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Synthesis of Palm Oil Based Trimethylolpropane Esters with Improved Pour Points Robiah Yunus,*,† Ahmadun Fakhru’l-Razi,† Tian Lye Ooi,‡ Rozita Omar,† and Azni Idris† Department of Chemical and Environmental Engineering, Faculty of Engineering, Universiti Putra Malaysia, 43400 UPM, Serdang, Selangor, Malaysia, and Advanced Oleochemical Technology Center, Malaysian Palm Oil Board, Lot 9/11, Jalan P/14, Seksyen 10, Bandar Baru Bangi, Selangor, Malaysia
Palm oil based trimethylolpropane (TMP) esters are potential biodegradable base stocks for environmentally friendly lubricants. To improve the low-temperature properties of palm oil based TMP esters, which are well below the requirements set by the lubricants’ manufacturers, the high oleic content palm oil based TMP ester with a pour point between -10 and -32 °C was synthesized. The synthesis of palm oil polyol esters was performed by transesterification of fractionated palm oil methyl esters with TMP using sodium methoxide as a catalyst. Nearly complete conversion to palm TMP triesters (98% w/w) was obtained. The palm oil methyl esters were fractionated at 150-180 °C and 0.1 mbar prior to the synthesis to reduce the saturated fatty acid content. The fractionation and reaction took place using the same experimental setup. The effects of composition on pour points, viscosity, and viscosity index of the high oleic content palm oil based TMP esters were also evaluated. The concentration of C16:0 methyl ester in the starting material should be below 10% w/w to ensure that the pour points of high oleic content palm oil based TMP esters are below -30 °C. In addition, the reaction conversion to triester must also be maintained above 90% w/w to produce TMP esters with excellent pour points. Operating temperature had a negligible effect on the reaction yield so long as the temperature was kept above 120 °C. There were small variations in the viscosities and viscosity index values of high oleic content palm oil based TMP, in the region of 50 cSt and 199, respectively. Introduction Today, most of the lubricants and functional fluids are derived exclusively from petrochemical or mineral bases. They account for 85-90% of the total world lubricants. While less than 15% of the world lubricants are synthetic oil based, the synthetic oil based lubricants offer high performance with superior lubricity, higher thermal stability, excellent oxidative stability, and lower volatility, and hence require fewer oil changes.1,2 Due to their poor oxidative stability, vegetable oil based lubricants account for only 1% of the total world lubricants. Modern lubricants are formulated from a range of base fluids and chemical additives. Synthetic oils can be made from petroleum or vegetable oil feedstock and are tailor-made for specific applications. Vegetable oils may be used for specialized applications in their unmodified forms. However, to enhance their properties, various types of compatible additives need to be added.3 Vegetable oils also may be synthesized to synthetic esters to overcome their low- and high-temperature limitations. The most natural synthetic esters are the branched polyol esters derived from neopentyl alcohol, trimethylolpropane, and pentaerythritol. These synthetic esters can be derived from combinations of various fatty acids and alcohols or methyl esters and * To whom correspondence should be addressed. Tel.: 603-89466268. Fax: 603-86567120. E-mail: robiah@ eng.upm.edu.my. † Universiti Putra Malaysia. ‡ Malaysian Palm Oil Board.
polyols. The vital feature of these esters is that, on the alcohol portion of the molecular structure, there is no hydrogen atom on the β-carbon. This feature provides them with high degrees of oxidative and thermal stability seldom found in vegetable oil based lubricants. The low-temperature properties of natural synthetic esters obtained from the reactions between palm oil based methyl esters and trimethylolpropane are generally inferior compared to other vegetable oil based lubricants due to a higher level of saturation. The values of the pour points of these palm oil based esters range from -4 to 4 °C, whereas the pour point could be as low as -15 °C as reported for rapeseed oil based polyol esters.4 A few authors have reported poor low-temperature properties of vegetable oils.5,6 Additives often improve the pour points, but usually some deficiencies remain.7 To enhance the low-temperature properties of vegetable oil based lubricants, various measures have been considered, including winterization followed by filtration of either the starting materials or the final products.8 However, none of these measures improved the pour points of the products significantly. The main objectives of this study were (i) to synthesize low pour point palm oil based trimethylolpropane (TMP) ester from fractionated methyl esters, (ii) to evaluate the properties of the high oleic content palm oil based TMP esters and compare them with conventional palm oil based TMP esters and commercial products, and (iii) to study the effect of fatty acid composition in palm oil methyl esters on pour point and lubricity of the natural synthetic lubricant.
10.1021/ie050530+ CCC: $30.25 © 2005 American Chemical Society Published on Web 09/29/2005
Ind. Eng. Chem. Res., Vol. 44, No. 22, 2005 8179 Table 1. Fatty Acid Composition of Distilled Palm Oil Methyl Esters fatty acids (% w/w)
before fractionation
C12:0 C14:0 C16:0 C18:0 C18:1 C18:2 C18:3 others
0.3 0.9 31.8 4.0 47.6 14.4 0.3 0.7
a
HOPOME Aa top fraction bottom fraction 0.5 1.8 55.6 1.9 30.2 9.5 0.2 0.3
0.0 0.1 5.5 6.2 67.5 18.8 0.8 1.1
HOPOME B top fraction bottom fraction 0.7 2.4 56.3 1.8 29.0 8.9 0.2 0.7
0.0 0.0 7.4 6.0 66.6 18.5 0.7 0.8
HOPOME C top fraction bottom fraction 0.5 1.8 50.5 2.3 33.9 10.2 0.2 0.6
0.0 0.0 10.7 5.8 64.2 17.8 0.7 0.8
HOPOME, high oleic content palm oil methyl ester.
Experimental Section The experimental work consists of fractionation of palm oil methyl esters, transesterification of high oleic content palm oil methyl ester, and pour point and viscosity measurements. Fractionation of Palm Oil Methyl Esters. Palm oil methyl esters (POME) were fractionated via vacuum distillation. Since POME have lower boiling points, they are relatively easier to vaporize compared to fatty acids. Hence, moderate temperatures between 150 and 190 °C were used in the operation under absolute pressure of 0.1-0.3 mbar. The temperature should not be too high to avoid the carryover of C18:1 fraction into the C16:0 fractions. The bottom product was enriched with the unsaturated methyl esters with a yield of approximately 50% w/w. Transesterification of High Oleic Content Palm Oil Methyl Ester. Transesterification of high oleic content palm oil methyl ester (HOPOME) with TMP was carried out using an alkaline catalyst under various operating conditions. The reaction was carried out in a 1 L three-neck reactor keeping approximately 0.5 L working volume. The oil bath was heated and maintained at a temperature 20 °C higher than the operating temperature. The POME was weighed into the reactor, after which the appropriate amount of TMP was added. The mixture was heated in the oil bath under reduced pressure until TMP melted at around 60 °C. The mixture was gradually heated to the operating temperature and refluxed under reduced pressure, 0.1 mbar for 2 h. The reaction product was sampled at certain time intervals for analyses with TLC and GC.9 Analysis was carried out using a high-temperature capillary column, SGE HT5, operated at a temperature gradient of 6 °C/ min starting from 80 °C up to 340 °C. Before injection, the sample was derivatized with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) in ethyl acetate at 40 °C for at least 10 min. This procedure provided a complete separation of reaction products: TMP, methyl esters, monoesters (ME), diesters (DE), and triesters (TE). The quantitative analyses of the final products were based on the weight percentages of the esters. At completion, the reaction mixture was cooled to room temperature and then vacuum filtered to remove the catalyst and solid materials formed during the reaction. The solid materials included the soap compounds and fatty acids. The filtered product was distilled under absolute pressure of 0.3 mbar at approximately 230 °C to remove the excess HOPOME. Since the effects of other operating parameters such as pressure, substrate ratios, and amount of catalyst were examined in another report,10 only the optimum values were used in the above syntheses, which include
the following: ratio of TMP to HOPOME (moles of TMP: moles of HOPOME) at 1:3.9; catalyst amount at 0.9% (w/w); absolute pressure of 0.3 mbar. However, the experiments on the effect of temperature were carried out to substantiate the results obtained earlier. Pour Point and Viscosity Measurements. The methods and apparatus for pour points measurements are based on ASTM D97.11 The low-temperature bath was supplied by Petrotest Instruments, Germany, and can maintain the temperature down to -38 °C using methanol as the cooling medium. The sample was first heated to 45 °C in a water bath maintained at 48 °C and then cooled to 27 °C in another water bath kept at 27 °C. The sample was then transferred to the lowtemperature bath kept at 0 °C. The cooling scheme specified by the test method was followed closely to ensure accuracy and repeatability of the results. The pour point is defined as the temperature at which there is no movement of the oil when the test jar is held in a horizontal position for 5 s. The kinematic viscosities at 40 and 100 °C were measured based on the method described in ASTM D445.11 The experiments were carried out in a constanttemperature bath of Tamson Zoetermeer, Holland, Model TV4000, using Ubbelohde capillary tube viscometers. The viscosity index (VI) is an arbitrary number used to characterize the variation of the kinematic viscosity with temperature. It was calculated according to ASTM D2270 based on the kinematic viscosities at 40 and 100 °C as
VI ) [((antilog N) -1)/0.00715] + 100 N ) (log H - log U)/log Y where U and Y are the kinematic viscosities at 40 and 100 °C, respectively, of the oil whose VI is to be calculated. H is the value obtained from Table 1 provided in standard ASTM D2270. Results and Discussion Fractionation of Palm Oil Methyl Esters (POME). The fatty acid compositions of POME are shown in Table 1. HOPOME A, HOPOME B, and HOPOME C were fractioned POME samples obtained by vacuum distillation at different temperatures. The poor low-temperature properties of palm oil based polyol esters were due mainly to higher percentages of saturated fatty acids (C16:0) present in the POME. Since vacuum was used in the reaction, vacuum distillation offered a perfect solution to the problem. The average C16:0 content in POME before distillation was around 32% w/w. After fractionation, HOPOME A contained the lowest C16:0 content at 5.5% (w/w), followed by HOPOME B at 7.4% and HOPOME C at 10.7%.
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Figure 1. Product distribution curves for the transesterification of palm oil based methyl esters with TMP at 150 °C and 0.3 mbar: monoesters (ME), diesters (DE), triesters (TE), trimethylolpropane (TMP), palm oil methyl esters (POME), and fatty acids (FA).
In sample HOPOME C, a total of 44% w/w C18:1 (oleic) and C18:2 (linolenic) were distilled together with C16:0, which resulted in a high fraction of C16:0 in bottom product. Although the difference in C16:0 content in bottom fractions of samples HOPOME A, HOPOME B, and HOPOME C were small, it will be shown later that the lubricants produced from HOPOME C had significantly higher pour points than HOPOME A and HOPOME B. Thus, it is vital that an uncontrolled distillation and overheating are avoided during the fractionation of POME to guarantee that low pour point lubricant is produced from the reaction. Gryglewicz et al.8 used a two-stage process of low-temperature crystallization to fractionate lard methyl esters enriched with unsaturated methyl esters at 46% yield. However, they managed to lower the saturated fatty acid content to only 17.4%. The fractionated POME (HOPOME A, HOPOME B, and HOPOME C) with a yield of 50% was then used in the synthesis of high oleic content palm oil based polyol esters (POTE). The byproduct of the palm oil methyl ester fractionation contained significant amounts of C16:0 fractions. Thus, it has a great potential as a starting material in the manufacture of biodegradable surfactants. Methyl
ester sulfonates (MES) or R-sulfo methyl esters (R-SME) derived from C16 methyl esters of vegetable oils have been regarded as potential surfactants in detergent formulation.12 Synthesis of High Oleic Content Palm Oil TMP Esters. The progression of the reaction between HOPOME and TMP conducted at 150 °C and 0.3 mbar is shown in Figure 1. The reaction was very fast at the beginning but somewhat sluggish as it approached the equilibrium. The curve exhibits special characteristics of multiple reactions in series, such as maximal intermediates (ME and DE) and behavior of reaction with changing mechanism of the final product, TE. A similar profile was also observed in previous work on the kinetics of transesterification of POME with TMP to polyol esters.13 At the initial stages of reactions, the curves for DE and TE had zero slopes, suggesting that DE and TE were not formed directly from the TMP. However, ME was formed directly from TMP because of its nonzero initial slope. A similar phenomenon was not evident in this study because the sampling started only after 5 min of reaction. The rate of formation of TE, as expected, was slow at the beginning, followed by a sudden increase in rate,
Ind. Eng. Chem. Res., Vol. 44, No. 22, 2005 8181 Scheme 1
and finally reached equilibrium as shown in Figure 1. During the course of reaction, DE competed with both TMP and ME for POME to form TE and hence slowed the rate of TE production. With the formation of ME from TMP followed by the decomposition of ME to form DE, there was a progressive accumulation of DE and depletion of TMP and ME. The process continued until the concentration of DE reached the maximum, decreased, and finally reached equilibrium. The sudden increase in rate of TE formation coincided with the point when the concentration of DE was at maximum. Furthermore, there was only a small concentration of DE and zero concentration of ME in the product, thus confirming the postulated reaction mechanism shown in Scheme 1. Yunus and co-workers13 derived the expressions for product distributions that relate the rate of change of the intermediates, ME and DE, with respect to the concentration of the limiting reactant, TMP. The maximum points on the distribution curves for the intermediates, ME and DE, were used to determine the rate constants. The rate constants that provided the best fit to the experimental data were applied in the rate equations. A straight-line plot that they obtained strongly supports the hypothesis that TMP transesterification follows second-order kinetics under the stipulated conditions. Under the operating conditions employed in this study, the reaction reached equilibrium in less than 1 h. After removal of excess HOPOME, the final product composition was approximately 97.4% TE, 1.1% DE, 0.2% ME, and 1.3% HOPOME. In previous work using POME, the reaction reached equilibrium in 45 min. The slight delay in the synthesis of high oleic content TMP esters can be attributed to the increase in the C18 fraction, which required more energy of reaction compared to the original palm oil methyl ester. However, the period is still far less than reported earlier on transesterification of rapeseed oil methyl ester of 10 h 4 and for animal fat based esters of 20 h.8 The presence of FA (palm fatty acids) in reaction products may be due to the hydrolysis of TE. High concentration of FA is detrimental to the lubricant because it would reduce the corrosion resistance. However, the FA content in palm oil based polyol ester is generally low, below 0.5% (w/ w). Figure 2 illustrates the effect of temperature on transesterification of HOPOME with TMP. The reaction temperatures were slightly higher than the optimum temperatures obtained earlier at 120 °C10 due to higher content of C18 fatty acids. The results also show that the reaction was relatively slow at 140 °C, where after 10 min of reaction only 66% of the total TE formed,
Figure 2. Effect of temperature and time on composition of triesters (TE) in the synthesis of high oleic content palm oil based polyol esters, HOPOME:TMP 3.9:1, catalyst 0.9 wt %.
whereas more than 81% formed at 150 °C. However, the reaction at both temperatures took about 45 min to complete. The final product compositions of high oleic content palm oil based polyol esters (POTE) synthesized at various temperatures are shown in Table 2. It is interesting to note that within the selected temperature range, 120-150 °C, temperature had a small but noticeable effect on the synthesis so long as the vacuum was maintained at about 0.2 mbar. However, our earlier work had shown that the reaction could also be carried out at 20 mbar without an appreciable effect on the yield of TE.10 The TE content was as high as 98% w/w. This is typical for a reversible reaction such as transesterification where the activation energies, Ea, for the forward and backward reactions are similar. The net heat of reaction becomes small and temperature has a negligible effect on reaction. In earlier experiments involving POME, similar results were obtained, except at 120 °C. This could be attributed to the amount of catalyst that was used in the synthesis involving POME. Instead of using at least 0.8-0.9% w/w catalysts, which were the optimum values found earlier,10 only 0.71% was added to the reaction at 120 °C. Therefore, it is concluded that if all optimum conditions are applied in the reaction, i.e., catalyst 0.8-0.9% w/w, HOPOME: TMP ratio of 3.8:1.0 to 3.9:1.0 (mole:mole), and at least 0.3 mbar vacuum, temperature will not be a significant factor as long as it is maintained in the aforementioned range of 120-150 °C. Pour Points. Lowering the palmitic fraction in POME proved effective in lowering the pour point (PP). The effects of fatty acid composition of POME on the pour points of the palm oil based TMP esters are shown in Table 3. Samples POTE1 to POTE6 represent high oleic content palm oil based TMP esters obtained from reactions between TMP and fractionated POME with different fatty acid compositions. The results indicate that the weight percentages of palmitic fraction, C16:0, and oleic fraction, C18:1, in the HOPOME influenced the PP. To maintain the PP of the palm oil based polyol esters below -30 °C, the C16:0 fractions have to be kept below 8% w/w. If the C16:0 fractions are higher than 8% but still below 9%, the PP will be dropped slightly to -29 °C. The most crucial finding was the effect of C16:0 contents on the PP when the fractions were above 9%.
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Table 2. Product Composition in Transesterification of Palm Oil Methyl Esters and Trimethylolpropane (TMP) Esters at Various Temperatures 110 °C
120 °C
130 °C
140 °C
150°C
97.4 1.7 0.2 0.3 0.6
97.0 2.2 0.0 0.0 0.8
97.4 1.1 0.2 0.0 1.3
92 0.3 0.0 0.0 2.5
91 1.8 0.0 0.0 1.1
HOPOMEa TE DE ME FA HOPOME
92.9 4.7 0.0 0.4 2.0
98.0 1.0 0.0 0.3 0.7
TE DE ME FA POME
93.0 4.2 0.0 0.0 2.8
93.3 3.9 1.4 0.1 1.3
POMEb
a
HOPOME, high oleic content palm oil methyl ester. b POME, palm oil methyl ester.
Table 3. Pour Points of Different Grades of High Oleic Content Palm Oil TMP Esters fatty acids (% w/w) C12:0 C14:0 C16:0 C18:0 C18:1 C18:2 C18:3 others
PPOTEa 0.3 0.9 31.8 4.0 47.6 14.4 0.3 0.7
pour point of TMPc ester (°C)
-1
a
b
POTE1b 0.0 0.0 7.8 6.0 66.2 18.3 0.7 0.9 -32
POTE2 0.0 0.0 5.8 6.2 68.1 18.6 0.8 0.4 -37
POTE3
POTE4
0.0 0.0 7.3 6.2 67.5 17.9 0.7 0.4
0.0 0.0 8.7 6.1 66.4 17.3 0.8 0.8
-36
-29
POTE5 0.0 0.0 9.8 6.2 66.0 18.0 0.7 1.2 -11
POTE6 0.0 0.0 10.1 5.8 64.7 17.7 0.7 0.9 -9
c
PPOTE, palm oil based TMP ester. POTE, high oleic content palm oil based TMP ester. TMP, trimethylolpropane.
Table 4. Characteristics of Different Grades of High Oleic Content Palm Oil TMP Esters product composition (% w/w) FA POME ME DE TE TE46 TE48 TE50 TE52 TE54 others viscosity at 100 °C (cSt) viscosity at 40 °C (cSt) viscosity index pour point of TMPa ester (°C) a
PPOTEa
POTE1b
POTE2
POTE3
POTE7
POTE8
POTE6
0.0 2.2 0.0 4.6 93.2 1.3 5.7 28.5 41.6 22.9 0.0
0.3 1.2 0.0 2.5 96.0 0.0 0.0 1.6 19.2 75.9 3.3
0.0 1.3 0.2 1.1 97.4 0.0 0.0 1.2 16.1 79.1 3.6
0.0 1.2 0.0 1.8 97.0 0.0 0.0 1.6 19.1 76.4 2.9
0.0 2.0 1.3 25.4 71.3 0.0 0.0 1.3 17.4 78.7 2.6
0.3 0.4 0.9 14.5 83.9 0.0 0.0 3.7 25.9 68.0 2.4
1.1 1.5 0.2 1.5 95.7 0.0 0.0 3.0 24.5 69.5 3.0
9.8 49.7 187 -1
9.9 48.4 196 -32
9.6 46.2 199 -37
9.5 45.5 199 -36
9.2 49.9 183 -15
10.0 50.7 189 -12
9.60 46.0 200 -9
PPOTE, palm oil based TMP ester. b POTE, high oleic content palm oil based TMP ester. c TMP, trimethylolpropane.
This is illustrated by the PP of POTE5 (C16:0 fractions of 9.8%), which increased markedly to -11 °C from -29 °C in POTE4 (C16:0 fractions of 8.7%). When the C16:0 fractions were below 9%, the change in C16:0 content of samples POTE1 (7.8%) and POTE4 (8.7%) by similar margins only changed the PP by 3 deg, from -32 °C in POTE1 to -29 °C in POTE4. The effect of C16:0 contents was more pronounced when the fractions were above 10% as shown in POTE6 (10.1%). The PP of POTE6 was further deteriorated to -9 °C. Analysis on the effect of carbon number on the PP of the palm oil based polyol esters also was carried out. TE46, TE48, TE50, TE52, and TE54 represent the triesters with different carbon numbers. For instance, a reaction between methyl oleate (C18:1) with TMP will produce polyol esters identified as ME18 if only one of its -OH groups in TMP was esterified, DE36 if two -OH groups were esterified, and TE54 if all -OH were esterified. Table 4 shows that samples with high TE contents of at least 90% w/w (high conversion) as well as containing a TE with a carbon number of 54 (TE54)
of at least 75% (w/w) will have a PP of less than -30 °C. In cases where the starting HOPOME contained a large amount of C16:0 (POTE6), which was reflected in the TE54 content at 69.5% w/w, the PP of the esters was high at -9 °C even when the reaction reached almost 96% w/w TE conversion. In addition, the PP also was affected by the extent of reaction. In the synthesis of POTE7, although the starting HOPOME contained a lower percentage of C16:0 at 6.5% w/w, poor reaction conversion to TE, 71% w/w, resulted in higher PP POTE of -15 °C. Hence, both factors, namely the fatty acid composition of fractionated POME and the reaction conversion, influenced the low-temperature properties of the palm oil based synthetic lubricants. As mentioned earlier, the effect of C16:0 in the HOPOME was so critical that it increased the PP from -30 to -9 °C when the amount of C16:0 increased above 10% w/w. The reaction conversion to TE also must be maintained above 90% w/w to ensure the esters have excellent pour points. The use of vacuum distillation to fractionate POME was proven
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more effective than the two-stage low-temperature crystallization process proposed by Gryglewicz.8 The two-stage crystallization method only reduced the C16:0 content to 13.5% w/w, and thus the PP of lard-based TMP esters was improved to only -10.5 °C. The increase in the level of unsaturation in POTE was likely to reduce the oxidative stability of the oil. However, the results from our previous study14 showed that the oxidative stabilities of POTE and PPOTE, which were derived from the original POME, were similar at an RBOT value of 14 min. The oxidative stability was determined using the ASTM method D2272, or the Rotary Bomb Oxidation Test (RBOT). Apparently, there was no detrimental effect of increasing oleic content (monounsaturation) on the oxidation stability of the POTE. However, it has been shown that the presence of multiple double bonds or polyunsaturation in vegetable oils greatly accelerates the oxidation polymerization, thus causing oxidative stability problems in vegetable oils. In fact, much effort has been spent on the hydrogenation of polyunsaturated oils into high oleic content oils such as high oleic sunflower oil (HOSO) to improve their oxidative stability.15 Viscosity and Viscosity Index (VI). The presence of partial esters, especially the diester, affected the VI of the POTE as shown in Table 4. Although samples POTE7 and POTE8 exhibit excellent lubricity at 40 °C (49.9 and 50.7 cSt), both recorded lower VI values at 183 and 189, respectively. This was probably due to hydrogen bonding from the -OH bonds in the partial esters. The intermolecular hydrogen bonding from the -OH bonds increased the viscosity of the oil. The exceptionally high viscosity also suggested that a similar phenomenon occurs in castor oil,6 which contains 88% esterified ricinoleic fatty acid. However, this filmforming ability was not stable and deteriorated at higher temperature, thus resulting in lower VI values. Castor oil exhibits a viscosity 5 times higher than most vegetable oils, but an extremely low VI value of only 90. It appears that there was no definite correlation between the fatty acid structure of the samples, i.e., the carbon number with the viscosity or VI. Some of the samples with low TE54 contents (POTE6) exhibited excellent VI values compared to the samples with high TE 54 contents (POTE1, POTE2, and POTE3). Conclusions The pour points of conventional palm oil based TMP esters, which were well below the requirements set by the lubricants’ manufacturers, were successfully reduced to -32 °C in high oleic content palm oil based TMP esters. The use of vacuum distillation to fractionate the POME prior to synthesis proved effective in lowering the PP of palm oil based lubricants compared to 25 °C for natural refined palm oil. Both factors, namely the fatty acid composition of fractionated POME and the reaction conversion, influenced the low-temperature properties of the palm oil based synthetic lubricants. The concentration of C16:0 methyl ester below 10% w/w will ensure that the PP of oil-based TMP esters will be below -30 °C. In addition, the reaction conversion to TE must be maintained above 90% w/w to ensure
that the esters have excellent PP. Operating temperature had a negligible effect on the reaction yield so long as the temperature was kept above 120 °C. The viscosities of high oleic content palm oil based TMP esters are almost constant at 50 cSt and VI values are around 199. Acknowledgment The authors acknowledge financial support from the Ministry of Science, Technology and the Environment, Malaysia, under an IRPA research grant (03-02-040145-EA001) and technical support from the Advanced Oleochemical Technology Center, Malaysian Palm Oil Board. Literature Cited (1) Moore, L. D.; Fels, D. R.; Seay, A. B.; Lopez, C.; Harris, K. E.; Peck, D. A. PAO-Based Synthetic Lubricants in Industrial Applications. Lubr. Eng. 2003, 59, 23. (2) Shanley, A.; Butcher, C. Lubricants: Aims for Higher Performance. Chem. Eng. 1999, 6, 69. (3) Glancey, J. L.; Knowlton, S.; Benson, E. R. Development of High Oleic Soybean Oil-Based Hydraulic Fluid, 1998 SAE Transactions. J. Commer. Veh. 1998, 107, 266. (4) Uosukainen, E.; Linko, Y.-Y.; La¨msa, M.; Tervakangas, T.; Linko, P. Transesterification of Trimethylolpropane And Rapeseed Oil Methyl Ester To Environmentally Acceptable Lubricants. J. Am. Oil Chem. Soc. 1998, 75, 1557. (5) Asadauskas, S.; Perez, J. M.; Duda, J. L. Lubrication Properties of Castor Oil-Potential Base Stock for Biodegradable Lubricants. Lubr. Eng. 1997, 53, 35. (6) Erhan, S. Z.; Asadauskas, S. Lubrication Basestocks from Vegetable Oils. Ind. Crop Prod. 2000, 11, 277. (7) Asadauskas, S.; Erhan, S. Z. Depression of Pour Vegetable Oil by Blending with Diluents Used for Biodegradable Lubricants. J. Am. Oil Chem. Soc. 1999, 76, 313. (8) Gryglewicz, S.; Piechocki, W.; Gryglewicz, G. Preparation of Polyol Esters Based on Vegetable and Animal Fats. Bioresour. Technol 2003, 87, 35. (9) Yunus, R.; Ooi, T. L.; Fakhru’l-Razi, A.; Basri, S. A Simple Capillary Column Gas Chromatography Method For Analysis of Palm Oil-Based Polyol Esters. J. Am. Oil Chem. Soc. 2002, 79, 1075. (10) Yunus, R.; Fakhru’l-Razi, A.; Ooi, T. L.; Iyuke, S. E.; Idris, A. Transesterification of Trimethylolpropane and Palm Oil Methyl Ester to Environmentally Acceptable Lubricants. J. Oil Palm Res. 2003, 15, 36. (11) Annual Book of ASTM Standards. Petroleum Products, Lubricants, and Fossil Fuels; American Society for Testing and Materials: Philadelphia, 1995. (12) Satsuki, T. Application of MES in Detergents. INFORM 1999, 3, 1099. (13) Yunus, R.; Ooi, T. L.; Fakhru’l-Razi, A.; Iyuke, S. E.; Biak, D. R. W. Kinetics of Transesterification of Palm-based Methyl Esters with Trimethylolpropane. J. Am. Oil Chem. Soc. 2004, 81, 497. (14) Yunus, R.; Fakhru’l-Razi, A.; Ooi, T. L.; Iyuke, S. E.; Idris, A. Lubrication properties of trimethylolpropane esters based on palm oil and palm kernel oils. Eur. J. Lipid Sci. Technol. 2004, 106, 52. (15) Asadauskas, S.; Perez, J. M.; Duda, J. L. Oxidative Stability and Anti Wear Properties of High Oleic Vegetable Oils. Lubr. Eng. 1996, 52, 877.
Received for review May 5, 2005 Revised manuscript received August 18, 2005 Accepted August 25, 2005 IE050530+
