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Preparation of biodiesel from Idesia polycarpa var. vestita fruit oil
i n d u s t r i a l c r o p s a n d p r o d u c t s 2 9 ( 2 0 0 9 ) 622–628
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Preparation of biodiesel from Idesia polycarpa var. vestita fruit oil Fang-Xia Yang a , Yin-Quan Su a , Xiu-Hong Li a , Qiang Zhang a , Run-Cang Sun b,c,∗ a b c
College of Forestry, The North-Western University of Agricultural and Forest, Yangling, China Institute of Biomass Chemistry and Technology, Beijing Forestry University, Beijing, China State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, Guangzhou, China
a r t i c l e
i n f o
a b s t r a c t
Article history:
The feasibility of producing biodiesel from Idesia polycarpa var. vestita fruit oil was studied.
Received 6 June 2008
A methyl ester biodiesel was prepared from refined I. polycarpa fruit oil using methanol and
Received in revised form
potassium hydroxide (KOH) in an alkali-catalyzed transesterification process. The exper-
14 December 2008
imental variables investigated in this study were catalyst concentration (0.5–2.0 wt.% of
Accepted 15 December 2008
oil), methanol/oil molar ratio (4.5:1 to 6.5:1), temperature (20–60 ◦ C) and reaction time (20–60 min). A maximum yield of over 99% of methyl esters in I. polycarpa fruit oil biodiesel was achieved using a 6:1 molar ratio of methanol to oil, 1.0% KOH (% oil) and reaction time
Keywords:
for 40 min at 30 ◦ C. The properties of I. polycarpa fruit oil methyl esters produced under opti-
Biodiesel
mum conditions were also analyzed for specifications for biodiesel as fuel in diesel engines
Idesia polycarpa var.
according to China Biofuel Systems Standards. The fuel properties of the I. polycarpa fruit
Methanolysis
oil biodiesel obtained are similar to the No. 0 light diesel fuel and most of the parameters
Fruit oil
comply with the limits established by specifications for biodiesel.
Transesterification
1.
Introduction
Biodiesel, namely fuel fatty acid methyl ester (FAME), has been thought as a good alternative to petroleum fuel and is receiving increasing attention worldwide (Dmytryshyn et al., 2004; Vicente et al., 1998). Vegetable oils and fats are the main feedstock for biodiesel. Currently, the technology of biodiesel production from vegetable oil feedstock is clearly defined. A sustainable supply of less expensive oil will be a crucial factor for biodiesel to be competitive commercially (Dorado and Lóperz, 2006). Idesia polycarpa var. vestita, usually a tall tree, about 15 m high, is mainly distributed in the provinces to the south of Qinling mountain and Huaihe River in China. Its red ripe fruit consists of yellow pulp and dark greenish yellow seed. Fig. 1 shows the close view of the fruits of I. polycarpa var.
∗
© 2009 Elsevier B.V. All rights reserved.
vestita and the seeds in its fruits. The oil contents in pulp and seed are about 26.15% and 26.26% (% dry basis), respectively. The yields of oil are 1.5–2.5 kg per tree and 2.25–3.75 tons per hectare, respectively. Its fruit is harvested by hand one time per year. Historically the tree was planted in a large scale for the purpose of eating its oil because the oil of I. polycarpa var. vestita contains unsaturated fatty acids and multiplex vitamin, which make it good to one who have cardiovascular or hyperlipidemia disease (Rui et al., 2004). However, with the development of medical technology, the fruit oil currently is underutilized for it having bitter taste and susceptible to oxidation. The oil from I. polycarpa var. vestita fruit can be recovered in high yield by mechanical expeller and the resulting defatted fruit meals have demonstrated both herbicidal activity on Monochoria vaginalis in rice field and function as fertilizer (Shi et al., 2005). Therefore, I. polycarpa fruit oil has
Corresponding author at: Institute of Biomass Chemistry and Technology, Beijing Forestry University, Beijing, China. E-mail address: [email protected] (R.-C. Sun). 0926-6690/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.indcrop.2008.12.004
i n d u s t r i a l c r o p s a n d p r o d u c t s 2 9 ( 2 0 0 9 ) 622–628
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Fig. 1 – Fruit of Idesia polycarpa var.
great potential of using as a feedstock for biodiesel production in terms of reducing the producing cost, because the fruit of I. polycarpa var. vestita can be explored comprehensively and the oil is under explored currently. Presently alkali-catalyzed transesterification process is adopted mostly in commercial scale for producing biodiesel. But the alkali-catalyzed transesterification process with vegetable oil will have a low conversion if the free fatty acid content in the parent oil is over 1% (w/w) (Ghadge and Raheman, 2005, 2006; Ramadhas et al., 2005). The acid value of I. polycarpa fruit oil produced by mechanical expeller is about 2 mg KOH g−1 (about 1% FFA) and increases on storage due to inappropriate condition. In addition, there are few reports for preparing biodiesel from tree seed oil (dos Santos et al., 2008; Ghadge and Raheman, 2006; Naik et al., 2008; Ramadhas et al., 2005), and there is no report for producing biodiesel from I. polycarpa fruit oil. The main objective of the present work was, therefore, to determine the feasibility of producing biodiesel from I. polycarpa fruit oil.
2.
Materials and methods
2.1.
Materials
The I. polycarpa fruit oil was donated by Gold Sun Oil Company of Hancheng city (Hanzhong, China). The oil was refined by neutralization with Na2 CO3 (105 g/kg, Na2 CO3 /oil) as described (Yang et al., 2007). The resulting refined oil was stored at 4–8 ◦ C until used. Palmitic acid methyl ester, stearic acid methyl ester, oleic acid methyl, linoleic acid methyl ester, linolenic acid methyl ester, palmitoleic acid methyl ester and tridecane acid methyl ester were purchased from Fluka (Sigma–Aldrich, USA) and were chromatographically pure. All other chemicals were obtained commercially and were of analytical grade.
2.2.
immersing the flask in a thermostatic water bath. All experiments were repeated in triplicate. To obtain the optimum transesterification condition of I. polycarpa fruit oil, the main variables, such as catalyst concentration (0.5–2.0 wt.% of oil), methanol/oil molar ratio (4.5:1 to 6.5:1), temperature (20–60 ◦ C) and reaction time (20–60 min) were investigated. About 200 ml refined I. polycarpa fruit oil was poured into the reaction flask and preheated to the desired reaction temperature. To maintain the catalytic activity, the solution of KOH and methanol was prepared freshly with a reflux condenser to avoid methanol losses and prevent moisture absorbance in an Erlenmeyer flask, and then preheated to the reaction temperature. Finally, the methanolic solution was added to the refined I. polycarpa fruit oil in the reaction flask and the measurement of time was started at this point. At consistently spaced periods, about 25 ml of sample was withdrawn and quickly mixed with 0.4 ml concentrated hydrochloric acid to stop the reaction. Each experiment was allowed to prolong for 2.5 h conduct to ensure the completion of the conversion of the fatty acids into fatty acid methyl esters (FAMEs) under constant stirring speed (600 rpm). The samples of reaction mixture were allowed to settle overnight. The lower layer, containing glycerol and impurities, was drained off. The upper layer, which contained FAME, was vaporized with a Rota-Evaporator at 60 ◦ C to eliminate most of the methanol. Water washing was found to be an inefficient method because of the large amount of water used and the soap emulsion was difficult to remove. After the entire methanol was boiled off, silica gel was added to the FAME phase. Stirred for about 0.5 h to remove the remaining methanol and KOH (Dmytryshyn et al., 2004). The silica gel was removed by filtration. Finally, the FAME was dried using anhydrous sodium sulphate at least for 4 h. After removing the sodium sulphate, the biodiesel produced was stored at 4–8 ◦ C in a refrigerator for subsequent analyses. The biodiesel yield was determined by gas chromatography and expressed in terms of the percentage (wt.%) fatty acid methyl esters formed.
Optimization of transesterification reaction 2.3.
All transesterification reactions were carried out under atmosphere pressure. The reaction vessel was a 2 l, 4-necked round bottom flask equipped with a reflux condenser, a digital variable speed mechanical stirrer, a thermometer and an inlet for the reactants. The reaction temperature was controlled by
Analyses of oils and fatty acid methyl esters
Acid values of crude oil, refined oil and biodiesel were determined by the acid–base titration technique as the standards of the authorities of China. The amount of methyl esters in the product of I. polycarpa fruit oil biodiesel was analysed on an
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i n d u s t r i a l c r o p s a n d p r o d u c t s 2 9 ( 2 0 0 9 ) 622–628
Agilent 6890 gas chromatograph (Agilent Technologies, USA) with a DB-WAX capillary column measuring 30 m × 0.32 mm i.d. × 0.25 m (Agilent Technologies, USA). The initial GC oven temperature was kept at 150 ◦ C for 0.5 min, heated at 25 ◦ C/min up to 190 ◦ C, then heated at 3 ◦ C/min up to 240 ◦ C, where it was kept for 3 min. The detector was a flame ionization detector (FID) with a detecting temperature of 300 ◦ C. A split ratio of 100:1 and the carrier gas of nitrogen (1 ml/min) were used. The biodiesel yield, described as the amount of FAMEs formed in the transesterification reaction, was quantified in the presence of tridecane acid methyl ester as internal standard. Approximately 0.16 g of the biodiesel products were weighed in a vial and dissolved with 5 ml acetone. A sample of tridecane acid methyl ester solution (0.2 g/100 ml acetone) was added. Then triplicate samples (1 l) of the solution of tridecane acid methyl ester and biodiesel product were injected into the GC. All samples were analysed at the same condition, and all peaks were quantified by internal standard method. The fatty acids were identified by comparison of retention times of the oil components with those of standards. Fuel properties (flash point, cetane index and viscosity etc.) of FAME were determined as per the standards prescribed by the authorities of China (GB standards, specifications for biodiesel and light diesel as fuel in diesel engines).
3.
Result and discussion
3.1.
Characterization of I. polycarpa fruit oil
acid, oleic acid and linoleic acid. Of these, linoleic acid (C18:2) is the most prevalent unsaturated fatty acid up to 70%, and total content of unsaturated fatty acids is over 83%; Palmitic acid (C16:0, 15.06%) is the predominate saturated fatty acid. Also significant is the disproportionately high content (5.5%) of oleic acid in I. polycarpa fruit oil compared to other more conventional oilseed crops. According to previous works of many researchers (dos Santos et al., 2008; Hamed et al., 2008; Holser and Harry-OKuru, 2006; Mether et al., 2006a,b; Naik et al., 2008; Neyda et al., 2008), this oil is of great potential for providing a novel source of triglycerides for converting to biodiesel in terms of its fatty acid composition. In addition, the basecatalyzed transesterification has been applied for biodiesel production successfully using the oils such as rapeseed oil (Rashid et al., 2008), J. curcas oil (Tiwari et al., 2007), Karanja oil (Naik et al., 2008) and soybean oil (Ji et al., 2006), and the I. polycarpa fruit oil has a very similar fatty acid composition with oleic acid and linoleic acid being the major acids (above 76%). Therefore, the I. polycarpa fruit oil could be potentially used as biodiesel producing feedstock in terms of its chemical composition.
3.2. Transesterification of the Idesia polycarpa var. seed oil The variables affecting transesterification such as catalyst concentration (0.5–2.0 wt.% of oil), methanol/oil molar ratio (4.5:1 to 6.5:1), temperature (20–60 ◦ C) and reaction time (20–60 min) were investigated to obtain an optimum reaction condition.
The quality of I. polycarpa fruit oil was expressed in terms of the physicochemical properties such as acid value, saponification value etc. These properties of crude I. polycarpa fruit oil were determined as per Bureau of China Standard. The acid value and the saponification value of the oil were 2.8–8.3 mg KOH g−1 and 188.7–193.9 mg KOH g−1 , respectively. The fatty acid profiles of I. polycarpa fruit oil are given in Table 1. The data listed in Table 1 for comparison purposes are the fatty acid profiles of rapeseed, soybean, Jatropha curcas and Karanja oils. These data demonstrates that the I. polycarpa fruit oil mainly contains five fatty acids viz. palmitic acid, stearic acid, palmitoleic
3.2.1.
Influence of catalyst concentration
The effects of KOH concentrations on the transesterification of the I. polycarpa fruit oil were investigated with concentration varying from 0.5% to 2.0% (based on the weight of oil, plus the amount needed to neutralize the free fatty acids in the refined I. polycarpa fruit oil). The reaction conditions during the whole process were fixed at: reaction temperature of 40 ◦ C, reaction time of 2.5 h, molar ratio of methanol to oil at 5:1 and stirring speed 600 rpm. Fig. 2 shows the yields of methyl esters at different catalyst concentrations. The lowest cata-
Table 1 – Properties of I. polycarpa fruit oil in comparison with the other oils. Fatty acid
I. polycarpa fruit oila (%)
Rapeseed oilb (%)
Jatropha curcas oilc (%)
Karanja oild (%)
Soybeane (%)
Saturated C16 C18
15.06 1.18
3.6 1.5
16.0 (max) 6–7.0
11.65 7.5
12.9 3.7
Unsaturated C16:1 C18:1 C18:2
6.5 5.5 70.6
61.6 21.7
1-3.5 42-43.5 33-34.4
51.59 16.64
0.1 22.2 52.9
1.1
0
>4.5
C18:3 a b c d e
I. polycarpa fruit oil represents Idesia polycarpa var. fruit oil. Rashid et al. (2008). Neyda et al. (2008). Naik et al. (2008). Holser and Harry-OKuru (2006).
7.9
i n d u s t r i a l c r o p s a n d p r o d u c t s 2 9 ( 2 0 0 9 ) 622–628
Fig. 2 – Influence of KOH concentration on methanolysis of I. polycarpa fruit oil (methanol/oil molar ratio 5:1, temperature 40 ◦ C, rate of stirring 600 rpm).
lyst concentration i.e. 0.5% of KOH was insufficient to catalyze the reaction for completion and the maximum yield of methyl esters was less than 90% during the reaction process. However, as it can be observed, the highest methyl esters yield (95.8%) was achieved for catalyst concentration of 1.0%. With the increase in the concentration of catalyst, there was a decrease in the yield of methyl esters. This is in accordance with the results obtained by Mether et al. (2006a,b), Rashid et al. (2008) and Sinha et al. (2008). The reason for this decreasing rend was due to the formation of soap in presence of high amount of catalysts, which increased the viscosity of the reactants and lowered the yield of ester. As can be seen, the yield of methyl ester was not significant among 1%, 1.5% and 2.0% KOH concentration (P > 0.05). However, the yield of methyl ester of 0.5% KOH concentration was lower than that of other KOH concentration (P < 0.05) at every reaction time point. Vicente et al. (1998) employed the factorial design of experiments and response surface methodology to optimize sunflower oil biodiesel production, and the results showed that the high catalyst concentrations should be avoided with NaOH as a catalyst. Therefore, 1.0% KOH was optimal in the reactions of this study.
3.2.2.
Influence of methanol/oil molar ratio
The alcohol to oil molar ratio is one of the important factors that affect the conversion efficiency of transesterification. Stoichiometrically, 3 mol of alcohol are required for each mol of triglyceride, in practice a higher molar ratio is used for getting greater yields of fatty acid methyl esters. However, too high molar ratio of alcohol to oil slows down the separation of the glycerin phase and the methyl ester phase (Antolín et al., 2002; Rashid and Anwar, 2008; Sharma et al., 2008) and lowers the yield of methyl esters (Rashid et al., 2008). Commonly, the molar ratio have no an effect on the acid value, peroxide, saponification and iodine value of fatty acid methyl esters (Mether et al., 2006a,b). The research results obtained from Muniyappa et al. (1996) showed that the optimal methanol
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Fig. 3 – Influence of molar ratio on methanolysis of I. polycarpa fruit oil (KOH 1%, temperature 40 ◦ C, rate of mixing 600 rpm).
amount should be 2–10 times of the stoichiometrical one. In the present work, the transesterification of refined I. polycarpa fruit oil was carried out at 4.5:1, 5:1, 5.5:1, 6:1 and 6.5:1 molar ratios of methanol to oil. The KOH catalyst concentration was fixed at 1%, the optimum concentration determined in the previous section. The reaction temperature was also set at 40 ◦ C. As shown in Fig. 3, the yield was greatly influenced by the quantity of methanol. When the molar ratio was increased from 4.5:1 to 6:1, the yield of methyl ester also increased from 92.4 ± 0.4% to 98.5 ± 0.8% after 30 min and the yield of methyl ester was significant higher at oil molar ratio to 6:1 than that of at other ratios (P < 0.05). A further increase in the methanol to oil molar ratio to 6.5:1 resulted in a significant decrease in yield (2.9%, P < 0.05) at 30 min. Therefore, the optimum quantity of methanol was 6:1 molar ratio of methanol to oil.
3.2.3.
Influence of reaction temperature
Transesterification can occur at different temperatures, depending on the oil used (Mether et al., 2006a,b). Alkaline alcoholysis of vegetable oils is normally performed at temperature range between 45 ◦ C and 65 ◦ C by the researchers (Sharma et al., 2008). The report from Oliverira et al. (2008) showed that the methanolysis of coffee oil carried out at room temperature lead to higher ester conversions than at higher temperatures with sodium methoxide as a catalyst. To study the effect of reaction temperatures on I. polycarpa fruit oil methanolysis, experimental trials were carried out at temperatures of room temperature 20 ◦ C, 30 ◦ C, 40 ◦ C and 60 ◦ C, with 1.0% KOH as a catalyst and a methanol/oil molar ratio of 6:1. The yields of I. polycarpa fruit oil methyl esters at different reaction temperatures are shown in Fig. 4. It was observed that 30 ◦ C was the optimum reaction temperature and the yield of methyl esters was 99.2 ± 0.4% after 30 min under this reaction temperature. This is in accordance with the results obtained by Oliverira et al. (2008). Thus, an optimal reaction temperature of 30 ◦ C was used for I. polycarpa fruit oil transesterification in this study.
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i n d u s t r i a l c r o p s a n d p r o d u c t s 2 9 ( 2 0 0 9 ) 622–628
Fig. 4 – Influence of temperature on methanolysis of I. polycarpa fruit oil (KOH 1%, MeOH/oil molar ratio 6:1, rate of mixing 600 rpm).
3.2.4.
Influence of reaction time
The yield of methyl esters of transesterification commonly increases with the reaction time. Mether et al. (2006a,b) transesterified Pongamia pinnata oil with methanol and KOH as a catalyst, the yield of methyl esters was more than 90% within 5 min, and from 0.5 h to 3 h the yield of methyl esters increased slowly from 96% to 97%. Freedman et al. (1984) transesterified peanut, cotton-seed, sunflower and soybean oil under the condition of a methanol/oil molar ratio 6:1, 0.5% NaOH catalyst and 60 ◦ C. An approximate yield of 80% was observed after 1 min for soybean and sunflower oils. After 1 h, the conversion was almost the same for all four oils (93–98%). In this study, as it can be seen from the above-mentioned results, the yields of methyl esters arrived at the maximum value at the reaction
Fig. 5 – Influence of reaction time on methanolysis of I. polycarpa fruit oil (KOH 1%, MeOH/oil molar ratio 6:1, rate of mixing 600 rpm, temperature 30 ◦ C).
time around 30 min and then there was slightly decrease starting from the reaction time 60 min. In order to investigate the optimum reaction time, experiments were carried out at reaction times of 20 min, 30 min, 40 min, 50 min and 60 min under the reaction condition of methanol/oil molar ratio 6:1, KOH 1%, stirring speed 600 rpm and reaction temperature 30 ◦ C. The influence of reaction time on the efficiency of methanolysis of I. polycarpa fruit oil is demonstrated in Fig. 5. It was observed that 40 min was the optimal reaction time. This is in consistent with the reports by other researchers, such as Mether et al. (2006a,b) mentioned above.
3.3.
Fuel properties of I. polycarpa fruit oil biodiesel
The I. polycarpa fruit oil methyl ester sample used to determine the fuel properties was prepared using the optimum condi-
Table 2 – Fuel properties of I. polycarpa fruit oil biodiesel. Properties
Test methods
Density (15 ◦ C) (kg/m3 ) Kinematic viscosity (40 ◦ C) (mm2 /s) CFPP (◦ C) Cloud point (◦ C) Cetane index Flash point (◦ C) Acid value (mg KOH/g) Carbon residue (10% dist. residue) Copper corrosion, 3 h at 50 ◦ C ◦
90% distillation temperature ( C)
Limits
GB/T1884 GB/T265 SH/T0248 GB/T510 GB/T11139 GB/T261 GB/T258 GB/T268 GB/T5096
– 1.9–6.0 e ≤4 e ≤0 e ≥45 >130 ≤0.8 ≤0.3 ≤1
GB/T6536
≤360
a Rapeseed oil methyl esters
880 4.15 -9 -3 50.4 165 0.25
Soybean oil methyl esters b,c
881–885 4.1–5.75 d −5
b , c ,d
f, d
48.84–56 168 c, d 0.3–0.45
d
1a e
331.7
I. polycarpa fruit oil methyl esters 886.20 4.12 −2 −4 47 >174 0.27 0.30 1a 354.50
◦
CFPP: cold filter plugging point ( C). a b c d e
f
Rashid et al. (2008). dos Santos et al. (2008). Albuquerque et al. (2009). Candeia et al. (2008). Represents the limit is for No. 0 light diesel fuel and the parameter determined as per the standards for light diesel fuel prescribed by the authority of China. Alcantara et al. (2000).
i n d u s t r i a l c r o p s a n d p r o d u c t s 2 9 ( 2 0 0 9 ) 622–628
tions determined in this study (600 rpm, 6:1 molar ratio of methanol to oil, 1.0% KOH, 30 ◦ C, and reaction time for 40 min). Some important fuel properties of I. polycarpa fruit oil biodiesel are presented in Table 2, in which most of these parameters are complied with the limits for use in diesel engine in China (China Biofuel Systems Group Ltd., Biodiesel Standards, 2007) and Europe (EN 14213). The data demonstrated in Table 2 for comparison purposes are the fuel properties of rapeseed and soybean oil methyl esters. Soybean oil and rapeseed oil are the two commonly used oil for biodiesel. As can be seen, the data in Table 2 indicate that the main fuel properties of I. polycarpa fruit oil methyl ester exhibit a similarity with that of the methyl esters of the two oils except that the cetane index of the I. polycarpa fruit oil biodiesel is slightly lower than that prescribed by the specifications for biodiesel, and also lower than that of soybean and rapeseed biodiesel. As mentioned by Knothe (2005), the properties of the various individual fatty esters that comprise biodiesel determine the overall fuel properties of the biodiesel fuel. Important fuel properties of biodiesel, such as cetane number, cold flow and viscosity and so on, are strongly influenced by the fatty acid profiles, viz. chain length, degree of unsaturation and branching of the chain of fatty acid. The cetane number, melting point, heat of combustion and viscosity of neat fatty compounds increase with increasing chain length and decrease with increasing unsaturation. The data in Table 1 also demonstrate that the values of total unsaturated fatty acids in I. polycarpa fruit oil, rapeseed and soybean oils are very similar (83.7% vs. 83.1% in soybean and 83.3% in rapeseed oils), however, the contents of linoleic acid and oleic acid are different. The linoleic acid content in I. polycarpa fruit, soybean and rapeseed oils are 70.6%, 52.9% and 21.7%, respectively. The oleic acid in I. polycarpa fruit, soybean and rapeseed oils are 5.5%, 22.2% and 61.6%, respectively. Further, the cetane numbers of methyl oleate and methyl linoleate are 59.3 and 38.2, respectively, in the IQTTM (Knothe, 2005). Therefore, oleic fatty acid in the oil exhibits a combination of improved cetane number and the relatively lower cetane number of I. polycarpa fruit oil biodiesel is well explained. In all, as performed in Table 2, the fuel properties of the I. polycarpa fruit oil biodiesel are similar to No. 0 light diesel.
4.
Conclusions
The above results revealed that the maximum yield of methyl esters in the I. polycarpa fruit oil biodiesel product was over 99% under the optimum reaction condition, viz. 600 rpm, 6:1 molar ratio of methanol to oil, 1.0% KOH, 30 ◦ C, and reaction time for 40 min. The I. polycarpa fruit oil biodiesel obtained has the fuel properties that comply with the limits established by China specifications for biodiesel and light diesel as fuel in diesel engines and is similar to the No. 0 light diesel fuel, except for a somewhat lower cetane index (47) than that prescribed by the standards for biodiesel. Thus, biodiesel derived from I. polycarpa fruit oil is an acceptable substitute for petrodiesel, also when compared to biodiesel fuels derived from other vegetable oils. Therefore, the I. polycarpa fruit oil can be potentially used as a raw feedstock for producing biodiesel in commercial scale in China.
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Acknowledgments This work was supported by the grants from the Natural Science Foundation of China (No. 30710103906), China Ministry of Education (No. 111), the Guangdong Natural Science Foundation (No. 07118057), and State Forestry Administration (200804015).
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Sharma, Y.C., Singh, B., Upadhyay, S.N., 2008. Advancements in development and characterization of biodiesel: a review. Fuel 87, 2355–2373. Sinha, S., Agarwal, A.K., Garg, S., 2008. Biodiesel development from rice bran oil: transesterification process optimization and fuel characterization. Energy Convers. Manage. 49, 1248–1257. Tiwari, A.K., Kumar, A., Raheman, H., 2007. Biodiesel production from jatropha oil (Jatropha curcas) with high free fatty acids: an optimized process. Biomass Bioenergy 31, 569–575. Vicente, G., Coteron, A., Martinez, M., Aracil, J., 1998. Application of the factorial design of experiments and response surface methodology to optimize biodiesel production. Ind. Crops Prod. 8, 29–35. Shi, W.S., Liu, J.L., Lei, Q., 2005. A Study on the Control Effect of Idesia polycarpa var. vestita Drugs on Monochoria vaginalis. J. Northwest Forestry Univ. 20, 119–121. Yang, F.X., Su, Y.Q., Li, X.H., 2007. The research on alkali-refining of Idesia polycarpa var.vestita bites. J. Northwest A & F Univ. (Nat. Sci. Ed.) 35, 203–207.
available at www.sciencedirect.com
journal homepage: www.elsevier.com/locate/indcrop
Preparation of biodiesel from Idesia polycarpa var. vestita fruit oil Fang-Xia Yang a , Yin-Quan Su a , Xiu-Hong Li a , Qiang Zhang a , Run-Cang Sun b,c,∗ a b c
College of Forestry, The North-Western University of Agricultural and Forest, Yangling, China Institute of Biomass Chemistry and Technology, Beijing Forestry University, Beijing, China State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, Guangzhou, China
a r t i c l e
i n f o
a b s t r a c t
Article history:
The feasibility of producing biodiesel from Idesia polycarpa var. vestita fruit oil was studied.
Received 6 June 2008
A methyl ester biodiesel was prepared from refined I. polycarpa fruit oil using methanol and
Received in revised form
potassium hydroxide (KOH) in an alkali-catalyzed transesterification process. The exper-
14 December 2008
imental variables investigated in this study were catalyst concentration (0.5–2.0 wt.% of
Accepted 15 December 2008
oil), methanol/oil molar ratio (4.5:1 to 6.5:1), temperature (20–60 ◦ C) and reaction time (20–60 min). A maximum yield of over 99% of methyl esters in I. polycarpa fruit oil biodiesel was achieved using a 6:1 molar ratio of methanol to oil, 1.0% KOH (% oil) and reaction time
Keywords:
for 40 min at 30 ◦ C. The properties of I. polycarpa fruit oil methyl esters produced under opti-
Biodiesel
mum conditions were also analyzed for specifications for biodiesel as fuel in diesel engines
Idesia polycarpa var.
according to China Biofuel Systems Standards. The fuel properties of the I. polycarpa fruit
Methanolysis
oil biodiesel obtained are similar to the No. 0 light diesel fuel and most of the parameters
Fruit oil
comply with the limits established by specifications for biodiesel.
Transesterification
1.
Introduction
Biodiesel, namely fuel fatty acid methyl ester (FAME), has been thought as a good alternative to petroleum fuel and is receiving increasing attention worldwide (Dmytryshyn et al., 2004; Vicente et al., 1998). Vegetable oils and fats are the main feedstock for biodiesel. Currently, the technology of biodiesel production from vegetable oil feedstock is clearly defined. A sustainable supply of less expensive oil will be a crucial factor for biodiesel to be competitive commercially (Dorado and Lóperz, 2006). Idesia polycarpa var. vestita, usually a tall tree, about 15 m high, is mainly distributed in the provinces to the south of Qinling mountain and Huaihe River in China. Its red ripe fruit consists of yellow pulp and dark greenish yellow seed. Fig. 1 shows the close view of the fruits of I. polycarpa var.
∗
© 2009 Elsevier B.V. All rights reserved.
vestita and the seeds in its fruits. The oil contents in pulp and seed are about 26.15% and 26.26% (% dry basis), respectively. The yields of oil are 1.5–2.5 kg per tree and 2.25–3.75 tons per hectare, respectively. Its fruit is harvested by hand one time per year. Historically the tree was planted in a large scale for the purpose of eating its oil because the oil of I. polycarpa var. vestita contains unsaturated fatty acids and multiplex vitamin, which make it good to one who have cardiovascular or hyperlipidemia disease (Rui et al., 2004). However, with the development of medical technology, the fruit oil currently is underutilized for it having bitter taste and susceptible to oxidation. The oil from I. polycarpa var. vestita fruit can be recovered in high yield by mechanical expeller and the resulting defatted fruit meals have demonstrated both herbicidal activity on Monochoria vaginalis in rice field and function as fertilizer (Shi et al., 2005). Therefore, I. polycarpa fruit oil has
Corresponding author at: Institute of Biomass Chemistry and Technology, Beijing Forestry University, Beijing, China. E-mail address: [email protected] (R.-C. Sun). 0926-6690/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.indcrop.2008.12.004
i n d u s t r i a l c r o p s a n d p r o d u c t s 2 9 ( 2 0 0 9 ) 622–628
623
Fig. 1 – Fruit of Idesia polycarpa var.
great potential of using as a feedstock for biodiesel production in terms of reducing the producing cost, because the fruit of I. polycarpa var. vestita can be explored comprehensively and the oil is under explored currently. Presently alkali-catalyzed transesterification process is adopted mostly in commercial scale for producing biodiesel. But the alkali-catalyzed transesterification process with vegetable oil will have a low conversion if the free fatty acid content in the parent oil is over 1% (w/w) (Ghadge and Raheman, 2005, 2006; Ramadhas et al., 2005). The acid value of I. polycarpa fruit oil produced by mechanical expeller is about 2 mg KOH g−1 (about 1% FFA) and increases on storage due to inappropriate condition. In addition, there are few reports for preparing biodiesel from tree seed oil (dos Santos et al., 2008; Ghadge and Raheman, 2006; Naik et al., 2008; Ramadhas et al., 2005), and there is no report for producing biodiesel from I. polycarpa fruit oil. The main objective of the present work was, therefore, to determine the feasibility of producing biodiesel from I. polycarpa fruit oil.
2.
Materials and methods
2.1.
Materials
The I. polycarpa fruit oil was donated by Gold Sun Oil Company of Hancheng city (Hanzhong, China). The oil was refined by neutralization with Na2 CO3 (105 g/kg, Na2 CO3 /oil) as described (Yang et al., 2007). The resulting refined oil was stored at 4–8 ◦ C until used. Palmitic acid methyl ester, stearic acid methyl ester, oleic acid methyl, linoleic acid methyl ester, linolenic acid methyl ester, palmitoleic acid methyl ester and tridecane acid methyl ester were purchased from Fluka (Sigma–Aldrich, USA) and were chromatographically pure. All other chemicals were obtained commercially and were of analytical grade.
2.2.
immersing the flask in a thermostatic water bath. All experiments were repeated in triplicate. To obtain the optimum transesterification condition of I. polycarpa fruit oil, the main variables, such as catalyst concentration (0.5–2.0 wt.% of oil), methanol/oil molar ratio (4.5:1 to 6.5:1), temperature (20–60 ◦ C) and reaction time (20–60 min) were investigated. About 200 ml refined I. polycarpa fruit oil was poured into the reaction flask and preheated to the desired reaction temperature. To maintain the catalytic activity, the solution of KOH and methanol was prepared freshly with a reflux condenser to avoid methanol losses and prevent moisture absorbance in an Erlenmeyer flask, and then preheated to the reaction temperature. Finally, the methanolic solution was added to the refined I. polycarpa fruit oil in the reaction flask and the measurement of time was started at this point. At consistently spaced periods, about 25 ml of sample was withdrawn and quickly mixed with 0.4 ml concentrated hydrochloric acid to stop the reaction. Each experiment was allowed to prolong for 2.5 h conduct to ensure the completion of the conversion of the fatty acids into fatty acid methyl esters (FAMEs) under constant stirring speed (600 rpm). The samples of reaction mixture were allowed to settle overnight. The lower layer, containing glycerol and impurities, was drained off. The upper layer, which contained FAME, was vaporized with a Rota-Evaporator at 60 ◦ C to eliminate most of the methanol. Water washing was found to be an inefficient method because of the large amount of water used and the soap emulsion was difficult to remove. After the entire methanol was boiled off, silica gel was added to the FAME phase. Stirred for about 0.5 h to remove the remaining methanol and KOH (Dmytryshyn et al., 2004). The silica gel was removed by filtration. Finally, the FAME was dried using anhydrous sodium sulphate at least for 4 h. After removing the sodium sulphate, the biodiesel produced was stored at 4–8 ◦ C in a refrigerator for subsequent analyses. The biodiesel yield was determined by gas chromatography and expressed in terms of the percentage (wt.%) fatty acid methyl esters formed.
Optimization of transesterification reaction 2.3.
All transesterification reactions were carried out under atmosphere pressure. The reaction vessel was a 2 l, 4-necked round bottom flask equipped with a reflux condenser, a digital variable speed mechanical stirrer, a thermometer and an inlet for the reactants. The reaction temperature was controlled by
Analyses of oils and fatty acid methyl esters
Acid values of crude oil, refined oil and biodiesel were determined by the acid–base titration technique as the standards of the authorities of China. The amount of methyl esters in the product of I. polycarpa fruit oil biodiesel was analysed on an
624
i n d u s t r i a l c r o p s a n d p r o d u c t s 2 9 ( 2 0 0 9 ) 622–628
Agilent 6890 gas chromatograph (Agilent Technologies, USA) with a DB-WAX capillary column measuring 30 m × 0.32 mm i.d. × 0.25 m (Agilent Technologies, USA). The initial GC oven temperature was kept at 150 ◦ C for 0.5 min, heated at 25 ◦ C/min up to 190 ◦ C, then heated at 3 ◦ C/min up to 240 ◦ C, where it was kept for 3 min. The detector was a flame ionization detector (FID) with a detecting temperature of 300 ◦ C. A split ratio of 100:1 and the carrier gas of nitrogen (1 ml/min) were used. The biodiesel yield, described as the amount of FAMEs formed in the transesterification reaction, was quantified in the presence of tridecane acid methyl ester as internal standard. Approximately 0.16 g of the biodiesel products were weighed in a vial and dissolved with 5 ml acetone. A sample of tridecane acid methyl ester solution (0.2 g/100 ml acetone) was added. Then triplicate samples (1 l) of the solution of tridecane acid methyl ester and biodiesel product were injected into the GC. All samples were analysed at the same condition, and all peaks were quantified by internal standard method. The fatty acids were identified by comparison of retention times of the oil components with those of standards. Fuel properties (flash point, cetane index and viscosity etc.) of FAME were determined as per the standards prescribed by the authorities of China (GB standards, specifications for biodiesel and light diesel as fuel in diesel engines).
3.
Result and discussion
3.1.
Characterization of I. polycarpa fruit oil
acid, oleic acid and linoleic acid. Of these, linoleic acid (C18:2) is the most prevalent unsaturated fatty acid up to 70%, and total content of unsaturated fatty acids is over 83%; Palmitic acid (C16:0, 15.06%) is the predominate saturated fatty acid. Also significant is the disproportionately high content (5.5%) of oleic acid in I. polycarpa fruit oil compared to other more conventional oilseed crops. According to previous works of many researchers (dos Santos et al., 2008; Hamed et al., 2008; Holser and Harry-OKuru, 2006; Mether et al., 2006a,b; Naik et al., 2008; Neyda et al., 2008), this oil is of great potential for providing a novel source of triglycerides for converting to biodiesel in terms of its fatty acid composition. In addition, the basecatalyzed transesterification has been applied for biodiesel production successfully using the oils such as rapeseed oil (Rashid et al., 2008), J. curcas oil (Tiwari et al., 2007), Karanja oil (Naik et al., 2008) and soybean oil (Ji et al., 2006), and the I. polycarpa fruit oil has a very similar fatty acid composition with oleic acid and linoleic acid being the major acids (above 76%). Therefore, the I. polycarpa fruit oil could be potentially used as biodiesel producing feedstock in terms of its chemical composition.
3.2. Transesterification of the Idesia polycarpa var. seed oil The variables affecting transesterification such as catalyst concentration (0.5–2.0 wt.% of oil), methanol/oil molar ratio (4.5:1 to 6.5:1), temperature (20–60 ◦ C) and reaction time (20–60 min) were investigated to obtain an optimum reaction condition.
The quality of I. polycarpa fruit oil was expressed in terms of the physicochemical properties such as acid value, saponification value etc. These properties of crude I. polycarpa fruit oil were determined as per Bureau of China Standard. The acid value and the saponification value of the oil were 2.8–8.3 mg KOH g−1 and 188.7–193.9 mg KOH g−1 , respectively. The fatty acid profiles of I. polycarpa fruit oil are given in Table 1. The data listed in Table 1 for comparison purposes are the fatty acid profiles of rapeseed, soybean, Jatropha curcas and Karanja oils. These data demonstrates that the I. polycarpa fruit oil mainly contains five fatty acids viz. palmitic acid, stearic acid, palmitoleic
3.2.1.
Influence of catalyst concentration
The effects of KOH concentrations on the transesterification of the I. polycarpa fruit oil were investigated with concentration varying from 0.5% to 2.0% (based on the weight of oil, plus the amount needed to neutralize the free fatty acids in the refined I. polycarpa fruit oil). The reaction conditions during the whole process were fixed at: reaction temperature of 40 ◦ C, reaction time of 2.5 h, molar ratio of methanol to oil at 5:1 and stirring speed 600 rpm. Fig. 2 shows the yields of methyl esters at different catalyst concentrations. The lowest cata-
Table 1 – Properties of I. polycarpa fruit oil in comparison with the other oils. Fatty acid
I. polycarpa fruit oila (%)
Rapeseed oilb (%)
Jatropha curcas oilc (%)
Karanja oild (%)
Soybeane (%)
Saturated C16 C18
15.06 1.18
3.6 1.5
16.0 (max) 6–7.0
11.65 7.5
12.9 3.7
Unsaturated C16:1 C18:1 C18:2
6.5 5.5 70.6
61.6 21.7
1-3.5 42-43.5 33-34.4
51.59 16.64
0.1 22.2 52.9
1.1
0
>4.5
C18:3 a b c d e
I. polycarpa fruit oil represents Idesia polycarpa var. fruit oil. Rashid et al. (2008). Neyda et al. (2008). Naik et al. (2008). Holser and Harry-OKuru (2006).
7.9
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Fig. 2 – Influence of KOH concentration on methanolysis of I. polycarpa fruit oil (methanol/oil molar ratio 5:1, temperature 40 ◦ C, rate of stirring 600 rpm).
lyst concentration i.e. 0.5% of KOH was insufficient to catalyze the reaction for completion and the maximum yield of methyl esters was less than 90% during the reaction process. However, as it can be observed, the highest methyl esters yield (95.8%) was achieved for catalyst concentration of 1.0%. With the increase in the concentration of catalyst, there was a decrease in the yield of methyl esters. This is in accordance with the results obtained by Mether et al. (2006a,b), Rashid et al. (2008) and Sinha et al. (2008). The reason for this decreasing rend was due to the formation of soap in presence of high amount of catalysts, which increased the viscosity of the reactants and lowered the yield of ester. As can be seen, the yield of methyl ester was not significant among 1%, 1.5% and 2.0% KOH concentration (P > 0.05). However, the yield of methyl ester of 0.5% KOH concentration was lower than that of other KOH concentration (P < 0.05) at every reaction time point. Vicente et al. (1998) employed the factorial design of experiments and response surface methodology to optimize sunflower oil biodiesel production, and the results showed that the high catalyst concentrations should be avoided with NaOH as a catalyst. Therefore, 1.0% KOH was optimal in the reactions of this study.
3.2.2.
Influence of methanol/oil molar ratio
The alcohol to oil molar ratio is one of the important factors that affect the conversion efficiency of transesterification. Stoichiometrically, 3 mol of alcohol are required for each mol of triglyceride, in practice a higher molar ratio is used for getting greater yields of fatty acid methyl esters. However, too high molar ratio of alcohol to oil slows down the separation of the glycerin phase and the methyl ester phase (Antolín et al., 2002; Rashid and Anwar, 2008; Sharma et al., 2008) and lowers the yield of methyl esters (Rashid et al., 2008). Commonly, the molar ratio have no an effect on the acid value, peroxide, saponification and iodine value of fatty acid methyl esters (Mether et al., 2006a,b). The research results obtained from Muniyappa et al. (1996) showed that the optimal methanol
625
Fig. 3 – Influence of molar ratio on methanolysis of I. polycarpa fruit oil (KOH 1%, temperature 40 ◦ C, rate of mixing 600 rpm).
amount should be 2–10 times of the stoichiometrical one. In the present work, the transesterification of refined I. polycarpa fruit oil was carried out at 4.5:1, 5:1, 5.5:1, 6:1 and 6.5:1 molar ratios of methanol to oil. The KOH catalyst concentration was fixed at 1%, the optimum concentration determined in the previous section. The reaction temperature was also set at 40 ◦ C. As shown in Fig. 3, the yield was greatly influenced by the quantity of methanol. When the molar ratio was increased from 4.5:1 to 6:1, the yield of methyl ester also increased from 92.4 ± 0.4% to 98.5 ± 0.8% after 30 min and the yield of methyl ester was significant higher at oil molar ratio to 6:1 than that of at other ratios (P < 0.05). A further increase in the methanol to oil molar ratio to 6.5:1 resulted in a significant decrease in yield (2.9%, P < 0.05) at 30 min. Therefore, the optimum quantity of methanol was 6:1 molar ratio of methanol to oil.
3.2.3.
Influence of reaction temperature
Transesterification can occur at different temperatures, depending on the oil used (Mether et al., 2006a,b). Alkaline alcoholysis of vegetable oils is normally performed at temperature range between 45 ◦ C and 65 ◦ C by the researchers (Sharma et al., 2008). The report from Oliverira et al. (2008) showed that the methanolysis of coffee oil carried out at room temperature lead to higher ester conversions than at higher temperatures with sodium methoxide as a catalyst. To study the effect of reaction temperatures on I. polycarpa fruit oil methanolysis, experimental trials were carried out at temperatures of room temperature 20 ◦ C, 30 ◦ C, 40 ◦ C and 60 ◦ C, with 1.0% KOH as a catalyst and a methanol/oil molar ratio of 6:1. The yields of I. polycarpa fruit oil methyl esters at different reaction temperatures are shown in Fig. 4. It was observed that 30 ◦ C was the optimum reaction temperature and the yield of methyl esters was 99.2 ± 0.4% after 30 min under this reaction temperature. This is in accordance with the results obtained by Oliverira et al. (2008). Thus, an optimal reaction temperature of 30 ◦ C was used for I. polycarpa fruit oil transesterification in this study.
626
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Fig. 4 – Influence of temperature on methanolysis of I. polycarpa fruit oil (KOH 1%, MeOH/oil molar ratio 6:1, rate of mixing 600 rpm).
3.2.4.
Influence of reaction time
The yield of methyl esters of transesterification commonly increases with the reaction time. Mether et al. (2006a,b) transesterified Pongamia pinnata oil with methanol and KOH as a catalyst, the yield of methyl esters was more than 90% within 5 min, and from 0.5 h to 3 h the yield of methyl esters increased slowly from 96% to 97%. Freedman et al. (1984) transesterified peanut, cotton-seed, sunflower and soybean oil under the condition of a methanol/oil molar ratio 6:1, 0.5% NaOH catalyst and 60 ◦ C. An approximate yield of 80% was observed after 1 min for soybean and sunflower oils. After 1 h, the conversion was almost the same for all four oils (93–98%). In this study, as it can be seen from the above-mentioned results, the yields of methyl esters arrived at the maximum value at the reaction
Fig. 5 – Influence of reaction time on methanolysis of I. polycarpa fruit oil (KOH 1%, MeOH/oil molar ratio 6:1, rate of mixing 600 rpm, temperature 30 ◦ C).
time around 30 min and then there was slightly decrease starting from the reaction time 60 min. In order to investigate the optimum reaction time, experiments were carried out at reaction times of 20 min, 30 min, 40 min, 50 min and 60 min under the reaction condition of methanol/oil molar ratio 6:1, KOH 1%, stirring speed 600 rpm and reaction temperature 30 ◦ C. The influence of reaction time on the efficiency of methanolysis of I. polycarpa fruit oil is demonstrated in Fig. 5. It was observed that 40 min was the optimal reaction time. This is in consistent with the reports by other researchers, such as Mether et al. (2006a,b) mentioned above.
3.3.
Fuel properties of I. polycarpa fruit oil biodiesel
The I. polycarpa fruit oil methyl ester sample used to determine the fuel properties was prepared using the optimum condi-
Table 2 – Fuel properties of I. polycarpa fruit oil biodiesel. Properties
Test methods
Density (15 ◦ C) (kg/m3 ) Kinematic viscosity (40 ◦ C) (mm2 /s) CFPP (◦ C) Cloud point (◦ C) Cetane index Flash point (◦ C) Acid value (mg KOH/g) Carbon residue (10% dist. residue) Copper corrosion, 3 h at 50 ◦ C ◦
90% distillation temperature ( C)
Limits
GB/T1884 GB/T265 SH/T0248 GB/T510 GB/T11139 GB/T261 GB/T258 GB/T268 GB/T5096
– 1.9–6.0 e ≤4 e ≤0 e ≥45 >130 ≤0.8 ≤0.3 ≤1
GB/T6536
≤360
a Rapeseed oil methyl esters
880 4.15 -9 -3 50.4 165 0.25
Soybean oil methyl esters b,c
881–885 4.1–5.75 d −5
b , c ,d
f, d
48.84–56 168 c, d 0.3–0.45
d
1a e
331.7
I. polycarpa fruit oil methyl esters 886.20 4.12 −2 −4 47 >174 0.27 0.30 1a 354.50
◦
CFPP: cold filter plugging point ( C). a b c d e
f
Rashid et al. (2008). dos Santos et al. (2008). Albuquerque et al. (2009). Candeia et al. (2008). Represents the limit is for No. 0 light diesel fuel and the parameter determined as per the standards for light diesel fuel prescribed by the authority of China. Alcantara et al. (2000).
i n d u s t r i a l c r o p s a n d p r o d u c t s 2 9 ( 2 0 0 9 ) 622–628
tions determined in this study (600 rpm, 6:1 molar ratio of methanol to oil, 1.0% KOH, 30 ◦ C, and reaction time for 40 min). Some important fuel properties of I. polycarpa fruit oil biodiesel are presented in Table 2, in which most of these parameters are complied with the limits for use in diesel engine in China (China Biofuel Systems Group Ltd., Biodiesel Standards, 2007) and Europe (EN 14213). The data demonstrated in Table 2 for comparison purposes are the fuel properties of rapeseed and soybean oil methyl esters. Soybean oil and rapeseed oil are the two commonly used oil for biodiesel. As can be seen, the data in Table 2 indicate that the main fuel properties of I. polycarpa fruit oil methyl ester exhibit a similarity with that of the methyl esters of the two oils except that the cetane index of the I. polycarpa fruit oil biodiesel is slightly lower than that prescribed by the specifications for biodiesel, and also lower than that of soybean and rapeseed biodiesel. As mentioned by Knothe (2005), the properties of the various individual fatty esters that comprise biodiesel determine the overall fuel properties of the biodiesel fuel. Important fuel properties of biodiesel, such as cetane number, cold flow and viscosity and so on, are strongly influenced by the fatty acid profiles, viz. chain length, degree of unsaturation and branching of the chain of fatty acid. The cetane number, melting point, heat of combustion and viscosity of neat fatty compounds increase with increasing chain length and decrease with increasing unsaturation. The data in Table 1 also demonstrate that the values of total unsaturated fatty acids in I. polycarpa fruit oil, rapeseed and soybean oils are very similar (83.7% vs. 83.1% in soybean and 83.3% in rapeseed oils), however, the contents of linoleic acid and oleic acid are different. The linoleic acid content in I. polycarpa fruit, soybean and rapeseed oils are 70.6%, 52.9% and 21.7%, respectively. The oleic acid in I. polycarpa fruit, soybean and rapeseed oils are 5.5%, 22.2% and 61.6%, respectively. Further, the cetane numbers of methyl oleate and methyl linoleate are 59.3 and 38.2, respectively, in the IQTTM (Knothe, 2005). Therefore, oleic fatty acid in the oil exhibits a combination of improved cetane number and the relatively lower cetane number of I. polycarpa fruit oil biodiesel is well explained. In all, as performed in Table 2, the fuel properties of the I. polycarpa fruit oil biodiesel are similar to No. 0 light diesel.
4.
Conclusions
The above results revealed that the maximum yield of methyl esters in the I. polycarpa fruit oil biodiesel product was over 99% under the optimum reaction condition, viz. 600 rpm, 6:1 molar ratio of methanol to oil, 1.0% KOH, 30 ◦ C, and reaction time for 40 min. The I. polycarpa fruit oil biodiesel obtained has the fuel properties that comply with the limits established by China specifications for biodiesel and light diesel as fuel in diesel engines and is similar to the No. 0 light diesel fuel, except for a somewhat lower cetane index (47) than that prescribed by the standards for biodiesel. Thus, biodiesel derived from I. polycarpa fruit oil is an acceptable substitute for petrodiesel, also when compared to biodiesel fuels derived from other vegetable oils. Therefore, the I. polycarpa fruit oil can be potentially used as a raw feedstock for producing biodiesel in commercial scale in China.
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Acknowledgments This work was supported by the grants from the Natural Science Foundation of China (No. 30710103906), China Ministry of Education (No. 111), the Guangdong Natural Science Foundation (No. 07118057), and State Forestry Administration (200804015).
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