 12.5%, 15%, 17.5%, 20%, 22.5% and 25% ethanol, representing values below and above the stoichiometric requirements. The transesterification process was repeated with different feedstock (ethanol and PKO) proportions keeping all other process parameters stated under Section 2.1. In all, seven treatments were considered using 100.0 g PKO with ethanol quantity varied from 10.0 g to 25.0 g at 2.5 g incremental step. As such, ethanol–PKO ratios 0.1, 0.125, 0.15, 0.175, 0.2, 0.225 and 0.25 were investigated. In each case, three different runs of experiment were carried out and average results evaluated.
O.J. Alamu et al. / Fuel 87 (2008) 1529–1533
1531
Table 3 Transesterification results for Treatment 1–7;
3. Results and discussion 3.1. Suitability of PKO biodiesel as fuel
Treatment
Qethanol QPKO
In characterizing the PKO biodiesel as alternative diesel fuel, the PKO biodiesel produced in Treatment 5 and the petroleum diesel, used as control, were analysed for fuel properties including viscosity, specific gravity, pour point, cloud point, flash point and sulphated ash. Others include boiling point, gross and net heat of combustion and acid value. Results obtained are presented in Table 2. With raw PKO having viscosity 32.40 mm2/s [20], the PKO biodiesel viscosity obtained (4.839 mm2/s) show 85.06% viscosity reduction. Values obtained for other properties have been compared with previous works on biodiesel from rapeseed, canola, beef tallow, soybean, frying oil and coconut oil [16,20,23,24]. These values have also been checked against various international standards for biodiesel including ASTM D6751 (US), EN 14214 (Europe) and BIS (India) [3,16]. Comparison made revealed good agreement with previous results as detailed out in Alamu et al. [2]. As evident from Table 2, the acid value of the PKO used is 5.2. Being a measure of oil quality, the acid value obtained is an indication of high free fatty acid and could be responsible for the observed pale coloration of the PKO biodiesel. It is also likely to be responsible for the quantity of KOH used since acid value greater than 1.0 requires more alkali catalyst to neutralize the free fatty acids as reported by Chitra et al. [22].
1 2 3 4 5 6 7
0.100 0.125 0.150 0.175 0.200 0.225 0.250
3.2. Effect of ethanol–PKO ratio on PKO biodiesel yield Through laboratory experiment, different variations of ethanol–PKO ratios (0.1, 0.125, 0.15, 0.175, 0.2, 0.225 and 0.25), representing Treatments 1–7, were used with other constant process parameters to produce PKO biodiesel. The concentration of KOH, reaction temperature and reaction time used with the ethanol variations were held constant at 1.0%, 60 C and 120 min, respectively. Results of the three runs of each of the experiment together with the average values, for each of the ethanol–PKO ratios investigated are presented in Table 3. Table 2 Measured PKO biodiesel and petroleum diesel fuel properties Fuel properties/parameters
(PKO biodiesel)
(Petroleum diesel)
Viscosity (@ 40 C) (mm2/s) Specific gravity (@ 60 F/60 F) Pour point (C) Cloud point (C) Flash point (C) Boiling point (C) Sulphated ash content (wt%) Gross heat of combustion (MJ/kg) Net heat of combustion (MJ/kg) Acid value for palm kernel oil (PKO) (mg KOH/g of sample) = 5.2
4.839 0.883 2 6 167 320 0.018 40.56 37.25
2.847 0.853 16 12 74 191 0.038 45.43 42.91
Qethanol QPKO
¼ ð0:1–0:25Þ
PKO biodiesel obtained (g)
Glycerol obtained (g)
Losses (g)
29.50 ± 0.08 54.00 ± 0.16 75.00 ± 0.89 89.00 ± 2.27 96.00 ± 0.53 93.50 ± 0.12 87.20 ± 0.29
70.20 ± 0.08 45.90 ± 0.08 37.50 ± 0.78 22.20 ± 0.08 20.50 ± 0.63 23.20 ± 0.08 35.80 ± 0.29
11.30 ± 0.08 13.60 ± 0.21 3.50 ± 0.71 7.30 ± 2.24 4.50 ± 1.09 6.80 ± 0.58 3.00 ± 0.29
Data are the average of three runs.
Results presented in Table 3 showed the amount of PKO biodiesel, glycerol and losses recorded from the transesterification reaction with ethanol–PKO feedstock mix of 0.1 (Treatment 1) to 0.25 (Treatment 7) Qethanol ¼ 0:1; 0:125; . . . ; 0:25 QPKO
ð1Þ
where Qethanol = quantity of ethanol (g); and, QPKO = quantity of PKO (g). The PKO biodiesel yield obtained for the various treatments (1–7) can be interpreted as: Treatment 1 < Treatment 2 < Treatment 3 < Treatment 4 < Treatment 5 > Treatment 6 > Treatment 7. From the results, average values of 29.5%, 54.0%, 75.0%, 89.0%, 96.0%, 93.5% and 87.25% PKO biodiesel yield were obtained for ethanol–PKO ratios 0.1, 0.125, 0.15, 0.175, 0.2, 0.225 and 0.25, respectively. In the same order, the average amount of glycerol formed and the losses recorded for the considered were 70.2 g, 45.9 g, 37.5 g, 22.2 g, 20.5 g, 23.2 g, 35.8 g and 11.3 g, 13.6 g, 3.5 g, 7.3 g, 4.5 g, 6.8 g, 3.0 g, respectively. It is observed that the biodiesel yield increases as the ethanol–PKO ratio increases only up to a threshold mix. Beyond this point, no further increase in biodiesel yield is observed. The observed ethanol–PKO threshold mix was 0.2. In other words, the minimum amount of ethanol corresponding to the highest biodiesel yield (96.0%) was 20 g; representing 20% by weight of the PKO. This clearly indicates that the optimum percentage of ethanol (by weight of PKO) required for transesterification of PKO, under the process parameters investigated was 20%. Moreover, when the concentration of ethanol was increased above or decreased below this value (20%), as evident in Fig. 1, there was no significant increase in the PKO biodiesel yield. The excess or shortfall in concentration of ethanol only contributed to the increased formation of glycerol and losses in the form of emulsion. 3.3. Effects of other parameters Other important process parameters such as reaction time, temperature and catalyst concentrations have been investigated. Different variations of reaction duration (30–120 min), reaction temperature (30–70 C) and KOH concentration (0.5–2.0% by mass of PKO) were studied
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versity, Ibogun Campus, Nigeria is acknowledged for granting permission to utilize the facilities for carrying out the transesterification reaction. The assistance rendered by Chevron, Apapa Installation, Lagos, Nigeria in making available materials for fuel characterization is acknowledged.
120
PKO biodiesel yield (%)
100
80
60
40
References
20
[1] Gupta PK, Kumar R, Panesar BS, Thapar VK. Parametric studies on bio-diesel prepared from rice bran oil. Agri Eng Int: CIGR Ejournal. 2007;IX [Paper No. EE 06 007]. [2] Alamu OJ, Waheed MA, Jekayinfa SO. Alkali-catalysed laboratory production and testing of biodiesel fuel from Nigerian palm kernel oil. Agri Eng Int: CIGR Ejournal 2007;IX [Paper No. EE 07 009]. [3] Girard P, Fallot A. Review of existing and emerging technologies for the production of biofuels in developing countries. Energy Sustain Develop 2006;X(2):92–108. [4] Batidzirai B, Faaij APC, Smeets E. Biomass and bioenergy supply from Mozambique. Energy Sustain Develop 2006;X(1):54–81. [5] Knothe G, Steidley KR. Kinematic viscosity of biodiesel fuel component and related compounds: influence of compound structure and comparison to petrodiesel fuel components. Fuel 2005;84: 1059–65. [6] Best G. Alternative energy crops for agricultural machinery biofuels – focus on biodiesel. Agri Eng Int: CIGR J Sci Res Develop 2006;VIII(13). [7] Conceicao MM, Candeia RA, Dantas HJ, Soledade LEB, Fernandes Jr VJ, Souza AG. Rheological behavior of castor oil biodiesel. Energy Fuel 2005;19(5):2185–8. [8] Yuan Y, Hansen A, Zhang Q. The specific gravity of biodiesel fuels and their blends with diesel fuel. Agri Eng Int: CIGR J Sci Res Develop 2004;VI [Paper No. EE 04 004]. [9] Marchetti JM, Miguel VU, Errazu AF. Possible methods for biodiesel production. Renew Sustain Energy Rev 2007;11(6):1300–11. [10] Margaroni D. Fuel lubricity. Indust Lubricat Tribol 1998;50(3):108–18. [11] Moron-Villarreyes JA, Soldi C, de Amorim AM, Pizzolatti MG, de Mendoncar Jr AP, D’orca MGM. Diesel/biodiesel proportion for bycompression ignition engines. Fuel 2007;86(12–13):1977–82. [12] Lebedevas S, Vaicekauskas A. Research into the application of biodiesel in the transport sector of Lithuania. Transport 2006;XXI(2):80–7. [13] Tat ME, Van Gerpen JH. Fuel property effect on biodiesel; 2003. ASAE Paper No. 036034. [14] Lin Y, Wu C, Chang YG. Combustion characteristics of wasteoil produced biodiesel/diesel fuel blend. Fuel 2007;86(12–13):1772– 80. [15] Murillo S, Miguez JL, Porteiro J. Performance and exhaust emissions in the use of biodiesel in outboard diesel engines. Fuel 2007;86(12– ):1765–71. [16] Peterson CL, Cruz RO, Perkings L, Korus R, Auld DL. Transesterification of vegetable oil for use as diesel fuel: a progress report; 1990. ASAE Paper No. 90-610. [17] Noureddini H, Zhu D. Kinetics of transesterification of soybean oil. J Am Oil Chem Soc 1997;74(11):1457–63. [18] Yunus R, Fakhru’lRazi A, Ooi TL, Iyuke SE, Idris A. Development of optimum synthesis method for transesterification of palm oil methyl esters and trimethylolpropane to environmentally acceptable palm oil-based lubricant. J Oil-palm Res 2003;15(2):35–41. [19] USDA (United States Department of Agriculture). Production Estimates and Crop Assessment Division. FAS; 1998. [20] Abigor RD, Uadia PO, Foglia TA, Haas MJ, Jones KC, Okpefa E, et al. Lipase-catalysed production of biodiesel fuel from some Nigerian lauric oils. Biochem Soc Trans 2000;28:979–81.
0 10
12.5
15
17.5
20
22.5
25
Quantity of ethanol (%)
Fig. 1. Variation of ethanol quantity with % PKO biodiesel yields for the different ethanol:PKO feedstock mix considered.
using the one variable at a time (OVAT) approach. The biodiesel yield increased with reaction time only up to 90 min. No further increase in yield occurred up to 120 min. Similarly, the yield increased only up to 60 C reaction temperature while the concentration of KOH corresponding to the maximum PKO biodiesel yield was found to be 1.0% as previously reported [21]. 4. Conclusions From the laboratory scale production and testing of PKO biodiesel, as well as the effect of ethanol–PKO ratio on biodiesel yield studied, the following conclusions can be drawn: • Nigerian PKO biodiesel gave promising results as alternative diesel fuel with fuel properties in good agreement with previous works and within limits set by international biodiesel standards. • For ethanol–PKO ratios 0.1, 0.125, 0.15, 0.175, 0.2, 0.225 and 0.25, PKO biodiesel yield of 29.5%, 54%, 75%, 89%, 96%, 93.5% and 87.2% were obtained under typical transesterification reaction conditions of 60 C temperature, 120 min reaction duration and 1.0% alkali catalyst (KOH) concentration. • A threshold mix exists, where further increase in the proportion of ethanol in the feedstock does not increase PKO biodiesel yield. • A maximum PKO biodiesel yield of 96% was obtained with ethanol–PKO ratio 0.2 under typical transesterification reaction conditions of 60 C temperature, 120 min duration and 1.0% alkali catalyst (KOH) concentration.
Acknowledgements Prof. R.O. Fagbenle and the Management of College of Engineering and Technology of the Olabisi Onabanjo Uni-
O.J. Alamu et al. / Fuel 87 (2008) 1529–1533 [21] Alamu OJ, Waheed MA, Jekayinfa SO. Biodiesel production from Nigerian palm kernel oil: effect of KOH concentration on yield. Energy Sustain Develop 2007;XI(3):59–64. [22] Chitra P, Venkatachalam P, Sampathrajan A. Optimisation of experimental conditions for biodiesel production from alkali-catalysed transesterification of Jatropha curcus oil. Energy Sustain Develop 2005;IX(3):13–8.
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[23] Graboski MS, McCormick RL. Combustion of fat and vegetable oil derived fuels in diesel engines. Prog Energy Combust Sci 1998;24:125–64. [24] Schwab AW, Bagby MO, Freedman B. Preparation and properties of diesel fuels from vegetable oils. Fuel 1987;66:1372–9.
Fuel 87 (2008) 1529–1533 www.fuelfirst.com
Effect of ethanol–palm kernel oil ratio on alkali-catalyzed biodiesel yield O.J. Alamu a
a,*
, M.A. Waheed b, S.O. Jekayinfa
c
Department of Mechanical Engineering, Olabisi Onabanjo University, Ibogun Campus, P.O. Box 304, Ifo Post Office, Ogun State, Nigeria b Department of Mechanical Engineering, Ladoke Akintola University of Technology, Ogbomoso, Nigeria c Department of Agricultural Engineering, Ladoke Akintola University of Technology, Ogbomoso, Nigeria Received 11 June 2007; received in revised form 6 August 2007; accepted 20 August 2007 Available online 12 September 2007
Abstract The finite nature of fossil fuel necessitates consideration of alternative fuel from renewable sources. Palm kernel oil (PKO) has been identified as a renewable resource from which biodiesel can be produced. The effect of ethanol–PKO ratio on PKO biodiesel yield was studied with a view to obtaining optimal feedstock ratio. Experiments were conducted for ethanol–PKO ratios 0.1, 0.125, 0.15, 0.175, 0.2, 0.225 and 0.25 under transesterification conditions of 60 C temperature, 120 min reaction time and 1.0% KOH catalyst concentration. Results obtained gave 29.5%, 54%, 75%, 89%, 96%, 93.5% and 87.2% average PKO biodiesel yield for the respective feedstock ratios. This shows increase in biodiesel yield with ethanol–PKO ratio up to 0.2. Standard fuel test results of the PKO biodiesel are within biodiesel specifications. 2007 Elsevier Ltd. All rights reserved. Keywords: Ethanol; Palm kernel oil; Biodiesel yield; Transesterification
1. Introduction Depletion of fossil fuel deposits, threat of supply instability, rising petroleum prices and increasing threat to the environment from exhaust emissions informed the reactivation of worldwide interest in renewable biofuels [1–3]. The production of biofuel to replace oil and natural gas is in active development in major parts of the world and in nascent status in numerous others [4–6], focusing on the use of cheap organic matter in the efficient production of liquid and gas biofuels which yield high net energy gain. Modern biofuels are a promising long term renewable energy source which has potential to address both environmental impacts and security concerns posed by current dependence on petroleum based fuels [1,2,4]. One such biofuel is biodiesel, defined as the mono-alkyl esters of vegetable oils and animal fats [5,7,8].
*
Corresponding author. Tel.: +234 803 385 8298. E-mail address: [email protected] (O.J. Alamu).
0016-2361/$ - see front matter 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.fuel.2007.08.011
Biodiesel products have been reported as a very modern and technological area for researchers due to its environmental advantages [9]. It is renewable, biodegradable, non-toxic, and typically produces about 65% less net carbon monoxide, 90% less sulphur dioxide and 50% less unburnt hydrocarbon emission than petroleum-based diesel [7,10]. It has also been stated in the literature that most research on biodiesel aims at reducing pollutant emission [11]. Increasing the use of biofuel could also lead to improved economic development and poverty alleviation, especially in rural areas, since it attracts investment in new jobs and business opportunities for small- and medium-sized enterprises in the fields of production, transportation, trade and use [6]. Biodiesel can be used in its pure form (B100) or may be blended with petroleum diesel in modern diesel engines [12,13]. Vegetable oil remains the major feedstock for biodiesel production. Animal fat and waste cooking oil have also been used [14,15]. Soybean (US), rapeseed (Europe), oil palm (South-East Asia) and canola, to mention a few have been successfully used as renewable vegetable oil sources to
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O.J. Alamu et al. / Fuel 87 (2008) 1529–1533
generate biodiesel with superior qualities over the petroleum-based fuels [16–18]. Oil palm (Elaeis guineensis Jacq.) produces fruit which consist of a hard kernel inside a shell, which is surrounded by a fleshy mesocarp. The mesocarp contains about 49% palm oil while the kernel contains about 50% palm kernel oil. Palm kernel oil is yellowish in color. It contains mainly lauric acid (C12:0) and more than 80% saturated fatty acids. World producers of palm kernel include Malaysia, Indonesia, Nigeria, Cote d’ivore, Colombia, Thailand, Zaire and Equador [19]. A few published works on laboratory production and testing of PKO biodiesel as alternative fuel have produced promising results [2,20,21]. However, economic considerations on PKO biodiesel production have not been explored in the literature. A number of such studies have appeared in prints on Jatropha curcus oil (India) [22], Soybean (Brazil) [17,20], and Palm oil (Malaysia) [18]. In these studies, the authors have indicated feedstock proportions as one of the important process parameters upon which biodiesel yield depends. In this work, laboratory scale biodiesel production through transesterification of PKO with ethanol using potassium hydroxide (KOH) catalyst is reported. Fuel characterization results for the produced PKO biodiesel through ASTM standard fuel tests are also reported, while the effect of ethanol–PKO ratio on biodiesel yield is investigated with a view to identifying the reactant proportions corresponding to optimum process yield. 2. Methods 2.1. Experimental materials and procedures Local palm kernel oil was purchased at Ogijo, Ogun State, Nigeria. The PKO contains many lauric acids, its fatty acid profile is presented in Table 1. Ethanol and the potassium hydroxide (KOH) used were manufactured by Aldrich Chemicals Co. Ltd., England. The blender used was a dry and wet mill blender 462; product of Nakai, Japan. Other materials used include scales, measuring beakers, translucent white plastic container with bung and screw-on cap, funnels, 2-l PET bottles, duct tape and thermometer.
Table 1 Fatty acid profile of PKO Type of fatty acid
Percentage
Lauric (C12:0) Myristic (C14:0) Palmitic (C16:0) Capric (C10:0) Caprylic (C8:0) Stearic (C18:0) Oleic (C18:1) Linoleic (C18:2) Others (unknown)
48.2 16.2 8.4 3.4 3.3 2.5 15.3 2.3 0.4
Reaction parameters for the transesterification process including reaction temperature, reaction time, catalyst concentration and PKO quantity were held constant at 60 C, 120 min, 1.0% KOH (wt% PKO) and 100 g PKO, respectively. Ten grams of ethanol was measured and poured into a plastic container after which 1.0 g of KOH was carefully added. The bung and the screw on the cap were replaced tightly. The container was shook a few times by swirling round thoroughly for about 2 min until the KOH completely dissolved in the ethanol, forming potassium ethoxide. Hundred grams of PKO was measured out in a beaker, pre-heated to 60 C and poured into the blender. The prepared potassium ethoxide was carefully poured into the PKO; the blender lid was secured tightly and the blender was switched on. The mixture was left to blend for 120 min after which it was poured into a 2-l PET bottle for settling. The reaction mixture was allowed to stand overnight while phase separation occurred by gravity settling. The next day, the golden/pale PKO biodiesel at the top was carefully decanted into a PET bottle leaving the light brown glycerol at the base. Washing of the biodiesel was carried out as previously reported [2,21]. The procedure was replicated three times and average biodiesel yield as well as glycerol yield was recorded. ASTM standard fuel tests were subsequently carried out on the PKO biodiesel. Specific gravity and viscosity measurements were made following ASTM standards D1298 and D445, respectively. The biodiesel was analysed for pour point, cloud point and flash point following ASTM standards D97, D25100-8 and D-56, respectively. Boiling points (ASTM D86), sulphated ash (ASTM D847), gross and net heat of combustion were also measured. Detailed procedures and instrumentation for these tests have been described [21]. As a standard for comparison, similar fuel characterization tests were conducted for Philips low sulphur diesel fuel (No. 2 Diesel) purchased at Total Fuel Station, Ifo, Ogun State, Nigeria.
2.2. Effect of ethanol–PKO ratio on PKO biodiesel yield The molar requirement of ethanol was found to be 15.33% (wt% PKO) [2]. To investigate the effect of ethanol–PKO ratio on PKO biodiesel yield, using ethanol as the variable feedstock, experiments were conducted with 10%, 12.5%, 15%, 17.5%, 20%, 22.5% and 25% ethanol, representing values below and above the stoichiometric requirements. The transesterification process was repeated with different feedstock (ethanol and PKO) proportions keeping all other process parameters stated under Section 2.1. In all, seven treatments were considered using 100.0 g PKO with ethanol quantity varied from 10.0 g to 25.0 g at 2.5 g incremental step. As such, ethanol–PKO ratios 0.1, 0.125, 0.15, 0.175, 0.2, 0.225 and 0.25 were investigated. In each case, three different runs of experiment were carried out and average results evaluated.
O.J. Alamu et al. / Fuel 87 (2008) 1529–1533
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Table 3 Transesterification results for Treatment 1–7;
3. Results and discussion 3.1. Suitability of PKO biodiesel as fuel
Treatment
Qethanol QPKO
In characterizing the PKO biodiesel as alternative diesel fuel, the PKO biodiesel produced in Treatment 5 and the petroleum diesel, used as control, were analysed for fuel properties including viscosity, specific gravity, pour point, cloud point, flash point and sulphated ash. Others include boiling point, gross and net heat of combustion and acid value. Results obtained are presented in Table 2. With raw PKO having viscosity 32.40 mm2/s [20], the PKO biodiesel viscosity obtained (4.839 mm2/s) show 85.06% viscosity reduction. Values obtained for other properties have been compared with previous works on biodiesel from rapeseed, canola, beef tallow, soybean, frying oil and coconut oil [16,20,23,24]. These values have also been checked against various international standards for biodiesel including ASTM D6751 (US), EN 14214 (Europe) and BIS (India) [3,16]. Comparison made revealed good agreement with previous results as detailed out in Alamu et al. [2]. As evident from Table 2, the acid value of the PKO used is 5.2. Being a measure of oil quality, the acid value obtained is an indication of high free fatty acid and could be responsible for the observed pale coloration of the PKO biodiesel. It is also likely to be responsible for the quantity of KOH used since acid value greater than 1.0 requires more alkali catalyst to neutralize the free fatty acids as reported by Chitra et al. [22].
1 2 3 4 5 6 7
0.100 0.125 0.150 0.175 0.200 0.225 0.250
3.2. Effect of ethanol–PKO ratio on PKO biodiesel yield Through laboratory experiment, different variations of ethanol–PKO ratios (0.1, 0.125, 0.15, 0.175, 0.2, 0.225 and 0.25), representing Treatments 1–7, were used with other constant process parameters to produce PKO biodiesel. The concentration of KOH, reaction temperature and reaction time used with the ethanol variations were held constant at 1.0%, 60 C and 120 min, respectively. Results of the three runs of each of the experiment together with the average values, for each of the ethanol–PKO ratios investigated are presented in Table 3. Table 2 Measured PKO biodiesel and petroleum diesel fuel properties Fuel properties/parameters
(PKO biodiesel)
(Petroleum diesel)
Viscosity (@ 40 C) (mm2/s) Specific gravity (@ 60 F/60 F) Pour point (C) Cloud point (C) Flash point (C) Boiling point (C) Sulphated ash content (wt%) Gross heat of combustion (MJ/kg) Net heat of combustion (MJ/kg) Acid value for palm kernel oil (PKO) (mg KOH/g of sample) = 5.2
4.839 0.883 2 6 167 320 0.018 40.56 37.25
2.847 0.853 16 12 74 191 0.038 45.43 42.91
Qethanol QPKO
¼ ð0:1–0:25Þ
PKO biodiesel obtained (g)
Glycerol obtained (g)
Losses (g)
29.50 ± 0.08 54.00 ± 0.16 75.00 ± 0.89 89.00 ± 2.27 96.00 ± 0.53 93.50 ± 0.12 87.20 ± 0.29
70.20 ± 0.08 45.90 ± 0.08 37.50 ± 0.78 22.20 ± 0.08 20.50 ± 0.63 23.20 ± 0.08 35.80 ± 0.29
11.30 ± 0.08 13.60 ± 0.21 3.50 ± 0.71 7.30 ± 2.24 4.50 ± 1.09 6.80 ± 0.58 3.00 ± 0.29
Data are the average of three runs.
Results presented in Table 3 showed the amount of PKO biodiesel, glycerol and losses recorded from the transesterification reaction with ethanol–PKO feedstock mix of 0.1 (Treatment 1) to 0.25 (Treatment 7) Qethanol ¼ 0:1; 0:125; . . . ; 0:25 QPKO
ð1Þ
where Qethanol = quantity of ethanol (g); and, QPKO = quantity of PKO (g). The PKO biodiesel yield obtained for the various treatments (1–7) can be interpreted as: Treatment 1 < Treatment 2 < Treatment 3 < Treatment 4 < Treatment 5 > Treatment 6 > Treatment 7. From the results, average values of 29.5%, 54.0%, 75.0%, 89.0%, 96.0%, 93.5% and 87.25% PKO biodiesel yield were obtained for ethanol–PKO ratios 0.1, 0.125, 0.15, 0.175, 0.2, 0.225 and 0.25, respectively. In the same order, the average amount of glycerol formed and the losses recorded for the considered were 70.2 g, 45.9 g, 37.5 g, 22.2 g, 20.5 g, 23.2 g, 35.8 g and 11.3 g, 13.6 g, 3.5 g, 7.3 g, 4.5 g, 6.8 g, 3.0 g, respectively. It is observed that the biodiesel yield increases as the ethanol–PKO ratio increases only up to a threshold mix. Beyond this point, no further increase in biodiesel yield is observed. The observed ethanol–PKO threshold mix was 0.2. In other words, the minimum amount of ethanol corresponding to the highest biodiesel yield (96.0%) was 20 g; representing 20% by weight of the PKO. This clearly indicates that the optimum percentage of ethanol (by weight of PKO) required for transesterification of PKO, under the process parameters investigated was 20%. Moreover, when the concentration of ethanol was increased above or decreased below this value (20%), as evident in Fig. 1, there was no significant increase in the PKO biodiesel yield. The excess or shortfall in concentration of ethanol only contributed to the increased formation of glycerol and losses in the form of emulsion. 3.3. Effects of other parameters Other important process parameters such as reaction time, temperature and catalyst concentrations have been investigated. Different variations of reaction duration (30–120 min), reaction temperature (30–70 C) and KOH concentration (0.5–2.0% by mass of PKO) were studied
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versity, Ibogun Campus, Nigeria is acknowledged for granting permission to utilize the facilities for carrying out the transesterification reaction. The assistance rendered by Chevron, Apapa Installation, Lagos, Nigeria in making available materials for fuel characterization is acknowledged.
120
PKO biodiesel yield (%)
100
80
60
40
References
20
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0 10
12.5
15
17.5
20
22.5
25
Quantity of ethanol (%)
Fig. 1. Variation of ethanol quantity with % PKO biodiesel yields for the different ethanol:PKO feedstock mix considered.
using the one variable at a time (OVAT) approach. The biodiesel yield increased with reaction time only up to 90 min. No further increase in yield occurred up to 120 min. Similarly, the yield increased only up to 60 C reaction temperature while the concentration of KOH corresponding to the maximum PKO biodiesel yield was found to be 1.0% as previously reported [21]. 4. Conclusions From the laboratory scale production and testing of PKO biodiesel, as well as the effect of ethanol–PKO ratio on biodiesel yield studied, the following conclusions can be drawn: • Nigerian PKO biodiesel gave promising results as alternative diesel fuel with fuel properties in good agreement with previous works and within limits set by international biodiesel standards. • For ethanol–PKO ratios 0.1, 0.125, 0.15, 0.175, 0.2, 0.225 and 0.25, PKO biodiesel yield of 29.5%, 54%, 75%, 89%, 96%, 93.5% and 87.2% were obtained under typical transesterification reaction conditions of 60 C temperature, 120 min reaction duration and 1.0% alkali catalyst (KOH) concentration. • A threshold mix exists, where further increase in the proportion of ethanol in the feedstock does not increase PKO biodiesel yield. • A maximum PKO biodiesel yield of 96% was obtained with ethanol–PKO ratio 0.2 under typical transesterification reaction conditions of 60 C temperature, 120 min duration and 1.0% alkali catalyst (KOH) concentration.
Acknowledgements Prof. R.O. Fagbenle and the Management of College of Engineering and Technology of the Olabisi Onabanjo Uni-
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