Low Oxidative Stability Research Articles

Moringa oleifera: A potential source for production of biodiesel and antioxidant additives

This work reports the use of Moringa oleifera oil and leaves as potential sources for the production of biodiesel and antioxidant additives for biodiesels, respectively. The M. oleifera methyl ester was prepared by a two-step reaction and exhibited physical–chemical properties that met the minimum or maximum limits of the EN 14214, emphasizing the high induction period (IP) of 19.3h. Ethanolic extracts of M. oleifera leaves were evaluated as additives to increase the IP value of biodiesels. The results indicate that the 98% (v/v) ethanolic extract increased IP values of soybean biodiesel from 3.8 to 10.3h using the 100μgg−1 of extract, showing better performance than the synthetic antioxidant tert-butyl-hydroquinone. The extract also provided similar efficiency to methyl esters produced from sunflower, colza, corn and residual cooking oils. These results evidence the promising use of M. oleifera not only for biodiesel production but also as a source of antioxidant additives for biodiesels with low oxidation stability.

Increase of Oxidation Stability of Biodiesel from Palm Fatty Acid Distillate (PFAD) by Antioxidant Additions

Biodiesel is a renewable energy, possesses high cetane number and flash points, resulting in its suitable uses in diesel machines and its safe distribution and storage, as well as low gas emission, and its function as lubricant. Disadvantages of the biodiesel include its high density and viscosity, resulting in plug and ineffective injection system, and low oxidation stability. This research studied about antioxidant additions to maintain oxidation stability of biodiesel. Induction period (IP) measuring kit, to measure oxidation stability, was constructed by using modified Rancimat principle. The best operation conditions were at temperature of 110 0 C and pressure of 6 hours).

Biodiesel Production from Jatropha Seeds

This work was performed to extract oil from Jatropha seeds and to study the optimum conditions of extraction. The extraction process was observed with regard to oil yield percent versus time to calculate the kinetic and thermodynamic parameter. On the other hand, Jatropha oil was used as feed stock for biodiesel production by alkali catalyzed methanolysis. The optimum condition for the production process was studied depending on the methyl ester content. The Jatropha biodiesel was blended with 10, 15, and 25% with petroleum diesel and the thermo-physical properties were studied. All the measured properties of Jatropha oil and biodiesel are determined by international standards ASTM6751-07b, with exception of lower oxidation stability.

Oxidation and low temperature stability of polymerized soybean oil-based lubricants

Oxidation and low temperature stability of polymerized soybean oil (PSO)-based lubricants have been investigated by the pressurized differential scanning calorimetry (PDSC) method. It was found that PSO samples have lower oxidative stability than their precursor, soybean oil. The main reason for the decreased stability is the generation of tertiary carbons during polymerization. By using antioxidant additives, the PSO samples responded very well and increased their onset temperature (OT) by 70–80°C. Thermogravimetric analyses have been performed on the PSO samples and it was observed that they are thermally stable at temperatures up to 250°C. Cold flow property data shows that the PSO samples are good for use in formulating high temperature lubricants. Two model compounds which have terminal double bonds, triacyl-10-undecenoate and allyl 10-undecenoate, have been polymerized. The oxidation stability of these two compounds was investigated by the PDSC method and compared to that of the PSO samples. This study will help us understand the relationships between oxidation stability and molecular structure of PSO-based lubricants. In addition, oxidation stability data of polyethylene (PE) and polypropylene (PP) were used in helping to explain the oxidation stability results of the PSO samples.

Application of artificial neural networks to predict viscosity, iodine value and induction period of biodiesel focused on the study of oxidative stability

In the search for alternative fuels that can gradually replace petroleum derivatives, biodiesel is highlighted as a substitute for diesel and it is defined as a biofuel obtained from transesterification of triglycerides. Despite of several advantages over mineral diesel, an elementary disadvantage of biodiesel is its low oxidative stability, which is strongly influenced by the unsaturation degree of its fatty acid methyl esters (FAMEs) and by the conditions to which biodiesel is exposed during storage, transporting and handling. The present work focuses on the optimization and application of artificial neural networks (ANNs) on prediction of viscosity, iodine value and induction period of biodiesel, properties that directly reflect its level of degradation, to evaluate the oxidative stability. The input variables were the percentages of the 13 most common FAMEs in biodiesels and the transesterification does not change the fatty esters profile of the raw material. In this case the ANN method allows predicting viscosity, iodine value and induction period, either before transesterification, after synthesis of biodiesel or during the storage. Therefore, this method can be useful as a tool to evaluate the potential of raw materials to produce a biodiesel with good oxidative stability and to reach improvements concerning official methods. The optimization process of the ANN occurred in three steps: test of algorithms for adjusting weights, test of stopping condition and test of activation functions, and the physicochemical properties were treated independently. For the set of test samples, which simulates real samples, the application of the optimized ANNs provided results with root mean squared errors (RMSE) of 0.55mm2/s, 3.49g/100g and 0.89h for viscosity, iodine value and induction period, respectively, what ensures the feasibility of the proposed method. A comparison between the proposed method and linear methods from literature, both based on the biodiesel composition indicates that our ANN model is much more adequate to the problem addressed.

Improving the Oxidation Stability of Karanja Oil Biodiesel

Biodiesel is an alternative fuel to diesel and is seeking wider acceptance because of its claimed environmental and socio-economic benefits. The fuel properties of biodiesel are similar to those of fossil fuel. However, one of its main obstacles remains its lower oxidative stability. This problem may be overcome by the addition of suitable antioxidant. In India, biodiesel is produced from non-edible karanja oil, which has considerable potential. Because karanja oil biodiesel contains a higher amount of unsaturated fatty acids, it is necessary to find a suitable method for improving its oxidation stability. We report a study on the effect of antioxidants on the stability of the fuel. The addition of antioxidants improves oxidation stability of karanja oil biodiesel.

Impact assessment of mechanical harvest on fruit physiology and consequences on oil physicochemical and sensory quality from 'Manzanilla de Sevilla' and 'Manzanilla Cacereña' super-high-density hedgerows. A preliminary study.

Super-intensive cultivation facilitates olive mechanized harvesting, allowing substantial savings in the production cost of virgin olive oil (VOO). However, the number of varieties adapted to this type of cultivation is small. This study explores the impact that harvesting with a grape straddle harvester of 'Manzanilla de Sevilla' and 'Manzanilla Cacereña' olives grown in super-intensive cultivation has on the physiology of the fruit and the quality of the oil subsequently extracted. For both cultivars, fruits harvested mechanically showed higher respiration and ethylene production and lower firmness than fruits harvested by hand. Their oils exhibited lower phenol contents, lower oxidative stability and lower presence of positive sensory attributes. However, in these oils the values of parameters used to assess the level of quality of VOO remained within the limits required for the best commercial category. Mechanical harvesting of 'Manzanilla de Sevilla' and 'Manzanilla Cacereña' super-high-density hedgerows induced physiological alterations in the fruits and a reduction in the contents of natural antioxidants and flavour components in the oils, though it did not result in a loss of the 'Extra' level of quality.

Sterol and Fatty Acid Compositions of Olive Oil as an Indicator of Cultivar and Growing Area

AbstractBecause of the importance of cultivar and growing area on the quality and quantity of extracted olive oil, this study examined the effects of two different growing areas (Qom (subdesertic) and Gorgan (Caspian zone) that have important differences in altitude, latitude, and climatic conditions on the physicochemical characteristics of extracted oils from three common cultivars (Beleydi, Mission and Koroneiki) growing in Iran. Independently of the growing area conditions, Beleydi cultivars showed the lowest values of oil content (16.93 ± 1.55 and 43.54 ± 0.18 % in Qom and Gorgan, respectively) the greatest acidity, even higher than the limits specified by the International Olive Council (IOC) regulations (1.04 and 0.46 % in Qom and Gorgan, respectively), and the lowest oxidative stability (9.0 and 6.7 h in Qom and Gorgan, respectively) among the studied cultivars. All cultivars growing in Qom had lower oil contents, but they had higher oleic acid and β‐sitosterol content and lower PUFA/SFA ratios in comparison with cultivars grown in Gorgan. Therefore, cultivars grown in Qom had higher oxidative stability. Finally, when principal component analysis (PCA) was applied, the fatty acid and sterol profiles could be used to separate olive samples according to their cultivar and growing area, respectively.

Effect of Operational Parameters on Determination of Oxidative Stability Measured by Rancimat Method

Operational parameters of Rancimat, including sample weight (3, 6, 9 g), airflow rate (10, 15, 20 L/h) and temperature (110, 120, 130°C) were evaluated to determine their effects on oxidative stability index, temperature coefficient, Q10 number, and shelf life prediction of ghee (anhydrous milk fat). These parameters showed statistically significant effects on the oxidative stability index. It was observed that when the sample weight and airflow rate at a given temperature were at saturated air condition, the oxidative stability indexes showed no significant differences (p < 0). As the temperature increased, oxidative stability index decreased and average coefficient of variation was minimal at 120°C. The conditions under which the ghee sample was saturated with air and had a relatively lower oxidative stability index, was with sample weight of 6 g, temperature at 120°C and an airflow rate of 15 L/h. Temperature coefficient and Q10 number were independent of sample weight and air flow rate, however, they had a significant effect on shelf life prediction of ghee.

4-(Trifluoromethyl)-benzonitrile: A novel electrolyte additive for lithium nickel manganese oxide cathode of high voltage lithium ion battery

In this work, 4-(Trifluoromethyl)-benzonitrile (4-TB) is used as a novel electrolyte additive for LiNi0.5Mn1.5O4 cathode of high voltage lithium ion battery. Charge–discharge tests show that the cyclic stability of LiNi0.5Mn1.5O4 is significantly improved by using 0.5 wt.% 4-TB. With using 4-TB, LiNi0.5Mn1.5O4 delivers an initial capacity of 133 mAh g−1 and maintains 121 mAh g−1 after 300 cycles with a capacity retention of 91%, compared to the 75% of that using base electrolyte (1 M LiPF6 in ethylene carbonate(EC)/dimethyl carbonate(DMC)). The results from linear sweep voltammetry, density functional theory calculations, electrochemical impedance spectroscopy, scanning electron microscope, energy dispersive spectroscopy, Fourier transform infrared, and inductively coupled plasma, indicate that 4-TB has lower oxidative stability than EC and DMC, and is preferentially oxidized on LiNi0.5Mn1.5O4 forming a low-impedance protective film, which prevents the subsequent oxidation decomposition of the electrolyte and suppresses the manganese dissolution from LiNi0.5Mn1.5O4.

The Oxidation Effect of Palm Oil Based Lubricant Using Four – Ball Tribotester

Lubrications industry is widely expand throughout the years. Well established mineral oil based promised the highest demand all over the world. But as the environmental concern is debated at most of world conferences, people are thinking to find the alternative for mineral oil replacement due to its non-biodegradable behaviour. The best suited source that having quite a par characteristic with mineral oil is vegetable oil. Vegetable oil is well known with its super bio-degradable characteristic. The source is renewable and does not require huge cost as compared to mineral and synthetic oil in term of exploration, development, production and transportation. Palm oil based is best suited among the vegetable oil series because of its stability and sources around the world. The major issue of palm oil based lubricant is low oxidative stability as the lubricant is commonly used at very high temperature and long shelf life application. Therefore some modification of molecule structure is needed by adding selected anti-oxidant at certain ratios. Tertier-butyl-hydroquinone (TBHQ) is used as anti-oxidantin this study. The results showing that a sufficient concentration of anti-oxidantprovides better solution for the low oxidative stability issues raised in palm oil based lubricants. The TBHQ also showed good characteristic in protecting two mating surfaces in wear scar analysis.

Experimental investigation of performance and regulated emissions of a diesel engine with Calophyllum inophyllum biodiesel blends accompanied by oxidation inhibitors

Biodiesel having higher unsaturation possesses lower oxidation stability, which needs treatment of oxidation inhibitors or antioxidants. It is expected that antioxidants may affect the clean burning characteristic of biodiesel. Calophyllum inophyllum Linn oil is one of the promising non-edible based feedstock which consists of mostly unsaturated fatty acids. This paper presents an experimental investigation of the antioxidant addition effect on engine performance and emission characteristics. Biodiesel (CIBD) was produced by one step esterification using sulfuric acid (H2SO4) as catalyst and one step transesterification using potassium hydroxide (KOH) as a catalyst. Two monophenolic, 2(3)-tert-Butyl-4-methoxyphenol (BHA) and 2,6-di-tert-butyl-4-methylphenol (BHT) and one diphenolic, 2-tert-butylbenzene-1,4-diol (TBHQ) were added at 2000 ppm concentration to 20% CIBD (CIB20). The addition of antioxidants increased oxidation stability without causing any significant negative effect of physicochemical properties. TBHQ showed the greatest capability in increasing stability of CIB20. The tests were carried out using a 55 kW 2.5 L four-cylinder diesel engine at constant load varying speed condition. The performance results indicate that CIB20 showed 1.36% lower mean brake power (BP) and 4.90% higher mean brake specific fuel consumption (BSFC) compared to diesel. The addition of antioxidants increased BP and reduced BSFC slightly. Emission results show that CIB20 increased NOx but decreased CO and HC emission. Antioxidants reduced 1.6–3.6% NOx emission, but increased both CO and HC emission compared to CIB20. However, the level was below the diesel emission level. Thus CIB20 blends with antioxidants can be used in diesel engines without any modification.

Production of free monounsaturated fatty acids by metabolically engineered Escherichia coli

BackgroundMonounsaturated fatty acids (MUFAs) are the best components for biodiesel when considering the low temperature fluidity and oxidative stability. However, biodiesel derived from vegetable oils or microbial lipids always consists of significant amounts of polyunsaturated and saturated fatty acids (SFAs) alkyl esters, which hampers its practical applications. Therefore, the fatty acid composition should be modified to increase MUFA contents as well as enhancing oil and lipid production.ResultsThe model microorganism Escherichia coli was engineered to produce free MUFAs. The fatty acyl-ACP thioesterase (AtFatA) and fatty acid desaturase (SSI2) from Arabidopsis thaliana were heterologously expressed in E. coli BL21 star(DE3) to specifically release free unsaturated fatty acids (UFAs) and convert SFAs to UFAs. In addition, the endogenous fadD gene (encoding acyl-CoA synthetase) was disrupted to block fatty acid catabolism while the native acetyl-CoA carboxylase (ACCase) was overexpressed to increase the malonyl coenzyme A (malonyl-CoA) pool and boost fatty acid biosynthesis. The finally engineered strain BL21ΔfadD/pE-AtFatAssi2&pA-acc produced 82.6 mg/L free fatty acids (FFAs) under shake-flask conditions and FFAs yield on glucose reached about 3.3% of the theoretical yield. Two types of MUFAs, palmitoleate (16:1Δ9) and cis-vaccenate (18:1Δ11) made up more than 75% of the FFA profiles. Fed-batch fermentation of this strain further enhanced FFAs production to a titer of 1.27 g/L without affecting fatty acid compositions.ConclusionsThis study demonstrated the possibility to regulate fatty acid composition by using metabolic engineering approaches. FFAs produced by the recombinant E. coli strain consisted of high-level MUFAs and biodiesel manufactured from these fatty acids would be more suitable for current diesel engines.

Physical and monolayer film properties of potential fatty ester biolubricants

The desire to replace petroleum‐based lubricants with alternatives that are environmentally friendly and made from sustainable sources has encouraged the development of biolubricants based on vegetable oils. To be good lubricants, the materials should have low melting points, appropriate viscosity and oxidative stability. In this paper, we report the melting point and viscosity of oleate esters of ethylene glycol, 1,2‐propanediol, 2,3‐butanediol, and pentaerythritol as well as the decanoate esters of 2,3‐butanediol and the 12‐methyltetradecanoate esters of 1,2‐propanediol. Polyol esters that have a free hydroxy group had lower melting points than the completely esterified polyols, but the completely esterified polyol esters exhibited less change in viscosity with temperature than those having a free hydroxy group. 2, 3‐Butanediol monooleate, which melted at −48.6°C shows promise as a biolubricant, but its viscosity index was estimated to be 100. Pentaerythritol oleate esters, with melting points below −10°C and viscosity indices in the range of 170–197, may be suitable candidates as biolubricants. The behavior of esters spread as a monomolecular film at air/water interface may provide insight into the way they behave when spread on metal or polar surfaces, so the pressure‐area isotherms of 2,3‐butanediol monoleate and selected esters are also reported.Practical applications: The structure and function relationships demonstrated can be used to synthesize biolubricants with desirable physical and performance properties.This figure shows the melting and viscosity properties of various types of synthesized biolubricants. Abbreviations: BDMO, 2,3‐butanediol monooleate; BDM10, 2,3‐butanediol monodecanoate; PGMO, 1,2‐propanediol monooleate; PET, pentaerythritol; R‐Ac, a group of acetylated ricinoleates; BuR, butyl ricinoleate; IsR, isopropyl ricinoleate; BuO, butyl oleate; IsO, isopropyl oleate; MeR‐11u, methyl 12‐undec‐10‐enylricinoleate.

The Effect of Temperature on Tribological Properties of Chemically Modified Bio-Based Lubricant

Vegetable oil has several characteristics that provide advantages for use as lubricant. This includes a high viscosity index, high flash point, high biodegradability, and friction and wear reduction properties. However, vegetable oil has some disadvantages such as low oxidation stability and low thermal stability. The transesterification process of palm oil using trimethylolpropane (TMP) alcohol has been proven to reduce the oxidation stability of vegetable oil. However, little research has been carried out on the effect of TMP ester as a lubricant in term of friction and wear. Therefore, this study investigated the effect of temperature on the tribological properties of TMP ester using a four-ball machine. The load and speed of the sample were set at 40 kg and 1,200 rpm, respectively. Temperature was varied between 50 and 100°C. It was found that TMP ester improved the friction properties by around 15–20%. At low temperature, TMP esters have a higher coefficient of friction (COF) compared to paraffin oil. However, as the temperature increased higher than 80°C, paraffin oil had a highere COF value. This is because at high temperature, the lubricant filmed formed by fatty acids tends to be less stable and breaks down more easily.

Comparison of oxidation stability of virgin olive oils from different locations of Turkey

Ten kinds of virgin olive oil of two major cultivars (Ayvalik and Memecik) produced in several areas of Turkey (Bayindir, Edremit, Ortaklar, Burhaniye, Ezine, Tire, Havran, Ayvalik, Altinoluk, and Kucukkuyu) were analysed. The quality characteristics, fatty acid composition, total phenol, ando-diphenol content of the samples were determined. Oxidative stability and free radical scavenging activity were determined using Rancimat test, Schaal oven test, and DPPH method. It was found that while Memecik oil from Ortaklar demonstrated the strongest oxidative stability, Ayvalik oil from Ezine had the lowest oxidative stability among the samples. Fatty acid composition and especially oleic acid/linoleic acid ratio was previously defined as a parameter that can help distinguish cultivars from one another; however, this study proved that total phenol, especially o-diphenol content of the oil, has the strongest effect on oxidative stability compared to other factors including fatty acid composition.

Fuel properties and rheological behavior of biodiesel from egusi (Colocynthis citrullus L.) seed kernel oil

In this study, egusi (Colocynthis citrullus L.) seed kernel oil has been evaluated as a feedstock for biodiesel production. The transesterification of the crude egusi seed kernel oil (CESKO) via methanol in the presence of sodium methoxide was performed and the resulting egusi oil methyl ester (EOME) was tested for its fatty ester composition, fuel properties and rheological behavior (at 25°C, 40°C and 55°C). The fuel properties of EOME measured met both the ASTM D6751 and EN 14214 biodiesel standards, with the exception of lower oxidative stability. The fatty ester composition and fuel properties of EOME were found comparable to those of conventional biodiesels from soybean, sunflower and safflower oils. The viscosity behavior of EOME and its blends with diesel fuel (at 25°C, 40°C and 55°C) was found to be pseudoplastic and Newtonian in nature and this agrees with those of other biodiesels reported in literature. From this study, the kinematic viscosity of EOME (3.91mm2/s) was found to be slightly lower than that of most biodiesels (≥4.0mm2/s) reported in literature.

Influence of blending soybean, sunflower, colza, corn, cottonseed, and residual cooking oil methyl biodiesels on the oxidation stability

Binary mixtures of soybean (SbMB), sunflower (SfMB), colza (CzMB), corn (CoMB), cottonseed (CsMB), and residual cooking oil (RMB) methyl biodiesels were prepared and the oxidation stability (induction period, IP) was measured. CoMB, SbMB, and particularly CzMB improved the oxidation stability of the binary mixtures, which was in agreement with measurements of polyunsaturated fatty acid content and antioxidants (TBHQ) originating from the vegetable oils used for biodiesel production. The oxidation stability of biodiesels with low oxidation stability such as CsMB and RMB was improved through blending with 90%(w/w) SbMB to satisfy EN 14214 (IP>6h). Considering ASTM D6751 (IP>3h), the oxidation stability of SfMB (0.88h) was improved by blending with 60%(w/w) SbMB while RMB only required 10%(w/w) SbMB in order to attend ASTM requirements. CzMB presented the highest IP value and therefore is the most effective blender to biodiesels with low oxidation stability. On the other hand, soybean oil is one of the major feedstocks for biodiesel production in the world and the use of SbMB as a common blending to other biodiesels such as CsMB, RMB and SfMB is demonstrated to be an alternative solution to prepare biofuels with improved oxidation stability.

Spray‐Dried Structured Lipid Containing Long‐Chain Polyunsaturated Fatty Acids for Use in Infant Formulas

Human milk fat (HMF) analogs are structured lipids (SLs) modified to have palmitic acid content at the sn-2 position of the triacylglycerol (TAG) and fatty acid composition comparable to HMF. Some of these SLs are also designed to incorporate long-chain polyunsaturated fatty acids (LCPUFAs) because of their important role in infant development. In this study, Maillard reaction products (MRPs), obtained from heated whey protein isolates and corn syrup solids (CSS) solution, were used as encapsulants for microencapsulation of 2 enzymatically synthesized SLs for infant formula applications. The encapsulated SL powders were obtained through spray-drying and evaluated in terms of their microencapsulation efficiency, chemical and physical properties, oxidative stability, and dispersibility. The microencapsulation efficiency of the SLs was 90%. Dispersibility test using particle size measurement demonstrated that these powders dispersed quickly into a homogeneous suspension. The encapsulated SL powders had low peroxide and thiobarbituric acid-reactive substances values. Lower oxidative stability was obtained in the powder containing SL with a higher degree of unsaturation and a lower concentration of tocopherols. The results demonstrated that the degree of fatty acid unsaturation and concentration of endogenous antioxidant in starting oils influenced the oxidative stability of the encapsulated SLs.

Physical, chemical, and lubricant properties of Brassicaceae oil

Rapeseed oil and canola oil have traditionally been used in industrial lubricant applications but oils of many species of Brassicaceae have similar properties. Oil from the seed of seven Brassicaceae species, Sinapis alba (yellow mustard), Camelina sativa (false flax), Brassica carinata (Ethiopian mustard), B. napus (rapeseed), B. juncea (oriental mustard), B. rapa (field mustard), and S. arvensis (wild mustard), were recovered by cold pressing and filtration without further refining. The physical, chemical, and lubricant properties of the oils were determined. B. napus had the highest oil yield when extracted by cold press and B. juncea* (low erucic B. juncea) had the highest oil content extracted by solvent. C. sativa oil had the lowest sterol content, mineral content, oxidative stability, and viscosity at 40 and 100°C and had the highest iodine value among tested oils. Iodine value had a strong negative correlation with oxidative stability in the tested oils. There was not any water in any of the oil samples. Overall, C. sativa oil had properties making it suitable for use as a fuel although its low oxidative stability and high iodine value could pose challenges; however, S. alba oil was more appropriate for use as a lubricant.