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Momordica charantia Seed Oil Methyl Esters: Kinetic Study and Fuel Properties a
Umer Rashid , Junaid Ahmad & Azhari Muhammad Syam
b c
a
d
, Robiah Yunus , Muhammad Ibrahim , Hassan Masood
e
a f
a
Institute of Advanced Technology , Universiti Putra Malaysia , 43400 , UPM Serdang , Selangor , Malaysia b
Department of Industrial Chemistry , Government College University , Faisalabad , 38000 , Pakistan c
Chemical Engineering Department , Universiti Teknologi PETRONAS, Bandar Seri Iskandar , Tronoh , 31750 , Perak , Malaysia d
Department of Environmental Sciences , Government College University , Faisalabad , 38000 , Pakistan e
Department of Chemical and Environmental Engineering , Universiti Putra Malaysia , 43400 , UPM Serdang , Selangor , Malaysia f
Department of Chemical Engineering, Faculty of Engineering , University of Malikussaleh , Lhokseumawe , 24351 , Nanggore Aceh Darussalam , Indonesia Accepted author version posted online: 20 Sep 2013.
To cite this article: International Journal of Green Energy (2013): Momordica charantia Seed Oil Methyl Esters: Kinetic Study and Fuel Properties, International Journal of Green Energy, DOI: 10.1080/15435075.2013.823090 To link to this article: http://dx.doi.org/10.1080/15435075.2013.823090
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ACCEPTED MANUSCRIPT Momordica charantia Seed Oil Methyl Esters: Kinetic Study and Fuel Properties Umer Rashida,*, Junaid Ahmadb,c, Robiah Yunusa, Muhammad Ibrahimd, Hassan Masoode and Azhari Muhammad Syama,f Downloaded by [Memorial University of Newfoundland] at 09:24 09 November 2013
a
Institute of Advanced Technology, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia b
Department of Industrial Chemistry, Government College University, Faisalabad-38000, Pakistan c
Chemical Engineering Department, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, Tronoh 31750, Perak, Malaysia
d
Department of Environmental Sciences, Government College University, Faisalabad-38000, Pakistan e
Department of Chemical and Environmental Engineering, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia
f
Department of Chemical Engineering, Faculty of Engineering, University of Malikussaleh, Lhokseumawe 24351, Nanggore Aceh Darussalam, Indonesia *To whom correspondence should be addressed. E-mail:
[email protected] Tel.; +60-603-8946-7393; Fax: (+60) 03 89467004; Institute of Advanced Technology, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia ABSTRACT Due to growing concerns such as increasing energy demand and the environmental issues related fossil energy problems caused by consumption of fossil energy, it is needed to focus on nonedible oils for biodiesel production. In the present research work, the seed oil of Momordica charantia (M. charantia) was for the first time appraised as possible non-edible oil for synthesis of biodiesel. M. charantia has oil content (36.10±4.20%), high acid value (1.82 mg KOH g-1) and its oil enable base-catalyzed transesterified for biodiesel production after acid pre-treatment.
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ACCEPTED MANUSCRIPT It was transesterified under standard conditions at 6:1 molar ratio of methanol to oil; sodium methoxide (1.00% wt in relation to oil mass) as a catalyst; 60 ℃ reaction temperature and 90 min
of reaction time. At optimum conditions biodiesel yield of 93.2% was acquired. The reaction
followed first order kinetics. The activation energy (EA) was 254.5 kcal mol-1 and the rate
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constant value was 1.30 × 10-4 min-1 at 60 °C. Gas chromatography (GC) investigation of M. charantia seed oil methyl esters (MSOMEs) depicted that the fatty acid composition comprises a high proportion of mono-unsaturated fatty acids (64.11±5.02%). MSOMEs were also characterized using Fourier Transform Infrared (FT-IR) and 1H Nuclear Magnetic Resonance (1H-NMR) spectroscopy. The tested fuel properties of the MSOMEs, except oxidative stability, were conformed to EN 14214 and ASTM D6751 standards. The low value oxidative stability of MSOMEs can be solved by adding antioxidants additives. In summary, M. charantia oil has potential as non-edible raw material for biodiesel production. Keywords: Momordica charantia seed oil; Methanolysis; Kinetic study; GC; 1H-NMR; FT-IR; Fuel properties
INTRODUCTION The gradual exhaustion of different petroleum reserves and the need for alternate energy sources arose. Serious environmental problems e.g. the widespread and intensive use of petroleum-fuels arises global warming (Nakpong and Wootthikanokkhan, 2010; Ahmad et al., 2013). Thus, the concern for environmental protection is increasing globally with worldwide attention for conservation of non-renewable natural resources (Liu et al., 2008; Anwar et al., 2010). Biodiesel as an alternative source is reported to show many advantages as compared to conventional
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ACCEPTED MANUSCRIPT (petroleum) diesel and these include, their extraction from renewable feedstocks, superior lubrication property and biodegradation, lesser toxicity (nature of feedstock), displacement of imported petroleum, higher flash point, and a reduction in most of the exhaust emissions (Moser and Vaughn, 2010; Rashid et al., 2011). Moreover, biodiesel is considered as green fuel because
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it does not contain any sulphur, aromatic hydrocarbons and metals (Çaynak et al., 2009). Demirbas (2009) defined biodiesel as a mixture of mono-alkyl esters (long chain fatty acids) derived from a renewable lipid feedstock may be vegetable oil or animal fat. The production is achieved through transesterification or alcoholysis, which is used to reduce the high viscosity of triglyceride (Meher et al., 2006). The vegetable oils or animal fats react with an alcohol in the presence of strong base catalyst (NaOH or KOH). This reaction yields a mixture of methyl esters along with a co-product called glycerol or glycerine (Ramadhas et al., 2005; Rashid et al., 2012; Li et al., 2012). The properties of resulting biodiesel are quite similar as that of petroleum-based diesel fuel (Kusdiana and Saka, 2004). Many papers have been published on the kinetics of transesterification, biodiesel properties and its application in diesel engine (Jain and Sharma, 2010). The studies are particularly performed to investigate the kinetics reaction parameters. These parameters then may be used to predict the extent of chemical reaction at given time under specific reactions conditions (Darnoko and Cheryan, 2000). Earlier, Noureddini and Zhu (1997) reported that only a few published papers are on kinetics of transesterification of simple esters which involved sodium hydroxide as the catalyst. A kinetics study using heterogeneous catalysis transesterification is reported in terms of the efficiency and economical aspects (Chantrasa et al., 2011). They also reported on the
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ACCEPTED MANUSCRIPT predominance of the hydrotalcite catalyst compared to other heterogeneous ones. According to Li and Rudolph, (2008) and Verziu et al. (2008), a few compounds are utilized as heterogeneous catalyst for the biodiesel production, particularly Magnesium Oxide (MgO) and Calcium Oxide (CaO) particularly attracted some researchers’ interest to conduct further investigation on
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kinetics of transesterification. Other solid catalyst use is Amberlyst resin, as reported by Pappu et al. (2011). In their work, Amberlyst 15 was applied as a catalyst for studying the kinetic models of methyl stearate transesterification with n-butanol as the excess reactant. The feedstock of biodiesel production in different regions varies according to geographical location and climatic conditions. For example, canola/rapeseed is mostly used in Europe, palm oil in tropical countries; soybean oil and animal fats are mainly used in the United States (Mittelbach and Remschmidt, 2004; Knothe et al., 2005; Moser, 2009). The supply of these oils is short in many countries. It can pose a threat to food production which eventually leads to higher food prices. Therefore, it is necessary to explore non-edible oils as the raw material of biodiesel (Wen et al., 2010; Rashid et al., 2011). Modern day researches are concentrates on the switch of basestock from edible to non-edible oils for sustainable biodiesel production without affecting the food security (Demirbas, 2008; Adelbowala et al., 2012). New and low cost nonedible oil crops may be identified for the production of economical oils suitable for biodiesel production (Kafuku and Mbarawa, 2010). Bitter gourd or Chinese melon (Momordica charantia), is a plant belongs to Cucurbitaceae family and is extensively used as tropical crop in many Asian countries as vegetable and a medicine (Prashantha et al., 2009). Normally, it is grown as an annual crop. However, it is
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ACCEPTED MANUSCRIPT frequently cultivated throughout the year in mild, frost-free winter’s areas. In the plain areas, the summer season crop is sown from January to June (Singh et al., 2006). M. charantia is commonly utilized in various industries e.g. in the decolourisation and removal of dyes in the textile industry. The removal of phenolic compounds from effluents in different industries has
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great possibility to become an important industrial crop. Oil extracted from M. charantia showed good drying characteristics due to high saponification value and low acid value, presence of a high amount of conjugated octadecatrienoic acids, moderate iodine value and the low set-totouch drying time (Prashantha et al., 2009); therefore, it has its application as “drying oil” in paints, coatings, and inks industries (Chang et al., 1996). However, the potential of bitter gourd oil as a feedstock for biodiesel production is still unidentified. The main objective of the current research is to explore the potential of non-edible oil of M. charantia seeds for biodiesel production. Furthermore, the produced biodiesel is characterized using GC, 1H-NMR, FT-IR and evaluated the fuel properties of the biodiesel produced from M. charantia oil.
MATERIAL AND METHODS Momordica charantia seeds were obtained from the Ayub Agriculture Research Institute (AARI), Faisalabad, Punjab, Pakistan. The seeds were cleaned manually to remove all extra matter (i.e. dust, dirt and immature broken seeds). All chemicals used in the experiments included methanol, sodium methoxide, isopropanol, phenolphthalein (1% in isopropanol), N,OBis(trimethylsilyl) trifluoroacetamide and reagents were analytical reagent (AR) grade and purchased from Merck Chemical Company (Darmstadt, Germany). Pure standards of fatty acid
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ACCEPTED MANUSCRIPT methyl esters (FAMEs) i.e. C16:0; C18:0; C18:1; C18:2; C18:3 were obtained from Sigma Chemical Company (St. Louis, MO, USA). Momordica charantia seeds (1000 g) were crushed using a commercial grinder and fed to a local
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extractor. M. charantia oil obtained was extracted from seeds by using electric oil expeller. The oil after extraction was subjected to filtration for purification using filtration apparatus. Pretreatment of M. charantia oil was done as per previous reported method by Rashid et al. (2013). Esterification was continued until the acid value was less than 1%. A one step of reaction was performed using the following method; firstly, M. charantia oil was poured into the three necks round-bottomed flask and heated to the specified temperature. Once the temperature of M. charantia oil was achieved, excess reactant (methanol) and catalyst were simultaneously added into the reaction. Maintain the reaction temperature as specified. The reactor was equipped with a thermometer, a sampling port and a reflux condenser under atmospheric condition as per our previous study (Yunus et al., 2002) under a constant stirring rate (650 rpm). Six sets of kinetics data were collected for three different reaction temperatures, namely 30°C, 45°C, and 60°C, respectively. The sample was collected at the specified reaction time. After the reaction, the mixture was allowed to cool down and equilibrate resulting in separation of two phases. Subsequent to separation of the two layers by sedimentation the upper methyl esters layer was purified by distilling the residual methanol at 70 °C and remaining catalyst was removed by successive rinses with hot distilled water. Finally, the residual water was removed with Na2SO4, followed by filtration (Rashid and Anwar, 2008). Thus, the samples
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ACCEPTED MANUSCRIPT were stored in an ice bath to avoid further reaction before the gas chromatography analysis was conducted. The yield of biodiesel was calculated as;
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Yield of biodiesel (%) =
grams of methyl esters produced × 100 grams of oil used in reaction
(1)
The gas chromatography samples preparation and analysis was performed base on the developed GC method by Yunus et al. (2002) was the following; approximately 0.03±0.005 g of sample was weighed in a 1.5 ml vial and diluted with 1.0 ml of ethyl acetate. The sample was swirled for few minutes to dissolve the mixture. N,O-Bis(trimethylsilyl) trifluoroacetamide, 0.5 ml, was then added to the mixture, swirled and finally transferred to a water bath at 40°C for 10 min. The GC analysis was performed on GC Agilent 6890 series equipped with FID detector and HT5, (SGE International, Australia) column (12m × 0.53 mm, and 0.15μm ID). Hydrogen at 26.7 ml/min was used as a carrier gas with split ratio of 1:1. The oven temperature was set at an initial temperature of 80°C, held for 3 min, increased at 6°C/min to 340°C and held for another 6 min. The injector and detector temperatures were 300°C and 360°C, respectively (Yunus et al., 2002). The FTIR spectrum of MSOMEs was recorded by inserting a drop of MSOMEs between diamond-composite FTIR-ATR sample holding plates on a Bruker Alpha FT-IR spectrometer (Bruker, Germany). The FTIR-ATR spectra were obtained by averaging 10 scans at 350-6000 cm–1 with a resolution of 2 cm–1 using Opus 6.5 Software (Bruker). A spectrum from the diamond-composite plates was recorded as a background. NMR spectra were obtained on a Varian (Palo Alto, CA, USA) VNMR spectrometer operating at 500 MHz (1H-NMR) with CDCl3 as solvent.
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ACCEPTED MANUSCRIPT The fuel properties of the MSOMEs were determined following ASTM and EU methods: cloud point (ASTM D2500), pour point (ASTM D97), kinematic viscosity (ASTM D445), oxidative stability (EN 14112), cetane number (ASTM D6890), cold filter plugging point (ASTM D6371), ash content (ASTM D874), flash point (ASTM D93), density (ASTM D5002), sulphur content
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(ASTM D4294), copper strip corrosion (ASTM D130), acid value (ASTM D974), free and bound glycerol (ASTM D 6584), methanol contents (EN 14110) and monoglyceride, diglyceride and triglyceride contents (EN 14105). Triplicate determinations were performed for every experiment and the data are presented as mean ± standard deviation.
RESULTS AND DISCUSSION Chemical Properties of Momordica charantia Oil Prior to base catalyzed transesterification, the acid value of Momordica charantia (M. charantia) oil was 0.42 mg KOH g-1. The saponification and peroxide values of M. charantia oil were 185.15 mg KOH g-1 and 4.99 m.eq kg-1, respectively. Although, iodine value of the M. charantia oil was calculated as 124.09 g I2 100g-1.
Kinetic Study Momordica charantia seed oil had used as the feedstock of transesterification in performing the kinetics study of the reaction. The progress of transesterification of M. charantia oil at various temperatures is shown in Figure 1.
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ACCEPTED MANUSCRIPT The kinetics study and mechanism of transesterification reaction will reflex the reaction rate constant, order of reaction and Arrhenius activation energies. As many researchers have reported that the whole mechanism of transesterification reaction occur under three step wises reaction as indicated by equation (2) to (4). Each intermediate step of reaction uses one mole of alcohol to
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react with n-glyceride compound, which further, produce one mole of alkyl ester (Diasakou et al., 1998; Yunus and Azhari, 2011). Due to the entire steps of reaction produce methyl ester compound, for that reason, all the intermediate compounds e.g. monoglyceride and diglyceride can be negligible and over all reaction conversion as one step described in equation (5). TG
+
MeOH
DG
+
ME
(2)
DG
+
MeOH
MG
+
ME
(3)
MG
+
MeOH
GL
+
ME
(4)
TG
+
3MeOH
3ME +
GL
(5)
where TG, DG, MG, GL and ME denote triglyceride, diglyceride, monoglyceride, glycerol and methyl ester. The effect of temperature on the transesterification of M. charantia oil has been studied in the present work. Since the oil is naturally liquid at room temperature (25°C), the minimum temperature selected in this work is 30°C. Below 30°C, the endothermic behaved reaction is not going on well or taking a longer time for the completion. The maximum temperature studied was 60°C in order to avoid much lost of methanol into atmosphere because of vaporization. Figure 1 depicts the yield of product (ME) at 60°C was 80% at first 10 minutes of reaction time. At 30°C,
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ACCEPTED MANUSCRIPT the yield of ME was 75% compared to 78% product yield at reaction temperature of 45°C. However, the maximum yield of product was achieved after 2 h of reaction time was 93.2%. Ilgen (2012) also reported on the transesterification of canola oil using 3.0 wt % of catalyst
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amount for 3 h of reaction time obtained the yield of product is about 91.78%. From the equation (5), the rate of reaction may be determined accordingly, based on a decreasing amount of reactant or an increasing amount of product. In this study, the increasing amount of ME product was selected. Since the percent yield of product was as a function of time, the first order rate of reaction can be derived as follows: -r = dME/dt
(6)
In this matter, dME is the % yield rate of product. The Equation (5) can be modified into the following equation (6) dME/dt = kME
(7)
in order to derive furthermore the equation (7) to determine the reaction rate constant (k). Assuming that the initial concentration of product at time = 0 is ME0, and the increasing concentration of product at time = t is MEt.
∫
MEt
ME 0
t
dME / ME = k ∫ dt
(8)
t0
k = 2.303 (log MEt – log ME0) / t
(9)
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ACCEPTED MANUSCRIPT Referring to Figure 2, after plotting the kinetics data on the first order graph was performed. The curves showed a straight line for entire reaction temperatures. This trend proved that the transesterification process matches to follow first order model. The determination of rate
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constants for the reaction also depends on the reaction order. Also, when reaction rate were plotted against temperatures, the graph produced a straight line curve as shown in Figure 3. Thus, this trend indicated that there is a close correlation between reaction rate constant with reaction temperature. Once reaction temperature was increased, the reaction rate constant increased proportionally. The calculation of reaction rate constants which is based on the increasing concentration of reactant was conducted and the results were as tabulated in Table 1. Using the equation (9), the reaction rate constants under optimum operational condition was computed as 1.19 x10-4 -1.30 x 10-4 min-1. The Arrhenius activation energy was determined by plotting the entire reaction rate constants against temperature in Kelvin (K) as indicated in Figure 4. The dependency of k on the reaction temperature follows the Arrhenius law as:
k = A exp(− E / RT )
(9)
Thus, Equation (10) was modified becoming the following equation. −E log 10 k = log 10 A + 2.303RT
(10)
where R is the universal gas constant and T is expressed in K.
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ACCEPTED MANUSCRIPT The Arrhenius activation energy (E) was estimated from the slope of a plot of log10 k versus 1/T. The value of Arrhenius activation energy is provided in Table 2. The frequency factor (A) was determined by the intercept. Berrios et al. (2010) reported the activation energy for biodiesel production via esterification reaction was 6.86 kcal mol-1 (28.7 kJ mol-1). The required activation
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energy for the transesterification reaction of waste cooking oil as Jain et al. (2011) reported was about 21.21 kcal mol-1 (88.76 kJ mol-1). The activation energy which attained in this study was the activation energy of first order reaction which converted directly triglyceride into biodiesel (methyl esters). The obtained value of activation energy was about 254.5 kcal mol-1, which is higher than other finding results. Thus, the transesterification reaction of M. charantia oil into MSOMEs is relatively more difficult to take place as reflected in its high activation energy compared to other oils. Particular values mostly reported for the activation energies of alkali-catalyzed homogeneous and heterogeneous transesterification reaction under three steps wises configuration were in the range of 10.5238.72 kcal mol-1 (Noureddini and Zhu, 1997; Liu et al., 2008; Vujicic et al., 2010).
Characterization of Momordica charantia Oil Methyl Esters (MSOMEs) Fatty Acid Methyl Esters (FAMEs) The fatty ester composition of MSOMEs as determined by GC is given in Table 3. The MSOMEs contain 37.2% unsaturated fatty acids (UFA), whereas the level of saturated fatty acid (SFA) was 64.11%. This result agrees well with profiles in the literature (Prashantha et al., 2009) with stearic (approximately 35.08%), palmitic (approximately 3.09%), linoleic (approximately
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ACCEPTED MANUSCRIPT 4.09%) and oleic acids (approximately 2.15%) being the most common fatty acids. Whereas, the seed oil is also rich in α-eleosteric acid (50.04%) which also were quite agreed with our results as depicted in Table 3.
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The 1H-NMR and FT-IR spectra of MSOMEs were also determined and reported in term of data in Table 4. The 1H-NMR spectrum agrees well with the spectra of vegetable oil methyl esters of similar composition, further confirmed by a calculation of the fatty acid profile with a procedure using peak integration values (Knothe and Kenar, 2004). The FT-IR spectra have been used to identify functional groups and the bands corresponding to various stretching and bending vibrations in MSOMEs as shown in Table 4.
Fuel Properties The fuel properties of the Momordica charantia seed oil methyl esters (MSOMEs) were determined and compared to the biodiesel American standard ASTM D6751 and European standard EN 14214, as depicted in Table 5. The cetane number (CN) is indicative of its combustion quality during compression ignition. Higher cetane number value depicted the better ignition quality of the fuel. The cetane number for MSOMEs has been found to be 64 (Table 5), which satisfied with quality standards that prescribe a minimum of 47 (ASTM D6751), and minimum of 51 (EN 14214) limits (Table 5). The CNs of the components of MSOMEs are methyl streate approximately 86.9, methyl oleate approximately 55 and methyl palmitate with about 85 (Knothe et al., 2003), in order that the CN of MSOMEs is well-explained in view of that each constituent contributes linearly to the overall
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ACCEPTED MANUSCRIPT CN. Therefore, the MSOMEs biodiesel agreed with the standards cab used as more ignitable fuel than other conventional biodiesel fuels. Kinematic viscosity (KV) represents the flow characteristics and the tendency of fluids to deform
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by either shear stress or tensile stress. Because, KV is an important parameter of fuel atomization and fuel distribution (Mittelbach, 1996). Hence, the kinematic viscosity at 40°C for MSOMEs was determined to be 4.48 mm2s-1, which is within the ranges specified by the biodiesel standards ASTM D6751 and EN 14214 (Table 5). The oxidation of biodiesel fuel is an important factor, which helps in assessing the quality of biodiesel. This oxidation stability is an indication of the degree of oxidation, potential reactivity with air, and may determine the need for antioxidants. Table 5 shows that the induction period of MSOMEs per the Rancimat oxidative stability test was (4.25 h) which meet the minimum prescribed in the ASTM D6751-10 (3h) but did not satisfied the EN 14214-12 (8h) standard. The reason for the higher oxidative stability time is the lower content of USFAs (37.2%), as compared to SFAs (61.99%) especially methyl eleostericate (approximately 56.47%; see Table 1). This result can be attributed to the better oxidative stability of eleostearic acid comparison to other comment fatty acids of the MSOMEs (Table 5). Therefore, MSOMEs stability can increase to the minimum restriction prescribed in the EN 14214 standard by adding antioxidants i.e. tertbutylhydro-quinone (TBHQ). The vital factors which determine the cold flow properties of fuels are cloud point (CP), pour point (PP) and cold filter plugging point (CFPP). In the present work the maximum values of CP and PP of the MSOMEs were determined to be 9 °C and 15 °C (Table 5). ASTM standard
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ACCEPTED MANUSCRIPT D6751, no mention of a low-temperature parameter in its specifications; rather a “report” is specified for cloud and pour point. However, each country can specify certain temperature limits for different times of year depending on climate conditions (Knothe et al., 2006). The CFPP is the temperature at which a fuel jams the filter due to the formation of agglomerates crystals.
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CFPP test was conducted according to ASTM D 6371 which showed the CFPP value for MSOMEs was 8 °C. This value is quite high because the MSOMEs composition has a high percentage (62.7%) of saturated fatty acids (Table 5). The temperature at which biodiesel will ignite, when exposed to a flame or spark is the fuel flash point (FP), is higher than the petro-diesel standards of transportation safety. This parameter is considered in storage, handling, and safety of fuels and other flammable materials. The FP in the present investigations was 162°C (Table 5) and is higher than the minimum values prescribed in ASTM D6751 and EN 14214. Airless combustion systems also depend greatly on density and the standard for biodiesel requires a higher density than 860-900 kgm-3 in EN 14214. The results achieved (889.4 kgm-3) showed that the MSOMEs produced was within the specification limits (Table 5). Other fuel properties of MSOMEs such as sulfur content, ash content, water content, copper strip corrosion, free and total glycerol, methanol contents, monoglyceride, diglyceride and triglyceride contents were also determined (Table 5). As expected, all other aforementioned properties of MSOMEs/biodiesel conformed to EN 14214 and ASTM D6751 standards.
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ACCEPTED MANUSCRIPT CONCLUSION Momordica charantia has relatively high oil content with low acid value, which facilitated direct methanolysis for biodiesel production without any acid pretreatment. The fatty acid composition
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of the M. charantia seed oil includes a high percentage of polysaturated fatty acids. The kinetics study of MSOMEs has been successfully performed under various reaction temperatures and other optimal reaction parameters. The reaction mechanism showed that the transesterification taking place in a single straight forward reaction. The reaction rate constants follow the first order reaction model. The obtained rate constant values are 1.19 × 10-4-1.30 × 10-4 min-1. The activation energy is higher compared to other similar studies i.e. 254.5 kcal mol-1. It is due to the reaction consumed a lot of internal energies to break down the intermediate hydrocarbon chains to yield the final products. The most results of fuel properties, except oxidative stability, compared well with EN 14214 and ASTM D6751. The oxidative stability of MSOMEs/biodiesel was unsatisfactory in line with these standards. The oxidative stability would require the use of antioxidants to meet specifications of EN 14214 and ASTM D6751 standards. It could be concluded from the results of the present investigation that M. charantia oil as a non-edible oil can be converted into biodiesel with very good yield and better quality of fuel properties. ACKNOWLEDGEMENT The data presented here is part of research thesis at Government College University Faisalabad (GCUF). The authors are thankful to Dr. Nasir Rasool and Dr. Muhammad Zubair from Chemistry Department, GCUF for their assistance.
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ACCEPTED MANUSCRIPT REFERENCES Adebowale, K. O., A. Adewuyi and K. D. Ajulo. (2012). Examination of fuel properties of the methyl esters of Thevetia peruviana seed oil. International Journal of Green Energy. 9 (3): 297-
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ACCEPTED MANUSCRIPT Kafuku, G. and M. Mbarawa. (2010). Biodiesel production from Croton megalocarpus oil and its process optimization. Fuel. 89 (9): 2556-2560. Knothe, G. and J.A. Kenar. (2004). Determination of the fatty acid profile by 1H-NMR
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ACCEPTED MANUSCRIPT List of Tables Table 1. Reaction rate constants at various temperatures
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Table 2. Arrhenius activation energy Table 3. Fatty ester profile of Momordica charantia oil methyl esters (MSOMEs) Table 4. FTIR and NMR Data for Momordica charantia oil methyl esters (MSOMEs) Table 5. Fuel properties of Momordica charantia oil methyl esters (MSOMEs)
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Table 1: Reaction rate constants at various temperatures
No.
Temperature ( °C)
Reaction rate constants (k) ( min-1)
R2
1
30
0.00119
0.94
2
45
0.00124
0.95
3
60
0.00130
0.90
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ACCEPTED MANUSCRIPT Table 2: Arrhenius activation energy
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Reaction Pathways
TG
ME
Activation Energy
R2
254.5 kcal mol-1
0.99
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ACCEPTED MANUSCRIPT Table 3: Fatty ester profile of Momordica charantia oil methyl esters (MSOMEs)
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FAMEs
MSOMEs (%)
Palmitic acid (C16:0)
3.09 ± 0.21
Stearic acid (C18:0)
34.11 ± 2.31
Oleic acid (C18:1)
2.15 ± 0.50
Linoleic acid (C18:2)
4.09 ± 0.67
α-Eleosteric acid (ctt, 9,11,13–18:3)
51.56 ± 5.18
β-Eleosteric acid (ttt, 9,11,13–18:3)
4.91 ± 2.69
Values are mean ± SD of triplicate determinations
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ACCEPTED MANUSCRIPT Table 4: FTIR and NMR data for Momordica charantia oil methyl esters (MSOMEs) Ester
FTIR (cm-1)
1
MSOMEs
3009, 2922, 2853, 1741, δ 5.33 (m, 2H), 3.63 (s, 3H),
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1460, 1168, 992, 723
H NMR (400 MHz, CDCl3)
2.28 (t, 2H), 2.03 (m, 2H), 1.25 (m, 28 H), 0.89 (t, 3H)
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Table 5: Fuel properties of Momordica charantia oil methyl esters (MSOMEs) Property
MSOMEs
ASTM D6751
EN 14214
Cetane number
64.0 ± 4.80
47 min
51 min
Kinematic viscosity (mm2/s; 40 °C)
4.48 ± 1.02
1.9-6.0
3.5-5.0
Oxidative stability (h)
1.99 ± 0.85
3 min
8 min
Cloud point (°C)
9.00 ± 2.12
Report
-a)
Pour point (°C)
15.00 ± 1.82
-b)
-a)
Cold filter plugging point (°C)
8.00 ± 2.00
-b)
-a)
Flash point (°C)
162 ± 11.20
93 min
120 min
Sulfur content (%)
0.012 ± 0.003
0.05 max
-
Ash content (%)
0.016 ± 0.12
0.02 max
0.02 max
Acid value (mg KOH/g)
0.40 ± 0.39
0.50 max
0.50 max
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ACCEPTED MANUSCRIPT Copper strip corrosion (50 °C, 3 h)
1a
No. 3 max
No. 1 min
Density (15°C), kg.m-3
889 ± 10.50
-
-
Monoglyceride content, %
0.71 ± 0.003
-
0.80 max
Diglyceride content, %
0.15 ± 0.002
-
0.20 max
Triglyceride content, %
0.13 ± 0.001
-
0.20 max
Methanol content, %
0.18 ± 0.002
-
0.20 max
Free glycerol
0.014 ± 0.001
0.020 max
0.020 max
Total glycerol
0.170 ± 0.03
0.240 max
0.250 max
Values are mean ± SD of triplicate determinations a)
Not specified. EN 14214 uses time and location-dependent values for the cold filter
plugging point (CFPP) instead. b)
Not specified.
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ACCEPTED MANUSCRIPT List of figures Figure 1. Methyl esters (ME) yield versus time for alkali catalyzed transesterification Figure 2. Plot of first order model
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Figure 3. Plot of reaction rate constant versus temperature Figure 4. Plot of reaction rate constants (k) versus temperature (K)
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Figure 1: Methyl esters (ME) yield versus time for alkali catalyzed transesterification
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Figure 2: Plot of first order model
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32
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Figure 3: Plot of reaction rate constant versus temperature
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Figure 4: Plot of reaction rate constants (k) versus temperature (K)
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