Sunflower biodiesel

The higher is the degree of unsaturation in ester chain of a biodiesel, the smaller is its oxidation stability. Sunflower biodiesel obtained by the ethyl route possesses a high amount of unsaturated fatty acids, mainly oleic acid (C18:1) and linoleic acid (C18:2), thus being more prone to the oxidation process. In Brazil, with the purpose of meeting the specifications of the Brazilian National Agency of Petroleum, Natural Gas and Biofuels (ANP), antioxidant additives, from synthetic and natural origins, have been added to the biofuel. Antioxidants are an alternative to prevent the oxidative deterioration of the fatty acid derivatives, as they are substances able to reduce the oxidation rate. In this study, the oxidative stability of sunflower biodiesel, obtained by the ethyl route and additivated with different concentrations of the antioxidants butylated hydroxytoluene (BHT) and t-butylhydroquinone (TBHQ), was evaluated by means of Pressure differential scanning calorimetry (P-DSC) and the Accelerated oxidative stability test (Rancimat, Method EN 14112). The results obtained by the two techniques showed the same oxidation tendency. Thus, P-DSC can be used as an alternative to determine the oxidative stability of biodiesel. The antioxidant TBHQ, added to biodiesel at the concentrations of 2000 and 2500 mg kg⁻¹, raised the oxidation induction time to a value higher than 6 h, the limit established by the Resolution ANP number 7/2008, thus being the best alternative among the studied antioxidants.     

Production of Biodiesel Fuel by Transesterification of Triglycerides in the Presence of Sodium Pyrophosphate

The possibility of using anhydrous sodium pyrophosphate and its decahydrate in transesterification of triacyl glycerides (with sunflower and rapeseed oils as examples) with methanol to obtain biodiesel fuel was examined. As shown by gas-chromatographic analysis, at the vegetable oil to methanol ratio of 1: 12, temperature of 65°C, reaction time of 2 h, and catalyst concentration of no less than 6 wt %, the maximal yield of methyl esters of fatty acids (biodiesel) was 93 and 69% when using Na₄P₂O₇ and Na₄P₂O₇·10H₂O, respectively. The catalytic effect of sodium pyrophosphate in the transesterification of triacyl glycerides was attributed to its methanolysis with the formation of sodium methylate. Water present in sodium pyrophosphate decahydrate causes hydrolysis of the formed sodium methylate; therefore, the yield of methyl esters of fatty acids is lower than with anhydrous pyrophosphate. Anhydrous sodium pyrophosphate can be used repeatedly no less than five times without significant decrease in the yield of methyl esters of fatty acids. Sodium pyrophosphate can be recommended for use in transesterification with other esters and alcohols.

     

生物柴油树种油脂脂肪酸组成对燃料特性的影响

以目前中国主要开发或具有开发潜能的10种生物柴油树种为研究对象,分析其果实或种子油脂脂肪酸组成对合成生物柴油燃料特性的影响。结果表明,木本植物生物柴油产品十六烷值、碘值、氧化安定性等燃料特性主要由原料油脂肪酸的不饱和度决定,脂肪酸不饱和度低于133.13,十六烷值(GB/T 20828-2007)和碘值(EN 14214)就可以达标。生物柴油产品冷滤点随着长碳链饱和脂肪酸的增加而升高,脂肪酸饱和碳链长度因子分别小于8.41和2.72时,可以满足冷滤点0℃和-10℃的要求。高品质生物柴油的原料中应该具有较高的单元不饱和脂肪酸含量。通过油脂脂肪酸单不饱和脂肪酸、多不饱和脂肪酸和饱和脂肪酸的组成绘制出生物柴油特性三角预测图,为预测生物柴油产品燃料特性提供参考依据。     

Comparative study of biodiesel oxidation stability using Rancimat,PetroOXY, and low P-DSC

Oxidation stability of biodiesel is one of the most important factors used to evaluate its quality, allowing its commercialization and ensuring its shelf life. In this context, several accelerated methods have been used to measure oxidative stability to predict the maximum storage time at which biodiesel can be submitted without compromising its quality. In the present study, the oxidation stability of two commercial biodiesel and of their blends with two antioxidants was evaluated using the standard methods described in the EN 14214 norm (Rancimat Method) and in ASTM D7545 (PetroOXY method), as well as by low pressurized differential scanning calorimetry (low P-DSC). Both biodiesel were obtained from soybean oil, produced by methylic and ethylic route. The antioxidants, which were used in different concentrations, have the following active components: bisphenol and phenol. The three assessed methodologies can be used to determine the effect of the commercial antioxidants on the oxidative stability of the studied biodiesel. As each method is based on the measurement of different parameters to obtain the respective oxidation induction time, their results cannot be compared directly. But when the results are expressed in terms of the percentage change of the respective oxidation induction times, there is a higher correlation between those obtained by Rancimat and PetroOXY methods than when compared with the results obtained by low P-DSC. Because of their characteristics, the bisphenolic antioxidant is more effective than the phenolic one and, at a same antioxidant concentration, the oxidation stability of the ethylic biodiesel is higher than that of the methylic one. Considering analysis time and sensitivity, the low P-DSC method is the one that better attends both parameters among the applied methods.     

Production of biodiesel by immobilized Candida sp. lipase at high water content

A new process for enzymatic synthesis of biodiesel at high water content (10–20%) with 96% conversion by lipase from Candida sp. 99–125 was studied. The lipase, a no-position-specific lipase, was immobilized by a cheap cotton membrane and the membrane-immobilized lipase could be used at least six times with high conversion. The immobilized lipase could be used for different oil conversion and preferred unsaturated fatty acids such as oleic acid to staturated fatty acids such as palmitic acid. The changes in concentration of fatty acids, diglycerides, and methyl esters in the reaction were studied and a mechanism of synthesis of biodiesel was suggested: the triglycerides are first enzymatically hydrolyzed into fatty acids, and then these fatty acids are further converted into methyl esters.     

Thermal stability evaluation of methylic biodiesel obtained for different oilseeds

Biodiesel is defined as a mixture of mono- or di-alquil esters of vegetable oil or animal fats. During long-term storage, oxidation caused by contact with air (autoxidation) presents a legitimate concern in relation to monitoring and maintaining fuel quality. Extensive oxidative degradation may compromise the quality by adversely affecting kinematic viscosity, acid value, or peroxide value. The oxidation susceptibility of biodiesel, due to the presence of triacilglycerides of poly-unsaturated fatty acids, was evaluated in this study. Samples of sunflower, castor, and soybean biodiesels were obtained through the transesterification reaction, with the intention of achieving the thermal stability study through thermogravimetrical analyses and differential scanning calorimetry high pressure. It was furthermore observed through thermogravimetry and pressure differential scanning calorimetry curves that castor biodiesel exhibited the highest thermal and oxidative stability.     

Monitoring lipase-catalyzed methanolysis of sunflower oil by reversed-phase high-performance liquid chromatography: elucidation of the mechanisms of lipases

Reversed-phase high-performance liquid chromatography (RP-HPLC) with UV detection at 210 nm was used to monitor the formation of the major compounds during the lipase-catalyzed transesterification reaction of sunflower oil with methanol. Individual triacylglycerols, diacylglycerols, monoacylglycerols as well as fatty acids and their corresponding methyl esters were separated using acetonitrile/acetone as a mobile phase and a combined linear gradient-isocratic-step gradient-isocratic elution procedure. Another relatively short method consisting of a linear gradient elution followed by an isocratic elution gave similar results, yet with lower resolution. HPLC/mass spectrometry with an ion trap analyzer and atmospheric pressure chemical ionization source was used for the identification of the individual compounds. Individual calibration curves obtained with UV detection at 210 nm were found to be of use for quantitative analyses of double-bond containing methyl esters and acylglycerols. The use of the RP-HPLC methods in the elucidation of the mechanisms of three immobilized lipases, namely Lipozyme TL IM, Lipozyme RM IM and Novozym 435, in biodiesel production was described.     

Characterization and kinetic study of sunflower oil and biodiesel

In this study, the physico-chemistry characterization and kinetic study of the thermal decomposition of sunflower oil and its biodiesel were carried out. Sunflower biodiesel was synthesized by the methanol route and basic homogeneous catalysis. The physicochemical characterization of the sunflower oil and biodiesel were performed according to standards set out in the ANP resolution, and both are in accordance to the specifications. The chromatographic analysis was obtained by GC-FID. The yield of conversion of 97.4 wt% of sunflower oil in methyl esters confirms the efficiency of the conversion of the fatty acids into esters. The thermal analysis was performed on a thermobalance, using heating rates of 5, 10, and 20 °C min⁻¹. In these three rates, we observed a single well-defined step of mass loss that describes the volatilization and decomposition of the sunflower oil and the biodiesel. The kinetic study was performed using equations of approximation and integration methods such as Coats–Redfern, Van Krevelen, and Horowitz–Metzger. The kinetic parameters reaction order (n) and apparent activation energy (E _a), obtained by applying these method were correlated.     

Catalytic conversions in green aqueous media: Part 4. Selective hydrogenation of polyunsaturated methyl esters of vegetable oils for upgrading biodiesel

This study deals with the influence of operating parameters on the selective hydrogenation of crude polyunsaturated methyl esters of linseed, sunflower and soybean oils in order to achieve high selectivities up to 79.8 mol% of monounsaturated (C18:1) fatty acid methyl esters (FAME) which is 1st generation biodiesel of increased oxidative stability, energy and environmental performance at a low pour point employing water-soluble Rh/TPPTS catalytic complexes [TPPTS = P(C₆H₄-m-SO₃Na)₃] in green aqueous/organic two-phase systems. This study also discloses the great potential of biphasic selective catalytic hydrogenation to produce 2nd generation biodiesel from polyunsaturated FAME of alternative, non-food oil feedstocks which are originally not suitable for biodiesel production or give poor quality biodiesel but combine the advantage that they would not affect food production. Because the mixture of methyl esters of linseed oil mainly consists of C18:3 FAME it constitutes a good model to investigate the effects of parameters on the whole spectrum of the stepwise hydrogenation: C18:3 (linolenates) → C18:2 (linoleates) → C18:1 (oleates)  C18:0 (stearate) and to obtain first information on the selective hydrogenation of alternative, non-food oils with a high C18:3 FAME content to make them suitable for 2nd generation biodiesel formulations.     

Analysis of thermal and oxidative stability of biodiesel from Jatropha curcas L. and beef tallow

The oxidation of oils and biodiesels occurs due to several factors: the quantity of double bonds and the presence of allylic and bis-allylic hydrogens. Esters (biodiesel) that have large amounts of unsaturated fatty acids are more susceptible to oxidation than saturated. The aim of this work was to analyze the thermal and oxidative stability of ethyl biodiesel from Jatropha curcas L. and beef tallow by thermogravimetric, pressure differential scanning calorimetry, and PetroOxy methods. The samples of biodiesel from beef tallow present higher oxidation stability compared to biodiesel from J. curcas. In relation to calorimetric curves of biodiesel from J. curcas and beef tallow stored by 60 days without and with antioxidant, there was verified displacement of peak temperature of the transition to higher temperatures, respectively. Just a sample of biodiesel from beef tallow stored for 60 days with 3,000 ppm of antioxidant t-butyl-hydroxyquinone was within the standard established by Brazilian National Agency of Petroleum, Natural Gas, and Biofuels (ANP). The biodiesel from beef tallow was more stable in terms of thermal and oxidative stability than biodiesel from J. curcas. The thermal and oxidative stability of biodiesel depends on its chemical structure; this corroborates the fact that the oils with a predominance of saturated fatty acids are more stable than the unsaturated.     

Determination of Biodiesel and Triacylglycerols in Diesel Fuel by LC

A high performance liquid chromatographic method was developed for quantifying blends of biodiesel (simple alkyl esters of fatty acids) in petrodiesel. The method uses a silica column with an isocratic mobile phase consisting of hexane and methyl t-butyl ether. Separated components were quantitated using either an evaporative light scattering detector (ELSD) or UV detector. Precision of injection and linearity of response of the ELSD and UV detectors over a range of biodiesel-petrodiesel blends [1–30 v/v %] were established by use of standards. The method also can be used for quantitating similar levels of oils or fats (triacylglycerols) in petrodiesel.     

Catalytic hydrogenation of fatty acid methyl esters

Catalytic hydrogenation of a mixture of fatty acid methyl esters, which are produced by re-esterification of vegetable (sunflower) oil and are contained in biodiesel fuel, was studied.     

Evaluating antioxidants efficiency during storage of ethylic and methylic biodiesel by low pressurized DSC and Rancimat methods

Efficiencies of four commercial antioxidants used during the storage of two biodiesel, BS-ethyl and BS-methyl, respectively obtained from soybean oil by ethylic and methylic routes, were evaluated by measuring their oxidative stability using a low pressurized DSC (low P-DSC) method developed by the authors and by Rancimat method, which is specified by the American ASTM D6751 and European EN 14214 standard methods. The operating temperature of the low P-DSC method was the same as that used in the Rancimat procedure (110 °C). The antioxidants, used in 500 mg kg^?1 content, have the following active components: phenol, biphenol, phenol + amine mixture, and a hydroquinone + organic acid mixture. Samples of each biodiesel–antioxidant mixture were evaluated simultaneously by the two methods, right after their preparation and 30, 60, 90, and 120 days of storage at 23 ± 1 °C. A non-dimensional oxidative induction time parameter, defined as the ratio between the oxidation induction time (OIT) or induction time (IT) values at a storage time t and at t = 0, was used to evaluate the antioxidant activity. For the same mixture, changes of this non-dimensional parameter calculated from OIT or IT show a similar trend with storage time, indicating that it can be determined either from low P-DSC or Rancimat method data. As the efficiency of the studied antioxidants depends on their composition, their interaction with each biodiesel, and on the storage time, this parameter can be used to indicate the best storage time for each antioxidant–biodiesel mixture.     

Antioxidative properties of hydrogenated cardanol for cotton biodiesel by PDSC and UV/VIS

Biodiesel is a non-toxic biodegradable fuel that consists of alkyl esters produced from renewable sources, vegetal oils and animal fats, and low molecular mass alcohols, and it is a potential substitute for petroleum-derived diesel. Depending on the raw materials used, the amount of unsaturated fatty acids can vary in the biodiesel composition. Those substances are widely susceptible to oxidation processes, yielding polymeric compounds, which are harmful to the engines. Based on such difficulty, this work aims to evaluate the antioxidant activity of cashew nut shell liquid (cardanol), as additive for cotton biodiesel. The oxidative stability was investigated by the pressure differential scanning calorimetry (PDSC) and UV/Vis spectrophotometer techniques. The evaluated samples were: as-synthesized biodiesel — Bio T₀, additivated and heated biodiesel — Bio A (800 ppm L⁻¹ of hydrogenated cardanol, 150°C for 1 h), and a heated biodiesel — Bio B (150°C, 1 h). The oxidative induction time (OIT) analyses were carried out employing the constant volume operation mode (203 psi oxygen) at isothermal temperatures of 80, 85, 90, 100°C. The high pressure OIT (HPOIT) were: 7.6, 15.7, 22.7, 64.6, 124.0 min for Bio T₀; 41.5, 77.0, 98.6, 106.6, 171.9 min for Bio A and 1.7, 8.2, 14.8, 28.3, 56.3 min for Bio B. The activation energy (E) values for oxidative processes were 150.0±1.6 (Bio T₀), 583.8±1.5 (Bio A) and 140.6±0.1 kJ mol⁻¹(Bio B). For all samples, the intensities of the band around 230 nm were proportional to the inverse of E, indicating small formation of hyper conjugated compounds. As observed, cardanol has improved approximately four times the cotton biodiesel oxidative stability, even after the heating process.     

质谱特征结合等效链长定性分析植物油中的脂肪酸

建立了质谱特征结合等效链长快速定性植物油中脂肪酸的方法。首先根据质谱特征判断脂肪酸的类型并鉴定出其中的饱和脂肪酸甲酯,然后利用它们的保留时间信息计算得到不饱和脂肪酸甲酯的等效链长值,与已建立的脂肪酸甲酯数据库对照实现不饱和脂肪酸甲酯的结构鉴定。用NaOH-甲醇对5种常见植物油(花生调和油、茶籽调和油、菜籽油、葵花籽油、大豆油)中的脂肪酸进行衍生和提取,采用DB-23石英毛细管柱(30m×0.25mm×0.25μm)分离脂肪酸甲酯的同系物和异构体,气相色谱质谱法(GC/MS)测定,结果表明,5种样品油中所含不饱和脂肪酸的组成和含量上均存在明显差异。本方法无需标准品即可快速定性检测脂肪酸同系物及异构体,适用于油脂、食品中脂肪酸的成分分析。     

气相色谱法在生物柴油生产工艺研究中的应用

综述了气相色谱法在生物柴油生产工艺研究中的应用,包括反应产物和生物柴油产品中脂肪酸甲酯含量和分布的测定,单脂肪酸甘油酯、二脂肪酸甘油酯和三脂肪酸甘油酯含量的测定,游离脂肪酸含量的测定以及微量甲醇含量的测定等。讨论了进样方式、色谱柱类型、硅烷化等因素对反应产物组成测定的影响;提出了一种采用双柱压力反吹的方式测定生物柴油产品中微量甲醇含量的方法：采用正丙醇作内标,甲醇与内标通过预切柱进入分析柱后,通过压力变化,将其余组分通过分流出口反吹出色谱系统;采用极性聚乙二醇色谱柱测定了8种不同植物油中脂肪酸甲酯的含量和分布。     

Comparison of the oxidative stability of soybean and sunflower oils enriched with herbal plant extracts

The present study was conducted to determine and compare the oxidative stability of soybean and sunflower oils using differential scanning calorimetry (DSC). These edible oils were enriched with marjoram (Origanum majorana L.), thyme (Thymus vulgaris L.), and oregano (Origanum vulgare L.) extracts at three different concentrations and synthetic antioxidant (BHA). The fatty acid composition of studied oils was determined by gas chromatography mass spectrometry to evaluate the content of unsaturated fatty acids that are sensitive to oxidation process. Oil samples were heated in the DSC at different heating rates (4.0, 7.5, 10.0, 12.5, and 15.0 °C min^?1) and oxidation kinetic parameters (activation energy, pre-exponential factor, and oxidation rate constant) were calculated. The results showed that the oxidative stability of sunflower oil samples enriched with oregano extracts and soybean oil supplemented with thyme extracts was improved compared to samples without the addition of herbal plant extracts and the synthetic antioxidant.     

Influence of the storage on the thermo-oxidative stability of methyl and ethyl esters by PDSC

Biodiesel oxidation is a complex process widely influenced by the chemical composition of the biofuel and storage conditions. Several oxidation products can be formed from these processes, depending on type and amount of the unsaturated fatty acid esters. In this work, fatty acid methyl and ethyl esters were obtained by base-catalyzed transesterification of soybean oil and physicochemically characterized according to standards from ASTM, EN, and ABNT. The thermal and oxidative stabilities of biodiesel samples were investigated during the storage process by pressure differential scanning calorimetry (PDSC) and by viscosity measurements. Absolute viscosities of biodiesels after accelerated aging were also determined. The viscosity increased as the aging temperature and time were raised. The results showed that oxidation induction can occur during storage, decreasing the biodiesel stability. PDSC analysis showed that during storage under climate simulation the values of high-pressure oxidative induction times (HPOIT) were reduced for both FAEE and FAME.     

Evaluation of a rapid method for preparation of fatty acid methyl esters for analysis by gas-liquid chromatography

The major limitation to fatty acid analysis by gas-liquid chromatography is associated with preparation of fatty acid methyl esters (FAME). In the present study, FAME preparations were made from plant oils (corn, olive, sunflower), sunflower oil margarine, lard and various animal tissue fats by a rapid transesterification involving tetramethylammonium hydroxide in methanol, and also by a longer conventional saponification-esterification method. Fats from animal (beef, mutton, pork) adipose tissues were extracted by a simpler modified procedure and also by the Folch method prior to the rapid and the conventional FAME preparations, respectively. FAME analysis on a gas-liquid chromatograph equipped with a Silar 10C glass capillary column indicated similar fatty acid composition of a given fat or oil, whether FAME was prepared by the rapid or the longer conventional method. The data obtained by both methods were very highly correlated for all the fats (r = 0.9895 - 0.9999). However, the rapid method showed a tendency for enhanced recoveries of lower chain fatty acids (e.g. 14:0), and also of unsaturated C18 isomers. Possibly, losses of fatty acids that occurred during the lengthy fat extraction, fatty acid esterification or ether-evaporation FAME concentration steps (conventional method) were minimised by the single transesterification step (rapid method). This rapid transesterification method appears to be an attractive alternative to FAME preparation from a wide variety of different fats for gas-liquid chromatographic analysis.     

Evaluation of a glycerol derived biofuel by thermal analysis

This work describes thermal analysis evaluation of a glycerol derived compound (fatty acid esters of (2,2-dimethyl-1,3-dioxolan-4-yl) methanol) developed to work as a biofuel. Mixtures of these ketal–glyceryl esters with fatty acid methyl esters typical of soybean biodiesel were prepared and evaluated in relation to biodiesel critical thermal properties such as temperature of crystallization, thermal stability and volatilization measured by differential scanning calorimetry and thermogravimetric analysis. The volatility of the products containing fatty acid methyl esters and (2,2-dimethyl-1,3-dioxolan-4-yl) methyl esters could be predicted by thermogravimetric analyses conducted in nitrogen that avoided time consuming distillation and greatly reduced material expenditure.