V. Punsuvon1,2*, R. Nokkaew2 and P. Somkliang2
2 Center of Excellence-Oil Palm, Kasetsart University, Bangkok, Thailand 10900
วันนี้ผมได้รับการติดต่อมาจาก ดร. อุทัย จารณาศรี ศิษย์เก่าดีเด่นของมหาวิทยาลัยเกษตรศาสตร์ นักเกษตรผู้มีความคิดนอกกรอบ แบบสุดๆอย่างที่ผมต้องขอยกย่องคนหนึ่งในประเทศไทย ท่านเป็นผู้คิดค้น วิจัย เรื่องการผลิตมะพร้าวกระทิ และนำไปพัฒนาจนสามารถผลิตต้นมะพร้าวกระทิออกเป็นเชิงพาณิชย์มากกว่า 10,000 ต้น ทำให้เกิดมีต้นมะพร้าวกระทิที่ทุกต้นและทุกลูกเป็นมะพร้าวกระทิทั้งหมด สร้างรายได้เป็นร้อยๆล้านบาท เป็น รายแรกของโลกก็ว่าได้ และท่านยังเป็นผู้จุดประกายความคิดให้ผมในเรื่องหยีน้ำเมื่อสองปีก่อนอีกด้วย
ท่านบอกว่ามีรายงานการวิจัยเรื่องหยีน้ำ ของอาจารย์ วิทยา พรรณสุวรรณ จากมหาวิทยาลัยเกษตรศาสตร์ ต้องการให้ผมช่วยเผยแพร่ ผมดีใจมากๆที่มีผู้สนใจในหยีน้ำมากขึ้น พอมองเห็นว่าเมืองไทยยังมีพืชพลังงานตัวใหม่ที่คนไทยจะพึ่งพิงได้ หากน้ำมันมีราคาแพงขึ้นไปในอนาคต ไม่ต้องไปแย่งน้ำมันปาล์มที่คนต้องใช้บริโภค จนประชาชนต้องเดือดร้อนกันไปทั้งประเทศ เนื่องราคานำมันปาล์มแพง และยังขาดตลาดอีกด้วย
เพราะฉะนั้น ผมอยากจะขอร้องท่านนักวิจัย นักการตลาด นักการเมือง นักอะไร ต่อนักอะไร ที่ไม่รู้จะเรียกชื่อว่าอย่างไงดี อย่าเพิ่งคิดอะไรสั้นๆ อย่าเพิ่งด่วนสรุปอะไรเร็ว คิดให้มากๆมองให้กว้างๆ
เพราะผมโดนด่ามาแล้วตั้งแต่เอาเรื่องหยีน้ำมาเสนอในบล็อกนี้ ว่าเรื่องน้ำมันปาล์มก็พอแล้ว เอาเรื่องหยีน้ำมาพูดให้คนไขว่เขวทำไม
Abstract: Pongamia pinnata is a fast-growing leguminous tree with the potential for high oil contain from seed. It can grow on stony, sandy or clayey, including verticals. It is highly tolerant of salinity and can be propagated either by seeds or by root suckers.
It grows abundantly along the coasts of southern region of Thailand, especially Ranong province. It is non-edible oil because it has toxic flavonoids compounds. However, the oil contains polyunsaturated fatty acids that they are important source of biodiesel. In this study, Crude oil was extracted from seeds with hexane solvent. Chemical and physical properties of crude oil were analyzed, such as acid value, iodine value, phosphorus content, viscosity and pour point. The result of fatty acid compositions showed that oil predominantly contained 68.27% unsaturated fatty acids (Oleic acid 44.89%, Linoleic acid 17.04%, Linolenic acid 3.55% and Erucic acid 2.79%). The total saturated fatty acid was 31.73% (Palmitic acid 12.63%, Stearic acid 6.65%, Arachidic acid 1.83%, and Behenic acid 10.62%). Pongamia pinnata oil was further studied to biodiesel by transesterification reaction. The yield of methyl esters was 78.26%. The preliminary physico-chemical characteristics relating tofuel properties of methyl esters were analyzed and followed up ASTM standard.
The results showed that the characteristics of methyl esters from Pongamia pinnata oil met the standard for biodiesel suggesting its possible new source of biodiesel production in the future of Thailand.
Pongamia pinnata belongs to the family Leguminaceae. It is a medium sized glabrous tree that generally attains a height of about 18 m and a trunk diameter >50 cm. It can grow under a wide range of agroclimatic condition and is a common sight around coastal areas, riverbanks tidal forests and roadsides. It can grow on most soil types ranging from stony to sandy to clayey, including verticals. It is highly tolerant of salinity and can be propagated either by seeds or by root suckers (Meher, 2004). In Thailand, it is commonly known as Hye Nam or Hye Talay. After 5-7 years of growth it bears fruits containing one to two kidney-shaped brownish-red kernels. It is one of the few nitrogen-fixing tree producing seed kernels containing 18-27% oil (Manju Bala, 2010). All parts of the plant have been used as a crude drug for the treatment of turmours, piles, skin diseases, itches, abscess, painful rheumatic joints wounds, ulcers, diarrhoa (Vigya kesari, 2010). Pongamia Piunata oil also finds use as a raw material in the soap and leather-tanning industries. Freshly extracted oil is yellowish orange to brown in colour having a disagreeable odour and a bitter taste. The presence of toxic flavonoids such as karanjin, pongapin and pon paglubrin make the oil inedible (Vismaya, 2010).
Pongamia pinnata oil is regarded as a potential fuel substitute that it contains 16-22 carbon atoms per molecule. Attempts have been made for the conversion of Pongamia pinnata oil to methyl esters or biodiesel by Meher et al (2004, 2006), Malaya Naik (2008). In addition, work on chemical composition, physico-chemical properties of its oil has been done by Vigya Kesari (2010)
However, the seed oil so far has not been commercially exploited in Thailand. Therefore, the oil content, chemical properties and fatty acid composition of the oil, the preparations as well as the chemical physical and fuel properties of methyl esters produced from the oil of pongamia pinnata were examined in this study.
Materials and Methods
Pongamia pinnata seed kernels (Fig 1) were collected from Ranong Province that located in the southern region of Thailand. The seed kernels were dried before extracting the oil. Standard fatty acid methyl esters were purchased from Nu-Chek Prep, Inc (Elysian, MN, USA). Absolute methanol (99.9%), hexane, potassium hydroxide were analytical grade.
Figure 1 Seed Kernels of Pongamia pinnata
2.2 Oil extraction
Seed kernels were ground with wiley mill and kept in a refrigerator at 4°C until needed. Soxhlet extraction of the ground seeds was accomplished with hexane for 6 h. Hexane was removed from the oil extracts by vacuum rotary evaporation. The oil was collected is amber jar bottles before experiment.
2.3 Physical properties of oil
Acid value (AV, mg KOH/g) titration was determined as described in AOCS official method Cd 3d-63.
Pour point (PP, °C) was determined following ASTM D5949.
The iodine value (IV, g I2/100 g) was determined as described in AOCS official method 1C-85.
Kinematic viscosity (cSt) was determined according to ASTM D445.
Phosphorus content (ppm) was determined according to AOCS official method Ca12-55.
Density at 15°C (g/cm3) was determined according to ASTMD 1298.
The average calculated molecular weight (MWcalc, g/mol) was determined by a weighted average method utilizing the fatty acid profiles. Specifically, the molecular weight of each fatty acid found in the vegetable oil was multiplied by its corresponding weight percentage as determined by GC. The sum of these values (minus the acidic proton) was multiplied by three and the glycerol fragment (minus the hydroxyl groups) was added, resulting in average calculated MWcalc of Pongamin pinnata oil.
Fatty acid composition by transesterification, by addition of sodium methoxide and sodium chloride, and one microlitre of the methyl esters extract was injected in split mode on to an DB-WAX 127-7012 column (30 m x 0.32 mmx 0.25 mm, Agilent Technologies, USA) and a flame ionization detector (FID). The operating conditions were the following: The temperatures of injector and detector were set at 250°C. The split ration was 1:50. Helium was used as carrier gas. Fatty acids were identified by comparing the retention times with reference fatty acid methyl esters standard.
Tocopherol, and Tocotrienols content were quantified by HPLC. Sample was diluted in hexane to a concentration of 50-100 mg/ml, filtered through 0.45 mm fitter and analyzed by Agilent HPLC, model 1100 series, DAD detector at 292 nm. The mobile phase consisted of hexane: 2-propanol (99.5:0.5 v/v) pumped at a rate of 1ml/min. Tocopherols and tocotrienol were separated using an Hypersil silica column (250 mm x 4.6 mm i.d., 5 mm, 150°A). Tocopherols and tocotrienol were identified by comparison to the retention times of know reference standards. A mixture of a-, b-, g-, d- tocopherols and tocotrienol standards was injected before analysis to verify HPLC response. Samples were quantified using external standards curve. The experiments were run in duplicate with the mean values reported.
2.4 Preparation of methyl esters from pongamia pinnata oil
Methanol was used as alcohol and potassium hydroxide (KOH) was used as catalyst for tranesterification. Molar ratio between alcohol and oil was 6:1 for the transesterification reaction. The catalyst amount was selected as 1.2% of the weight of oil. The experiment was carried out in laboratory scale with 3 h of reaction time, 60°C of reaction temperature and 500 rpm of stirring rate. After the transesterification reaction, the glycerin layer was separated in a separation funnel. The esters layer was washed with warm water. After washing, the methyl esters was subjected to a heating at 100°C to remove excess alcohol and water.
2.5 Characterization of methyl esters properties
The methyl esters was characterized by determining its viscosity, density, pour point, flash point, acid value, total-free glycerin, mono-di-tri glyceride. In order to determine the properties of the methyl esters, the following test methods were used: Density at 15°C (ASTM D941), viscosity at 40°C (ASTM D445), pour point (ASTM D97), flash point (ASTM D93), mono-, di-and tri-glyceride, total-free glycerin (EN 14105), acid value (AOC S cd 3a-64).
Results and Discussion
Physical properties of oil
The yield of extracted oil by hexane was 25.32 mass% of the dry original seed kernel weight. The crude oil obtained was brownish in appearance. The physical properties of Pongamia pinnata crude oil was shown in table 1.
Table 1: Physical properties of Pongamia pinnata crude oil
|Pour Point, °C||11.50|
|Kinematic viscosity at 40°C, cSt||36.10|
|Acid value, mg KOH/g||4.08|
|Iodine value, g I2/100 g||74.01|
|Phosphorus content, ppm||234.92|
From tables, the average calculated molecular weight (Mw calc) was 893 g/mol based on fatty acid composition in this study. Acid value referred to the amount of potassium hydroxide required to neutralize the free fatty acid in sample. Pongamia pinnata oil was found to contain 4.08 mg KOH/g. The iodine value is a measure of the unsaturation level in oil. A high iodine value is an indication of the presence of high unsaturation levels in oil. The determined iodine values of pongamia piunata oil was 74.01 g/100 g. This value is well within the value of 120 g/100 g as specified in EN14214 for using the oil as a biodiesel feed stock. The ability of fluid to pump and flow within an engine is determined by its viscosity. The viscosity obtained from pongamia pinnata oil was 36.11 cSt. The measured pour point was 11.5°C and phosphorus content was 234.92 ppm.
The fatty acid composition of the oil given in table 2 was relatively calculated from peak areas of GC chromatogram (Figure 2)
Table 2: Fatty acid compositions (area %) of crude oil
|Fatty acid||Retention time (min)||%|
|Palmitic acid (16:0)||12.519||12.63|
|Stearic acid (18:0)||14.278||6.65|
|Oleic acid (18:1)||14.465||44.89|
|Linoleic acid (18:2)||14.852||17.04|
|Linolenic acid (18:3)||15.388||3.55|
|Arachidic acid (20:0)||16.073||1.83|
|Behenic acid (22:0)||17.427||10.62|
|Erucic acid (22:1)||18.931||2.79|
S Sata = C16:0 + C18:0 + C20:0 + C22:0
S Monounsatb = C18:1 + C22:1
S Polyunsatc = C18:2 + C18:3
Figure 2 GC chromatogram of Pongamia Pinnata oil
Table 2 and Fig 2 show the fatty acid composition of Pongamia pinnata oil. The result of fatty acid compositions showed that oil predominantly contained 68.27% unsaturated fatty acid (oleic acid 44.89%, Linoleic acid 17.04%, Linolenic acid 3.55% and Erucic acid 2.79%). The total saturated fatty acid was 31.73% (Palmitic acid 12.63%, Stearic acid 6.65%, Arachidic acid 1.83% and Behenic acid 10.62%). The composition of saturated fatty acid and unsaturated fatty acid were different from what has been reported earlier (Vigga, 2010, Manju 2010). The differences in fatty acid composition may be due to the seed material is from different genotypes and from different ecological conditions.
Pongamia pinnata oil from southern region of Thailand consist of a larger amount of monounsaturated fatty acids (47.68%) than polyunsaturated fatty acids (20.59%), so this oil is suitable for biodiesel feedstock. Oil containing high amount of polyunsaturated fatty acids tend to exhibit a poor oxidation stability and may not be able to be used at low temperatures due to a high pour point (Zahira yaakob, 2010).
The results of tocopherols and tocotrienols content in Pongamia pinnata oil were quantified from chromatrogram (Figure 3) and the amount was shown in Table 3
Figure 3 HPLC chromatogram of tocopherols and tocotrienols in Pongamia Pinnata oil
Table 3: The amount of tocopherols and tocotrienols in Pongamia pinnata oil
|Compound||Retention (min)||Amount (ppm)|
The total tocopherols content in pongamia pinnata oil was 5593.64 ppm and total tocotrienol content was 21520.81 ppm. The extremely high content of d-tocotrienol in this oil was noteworthy. The total content of both tocopherols and tocotrienol was 27114.45 ppm that indicated the oil had high oxidative stability.
Properties of Pongamia Pinnata oil methyl esters
The methyl esters yield was 78.26% after transesterification that obtained from divided the weight esters with the weight of oil and multiplied with 100. The fuel properties are given in Table 4.
Table 4: Fuel properties of Pongamia pinnata oil methyl esters
|Properties||Unit||Pongamia pinnata oil methyl esters||EN 14214||ASTM D6751|
|Viscosity (at 40°C)||cSt||5.87||3.50-5.00||1.9-6.0|
|Flash point||°C||140||120 min||130 min|
|Acid value||mgKOH/g||0.84||0.50 max||0.80 max|
|Total glycerine||%(mass)||0.24||0.25 max||0.24 max|
|Free glycerine||%(mass)||0.00||0.02 max||0.02 max|
From Table 4 the measured fuel properties were suitable for the standards. This means that high fuel quality methyl esters was produced from crude Pongamia pinnata oil that original source from the southern region of Thailand in this study. The result also indicate this methyl esters can be used in the most modern engines without any modification. .
The purity of methyl esters in biodiesel by GC followed EN 14103:2003 standard.
The result showed chromatogram in figure 4 and percent methyl esters content in table 5
Figure 4 GC chromatogram of Pongamia Pinnata oil methyl esters
Table 5 Methyl esters content in Pongamia Pinnata oil methyl esters
|Methyl esters||Retention time (min)||%|
The purity of methyl esters calculated from methyl esters content in table 5 was 87%.
Based on the physicochemical evaluation of Pongamia pinnata oil and its methyl esters, Pongamia pinnata tends to be another promising energy plant in the future of Thailand as its oil is regarded as a potential fuel substitute. The preliminary results presented serve as a basic Knowledge regarding oil content, physical and chemical properties, composition of fatty acid, composition of tocopherols and tocotrienols as well as physicochemical characteristics of methyl esters derived from Pongamia pinnata oil. These may be useful for future utilization of Pongamia pinnata as an alternative source for biodiesel production in Thailand.
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This work was supported by Center of Excellence-Oil Palm, Kasetsart University.