Bioresource Technology 96 (2005) 1425–1429
Preparation of biodiesel from crude oil of Pongamia pinnata Sanjib Kumar Karmee, Anju Chadha
Laboratory of Bioorganic Chemistry, Department of Biotechnology, Indian Institute of Technology, Madras, Chennai-600 036, India Received 22 July 2004; received in revised form 7 December 2004; accepted 10 December 2004 Available online 17 February 2005
Abstract Biodiesel was prepared from the non-edible oil of Pongamia pinnata by transesteriﬁcation of the crude oil with methanol in the presence of KOH as catalyst. A maximum conversion of 92% (oil to ester) was achieved using a 1:10 molar ratio of oil to methanol at 60 C. Tetrahydrofuran (THF), when used as a co-solvent increased the conversion to 95%. Solid acid catalysts viz. Hb-Zeolite, Montmorillonite K-10 and ZnO were also used for this transesteriﬁcation. Important fuel properties of methyl esters of Pongamia oil (Biodiesel) compare well (Viscosity = 4.8 Cst @ 40 C and Flash point = 150 C) with ASTM and German biodiesel standards. 2005 Elsevier Ltd. All rights reserved. Keywords: Pongamia pinnata; Biodiesel; Non-edible oil; Base catalyst; Solid acids; Transesteriﬁcation
1. Introduction Oil of Pongamia pinnata (Legumnosae; Pappilonaceae) is a nonedible oil of Indian origin (Lakshmikanthan, 1978). It is found mainly in the native Western Ghats in India, northern Australia, Fiji and in some regions of Eastern Asia. This medium sized (max ht. 18 m) tree is found almost throughout India upto an altitude of 1200 m. It grows fast and matures after 4–7 years yielding fruits which are ﬂat, elliptic and 7.5 cm long. Each fruit contains 1 to 2 kidney shaped brownish red kernels. The oil content of the kernel is 30– 40% (Lakshmikanthan, 1978). A single tree is said to yield 9–90 kg seed per tree, indicating a yield potential of 900–9000 kg seed/ha (assuming 100 trees/ha), 25% of which might be rendered as oil. In general, Indian mills extract 24–27.5% oil, and the village crushers extract 18–22% oil. The oil contains primarily eight fatty acids viz. palmitic, stearic, oleic, linoleic, lignoceric,
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eicosenoic, arachidic and behenic (Lakshmikanthan, 1978). Of these, the four which are commonly found in most oils, including Pongamia, are the saturated acids, palmitic (Hexadecanoic acid) and stearic (Octadecanoic acid) and the unsaturated acids, oleic (Octadec-9enoic acid) and linoleic (9,12-octadecadienoic acid). Pongamia oil contains oleic acid (44.5–71.3%) as the major fatty acid followed by linoleic (10.8–18.3%), palmitic (3.7–7.9%) and stearic (2.4–8.9%) acids. In addition to these four fatty acids, Pongamia oil also contains eicosenoic acid (9-eicosenoic acid) in reasonable amounts (9.5–12.4%). This dark brown oil has a repulsive odor and shows fungicidal properties. Presently Pongamia oil is being used by farmers in Karnataka (a southern state in India) to run generators which irrigate their ﬁelds (Shrinivasa, 2001). It is popular due to its low cost and ready availability. However, as for other oils there are limitations in the use of this nonedible oil as fuel. Its high viscosity and poor combustion characteristics can cause poor atomization, fuel injector blockage, excessive engine deposit and engine oil contamination. Even though straight vegetable oil (SVO) is being used as a fuel instead of diesel, it is a well documented fact that esteriﬁed oil has better fuel
S.K. Karmee, A. Chadha / Bioresource Technology 96 (2005) 1425–1429
properties (Ma and Hanna, 1999). The most commonly used oils for the production of biodiesel are soybean (Freedman et al., 1986; Noureddini and Zhu, 1997), sunﬂower (Antolı´n et al., 2002; Mohamed and Bornscheuer, 2003), palm (Darnoko and Cheryan, 2000a), rapeseed (Kusdiana and Saka, 2001) canola (Zhou et al., 2003), cotton seed (Ko¨se et al., 2002) and jatropha (Foidl et al., 1996). Most of these oils are edible except jatropha (Foidl et al., 1996). In India the prohibitive cost of edible oils prevents their use in Biodiesel preparation, but nonedible oils are aﬀordable for Biodiesel production. Biodiesel is synthesized from oils and fats (Ma and Hanna, 1999) by using either chemical or biocatalysts (Shimada et al., 2002). Chemically, the reaction is catalyzed by either an acid or a base. The transesteriﬁcation reaction of triglycerides is known to be a three step process. The kinetic studies of transesteriﬁcation of soybean (Freedman et al., 1986; Noureddini and Zhux, 1998), palm (Darnoko and Cheryan, 2000b), rapeseed (Kusdiana and Saka, 2001) and monoglycerides of Pongamia oil (Karmee et al., 2004) have been reported. More recently research on alcoholysis of oil has focused on the use of heterogeneous catalysts. Generally solid acids (Otera, 2003) have the advantage of being easily removed by ﬁltration and be used for large scale production. Zeolites and metal catalysts have also been used for the transesteriﬁcation of soybean oil (Suppes et al., 2004). Even though base catalyzed transesteriﬁcation of oils is the widely accepted method of preparing Biodiesel, the chemical properties and purity of each oil warrants complete optimization of the reaction conditions. This paper reports for the ﬁrst time details of the process of base catalyzed transesteriﬁcation of crude Pongamia oil with methanol wherein the progress of transesteriﬁcation was monitored by 1H NMR (Knothe, 2000; Karmee et al., 2004). Hb-Zeolite, Montmorillonite K-10 and ZnO were also tried as catalysts for this transesteriﬁcation reaction. The fuel properties of Pongamia oil methyl esters (Biodiesel) on comparison with those of accepted Biodiesel standards indicate that esteriﬁcation of oil does improve its properties making it similar to diesel.
2. Methods 2.1. Materials and apparatus All chemicals were bought locally. Methanol was dried and distilled before use. Crude Pongamia oil was a gift from Professor U. Shrinivasa, IISc, Bangalore, India. All 1H NMR were recorded on a Bruker 400 MHz Instrument. Fatty acid methyl ester content in the esteriﬁed oil was determined by Gas Chromatograph (Nucon, India) equipped with a FID detector (Saglik et al., 2002).
2.2. Transesteriﬁcation of crude oil of Pongamia pinnata 2.2.1. Transesteriﬁcation of crude Pongamia oil using KOH To 10 g of crude Pongamia oil, a known amount of catalyst KOH, 0.1 g (1 wt%) (Freedman et al., 1986; Darnoko and Cheryan, 2000b; Karmee et al., 2004) dissolved in the required amount of methanol was added. The temperature i.e. 45 C or 60 C was maintained as desired. Samples were removed at 10-min intervals, neutralized using glacial acetic acid and washed with water (10 ml · 3) to remove unreacted base, glycerol and trace amount of soap and extracted with n-hexane. The organic layer was separated and concentrated to get the soap- and glycerol-free sample whose 1H NMR was taken using CDCl3–TMS as internal standard. Two different molar ratios of oil to methanol (1:3 and 1:10) were tested at two diﬀerent temperatures i.e. 45 C and 60 C. 2.2.2. Transesteriﬁcation of crude Pongamia oil using solid acids at 120 C (oil to methanol molar ratio 1:10) To Pongamia oil (5 g) at 120 C, a known amount (0.575 g) of solid acid catalyst (Hb-Zeolite, Montmorillonite K-10 or ZnO) was added (Suppes et al., 2004) followed by the required amount of methanol (3.9 ml) under dry conditions. Samples were removed at 6 h intervals. The reactions were run for 24 h after which each sample was ﬁltered to remove the catalyst and after routine workup was characterized by 1H-NMR as given above.
3. Results and discussion 3.1. Eﬀect of molar ratio of oil:methanol and temperature on transesteriﬁcation of Pongamia oil Transesteriﬁcation of Pongamia oil was studied at two diﬀerent molar ratios of oil:methanol (1:3 and 1:10) at 45 C (Fig. 1). At a molar ratio of 1:3 a maximum conversion 80% was observed whereas at 1:10 molar ratio the conversion was 83% with an initial lag time. The initial lag phase is usually attributed to transport eﬀects required to transfer the methanol into the oil phase (Freedman et al., 1986; Noureddini and Zhu, 1997). At a molar ratio of 1:10 (oil:methanol), increasing the reaction temperature from 45 C to 60 C resulted in a signiﬁcant increase in conversion from 83% to 92% (Fig. 2). The eﬀect of temperature on NaOH (0.2 wt%) catalyzed transesteriﬁcation of soybean oil (Noureddini and Zhu, 1997) with a molar ratio (1:6; oil to methanol) was studied at 30, 40, 50, 60 and 70 C (NRe = 6200). At 60 and 70 C, high conversion (90%) was observed whereas below 60 C the conversion was <80%. It is important to note that crude Pongamia oil was used in
S.K. Karmee, A. Chadha / Bioresource Technology 96 (2005) 1425–1429 100 95 90 85 80 75 70 65 60 55 50 45 40 35 30 25 20 15 10 5 0
Oil:MeOH(1:3) at 45°C Oil:MeOH(1:10) at 45°C
Fig. 1. Conversion of Pongamia oil to Fatty acid methyl esters at two diﬀerent molar ratio of. 1:10 and 1:3 (oil:methanol) at 45 C.
Oil:MeOH(1:10) at 45°C Oil:MeOH(1:10) at 60°C
Biodiesel from rapeseed oil (Kusdiana and Saka, 2001) was prepared in supercritical methanol at a molar ratio of 1:42 (oil:methanol) in the absence of catalyst where the temperature was as high as 240 C. The conversion was 95% after 240 s. Fatty acid methyl esters from jatropha oil (Foidl et al., 1996) were prepared (92% yield) in a two step process with an oil to methanol molar ratio of 1:4.5 at 30 C and reaction time of 10 h. The optimized conditions for transesteriﬁcation of heated reﬁned sunﬂower oil and used frying oils were recently reported (Marinkovic and Tomasevic, 2003). The methanolysis of diﬀerent used frying oils were performed at 25 C with 0.5–1.5% (KOH or NaOH) with a molar ratio of oil to methanol as 1:4.5, 1:6, and 1:9 and 1% KOH, 25 C, 1:6 molar ratio was found to be optimum.
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100
100 95 90 85 80 75 70 65 60 55 50 45 40 35 30 25 20 15 10 5 0
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100
Time (minutes) Fig. 2. Conversion of Pongamia oil to Fatty acid methyl esters at two diﬀerent temperatures 45 C and 60 C at 1:10 (oil:methanol) molar ratio.
this study for biodiesel preparation and since the degree of reﬁnement of the vegetable oil aﬀects the yield of ester formation (Freedman et al., 1984; Marinkovic and Tomasevic, 2003) the conversion can only be expected to improve when reﬁned Pongamia oil is used. Using alkaline catalyst (0.5% of NaOH or methoxide) at 60 C and a molar ratio of 1:6 (oil:methanol) with fully reﬁned oils resulted in complete conversion to methyl esters in 1 h but at a moderate temperature (32 C) these oils were transesteriﬁed up to 99% in 4 h. Palm oil was transesteriﬁed with 1 wt% KOH at 60 C and a molar ratio of 1:6 (oil:methanol), using a continuous stirred tank reactor (Darnoko and Cheryan, 2000a) to give a yield of 58.8% of methyl ester at a reactor residence time of 40 min which increased to 97.3% at a residence time of 60 min.
3.2. Comparison between solid acid catalyzed and KOH catalyzed transesteriﬁcation As solid acids can be easily removed by ﬁltration and reused, in our present study we have tested the potential of Montmorillonite K-10, Hb-Zeolite and ZnO for transesteriﬁcation of crude Pongamia oil at 120 C with 1:10 molar ratio of oil:methanol. The reactions were run for 24 h. ZnO gave a good conversion of 83%, while HbZeolite and Montmorillonite K-10 catalyzed transesteriﬁcations, gave low conversions of 59% and 47% respectively. The results obtained are summarized in Table 1. Recent studies on transesteriﬁcation of soybean with methanol in the presence of a series NaX faujasite zeolites, ETS-10 Zeolite, and metal catalyst (Suppes et al., 2004) shows that NaX containing occluded sodium oxide and occluded sodium azide gave >90% conversion at 120 C in 24 h. Among the metal catalysts, ZnO gave the highest conversion of 80% at 120 C in 24 h. In essence, KOH catalyzed transesteriﬁcation of crude Pongamia oil, resulted in high conversion 92% in 1.5 h at 60 C with a molar ratio 1:10 (oil:methanol), whereas solid acid catalyzed transesteriﬁcation of this oil requires higher temperature (120 C) and longer reaction times (24 h). 3.3. Eﬀect of THF as a co-solvent on transesteriﬁcation of Pongamia oil The transesteriﬁcation of Pongamia oil increased to 95% at 60 C in 1.5 h at a molar ratio of 1:10 (oil: Table 1 Conversion of crude Pongamia oil to methyl esters over solid catalysts Solid acids
Montmorillonite K-10 Hbeta-Zeolite ZnO
47 59 83
2.1 2.5 2.3
At 120 C in 24 h at a molar ratio of 1:10 (oil:methanol).
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Table 2 Fuel parameters of Pongamia FAME, ASTMa and German Biodiesel standarda Parameters
ASTM standard for 100% biodiesel
German biodiesel standard DIN V51606
Viscosity (Cst) Acid value (mg KOH/gm) Flash point (C) Sulfated ash (wt%)
4.8 (40 C) 0.62 150 0.005
1.9–6.0 (40 C) 0.80 max 130 min 0.020 max
3.5–5.0 (40 C) 0.5 100 min 0.01
http://www.biodiesel.org (Accessed on 16.07.04).
methanol) with the addition of THF as co-solvent (Boocock et al., 1996). A co-solvent like THF produces an oil-dominant one phase system in which methanolysis speeded up. In the absence of THF, the low oil concentration in methanol slows down the reaction due to the slow dissolution of oil in methanol and this is also reﬂected in an intial lag phase (Freedman et al., 1986; Karmee et al., 2004). THF is the best co solvent for this purpose because it is miscible with both water and methanol due to hydrogen bonding. Moreover, its boiling point is close to that of methanol and can be co-distilled with methanol. 4. Fuel properties of fatty acid methyl esters in comparison with Pongamia oil and diesel The two important fuel properties viz, viscosity and ﬂash point of methyl esters of Pongamia oil were found to be 4.8 Cst (40 C) and 150 C (Table 2) respectively. Pongamia oil itself has a high viscosity of 74.14 Cst (30 C) which drops down dramatically on transesteriﬁcation 4.8 Cst (40 C). Both these properties meet the speciﬁcations of ASTM and German biodiesel standards. 5. Conclusion Crude Pongamia oil was transesteriﬁed using KOH as catalyst and methanol to form Biodiesel. The conversion was 92% at 60 C with 1:10 molar ratio (oil:methanol) for KOH (1% by wt) catalyzed transesteriﬁcation. ZnO, Hb-Zeolite and Montmorillonite K-10 also catalyze the transesteriﬁcation of Pongamia oil. They require longer reaction time (24 h) and the conversion is 83% for ZnO but low (47–59%) for Hb-Zeolite and Montmorillonite K-10. The fuel properties especially viscosity (4.8 Cst @ 40 C) and ﬂash point (150 C) of the transe steriﬁed product (biodiesel) compare well with accepted biodiesel standards i.e. ASTM and German biodiesel standards. Acknowledgement Financial support from MNES, Government of India is gratefully acknowledged.
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