The Effect of Branched-Chain Fatty Acid Alkyl Esters on the Cold-Flow Properties of Biodiesel

Biodiesel (fatty acid methyl esters [FAME]) is produced from various fats, oils, and greases (FOG) using catalytic transesterification with methanol. These fuels have poor cold-flow properties depending on the fatty acid (FA) composition of the parent FOG. Improving the cold-flow properties of biodiesel will enhance its prospects for use during cooler months in moderate temperature climates. This work is a study on the use of skeletally branched-chain alkyl esters (BCAE) composed of the isopropyl, n-butyl, and 2-ethylhexyl esters of iso-oleic acid isomers (iPr-iOL, nBu-iOL, and 2EH-iOL). These BCAE additives were tested in blends with linear-FAME (L-FAME) derived from soybean oil (SME), lard (LME), tallow (TME), and sewage scum grease (SGME). Binary L-FAME/SME admixtures were also studied. Admixtures were tested for the effects of the additives on cloud point (CP), pour point (PP), and kinematic viscosities at standard (ν⁴⁰ = 40 °C) and low temperatures (T_L) = CP + 5 °C (ν^L). Although the BCAE additives were more effective than SME, relatively large additive concentrations (y_Add) were needed to depress CP and PP by more than 2 °C. Admixtures with high concentrations of BCAE additive had ν⁴⁰ > 6.0 mm² s⁻¹, the maximum limit in ASTM fuel specification D 6751. While the iPr-iOL and nBu-iOL additives may be blended at concentrations up to y_Add = 0.50, 2EH-iOL should not exceed y_Add = 0.28 in LME, 0.31 in SGME, 0.35 in TME, or 0.41 in SME to avoid driving the admixture out of specification. Some anomalies observed in the results at low y_Add for SGME/BCAE admixtures were speculated to have been affected by the low-temperature rheology of SGME.     

Differential Scanning Calorimetric Study of Solidification Behavior of Monoacylglycerols to Investigate the Cold-Flow Properties of Biodiesel

Monoacylglycerols (MAG) are impurities present in biodiesel as a result of incomplete reactions. MAG often solidify in biodiesel even at room temperature because of their high melting points. This worsens the cold-flow properties such as the cloud point and pour point. We hypothesized that several types of MAG solidify simultaneously; therefore, we performed differential scanning calorimetry of binary mixtures of MAG to elucidate their interactions during solidification. Three thermodynamic formulas were then applied to the experimental results: (1) non-solid-solution, (2) solid-solution, and (3) compound formation models. Binary mixtures of MAG showed complicated liquidus curves with multiple upward convex shapes, with which only the compound formation model fitted well. This model was applied to multicomponent mixtures that consisted of MAG and fatty acid methyl esters (FAME) as surrogate biodiesel fuels. We confirmed that the model still worked well. The results show that the compound formation model has good potential for predicting the cold-flow properties of biodiesel.     

The addition of alkoxy side-chains to biodiesel and the impact on flow properties

Butyl biodiesel was synthesised from canola oil and subsequently epoxidised via the in situ peroxyacetic acid method converting 45% of the unsaturated portion. Alkoxy butyl biodiesel was synthesised under acid conditions with a range of both straight-chain and branched alcohols. Alkoxylation of butyl biodiesel with methanol, ethanol and n-propanol did not improve the cloud or pour point over that for conventional methyl biodiesel. Alkoxylation with alcohols larger than butanol including n-pentanol, n-hexanol and n-octanol produced cloud points that were 5 °C lower than that for methyl biodiesel. The lowest cloud point achieved was for 2-ethylhexoxy butyl biodiesel at −6 °C, representing a 6 °C reduction in cloud point over methyl biodiesel. Alkoxylation did not have a significant effect on the pour point of biodiesel. Alkoxylation of butyl biodiesel resulted in significant increases in viscosity. The kinematic viscosity generally increased with increasing alkoxy chain length and ranged from 6.67 mm² s⁻¹ for methoxy butyl biodiesel to 9.76 mm² s⁻¹ for ethylhexoxy butyl biodiesel, more than double the value for methyl biodiesel. The improved low-temperature properties of the longer-chain alkoxy biodiesel were most likely due to the protruding alkoxy chain, which also resulted in an increase in viscosity. The use of alcohols larger than pentanol does not provide significant benefit in terms of low-temperature properties, and results in an undesirable increase in viscosity.     

The Effect of Natural and Synthetic Antioxidants on the Oxidative Stability of Biodiesel

A significant problem associated with the commercial acceptance of biodiesel is poor oxidative stability. This study investigates the effectiveness of various natural and synthetic antioxidants [α-tocopherol (α-T), butylated hydroxyanisole (BHA), butyl-4-methylphenol (BHT), tert-butylhydroquinone (TBHQ), 2, 5-di-tert-butyl-hydroquinone (DTBHQ), ionol BF200 (IB), propylgallate (PG), and pyrogallol (PY)] to improve the oxidative stability of soybean oil (SBO-), cottonseed oil (CSO-), poultry fat (PF-), and yellow grease (YG-) based biodiesel at the varying concentrations between 250 and 1,000 ppm. Results indicate that different types of biodiesel have different natural levels of oxidative stability, indicating that natural antioxidants play a significant role in determining oxidative stability. Moreover, PG, PY, TBHQ, BHA, BHT, DTBHQ, and IB can enhance the oxidative stability for these different types of biodiesel. Antioxidant activity increased with increasing concentration. The induction period of SBO-, CSO-, YG-, and distilled SBO-based biodiesel could be improved significantly with PY, PG and TBHQ, while PY, BHA, and BHT show the best results for PF-based biodiesel. This indicates that the effect of each antioxidant on biodiesel differs depending on different feedstock. Moreover, the effect of antioxidants on B20 and B100 was similar; suggesting that improving the oxidative stability of biodiesel can effectively increase that of biodiesel blends. The oxidative stability of untreated SBO-based biodiesel decreased with the increasing indoor and outdoor storage time, while the induction period values with adding TBHQ to SBO-based biodiesel remained constant for up to 9 months.     

Properties and Stability of Hazelnut Oil Organogels with Beeswax and Monoglyceride

The objectives of this study were to produce and characterize hazelnut oil (HO) organogels with beeswax (BW) and monoglyceride (MG) organogelators. Oil binding capacities of most samples were over 99 %. As the organogelator level increased, crystal formation time decreased, but solid fat content (SFC %) was enhanced. Although the highest SFC was 8.52 % among the organogel samples, it was 30.35 % in the commercial shortening (CS) at 20 °C. The peak melting temperature of CS was 41.86 °C, and almost all organogels had very close values to it. Melting enthalpies of the samples ranged from 0.48 to 13.40 J/g. Firmness and stickiness values of all samples were measured each month during 90 days of storage. There was no important change during storage. The organogels were texturally very stable, and were very homogenous and smooth in structure. Polarized light microscopy pictures revealed needle-like crystals for BW and rosette-like aggregates for MG organogels. The X-ray diffraction measurements of the crystals also showed the difference of the two types. There would be some hydrogen bonding in only MG organogels as predicted from the infrared spectra. The organogels were very stable against oxidation during storage. HO organogels can be used as shortening or margarine-like fat stock.     

超声波法制备生物柴油

在超声波条件下,以大豆油为原料,氧化钙为催化剂,利用正交试验研究了催化剂用量、油醇比、反也时间和反应温度等对生物柴油产率的影响。南实验得最佳工艺条件为：油醇比（质量）为0．9：1,反应时间为30min,反应温度为45℃,催化剂用量为0．9％（占原料油用量的质量分数）。在该条件下制备的生物柴油收率可达96％,其凝点为-2．2℃闪点为112℃,运动粘度为3．93mm／s,其性能与0号石化柴油比较接近。     

Diesters from Oleic Acid: Synthesis,Low Temperature Properties,and Oxidation Stability

Several diesters were prepared from commercially available oleic acid and common organic acids. The key step in the three step synthesis of oleochemical diesters entails a ring opening esterification of alkyl 9,10-epoxyoctadecanoates (alkyl: propyl, isopropyl, octyl, 2-ethylhexyl) using propionic and octanoic acids without the need for either solvent or catalyst. Each synthetic diester was evaluated for both low temperature operability and oxidation stability through measurement of cloud point, pour point, oxidation onset temperature, and signal maximum temperature. It was discovered that increasing chain length of the mid-chain ester and branching in the end-chain ester had a positive influence on the low temperature properties of diesters. Improved oxidation stability is achieved when the chain length of the mid-chain ester is decreased. Additionally, the mid-chain ester plays a larger role in oxidation stability than the end-chain ester. These products may prove useful in the search for bio-based industrial materials, such as lubricants, surfactants, and fuel additives. Product names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by USDA implies no approval of the product to the exclusion of others that may also be suitable.     

Alkoxylation of biodiesel and its impact on low-temperature properties

A property of biodiesel that currently limits its use to blends of 20% or less is its relatively poor low-temperature properties. Alkoxylation of the unsaturated portion of biodiesel offers the potential benefit of reduced cloud point without compromising ignition quality or oxidation stability. Conventional biodiesel was synthesised from canola oil and the alcohols methanol, ethanol and butanol, epoxidised in situ, and alkoxylated by acid-catalysed oxirane ring opening in the presence of the alcohol of the ester group. Optimal conditions for epoxidation were H₂O₂/biodiesel molar ratio of 2:1, acetic acid/biodiesel molar ratio of 0.2:1, 2 wt% H₂SO₄, 6 h reaction at 60 °C. Alkoxylation resulted in alkoxy substitution rates of 37.1% (methyl), 34.3% (ethyl) and 32.9% (butyl). Selectivity for alkoxy biodiesel was 89.0%, 82.7% and 81.7% for methoxy, ethoxy and butoxy biodiesel, respectively. The cloud point for methyl and ethyl biodiesel increased slightly, while a reduction of 1 K was achieved for butyl biodiesel. The presence of by-products negated much of the expected improvement in cloud point for butoxy butyl biodiesel. Further optimisation work is required to improve both conversion and selectivity if significant improvements in cloud point are to be achieved.     

Predicting Properties of Biodiesel Fuels using Mixture Topological Index

A new topological index for individual components based on the information of molar mass, bond length and bond energy was established to reflect the molecular structure of fatty acid methyl esters (FAME). Combined with the modified Grunberg–Nissan or Hind equation, the two series mixture topological index values of the biodiesels (mixture of FAME) were calculated, respectively. Some basic properties such as the density, viscosity, flash point (FP), high heating value (HHV) for biodiesel were correlated with these mixture topological indexes to find the relationship of structure and properties. The results show that the topological index can reflect the information of the molecular structure for FAME, such as the size of molecule, unsaturated bond, intensity of bond and branch degree. The modified Grunberg–Nissan equation has a higher precision of predicting for the properties of biodiesel studied than the Hind equation.     

生物柴油降凝机理的研究进展

生物柴油是可再生清洁燃料,能够减缓人类对石化柴油的依赖,然而生物柴油凝固点和粘度相对较高,低温流动性较差,冬季低温环境下结晶体易堵塞发动机管道和过滤器,使发动机无法正常工作。主要综述了生物柴油的性质、特点、降凝剂的作用机理及其研究方法。并对生物柴油的前景做了展望。     

生物柴油技术在国内的研究进展

简单介绍了生物柴油的优点及其制备技术.以及生物柴油在一些发达国家的生产和使用现状。介绍了生物柴油在国内的研究开发现状,分析了当前生物柴油生产与使用过程中存在的一些问题,并对生物柴油在国内的发展前景作了展望。     

The Effect of Pulsed Microwave Power on Transesterification of Chlorella sp. for Biodiesel Production

Pulsed microwave technique was employed for the production of biodiesel from Chlorellasp. via transesterification. Real-time microwave power and temperature profiles were used for the evaluation of efficiency of biodiesel production. The effect of power setting was determined in the range of 100–1000 W at the fixed reaction time (10 min) and temperature (60°C). In this work, the highest yield of biodiesel per unit energy consumption observed was 0.53% by weight of crude lipid per kilo joule at 250 W. From the results in this study, the efficiency of biodiesel production was correlated to the uniform pulse intensity and pulse frequency during the reaction process provided at the power setting of 250 W.     

The Effect of Monoglyceride Addition on the Rheological Properties of Pistachio Spread

Pistachio nut (Pistacia vera L.) is one of the most delicious and nutritious nuts in the world. In this study, monoglycerides (0.0–1.5 %) as lipophilic emulsifiers were used to prevent oil separation in pistachio spread A (containing 50.0 % pistachio paste, 30.0 % icing sugar and 20.0 % red palm oil) and B (containing 58.3 % pistachio paste, 25.0 % icing sugar and 16.7 % red palm oil). Changes in rheological behavior of pistachio spreads were investigated. The highest work of shear (which indicates spreadability) was observed in Formulations A and B containing 1.5 % monoglycerides. Addition of emulsifier significantly (P < 0.05) influenced the consistency index (K), thixotropic area (A), yield stress (τ ₀) and coefficient correlation (R) of pistachio spreads. All the pistachio spreads that contained emulsifier exhibited a higher storage modulus (G′) than the loss modulus (G″).     

NaOH/PAM催化剂对合成生物柴油的影响

大麻籽油和甲醇经NaOH/PAM催化合成生物柴油,本实验在醇油比固定的情况下考察了催化剂的碱含量、催化剂用量对酯交换转化率的影响、碱量及反应时间分别对转化率和皂化百分数的影响,采用红外光谱技术对催化剂进行分析,确定了较适宜的反应条件.结果表明:实际碱量随NaOH添加量的增加而增加；催化剂用量增加,原料油转化率增加；反应时间的增加,原料油转化率曲线增加到一定水平后趋于平缓；较适宜的反应条件为PN-4催化剂用量3％,反应时间为60 min.     

Evaluation and Predictive Model Development of Oxidative Stability of Biodiesel on Storage

Biodiesel comprises mono-alkyl esters of long-chain fatty acid methyl esters (FAME) derived from a renewable lipid feedstock. A major technical issue with the use of biodiesel is that it is more prone to oxidation during storage, when compared to petroleum fuel, due to the high content of polyunsaturated methyl esters that are easily oxidizable to compounds such as acids, aldehydes, and alcohols. Biodiesel (Jatropha and Pongamia) and antioxidants (Turmeric and butylated hydroxytoulene) were used for this study. We found that the acid value and viscosity for pongamia biodiesel increased significantly by 41.17% and 44.0% and that for jatropha biodiesel increased by 31.5% and 37.0%, respectively, after being stored for 3 months. The impact of antioxidants on the storage stability of biodiesel was examined according to the ASTM D4625 12-week procedure, and best results were found at a concentration level of 2500 ppm. The specific objective of this investigation is to develop models to determine the viscosity of biodiesel at any time “t” during long-term storage based on these experimental trials for upto 12 weeks. In addition, the models were used to predict the level of antioxidants that are to be added to biodiesel in order to minimize the effects of oxidative degradation during storage. The developed model recorded an adjusted R² of 0.86 and a modeling efficiency of 0.88.     

生物柴油低温流动性能的研究

生物柴油是典型的绿色能源,主要成分是脂肪酸甲酯。生物柴油的低温流动性与饱和脂肪酸甲酯的含量及分布有关,还与脂肪酸酯支链程度有关。综述了改善生物柴油低温流动性的方法,分析了降凝剂对生物柴油的降凝机理以及今后的研究方向。     

Model Reactions Involving Ester Functional Groups during Thermo-Oxidative Degradation of Biodiesel

Biodiesel is a renewable fuel used in diesel engines that is typically blended with diesel fuel. However, biodiesel is susceptible to oxidation, which has the potential to produce higher molecular weight materials that may adversely impact vehicle fuel-system performance. To investigate the chemical reactions potentially important in biodiesel oxidation, four different types of chemical reactions involving esters were studied: (1) ester formation (reactions of acids with alcohols), (2) alcoholysis (reactions of alcohols with esters), (3) acidolysis (reaction of acids with esters), and (4) ester exchange (reactions between two esters). Experiments with representative model compounds were used to evaluate these reactions at 90 °C with aeration; conditions previously used to simulate thermo-oxidative degradation during biodiesel aging. Reactions were monitored using gas chromatography, fourier transform infrared (FTIR) spectroscopy, and total acid number (TAN). Evidence is presented suggesting that alcoholysis and ester formation (Reactions 1 and 2), catalyzed by carboxylic acids, are important reactions of esters that could lead to larger molecules. Acidolysis (Reaction 3) proceeded at a comparatively slow rate and ester exchange reaction products (Reaction 4) were not detected under these aging conditions.     

Biodiesel influence on tribology characteristics of a diesel engine

This paper deals with the influence of biodiesel on some tribology characteristics of a bus diesel engine with a mechanically controlled fuel injection system. The tests have been performed on a fully equipped engine test bed, on a fuel injection test bed and on a discharge coefficient testing device. The tested fuel was neat biodiesel produced from rapeseed. Attention was focused on the biodiesel influence on the pump plunger surface roughness, on the carbon deposits in the combustion chamber, on the injector and in the injector nozzle hole. The pump plunger surface was analyzed by experimentally determined roughness parameters and by a microscope. The carbon deposits at fuel injector and in the combustion chamber were examined using endoscopic inspection. The deposits in the injector nozzle were investigated indirectly by measuring the nozzle discharge coefficient. Numerical simulation has been performed in order to estimate the influence of the discharge coefficient variation on the computed injection characteristics. The obtained results indicate that biodiesel usage may even improve the pump plunger lubrication conditions. Furthermore, the carbon deposits in the combustion chambers did not vary significantly in quantity but they were noticeably redistributed. Finally, it was found out that the variation of the nozzle discharge coefficient has to be taken into account only if high accuracy of numerical simulation is desired.     

Physicochemical Properties of Purified Biodiesel Based on Oil Recovered from Catfish (Ictalurus punctatus) Viscera

The effects of neutralization, transesterification, and adsorption on the physicochemical properties of fatty acid methyl esters (FAME) obtained from crude catfish oil (CO) were investigated. CO was recovered from catfish viscera and subjected to: neutralization (NCO) with 20 (g/100 g) NaOH solution, transesterification (BIO) with methyl alcohol (1:6 molar ratio, oil: alcohol) and 1 (g/100 g) (w/w) NaOH, and purification by adsorption (PBIO) with activated earth (10 g/100 g of BIO). CO, NCO, BIO, and PBIO were evaluated for FAME, free fatty acids (FFA), peroxide value (PV), cloud and flash points, free and total glycerin, rheological properties, and minerals. Catfish viscera had a lipid content of 28.5 g/100 g (wet basis), of which 20.9 g were recovered as CO (73.33% yield). Furthermore, 84.67 g of NCO, 77.53 g of BIO, and/or 60.22 g of PBIO were produced from 100 g of CO processed. NCO had significantly (P < 0.05) lower FFA, density, cloud point, flash point, and diacylglycerols content than CO. Meanwhile, PBIO had significantly (P < 0.05) lower PV and cloud points when compared to BIO. CO, NCO, BIO, and PBIO behaved as Newtonian fluids at 25 °C. BIO and PBIO adhere to the american society for testing and materials (ASTM) biodiesel standards for FAME, moisture, density, cloud point, free and total glycerin, Na, P, and S. This study demonstrated the feasibility of converting high-viscosity CO into low-viscosity PBIO with promising physicochemical attributes. PBIO has the potential to serve as a viable alternative biofuel.     

A Mathematical Model for Estimating Molecular Compressibility of Fatty-Acid Methyl Ester and Biodiesel

In this study, the molecular compressibility (k_m) of a fatty-acid methyl ester (FAME) or a biodiesel is correlated with ΔG, , via the Gibbs energy additivity method, where MW is the molecular weight of the FAME or the average MW of the biodiesel. The Gibbs energy associated with molecular compressibility () is further correlated with the structure of FAME. Thus, the relationship between the structure (of a FAME or a biodiesel) and the physical property (k_m) is established. Thus, k_m of a FAME at different temperatures can be easily estimated from the carbon numbers of fatty acid (z) and the number of double bonds (n_d) with good accuracy. For biodiesel, k_m is calculated from the same equation with the average z (z_(ave)) and average n_d (n_d(ave)). k_m is not temperature independent and a slight change in k_m depends on the structure of the FAME and biodiesel. For FAME having 14 carbon atoms or less in the fatty acid, k_m decreases as temperature is increased. On the other hand, for FAME with a longer chain length (16 or higher), k_m increases as temperature is increased. Similarly, a double bond in the long-chain FAME is more sensitive to temperature than the saturated FAME.