Effect of Biodiesel Production Parameters on Viscosity and Yield Of

Alexandria Engineering Journal (2015) xxx, xxx–xxx

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ORIGINAL ARTICLE Eﬀect of biodiesel production parameters on viscosity and yield of methyl esters: Jatropha curcas, Elaeis guineensis and Cocos nucifera

Godwin Kafui Ayetor a,*, Albert Sunnu b, Joseph Parbey a a Koforidua Polytechnic, Faculty of Engineering, Box 981, Koforidua, Ghana b Kwame Nkrumah University of Science and Technology, Department of Mechanical Engineering, Kumasi, Ghana

Received 29 August 2014; accepted 29 September 2015

KEYWORDS Abstract In this study, the effect of H2SO4 on viscosity of methyl esters from Jatropha oil (JCME), Jatropha curcas; palm kernel oil (PKOME) from Elaeis guineensis species, and coconut oil (COME) has been stud- Palm kernel oil; ied. Effect of methanol to oil molar mass ratio on yield of the three feedstocks has also been studied. Biodiesel; Methyl ester yield was decreased by esterification process using sulphuric acid anhydrous (H2SO4). Coconut oil; Jatropha methyl ester experienced a viscosity reduction of 24% (4.1–3.1 mm2/s) with the addition of Transesterification; 1% sulphuric acid. In this work palm kernel oil (PKOME), coconut oil (COME) and Jatropha oil Viscosity (JCME) were used as feedstocks for the production of biodiesel to investigate optimum parameters to obtain high yield. For each of the feedstock, the biodiesel yield increased with increase in NaOH concentration. The highest yield was obtained with 1% NaOH concentration for all. The effect of methanol in the range of 4:1–8:1 (molar ratio) was investigated, keeping other process parameters fixed. Optimum ratios of palm kernel oil and coconut oil biodiesels yielded 98% each at methanol: oil molar ratio of 8:1. The physiochemical properties obtained for each methyl showed superior properties compared with those reported in published data. Ó 2015 Faculty of Engineering, Alexandria University. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

1. Introduction with the invention of diesel engine originally used peanut oil as fuel. Over 100 other feedstocks have since been discovered Biodiesel produced from vegetable oil has been long known as for the production of biodiesel. The choice of feedstock a viable alternative to petroleum diesel. It is known to be adapted by a country depends on availability, cost and biodegradable, renewable, produce lesser emissions, nontoxic whether it is edible or not. Argentina prefers to use soybean and free from sulphur. Rudolf Diesel (1858–1913), credited oil contrary to china who has a high demand for soybean for preparation of Chinese food [1]. However edible palm oil is preferred in Asian countries since they have surplus in pro- * Corresponding author. Tel.: +233 243129514/576414148. E-mail addresses: [email protected], [email protected] duction while rapeseed oil is preferred in Europe. Other coun- (G.K. Ayetor). tries such as Ghana are struggling to choose their preferred Peer review under responsibility of Faculty of Engineering, Alexandria feedstock since there is not enough of any of the oils whether University. edible or not. http://dx.doi.org/10.1016/j.aej.2015.09.011 1110-0168 Ó 2015 Faculty of Engineering, Alexandria University. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Biodiesel is the only and first commercial scale fuel to have 1. Flat bottom reaction flask (250 ml) with three necks to con- met America’s EPA definition as an advanced biofuel, since it tain the oil. reduces greenhouse gas emissions by more than 50% com- 2. Scilogex MS-H-S Magnetic stirrer with hot plate was used. pared with petroleum diesel. However, in spite of numerous It had two separate regulators for regulating heat and stir- advances in biodiesel production technology no major Original ring rate respectively. Equipment Manufacturer (OEM) gives warranty for the use of 3. Electronic Beam Balance with 200 g min. and 6000 g max. B100 (100% biodiesel). Use of B20 (20% biodiesel blended e =10d, d = 1 g was used to take weight of oils before with 80% petroleum diesel) or below does not void warranties and after (trans) esterification. for 90% of the medium and heavy duty truck vehicles. This 4. Reaction ingredients for the (Trans) esterification include position of the OEM is because no biodiesel is the same. Even 99.8% methanol, NaOH, 98% sulphuric acid. physiochemical properties of biodiesel from the same feedstock 5. Other instruments used include may differ depending on the species, mode of oil preparation, a. Separating funnel. water content, type or concentration of catalyst, molar ratio of b. 8000 ml beaker. alcohol and even reaction time. The quality of feedstock is not c. Spatula. guaranteed. This is why in order to protect consumers from d. Filter paper. unwittingly purchasing substandard fuel, OEMs have stated e. Graduated eye dropper. formally that the biodiesel must meet ASTM D-6751 (Ameri- f. Graduated syringe. can society for testing and materials) [2,3] and/or EN14214 g. Pipette. (European committee for standardization). Appropriate feedstock selection and production technology is therefore vital for biodiesel production [4]. Feedstock such 2.2. Experimental procedure as coconut oil and palm kernel oil has not been properly investigated for biodiesel production in terms of production tech- Acid-catalysed (Trans) esterification requires a much longer nology. Some have studied high physicochemical properties time than alkali-catalysed Trans esterification (4). This is of coconut oil focusing on temperature and pressure neglecting why base-catalysed (Trans) esterification is used in this work. physiochemical properties [5]. Others studied in situ (Trans) A Two-step process was used in the production of coconut esterification of coconut oil using mixtures of methanol oil biodiesel. An alkaline-catalysed esterification using NaOH and tetrahydrofuran but did not consider yield or catalyst con- to convert FFAs in coconut oil to methyl esters to reduce centration [6]. Catalyst (KOH) concentration and methanol to FFA was carried out for an hour. In the second step acid- oil ratio have been investigated for the production of coconut catalysed Trans esterification was carried out where the pre- oil but their combined effect on yield has been neglected and treated oil was then converted to methyl ester to further reduce base catalysed (Trans) esterification has not been considered FFA and hence the viscosity. [7]. Ethanolysis of coconut oil to produce biodiesel has been Both esterification and (Trans) esterification were conducted done but the effect of methanol, catalyst concentration and in a laboratory-scale experiment. The raw coconut oil (200 g) their effect on coconut biodiesel yield has not been specified was preheated for an hour to ensure removal of water as a pre- [8]. caution of the oil probably not being well prepared. The preheat- Though prevalent in West Africa, not much work has also ing was terminated when visual inspection showed that there were been done on palm kernel oil (B100) as biodiesel [PKOME]. no more bubbles. For all test runs for the variations, temperature Studies carried out on PKOME considered KOH and not was kept constant and stirring was at same speed. Methanol NaOH as base catalyst [9,10]. While characterisation in the lit- mixed with NaOH was added to the preheated coconut mixture erature have not included cetane number and calorific value [10] in the flat bottom reaction flask and stirred for an hour. Test runs and neither are the species from which the oil was obtained men- for NaOH and H2SO4 catalyst concentrations were all done at tioned, there are many species of palm oil from which palm ker- 0.6, 0.8,1 and 1.2 (w/w). The weight measurement (wt.%) was nel oil can be produced. These species include Elaeis oleifera used instead of (v%) because weight gives a more precise mea- commonly called American oil palm, Elaeis guineensis also called surement since volume changes once there is evaporation of the the African oil palm and Butia capitata also called Jelly palm liquid. Methanol:oil molar ratio variations were done at 1:4, usually grown in the Argentina, Brazil and Uruguay. 1:5, 1:6, 1:7 and 1:8. The mixture was stirred for some time at This research investigates the effect of process parameters the same rate and time for all test runs. In the second step including methanol:oil ratio, NaOH base catalyst concentra- H2SO4 was added to the pre-treated mixture and quickly stirred tion on coconut, palm kernel and Jatropha biodiesel yield. for about an hour. The essence of adding H2SO4 was to further The influence of sulphuric acid (H2SO4) on viscosity is also reduce FFA and hence the viscosity of the biodiesel. Wet washing investigated for the three feedstocks. was then carried out with hot distilled water at 60 °Candthen dried to obtain the Coconut oil biodiesel. The same procedure was carried for Palm kernel oil and Jatropha oil. 2. Materials and methods Each of the procedure mentioned above was repeated for each variation of base catalyst (NaOH), acid catalyst 2.1. Materials (H2SO4) and methanol:oil molar ratio. The effect of base catalyst concentration, acid catalyst concentration and methanol: (Trans) esterification of vegetable oil to biodiesel was carried oil molar ratio on biodiesel yield of coconut, Jatropha and out in a laboratory scale experiment. The materials used Palm kernel oils was studied. Yield of biodiesel obtained was include calculated as

weight of biodiesel produced wax crystals first appear in the oil when it is cooled is termed Yield ¼ 100 intital weight of oil cloud point. This is usually visible to the naked eye. The cloud point obtained for PKOME (6 °C) compares very well with petroleum diesel (2 °C) though there are no specified limits pre- 3. Results and discussion scribed for both ASTM and EN standards. Pour point obtained for both PKOME and petroleum diesel was the same 3.1. Characterisation at 1 °C. This implies that the lowest temperature at which both palm kernel oil biodiesel (obtained in this work) and petroleum Palm kernel oil methyl ester (PKOME) was characterised diesel can be poured is the same. Calorific value and also together with petroleum diesel according to the ASTM lower/upper heating values can be used to distinguish among D6751. Table 1 shows the properties of PKOME obtained in different fuels their likelihood to produce more or less power comparison with petroleum diesel and international standards. or torque per the same volume. It compares the energy content Compared to published works, these are the best properties per litre for the various fuels under consideration. At 44 MJ/kg of PKOME ever obtained [9,11,12]. Viscosity of PKOME palm kernel oil biodiesel is close to petroleum diesel (46 MJ/kg) compares very well with petroleum diesel and passes the two and meets the standards. Compared to Petroleum diesel, major international standards for biodiesel (ASTM D6751 biodiesel has been generally reported to have lesser Heating and EN14214). Viscosity is the major reason why transesterifi- value [19]. This is because for biodiesel, carbon and hydrogen cation is necessary [13]. The viscosity of crude palm kernel oil are the sources of thermal energy while oxygen is ballast. measured was 29 mm2/s compared to palm kernel oil biodiesel Petroleum diesel fuel is made up of a mixture of various hydro- of 3.7 mm2/s. If fuel viscosity is too high, it may cause too carbon molecules and contains little oxygen (less than 0.3%), much pump resistance, filter damage, poor combustion, while biodiesel contains significant amount of oxygen (9%). increased exhaust smoke and emissions [14]. In general, higher Hence due to its high oxygen content, biodiesel has lower viscosity leads to poorer fuel atomisation [15]. Viscosity of Heating values than petroleum diesel [20], except combustion PKOME is still slightly higher than petroleum diesel and this efficiency of biodiesel will be higher, due to the higher oxygen is reported in the literature that biodiesel has higher viscosity content. This presupposes that the stoichiometric air/fuel ratio compared to Petroleum diesel due to high fatty acid composi- of biodiesel will be lower than that of diesel because lesser air tion [16,17]. Fatty acid composition determines the degree of will be required to burn biodiesel compared to conventional saturation and the higher the composition the higher the diesel [21]. This is why some level of modification is required degree of saturation. Viscosity increases with increasing degree in a diesel engine for optimum operation of biodiesel. It is also of saturation. for this same reason that many have reported higher NOx Cetane Number (CN), a dimensionless parameter, is a mea- emissions for biodiesel fuelled engines [22–25]. sure of fuel quality and is vital in determining whether a fuel is Acid value is a measure of auto-oxidation, storage stability suitable for use in a compression ignition engine. The best CN or mental contamination [26]. The acid value for PKOME is obtained for PKOME as a result of the optimisation was 50 higher than petroleum diesel but falls within the required lim- compared to petroleum diesel of 49 and met both ASTM its. However, it is an indication that PKOME is more unstable and EN standards. The longer the fatty acid carbon chains compared with petroleum diesel. the more saturated the molecules, the higher the CN [18]. Since The results show the Density of PKOME (878 kg/m3) biodiesel is largely composed of long-chain hydrocarbon exceeds that of petroleum diesel (839 kg/m3) but well within groups (with virtually no branching or aromatic structures) it the standards. It has been generally reported that biodiesel typically has a higher CN than petroleum diesel. has a higher density than petroleum diesel. This is why biodie- Flow properties such as pour point (PP) and cloud point sel is considered already ‘chemically advanced’ in terms of (CP) are important in determining performance of fuel flow injection timing [27]. Implying for the same engine it will take system. Viscosity is known to be influenced strongly by tem- a shorter time for biodiesel compared to petroleum diesel to perature and is inversely proportional. Operating a diesel travel from injection pump to the injector. The high density engine at low temperatures especially in cold climate regions hence compensates for the lower calorific or heating value. can be difficult because of high viscosities. This is why low It can be also be seen from the Table 1, that coconut oil bio- temperature properties are necessary to determine feasibility diesel possesses the lowest kinematic viscosity compared with of use in cold countries. The temperature at which cloud diesel and falls well within the required standards. Kinematic

Table 1 Physiochemical properties obtained for JCME, PKOME and COME. Properties PKOME COME Petroleum diesel ASTM D6751 EN 14214 Kinematic Viscosity @ 40 °C (mm2/s) 3.7 2.4 2.6 1.9–6 3.5–5 Cetane number 50 55 49 47 min 51 min Pour point (°C) 1 -5 1 15 to 6 – Cloud point (°C) 6 2 2 – – Flash point (°C) 170 122 90 93 min 120 min High caloriﬁc value (MJ/kg) 44 42 46 – 35 Acid value (mol%) 3.4 2 0.17 0.5 max 0.5 max Density (kg/m3) 878 894 839 880 860–900

Table 2 Viscosity of PKOME for varying concentrations of H2SO4. 2 2 H2SO4 (wt.%) Viscosity of experimental runs (mm /s) Average viscosity (mm /s) Run 1 Run 2 Run 3 0 5.7 5.8 5.7 5.7 0.6 5.1 5.0 5.1 5.1 0.7 4.8 4.8 4.8 4.8 0.8 4.5 4.6 4.6 4.6 0.9 4.1 4.2 4.2 4.2 1 3.7 3.6 3.7 3.7

viscosity of coconut oil dropped from 27 mm2/s to 2.4 mm2/s wear and power loss due to injector or pump leakage if viscos- after transesterification. The kinematic viscosity of COME ity is too low. The results show the higher the sulphuric acid was found to be lower than petroleum diesel (2.6 mm2/s). the more favourable the result as the Kinematic viscosity of Cetane number of 55 was obtained for COME and that of pet- PKOME was reduced from 5.7 mm2/s to 3.7 mm2/s. roleum diesel was 49. Since a shorter ignition delay (ID) corre- The effect was even more profound with coconut oil methyl sponds to a higher CN and vice versa it implies this COME ester as addition of 1% H2SO4 reduced the viscosity from will ignite at a lower temperature than petroleum diesel. A fuel 3.9 mm2/s to 2.4 mm2/s (about 40% reduction). The viscosity with higher cetane number will ignite at lower temperatures reduced steadily as the sulphuric acid concentration was and have a very short ignition delay. If the period between increased (Table 3). the injection and the start of the ignition takes too long (low Jatropha methyl ester experienced a viscosity reduction of CN) a strong diesel knock could occur leading to misfiring. 24% (4.1–3.1 mm2/s) with the addition of 1% sulphuric acid If a CN is too high, combustion can occur before the fuel (Table 4). The favourable effect of sulphuric acid on the viscos- and air are properly mixed, resulting in incomplete combustion ity may be due to the fact that the acid further acts as a drying and smoke. Cetane number obtained for COME fell well agent drying any remaining water and dissolving any remain- within the standards and was much better than petroleum ing free fatty acid. diesel. Pour point of COME (5 °C) measured is better than 3.3. Effect of methanol to oil ratio on yield petroleum diesel (1 °C). Calorific value of petroleum diesel is better than coconut oil biodiesel as expected due to excess Ideally, one mole of biodiesel requires 3 mol of alcohol in oxygen which is ballast in biodiesel. Density of the biodiesel transesterification. However, due to the reversible nature of was higher than petroleum diesel which is convenient since the reaction, excess alcohol is usually used in transesterifica- the higher speed will make up for the low calorific value. tion in order to shift the reaction to the product side [29]. The effect of methanol in the range of 4:1–8:1 (molar ratio) 3.2. Effect of sulphuric acid (H2SO4) on viscosity was investigated, keeping other process parameters fixed. The reaction temperature was kept constant at 65 ± 1 °C, and Effect of sulphuric acid on viscosity of PKOME and COME reaction was performed for 1 h. The reaction was performed was investigated as described in the experimental procedure. with constant concentrations of NaOH. Analyses of the three For this experiments three runs of the same experiment were oils (JCME, PKOME and COME) revealed that, increase in conducted for both feedstocks and the average found is dis- methanol/oil ratio produces a corresponding increase in the played in the Table 2. Kinematic Viscosity is a measure of yield till the optimum yield is achieved (Fig. 1). resistance to flow of a liquid due to internal friction of one part This is because higher mass ratio of reactant increases the of a fluid moving over another. If viscosity is too high it may contact between the methanol and oil molecules so the methyl lead to pump damage and filter clogging, poor combustion and ester concentration increases with increasing mass ratio of increased emissions [15,28]. methanol to oil. Neither low nor high viscosity is considered favourable in a The optimum methanol:oil molar ratio for biodiesel pro- diesel engine. Some injection pumps can experience excessive duction from Jatropha curcas methyl ester is 6:1. But it seems

Table 3 Viscosity of COME for varying concentrations of H2SO4. 2 2 H2SO4 (wt.%) Viscosity of experimental runs (mm /s) Average viscosity (mm /s) Run 1 Run 2 Run 3 0 3.9 3.8 3.9 3.9 0.6 3.6 3.4 3.8 3.6 0.7 3.3 3.2 3.2 3.2 0.8 2.9 2.8 2.9 2.9 0.9 2.6 2.6 2.7 2.6 1 2.4 2.4 2.4 2.4

Table 4 Viscosity of JCME for varying concentrations of H2SO4. 2 2 H2SO4 (wt.%) Viscosity of Experimental Runs (mm /s) Average viscosity (mm /s) Run 1 Run 2 Run 3 0 4.1 4.1 4.2 4.1 0.6 4.1 4.0 4.0 4.0 0.7 3.9 3.8 3.8 3.8 0.8 3.7 3.7 3.6 3.7 0.9 3.4 3.3 3.4 3.4 1 3.1 3.1 3.2 3.1

100 100 98

98 96

96 94 92 PKOME 94 PKOME 90 JCME 92 JCME COME

Biodiesel yield (%) 88 90 COME

Biodieseil yield (%) 86

88 84 0.6 0.7 0.8 0.9 1 86 NaOH catalyst concentraon 4:01 5:01 6:01 7:01 8:01 Methanol:Oil (Molar rao) Figure 2 Effect of catalyst variation on biodiesel yield.

Figure 1 Effect of alcohol:oil molar ratio on biodiesel yield. 4. Conclusion that after the optimum yield was reached the yield began to In this work palm kernel oil, coconut oil and Jatropha curcas decline for JCME. This implies that when excess alcohol is oil were used as feedstocks for the production of biodiesel to used beyond a certain limit in transesterification, the polarity investigate optimum parameters to obtain high yield and best of the reaction mixture is increased, thus increasing the solubil- quality of biodiesel. A Two-step process was used in the bio- ity of glycerol back into the ester phase and promoting the diesel production using NaOH. In the second step sulphuric reverse reaction between glycerol and ester or glycerides acid was added in portions (0.6%, 0.7%, 0.8%, 0.9% and thereby reducing the ester yield. 1%) to investigate its effect on viscosity. The base-catalyst Optimum ratios of palm kernel oil and coconut oil biodie- was varied, and alcohol:oil molar ratio was also varied to sels yielded 98% each at methanol:oil molar ratio of 8:1. obtain optimum parameters for each feedstock. For each of Therefore depending on the type of feedstock and perhaps the feedstock, the biodiesel yield increased with increase in cat- even the quality (mode of preparation), the optimum metha- alyst concentration. The highest yield was obtained with 1% nol:oil molar ratios differ. catalyst concentration for all. At 1% NaOH concentration a yield of 98%, 96% and 95% was obtained for PKOME, 3.4. Effect of base catalyst concentration on yield JCME and COME respectively at 6:1 methanol:oil ratio. This shows that the optimum conditions for NaOH catalysed Selecting a catalyst for (Trans) esterification is very important (Trans) esterification required more catalyst. The results show in determining the outcome of biodiesel production process the higher the sulphuric acid concentration the more favour- but this is dependent on the type and quality of feedstock. In able the result as the Kinematic viscosity of PKOME was this work, base catalysed transesterification was conducted reduced from 5.7 mm2/s to 3.7 mm2/s. The effect was even with a 6:1 M ratio of methanol to oil at 500C for 2 h. NaOH more profound with coconut oil methyl ester as addition of 2 2 catalysed (Trans) esterification of Jatropha curcas Oil, Palm 1% H2SO4 reduced the viscosity from 3.9 mm /s to 2.4 mm /s kernel Oil and Coconut oil was investigated by varying NaOH (about 40% reduction). Jatropha methyl ester experienced a concentrations as shown in Fig. 2. The molar ratios varied are viscosity reduction of 24% (4.1–3.1 mm2/s) with the addition 0.6, 0.7, 0.8, 0.9 and 1. of 1% sulphuric acid. The favourable effect of sulphuric acid For each of the feedstock, the biodiesel yield increased with on the viscosity is due to the fact that the acid further acts increase in catalyst concentration. The highest yield was as a drying agent drying any remaining water and dissolving obtained with 1% catalyst concentration for all. At 1% NaOH any remaining free fatty acid. The effect of methanol in the concentration a yield of 98%, 96% and 95% was obtained for range of 4:1–8:1 (molar ratio) was investigated, keeping other PKOME, JCME and COME respectively at 6:1 methanol:oil process parameters fixed. Analyses of the three oils revealed ratio. This shows that the optimum conditions for NaOH that, increase in methanol/oil ratio produces a corresponding catalysed (Trans) esterification required more catalyst. increase in the yield till the optimum yield is achieved. This

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