Figure 1.
Methyl ssters of: (a) palm oil, (b) candlenut oil, and (c) sunflower seed oil.
Biodiesel products show corrosive properties. Biodiesel contains components of saturated and unsaturated esters which tend to be unstable, sensitive to light, temperature, and metal ions. Thus, the study aims to synthesize biodiesel from various vegetable oils (palm oil, sunflower seed oil, and candlenut oil), and to analyze its corrosiveness to ferrous nails and characterization of biodiesel. The research stages were: synthesis of methyl ester and its characterization, and corrosion test. The results showed that the methyl ester characteristics of the samples meet requirements with SNI7182 : 2015. In GC-MS results, the largest components of methyl esters from candlenut oil and sunflower seed oil were 35.04% methyl oleate and 46.79% methyl oleate respectively, while in palm oil, the largest components were 41.60% methyl oleate and 41.16%. methyl palmitate. Corrosion test showed that the corrosion rate of ferrous nail in biodiesel at room temperature was lower than 70 ℃. Based on GC-MS and SEM results, biodiesel contained high unsaturated fatty acids and had a corrosion rate, i.e., at room temperature, the methyl ester of palm oil, candlenut oil, and sunflower seed oil were 0.006 mpy, 0.011 mpy, and 0.011 mpy respectively, while at 70 ℃, they were 0.011 mpy, 0.016 mpy, and 0.017 mpy, respectively. The results corresponded to SEM results at high temperature and significantly high content of unsaturated fatty acids. It was indicated by the formation of pits.
Citation: Aman Santoso, Novita Agustin, Sumari Sumari, Siti Marfuah, Rini Retnosari, Ihsan Budi Rachman, Anugrah Ricky Wijaya, Muhammad Roy Asrori. Synthesis of methyl esters from palm oil, candlenut oil, and sunflower seed oil and their corrosion phenomena on iron nail[J]. AIMS Materials Science, 2022, 9(5): 719-732. doi: 10.3934/matersci.2022044
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Biodiesel products show corrosive properties. Biodiesel contains components of saturated and unsaturated esters which tend to be unstable, sensitive to light, temperature, and metal ions. Thus, the study aims to synthesize biodiesel from various vegetable oils (palm oil, sunflower seed oil, and candlenut oil), and to analyze its corrosiveness to ferrous nails and characterization of biodiesel. The research stages were: synthesis of methyl ester and its characterization, and corrosion test. The results showed that the methyl ester characteristics of the samples meet requirements with SNI7182 : 2015. In GC-MS results, the largest components of methyl esters from candlenut oil and sunflower seed oil were 35.04% methyl oleate and 46.79% methyl oleate respectively, while in palm oil, the largest components were 41.60% methyl oleate and 41.16%. methyl palmitate. Corrosion test showed that the corrosion rate of ferrous nail in biodiesel at room temperature was lower than 70 ℃. Based on GC-MS and SEM results, biodiesel contained high unsaturated fatty acids and had a corrosion rate, i.e., at room temperature, the methyl ester of palm oil, candlenut oil, and sunflower seed oil were 0.006 mpy, 0.011 mpy, and 0.011 mpy respectively, while at 70 ℃, they were 0.011 mpy, 0.016 mpy, and 0.017 mpy, respectively. The results corresponded to SEM results at high temperature and significantly high content of unsaturated fatty acids. It was indicated by the formation of pits.
Consumption of fossil fuels increases rapidly and is categorized as non-renewable fuels [1]. As an impact, there will be an energy crisis in the future [2]. Moreover, fossil fuels cause problems of environment pollution. To reduce fossil fuel usage, researchers have begun exploring alternative fuels [3] that are renewable raw materials in nature and cheap production, such as biodiesel [4].
Biodiesel is a renewable fuel derived from vegetable oils or animal fats. Some of the advantages of biodiesel include higher combustion efficiency and cetane number compared to petroleum-derived diesel fuel, as well as having lower sulphur and aromatic compounds, so that the emission of harmful gases from combustion is lower than petroleum-derived diesel fuel. A common method for the biodiesel synthesis was transesterification [5]. The reaction was a conversion reaction between triglycerides and alcohol to form fatty acid methyl esters and glycerol as a by-product [6]. The synthesis could reduce the viscosity of vegetable oil, so it can be used as fuel for diesel engines [7].
Biodiesel products contained saturated and unsaturated esters which were unstable, sensitive to light, temperature, and metal ions [8]. When compared to diesel fuel, biodiesel contained water vapor, organic acids, aldehydes, peroxides, ketones, and esters that caused corrosion in the fuel combustion system [9]. In addition, several studies have shown that the use of biodiesel was more corrosive than ordinary diesel fuel [8]. The corrosiveness of biodiesel can also be affected by the stability of the biodiesel. The content of biodiesel can affect the stability of biodiesel against oxidation in the air. The stability level of biodiesel will decrease if the linoleic acid content in biodiesel increases [10]. Therefore, this study demonstrates corrosiveness of biodiesel on iron nail surfaces. Because iron nails are local commercial materials that corrosion occurs. This study introduces the demonstration by using an iron nail that is common for alloy based-machine material with low quality.
Three raw materials for biodiesel synthesis were from unique vegetable oils, namely palm oil, candlenut oil, and sunflower seed oil [11]. Palm oil has a relatively high oil content (40%) [12]. Crude palm oil has a higher viscosity coefficient value than diesel fuel, so it cannot be directly used as diesel fuel. Candlenut oil has an iodine number of 136–167 which means it has a high content of unsaturated fatty acids [13]. In addition, there is vegetable oil that can be used as a source of biodiesel, namely sunflower seed oil. Sunflower seeds contain an oil percentage of 45%–50% of the total mass of extracted seeds [14]. So, these three types of vegetable oil will study a composition of the most dominant fatty acids that determine the corrosion activity of ferrous nails. The main difference from various vegetable oils is the type of fatty acid present in the triglyceride molecule, resulting in a different composition of fatty acid methyl esters. These differences can affect the properties of biodiesel fuel. Fatty acid composition can also determine the degree of saturation/unsaturation and molecular weight of vegetable oils [12].
Therefore, the use of biodiesel has a corrosive effect [10]. The research studied: (1) synthesis of methyl esters from various vegetable oils (palm oil, candlenut oil, and sunflower seed oil) by base-catalysed transesterification, (2) characterization of methyl esters from various vegetable oils (palm oil, candlenut oil, and sunflower seed oil) as biodiesel, (3) constituent components of methyl esters from various vegetable oils (palm oil, candlenut oil, and sunflower seed oil), and (4) corrosiveness of methyl esters from various vegetable oils (palm oil, candlenut, and sunflower seed oil). The characteristics of the synthesized methyl ester were studied to contribute toward corrosion phenomena. Therefore, this preliminary study was performed to find the main characteristic contribution on corrosion phenomena.
The tools in the study were a set of reflux apparatus, which consisted of reflux condenser, three-neck flask, stative, clamps, thermometer, and magnetic stirrer-hotplate, glassware, pycnometer, Thin-Layer Chromatography (TLC) plate of gel silica GF254 type, universal indicator, Ostwald viscosmeter, refractometer, analytical balance, thermostat, Gas Chromatography-Mass Spectrometry (GC-MS) (Shimadzu QP2010 Plus), and Scanning Electron Microscopy (SEM) (FEI Inspect-S50). The materials in the study were palm oil, candlenut oil, sunflower seed oil, anhydrous MgSO4, formic acid p.a. (Sigma Aldrich), diethyl ether p.a. (Sigma Aldrich), n-hexane p.a. (Sigma Aldrich), crystalline iodine, 95% alcohol, phenolphthalein indicator, KOH p.a. (Sigma Aldrich), oxalic acid p.a. (Sigma Aldrich), hydrochloric acid p.a. (Sigma Aldrich), methanol p.a. (Sigma Aldrich), sulfuric acid p.a. (Sigma Aldrich), aquadest, and iron nails from Local material for buildings.
Synthesis of Methyl Ester was conducted by two methods: esterification-transesterification for Candlenut Oil, and transesterification for palm oil and sunflower seed oil. Before the synthesis, palm oil, candlenut oil, and sunflower seed oil were characterized by density, viscosity, refractive index, acid number, saponification number, determination of free fatty acid (FFA). The characterization procedure applied Santoso's research [4,15].
The esterification procedures were: oil: methanol mixture with a volume ratio of 1:12 and 3% w/w H2SO4 catalyst were mixed into a three-neck flask. The mixture was heated to a constant temperature of 65 ℃ while stirring for 3 h. After that, the mixture was cooled to room temperature. The mixture was then separated using a separating funnel for 24 h. The top layer contained H2SO4 and unreacted methanol, while the bottom layer was a mixture of triglycerides (oil) and fatty acid methyl esters. The bottom layer was washed with warm distilled water. It was then added anhydrous MgSO4 to remove the remaining water. Furthermore, the free fatty acid (FFA) content was tested, if the FFA content in the oil was < 2%, then it was continued with the transesterification process.
The transesterification procedures were: oil: methanol mixture in volume ratio of 6:1 with 1% w/w KOH catalyst was mixed into a three-neck flask. The mixture was heated until a constant temperature of 65 ℃ with stirring for 4 h. The reaction process was controlled by TLC analysis until a big difference of Rf between the sample node and the synthesis results was obtained. Furthermore, the characterization carried out on the methyl ester included: density, viscosity, refractive index, acid number, saponification number, GC-MS test [16].
Characterizations of methyl ester were carried out as follow [4]:
1. Density. The alkyl ester was poured in 10 mL of the pycnometer until it was full and there should be no bubbles. Then the weight was weighed and then the weight of the empty pycnometer flask was reduced. For the calculation of density used the Eq 1:
| density(ρ)=sample mass in pycnometer(g)-mass of pycnometer (g)volume of pycnometer (mL) | (1) |
2. Viscosity. The sample was put into an Ostwald viscosmeter tube, and sucked until it passed the two boundary marks. Next, the time noted from the top calibration mark to the bottom calibration mark. Then, it was calculated using the Eq 2:
| ηaquadestηsample = ρaquadest×t aquadestρsample×t sample | (2) |
Which η = viscosity (cSt), ρ = density (g/mL), and t = time (s).
3. Refractive index. Abbe refractometer was used, oil was dripped on the surface of the glass preparation that had been previously cleaned with ethanol. The reading of the refractive index was observed when the bright and dark dividing line was right at the cross of the observation lens. It was performed at a temperature of 26 ℃. For the calculation used the Eq 3:
| n = n′+k(T′–T) | (3) |
Which n = refractive index (25 ℃), n′ = refractive index (observed temperature), k = correction factor (0.00045), T = 25 ℃), and T′ = observed temperature.
4. Acid number. To test the acid number, 1.00 g of CPO was put into a 100 mL Erlenmeyer and then 5.00 mL of alcohol was added. The mixture was heated in a boiling water bath for 10 min. The mixture was then added to the phenolphthalein indicator and then it was titrated with 0.1 N·KOH (which has been standardized with oxalic acid) until a pink colour was formed. To determine the number of acids used the Eq 4:
| acid number = {volume(mL)×Normality(N)×molecular weigh(gmol)}of KOHsample mass (g) | (4) |
5. Saponification number. 0.5 grams of the synthesized methyl ester was added into 250 mL Erlenmeyer with 5 mL n-hexane and 25 mL KOH 0.5 M. The mixture was stirred until homogeneous. The mixture was then heated to boiling for 30 min. The mixture was then cooled at room temperature. The mixture with 5 drops of Phenolphthalein indicator was titrated with HCl 0.5 M. The titration was also carried out on a blank sample.
| saponification number = (V2–V1)×M ×molecular weigh (gmol) of KOHsample mass (g) | (5) |
In Eq 5, Which V2 = Volume of HCl for blank titration (mL), V1 = Volume of HCl for sample titration (mL), and M = molarity of HCl (mol/L).
Corrosion testing was carried out using the immersion test method based on ASTM G-31. Corrosion test procedures were carried out as follows: Iron nails were sanded for 10 min to clean dirt and corrosion crust on the surface. Then, it was rinsed with acetone. After drying, the nails were weighed. Then, each of the nails was dipped in the methyl ester samples in a test tube for 40 d at room temperature and 70 ℃. After that, it was dried in an oven to evaporate the remaining methyl ester with a temperature of 200 ℃ until a constant weight was obtained. Next, it was continued with weighing to determine the amount of mass lost due to corrosion. So, the corrosion rate was measured. In addition, the remaining nails were analysed by Scanning Electron Microscopy (SEM).
Corrosion rate (mpy–millimetre per year) was calculated as Eq 6 [17,18]:
| corrosion rate(mpy) = 8.76 ×Δm(ρ×t ×A) | (6) |
Which Δm = final mass (g)−initial mass (g), ρ = density (g/mL), t = dip time (hour), and A = area (m2).
Transesterification of palm oil and sunflower seed oil was evaluated by TLC. The TLC test results showed a large difference in Rf between the two nodes (vegetable oil and synthetic product) after 4 h of synthesis (Figure 1). The Rf value can be used as evidence in identifying the compound, if the identification of the Rf value produces the same value, the compound can be said to have the same or similar characteristics. If the Rf value is different, the compound can be said to be a different compound [19,20]. Importantly, the TLC test result did not show 100% formation of methyl ester. It was a qualitative analysis as the indicator of the occurred transesterification. Therefore, it was strongly indicated that a reaction product (methyl ester) has been formed because the Rf of the initial compound (vegetable oil) and the synthesized compound were different.
The results of the obtained methyl ester can be seen in Figure 1. The yield of methyl ester from palm oil was 74.34%, while the yield of methyl ester from sunflower seed oil was 75.65%. The yield of methyl ester from candlenut oil was 76.40%. The reaction that occurs between triglycerides and 3 moles of methanol with a KOH catalyst produces 3 mol of methyl ester and 1 mol of glycerol in the transesterification process [7]. The reaction can take place completely if an excess of methanol is added to form a product. Also, catalysts are used to speed up the formation of methyl esters.
The results of the synthesis of methyl esters of palm oil, candlenut oil, and sunflower seed oil were characterized as shown in Table 1.
| parameter | SNI 7182:2015 | Palm | Candlenut | Sunflower Seed | |||
| methyl ester | Oil | methyl ester | Oil | methyl ester | Oil | ||
| density (g/mL) | 0.85–0.89 | 0.879 | 0.946 | 0.887 | 0.957 | 0.880 | 0.951 |
| viscosity (cSt) | 2.3–6.0 | 5.88 | 71.88 | 4.48 | 46.93 | 5.78 | 71.02 |
| refractive index | 1.3–1.45 | 1.444 | 1.471 | 1.445 | 1.476 | 1.448 | 1.472 |
| acid number (mg KOH/g) | max 0.5 | 0.55 | 2.65 | 0.46 | 5.21 | 0.49 | 2.36 |
| saponification number (mg‧KOH/g) | 184.8 | 224.0 | 198.8 | 254.8 | 156.8 | 198.8 | |
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Based on the results of the density data in Table 1, the three types of oil showed that the density of methyl esters is lower than the density of vegetable oils, because the molecular weight of methyl esters was lower, so the intermolecular forces on fatty acid methyl esters were smaller than the intermolecular forces molecules in the oil. The greater the intermolecular forces, the more difficult it for the substance to flow, the more viscous the liquid and the greater the viscosity [21]. Based on the results of the viscosity data in Table 1, the three types of oil showed that the viscosity of methyl esters is lower than the viscosity of vegetable oils, because the molecular weight of methyl esters was smaller than that of oil, so the liquid was not thick and it flowed easily. The value of the refractive index aimed to determine the purity of the methyl ester produced. Based on the results of the refractive index data in Table 1, the three types of oil showed that the refractive index of methyl esters is lower than the refractive index of vegetable oils, because the refractive index of a compound will decrease as the carbon chain and double bonds of the compound decrease. Based on the results of the acid number data in Table 1, the three types of oil indicate that the methyl ester acid number is lower than the vegetable oil acid number, because the smaller the acid number, the smaller the free fatty acids contained in the oil. The smaller the saponification number, the longer the alkyl chain attached to the oil. In addition, the smaller the number of saponification, the smaller the number of milligrams and the number of moles of the required KOH, and the large number of mg·KOH indicated the large number of methyl ester molecules. Based on the results of the saponification number data in Table 1, the three types of oil indicated that the saponification number of methyl esters is lower than the saponification number of vegetable oils, because to saponify one molecule of methyl ester it took one molecule of KOH, while one molecule of triglycerides requires three molecules of KOH. The required KOH to saponify methyl esters is less than the required KOH to saponify triglycerides [22].
Finally, the resulting free fatty acid content was 1.39% palm oil and 1.11% sunflower seed oil. The content values have met the requirements for the transesterification process of < 2%. In candlenut oil, the produced free fatty acid content was 2.55%, the value of the content did not meet the requirements for the transesterification process, so it is necessary to carry out an esterification to reduce the value of free fatty acid levels in candlenut oil. High concentrations can interfere with the transesterification reaction, due to the free fatty acids reacting with a base, so that the reaction products produce soap and it inhibits the formation of maximum products.
GC results of palm oil, candlenut oil, and sunflower seed oil showed the number of methyl ester components based on the number of peaks produced as shown in Figure 2.
The chromatogram showed that there were components of the sample. Then, the main components of fatty acid methyl esters were analysed by MS based on their fragmentation. Mass spectrum analysis has been referred as the WILEY8.LIB library and analysis of fragmentation patterns (data not shown here). The retention time and area of the main components of fatty acid methyl esters were shown in Table 2.
| Peak to | Retention Time (min) | Area | Content (%) | Compound |
| Palm Oil | ||||
| 3 4 5 |
29.089 35.360 35.549 |
22662901 4384965 22902966 |
41.16 7.96 41.60 |
methyl palmitate methyl linoleate methyl oleate |
| 6 | 36.283 | 2443446 | 4.44 | methyl stearate |
| Candlenut Oil | ||||
| 1 2 3 |
6.3330 12.412 17.846 |
5095971 2091120 13146807 |
9.19 3.77 23.71 |
methyl caprylate methyl caprate methyl laurate |
| 4 5 6 7 8 |
22.562 29.086 35.369 35.554 36.287 |
3269184 2457367 6683214 19431707 1894515 |
5.90 4.43 12.05 35.04 3.42 |
methyl myristate methyl palmitate methyl linoleate methyl oleate methyl stearate |
| Sunflower Seed Oil | ||||
| 1 2 3 |
29.049 35.355 35.532 |
1659589 654953 16413036 |
4.73 18.67 46.79 |
methyl palmitate methyl linoleate methyl oleate |
| 4 | 36.275 | 1103121 | 3.14 | methyl stearate |
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Based on the results of the GC-MS test, it can be stated that the synthesis of palm oil was a methyl ester compound. The largest methyl ester content was methyl oleate at 41.60%, so the components of the methyl ester indicated that biodiesel from palm oil contained high amounts of unsaturated fatty acids. However, palm oil also contained a fairly high amount of saturated fatty acids, namely methyl palmitate of 41.16%. The largest methyl ester from candlenut oil was methyl oleate about 35.04%. The largest methyl ester from sunflower seed oil was methyl oleate about 46.79%, so that the constituent components of the methyl ester indicated that biodiesel from sunflower seed oil contained high amounts of unsaturated fatty acids.
The characteristic of the synthesized methyl ester was clear. For more study, the synthesized methyl ester was tested about corrosiveness properties. As a preliminary study, the corrosiveness properties were performed by corrosion phenomena in iron nails.
Differences in the raw materials used for biodiesel production will produce biodiesel with varying properties. Biodiesel contains components of saturated esters and unsaturated esters which tend to be unstable, sensitive to light, temperature, and metal ions [8]. The content of biodiesel can affect the stability of biodiesel against oxidation by oxygen in the air. The high content of unsaturated fatty acids (methyl oleic and methyl linoleic) tends to cause biodiesel to be easily oxidized by air to form free radicals that lead to the formation of corrosive organic compounds [23] or also leads to reactions that form new products such as aldehydes, ketones, lactones, formic acid, acetic acid, and propionic acid [24], especially such as defect/unknown product [25].
The corrosion test was shown in Figure 3. The corrosion test showed that the corrosion rate of the nail immersed in biodiesel was affected by temperature, and the test was carried out at room temperature and temperature of 70 ℃. It was carried out for 40 d, because the corrosion effect did not show after 10, 20, 30 d significantly.
The data in Figure 3 showed that the corrosion rate of the immersed ferrous nail in biodiesel was affected by temperature. Corrosion test results showed that increasing the temperature of biodiesel will tend to increase the corrosion rate of ferrous nails because increasing the temperature of biodiesel will increase the kinetic energy of molecules so the interaction of molecules will increase, including the amount of the absorbed oxygen [18]. On the other hand, the figure showed that the various oil feedstock used to produce biodiesel could also affect its corrosive properties [10]. For previous study, the corrosion phenomena listed in Table 3. The two types of biodiesels, namely methyl esters of candlenut oil and sunflower seed oil, had components containing unsaturated fatty acids with more carbon double bonds and less hydrogen, so it was susceptible to oxidation. The oxidation of biodiesel can reduce the quality of fuel for the engine due to the formation of oxidation products such as aldehydes, alcohols, short chain carboxylic acids, and sediments [26]. However, methyl ester of palm oil has the opposite result, because it has a component containing a fairly high content of unsaturated fatty acids, and a high content of saturated fatty acids. According to previous study [27], composition of fatty acids was strongly linear related to the corrosion rate in gray cast iron. Besides, higher content of unsaturated fatty acids in biodiesel, greater effect on the corrosion in gray cast iron [10,27]. So, this demonstration work showed different corrosion rates because of the difference in chemical compounds and characteristics of the synthesized methyl esters.
| methyl ester from | sample | Conditions | Time (h) | Corrosion rate (mpy) | Ref. |
| sun flower | gray cast iron (93.41% Fe) | T = 18 ℃, P = 74.46 kPa | 450 | 0.0028 | [27] |
| soybean | 0.0019 | ||||
| lard | 0.0016 | ||||
| tallow | 0.0013 | ||||
| coconut | 0.0011 | ||||
| moringa | mild steel (98.8% Fe) | T = 60 ℃ | 1100 | 0.0005 | [28] |
| palm | gray cast iron (94.2% Fe) | T = 25 ℃ | 1200 | 0.0020 | [29] |
| palm | gray cast iron (94.2% Fe) | T = 25 ℃ | 2880 | 0.0028 | [30] |
| rapeseed | mild steel (22.71% Fe) | T = 43 ℃ | 1440 | 0.01819 | [17] |
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The SEM results in Figure 4 showed that the corrosion was spread on the ferrous surface marked by the formation of dark coloured pits, also obtained in the previous study [17,31,32]. The increasing temperature will lead to an increase in the size of the hole (pit) and will spread evenly on the iron nail. This was because the corrosion rate of iron increases with increasing temperature. The nail surface in contact showed the damage, due to corrosion in biodiesel. These nails were very reactive to organic acids formed due to the degradation process in biodiesel. According to previous study [17], elemental composition of corrosion phenomenon on mild steel by XPS results (at%: atomic percentage of metal element) were C (26.28%), O (51.01%), Fe (22.71%) before corrosion and C (42.7%), O (43.55%), and Fe (13.75%) after corrosion. Compared with this demonstration study, it was correlated that Fe content of iron nail reduces after immersion test.
The chemical reactions describing the corrosion mechanism of iron-based alloys in biodiesel are presented in Eqs 7–11 [33]. In this work, iron may be oxidized as an oxide compound and methyl ester may be produced hydrocarbon derivatives.
| 4Fe+3O2→ 2Fe2O3 | (7) |
| 2Fe+O2+H2O→2Fe(OH)2 | (8) |
| 4Fe(OH)2+O2→2Fe2O3⋅H2O+ 2H2O | (9) |
| RCOOR1→ RCOO∗+R∗1 | (10) |
| 2RCOO∗+ Fe →FeCO3+ R - R + CO | (11) |
Based on Figure 4, it is possible that the nail weight will be reduced after the immersion test. The presence of dissolved nails in biodiesel can accelerate the catalytic reaction of the biodiesel degradation process, because nails can directly react with fatty acids to produce fatty acid alkyl radicals [34]. During the oxidation process of biodiesel by oxygen in the air, methyl esters from biodiesel formed free radicals and double bonds that form new products such as aldehydes, ketones, lactones, formic acid, acetic acid, and propionic acid [24]. Biodiesel is hygroscopic because it easily absorbs moisture and water, so that it can form dew on nail surfaces that have the potential to cause corrosion [26].
The study has resulted in the following conclusions: (1) synthesis of methyl esters by base-catalysed transesterification (KOH) can be carried out on palm oil, candlenut oil and sunflower seed oil, but esterification was carried out first to reduce free fatty acid levels in candlenut oil, (2) the characteristics of the synthesized methyl esters from various vegetable oils (palm oil, candlenut oil, and sunflower seed oil) were carried out with the parameters of density, viscosity, refractive index, and acid number, and met requirements of the biodiesel standards of SNI7182 : 2015, (3) the components of the methyl esters from candlenut oil and sunflower seed oil contained high amounts of unsaturated fatty acids, while the components of methyl esters from palm oil contained a fairly high content of unsaturated fatty acids, and a high content of saturated fatty acids, and (4) the unsaturated fatty acid content of the three types of vegetable oil caused biodiesel to be easily oxidized by oxygen in the air. Corrosion rates of the methyl ester of palm oil, candlenut oil, and sunflower seed oil were 0.006 mpy, 0.011 mpy, and 0.011 mpy respectively at room temperature, and also 0.011 mpy, 0.016 mpy, and 0.017 mpy, respectively at 70 ℃. Therefore, biodiesel from candlenut oil and sunflower seed oil was more corrosive than palm oil based on SEM results. It was indicated by the formation of pits. The corrosiveness problem will be a challenge regarding the produced by-products and their effects.
On this occasion, the author would like to thank to Lembaga Penelitian dan Pengabdian Masyarakat Universitas Negeri Malang (LPPM UM) by funding this research.
The authors declare no conflict of interest.
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| 2. | Andrian FERNANDES, Erwin ERWIN, Arif WAHYUDIANTO, Harlinda KUSPRADINI, Effect of Keruing and Meranti Wood Extracts on the Nail Corrosion Rate, 2024, 52, 1017-0715, 555, 10.5658/WOOD.2024.52.6.555 |
Figures(4) / Tables(3)
Aman Santoso, Novita Agustin, Sumari Sumari, Siti Marfuah, Rini Retnosari, Ihsan Budi Rachman, Anugrah Ricky Wijaya, Muhammad Roy Asrori. Synthesis of methyl esters from palm oil, candlenut oil, and sunflower seed oil and their corrosion phenomena on iron nail[J]. AIMS Materials Science, 2022, 9(5): 719-732. doi: 10.3934/matersci.2022044
| parameter | SNI 7182:2015 | Palm | Candlenut | Sunflower Seed | |||
| methyl ester | Oil | methyl ester | Oil | methyl ester | Oil | ||
| density (g/mL) | 0.85–0.89 | 0.879 | 0.946 | 0.887 | 0.957 | 0.880 | 0.951 |
| viscosity (cSt) | 2.3–6.0 | 5.88 | 71.88 | 4.48 | 46.93 | 5.78 | 71.02 |
| refractive index | 1.3–1.45 | 1.444 | 1.471 | 1.445 | 1.476 | 1.448 | 1.472 |
| acid number (mg KOH/g) | max 0.5 | 0.55 | 2.65 | 0.46 | 5.21 | 0.49 | 2.36 |
| saponification number (mg‧KOH/g) | 184.8 | 224.0 | 198.8 | 254.8 | 156.8 | 198.8 | |
DownLoad:
CSV
| Peak to | Retention Time (min) | Area | Content (%) | Compound |
| Palm Oil | ||||
| 3 4 5 |
29.089 35.360 35.549 |
22662901 4384965 22902966 |
41.16 7.96 41.60 |
methyl palmitate methyl linoleate methyl oleate |
| 6 | 36.283 | 2443446 | 4.44 | methyl stearate |
| Candlenut Oil | ||||
| 1 2 3 |
6.3330 12.412 17.846 |
5095971 2091120 13146807 |
9.19 3.77 23.71 |
methyl caprylate methyl caprate methyl laurate |
| 4 5 6 7 8 |
22.562 29.086 35.369 35.554 36.287 |
3269184 2457367 6683214 19431707 1894515 |
5.90 4.43 12.05 35.04 3.42 |
methyl myristate methyl palmitate methyl linoleate methyl oleate methyl stearate |
| Sunflower Seed Oil | ||||
| 1 2 3 |
29.049 35.355 35.532 |
1659589 654953 16413036 |
4.73 18.67 46.79 |
methyl palmitate methyl linoleate methyl oleate |
| 4 | 36.275 | 1103121 | 3.14 | methyl stearate |
DownLoad:
CSV
| methyl ester from | sample | Conditions | Time (h) | Corrosion rate (mpy) | Ref. |
| sun flower | gray cast iron (93.41% Fe) | T = 18 ℃, P = 74.46 kPa | 450 | 0.0028 | [27] |
| soybean | 0.0019 | ||||
| lard | 0.0016 | ||||
| tallow | 0.0013 | ||||
| coconut | 0.0011 | ||||
| moringa | mild steel (98.8% Fe) | T = 60 ℃ | 1100 | 0.0005 | [28] |
| palm | gray cast iron (94.2% Fe) | T = 25 ℃ | 1200 | 0.0020 | [29] |
| palm | gray cast iron (94.2% Fe) | T = 25 ℃ | 2880 | 0.0028 | [30] |
| rapeseed | mild steel (22.71% Fe) | T = 43 ℃ | 1440 | 0.01819 | [17] |
DownLoad:
CSV
| parameter | SNI 7182:2015 | Palm | Candlenut | Sunflower Seed | |||
| methyl ester | Oil | methyl ester | Oil | methyl ester | Oil | ||
| density (g/mL) | 0.85–0.89 | 0.879 | 0.946 | 0.887 | 0.957 | 0.880 | 0.951 |
| viscosity (cSt) | 2.3–6.0 | 5.88 | 71.88 | 4.48 | 46.93 | 5.78 | 71.02 |
| refractive index | 1.3–1.45 | 1.444 | 1.471 | 1.445 | 1.476 | 1.448 | 1.472 |
| acid number (mg KOH/g) | max 0.5 | 0.55 | 2.65 | 0.46 | 5.21 | 0.49 | 2.36 |
| saponification number (mg‧KOH/g) | 184.8 | 224.0 | 198.8 | 254.8 | 156.8 | 198.8 | |
| Peak to | Retention Time (min) | Area | Content (%) | Compound |
| Palm Oil | ||||
| 3 4 5 |
29.089 35.360 35.549 |
22662901 4384965 22902966 |
41.16 7.96 41.60 |
methyl palmitate methyl linoleate methyl oleate |
| 6 | 36.283 | 2443446 | 4.44 | methyl stearate |
| Candlenut Oil | ||||
| 1 2 3 |
6.3330 12.412 17.846 |
5095971 2091120 13146807 |
9.19 3.77 23.71 |
methyl caprylate methyl caprate methyl laurate |
| 4 5 6 7 8 |
22.562 29.086 35.369 35.554 36.287 |
3269184 2457367 6683214 19431707 1894515 |
5.90 4.43 12.05 35.04 3.42 |
methyl myristate methyl palmitate methyl linoleate methyl oleate methyl stearate |
| Sunflower Seed Oil | ||||
| 1 2 3 |
29.049 35.355 35.532 |
1659589 654953 16413036 |
4.73 18.67 46.79 |
methyl palmitate methyl linoleate methyl oleate |
| 4 | 36.275 | 1103121 | 3.14 | methyl stearate |
| methyl ester from | sample | Conditions | Time (h) | Corrosion rate (mpy) | Ref. |
| sun flower | gray cast iron (93.41% Fe) | T = 18 ℃, P = 74.46 kPa | 450 | 0.0028 | [27] |
| soybean | 0.0019 | ||||
| lard | 0.0016 | ||||
| tallow | 0.0013 | ||||
| coconut | 0.0011 | ||||
| moringa | mild steel (98.8% Fe) | T = 60 ℃ | 1100 | 0.0005 | [28] |
| palm | gray cast iron (94.2% Fe) | T = 25 ℃ | 1200 | 0.0020 | [29] |
| palm | gray cast iron (94.2% Fe) | T = 25 ℃ | 2880 | 0.0028 | [30] |
| rapeseed | mild steel (22.71% Fe) | T = 43 ℃ | 1440 | 0.01819 | [17] |
