Energy & Fuels 2006, 20, 1341-1344
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HFRR Studies on Methyl Esters of Nonedible Vegetable Oils A. K. Bhatnagar,* Savita Kaul, V. K. Chhibber, and A. K. Gupta Indian Institute of Petroleum, Mohkampur, Dehradun 248005, Uttaranchal, India ReceiVed NoVember 18, 2005. ReVised Manuscript ReceiVed March 1, 2006
The article describes the systematic studies on the lubrication properties of biodiesel, low sulfur diesel fuel, and their blends. Biodiesel from nonedible oils (e.g., Jatropha curcas, Pongamia glabra, Madhuca indica, and Salvadora oleoides) were prepared by base-catalyzed transesterification using methanol; high-speed diesel (HSD) used was from Panipat refinery. The lubricity evaluation of biodiesel and its blends (5-50%) was carried out as per the ISO-12156 method using high-frequency reciprocating rig (HFRR) test rig. The results indicate that addition of biodiesel to HSD improves the lubricity and provides a stable film on the metal surface. Addition of biodiesel substantially reduces wear scar diameter (WSD). The results were also comparable with pure ester-type compounds synthesized in our laboratory. We concluded that the preferred range of blending biodiesel is 5-20%. WSD of neat HSD is around 0.37 mm, whereas that of all four biodiesels is below 0.20 mm, which is around 50% or less than HSD used. The reduction in WSD at 5% blend is not appreciable except in the case of Salvadora biodiesel, which contains a high percentage of sulfur. At 20% level, around 45% reduction in WSD can be achieved.
Introduction Recent concern over the environmental impact of dieselpowered equipment has driven various countries to legislate reduction in vehicle exhaust emission levels and improvement in diesel fuel quality. These reductions in exhaust emissions have been achieved by the changes made in engine design such as increased fuel injection pressure and control of the fuel injection. The hardware changes in engines require improved diesel fuel lubricity to avoid excessive wear of the fuel injection system.1,2 The modification of diesel fuel quality has been achieved by increased use of secondary refinery processes such as hydrotreating and hydrocracking. These processes generally improve ignition quality, color, and thermal stability of the fuel but tend to reduce polar compounds of sulfur, oxygen, and nitrogen, which are responsible for fuel lubricity.3 Oxygencontaining compounds such as fatty acids and their derivatives are superior friction-reducing agents. The compounds adsorb or react on rubbing surfaces to reduce adhesion between contacting asperities and limit friction, wear- and seizure. Due to environmental benefits, production and use of fatty acid methyl ester (FAME), commonly known as biodiesel, as alternative fuel have increased significantly in many countries, including the United States, Austria, France, Germany, and Italy and picking up in many others including India. Use of biodiesel as a diesel fuel lubricity improver has been reported recently.4,5 * Corresponding author. Phone: 0135-2660123. Fax: 0135-2660202. E-mail:
[email protected]. (1) Mitchell, K. Lubricity of Winter Diesel Fuel, Part 2. Pump Rig Test Rig, Test Results; SAE Paper 961180; Society of Automotive Engineers: Washington, DC, 1996. (2) Mitchell, K. The Lubricity of Winter Diesel Fuels, Part 3. Further Pump Rig Tests; SAE Paper 961944; Society of Automotive Engineers: Washington, DC, 1996. (3) Nikanjam, M. Diesel Fuel Lubricity AdditiVe Study; SAE Paper 942014; Society of Automotive Engineers: Washington, DC, 1994. (4) Galbraith, R. M.; Hertz, P. B. The Rocle Test for Diesel and Biodiesel Fuel Lubricity; SAE Paper 972862; Society of Automotive Engineers: Washington, DC, 1997.
Lubricity additives have been added to fuels to protect the engine from excessive wear. Methyl esters of vegetable oils have also been studied for boundary lubrication.6 However, the major emphasis has almost always been put on their antiwear properties. Studies indicated that biodiesel produced from rapeseed oil and canola oil could serve as an alternative to synthetic additives to meet lubricity requirements. However, the impact of adding biodiesel prepared from nonedible oils such as Jatropha curcas, Salvadora oleoides, Pongamia glabra, and Madhuca indica on the fuel lubricity has not been examined thus far. These types of vegetable oils comprise interesting candidates for biodiesel production, especially in India where these species are grown in arid and semiarid lands and wastelands. The objective of this article is to present the lubricity evaluation of low-sulfur diesel additized with four samples of biodiesel as 5-50% blend by high-frequency reciprocating rig (HFRR). Experimental Section Biodiesel of Jatropha curcas, Salvadora oleoides, Pongamia glabra, and Madhuca indica was synthesized by transesterifying the oils with methanol at 60-70 °C in the presence of basic catalyst. After separation of glycerol, biodiesel was purified by washing with hot water and finally dried using molecular sieves. Physicochemical properties of biodiesel samples were determined by ASTM methods. To assess the impact of biodiesel blends on the lubrication properties of high-speed diesel, all lubricity measurements were carried out using the HFRR apparatus according to the ISO-12156 method. The test temperature was 60 °C, and the volume of the fuel sample used was 20 mL. Tests were performed at a frequency of 50 Hz at 2 N load for a duration of 90 min. The lubricating efficiency of the fuel was estimated by measuring the average wear (5) Geller, D. P.; Goodrum, J. W. Effect of specific fatty acid methyl ester on diesel fuel lubricity. Fuel 2004, 83, 2351-56. (6) Wain, K. S.; Perez, J. M.; Chapman, E.; Boehman, A. L. Alternative and low sulphur fuel options: boundary lubrication performance and potential problems. Tribol. Int. 2005, 38, 313-319.
10.1021/ef0503818 CCC: $33.50 © 2006 American Chemical Society Published on Web 04/28/2006
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Bhatnagar et al.
Figure 1. Effect of addition of biodiesel on lubrication properties (wear scar diameter) of HSD.
Figure 2. Effect of addition of biodiesel on lubrication properties (friction coefficient) of HSD.
scar diameter (WSD) of the spherical specimen by using a photomicroscope. Other properties that were measured were the contact potential and friction coefficient.
Results and Discussion Reduction of sulfur content in diesel fuel for Euro III and Euro IV fuels results in the lubricity loss due to sulfur removal. This can be easily compensated by addition of an appropriate amount of biodiesel or fatty acid methyl esters. Oxygencontaining compounds such as fatty acids or their derivatives act as friction-reducing agents. The compounds adsorb or react on rubbing metal surfaces to reduce adhesion between containing asperities and limit friction wear and seizure. Vegetable oilbased FAME mixtures consistently show better performance as lubricity-enhancing additives than do their single fatty acidbased counterparts.5 Biodiesel blends offer superior lubricating properties, which may reduce engine wear and extend the life of the fuel injection system. Lubricity behavior of biodiesel from nonedible oils additized with HSD has not been studied,
although many reports are available on other fuels such as aviation kerosene and diesel.7,8 The results of the HFRR testing on mixtures of diesel fuel with biodiesel from Jatropha curcas, Pongamia glabra, Salvadora oleoides, and Madhuca indica are shown in Figures 1 and 2. The esters were mixed with reference diesel fuel at the following concentrations: 5, 10, 15, 20, and 50% on weight basis. The properties of this reference fuel and also of various biodiesel are shown in Table 1. All the biodiesel samples meet proposed BIS and ASTM specifications. The 100% reference diesel was tested in each analysis, and the value is given in Tables 2-5. The WSD values for neat base fuel, biodiesel from Jatropha, Pongamia, Salvadora, and Madhuca are 0.372, 0.137, 0.200, (7) Anastopoulos, G.; Lois, E.; Zannikos, F.; Kalligeros, S.; Teas, C. HFRR lubricity response of an additized aviation kerosene for use in CI engines. Tribol. Int. 2002, 35, 599-604. (8) Anantopoulous, G.; Lois, E.; Zannikos, F.; Kalligeros, S.; Teas, C. Influence of aceto acetic esters and dicarboxylic acid esters on diesel fuel lubricity. Tribol. Int. 2001, 34, 749-755.
HFRR Studies on Methyl Esters of Nonedible Vegetable Oils
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Table 1. Fuel Characteristics of Petrodiesel and Biodiesel from Various Nonedible Oil S No. 1 2 3 4 5 6 7 8 9 10 11 12 13
characteristics
unit
density at 15 °C pour point total sulfur kinematic viscosity at 40 °C flash point CCR ash content copperstrip corrosion, 2 h 100 °C oxidation stability (UOP-413) molecular weight acid value cetane number ASTM distillation D-86 IBP 5 % vol 10 % vol 20 % vol 30 % vol 40 % vol 50 % vol 60 % vol 70 % vol 80 % vol 90 % vol 95 % vol FBP distillate residue loss
kg/mt3 °C ppm cSt °C wt % wt % mg/100 g mgKOH/g °C °C °C °C °C °C °C °C °C °C °C °C °C
Jatropha curcas
Pongamia glabra
Salvadora oleoides
Madhuca indica
879.4 +3 90% saturated acids and high content of (9) Chopra, A.; Jain, C.; Sheshadri, T. R. Curr. Sci. 1968, 37, 121.
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sulfur (Table 1), while Mahua contains 45-50% saturates and Pongamia and Jatropha have >90% unsaturates. It appears from the data that unsaturation does not affect the lubricity characteristic of long-chain fatty esters. Consequently, biodiesel is a potential candidate for improving the poor lubrication properties of low-sulfur automotive diesel (HSD, sulfur ≈ 500 ppm). HFRR lubricity characteristics of two (ester-type) compounds, 2-ethyl hexyl oleate and octadecyl phosphate, were compared with pure biodiesel. The results are very comparable and are presented in Table 6. Conclusion The beneficial effect of biodiesel produced from nonedible seed oilssJatropha, Pongamia (Karanj), Salvadora (Pilu), and Madhuca indica (Mohua)sto improve the lubrication properties of low-sulfur diesel fuels in concentrations above 5-20% is
Bhatnagar et al. Table 6. Comparison of Lubricity Characteristics of Biodiesels and Synthesized Ester-Type Components S No.
characteristics 100%a
WSD mm
friction coefficient (µ)
contact potential (mV)
1 2 3 4 5 6
BD-1 BD-2 BD-3 BD-4 2-ethyl hexyl oleate octadecyl phosphate
0.137 0.200 0.138 0.171 0.200 0.210
0.28 0.25 0.28 0.28 0.21 0.21
47 44-48 42-45 47 40 39
a BD-1 ) Jatropha curcas biodiesel. BD-2 ) Pongamia glabra biodiesel. BD-3 ) Salvadora oleoides biodiesel. BD-4 ) Madhuca indica biodiesel. ESTER-1 ) 2-Ethyl hexyl oleate. ESTER-2 ) Octadecyl phosphate.
comparable with the effects in the known literature as well as with that of pure ester-type compounds. EF0503818
