Acid-catalyzed alcoholysis of soybean oil

In an effort to increase utilization of fats and oils with high concentrations of FFA, acid catalysts were investigated at elevated temperatures to determine their efficacy under various operating conditions. Acid-catalyzed alcoholysis of soybean oil using sulfuric, hydrochloric, formic, acetic, and nitric acids was evaluated at 0.1 and 1 wt% loadings at temperatures of 100 and 120°C in sealed ampules, but only sulfuric acid was effective. Kinetic studies at 100°C, 0.5 wt% sulfuric acid catalyst, and nine times methanol stoichiometry provide >99 wt% conversion of TG in 8 h and less than 0.8 wt% FFA concentrations at less than 4 h. Reaction conditions near 100°C at 0.1 to 0.5 wt% were identified as providing the necessary conversions in a 24-h batch cycle while not darkening the product as is typical with high temperatures and catalyst loadings. The oxygen/air contained in the reaction ampules at the onset of the reaction was not sufficient to color the product, but the product darkened if atmospheric air contacted the reacting mixture. The presence of small amounts of stainless steel significantly decreased conversions.     

相转移催化大豆油醇解研究

通过催化大豆油与甲醇进行酯交换反应合成脂肪酸甲酯(FAME),研究了相转移催化剂对油脂醇解的催化性能。考察了不同醇油摩尔比、催化剂用量、反应时间和反应温度对大豆油醇解反应的影响,得到了较佳工艺条件:n(甲醇)∶n(大豆油)为6∶1,催化剂用量为大豆油质量的1.0%,35℃~40℃下反应1 h。结果表明:苄基三乙基氢氧化铵是油脂醇解的有效催化剂,在优化工艺条件下甲酯产率达91%以上。     

In-situ alcoholysis of soybean oil

In-situ alcoholysis of soybean oil with methanol, ethanol,n-propanol, andn-butanol was investigated, as well as the extraction of the oil with these solvents, to explain the progress ofin-situ alcoholysis and to determine the parameters that affect this reaction. Because methanol is a poor solvent for soybean oil, the amount of oil dissolved in methanol and converted to methyl esters was low afterin-situ alcoholysis. Ethyl, propyl, and butyl esters of soybean fatty acids could be obtained in high yields fromin-situ alcoholysis of soybean oil with these alcohols.In-situ alcoholysis proceeded through dissolution and alcoholysis of triglycerides successively, and the overall reaction rate was determined by the extraction and alcoholysis rates. The parameters, affecting yield and purity of the product esters, were mainly those that favor extraction rate.     

Kinetics of transesterification of soybean oil

Transesterification of soybean oil with methanol was investigated. Three stepwise and reversible reactions are believed to occur. The effect of variations in mixing intensity (Reynolds number=3,100 to 12,400) and temperature (30 to 70°C) on the rate of reaction were studied while the molar ratio of alcohol to triglycerol (6:1) and the concentration of catalyst (0.20 wt% based on soybean oil) were held constant. The variations in mixing intensity appear to effect the reaction parallel to the variations in temperature. A reaction mechanism consisting of an initial mass transfer-controlled region followed by a kinetically controlled region is proposed. The experimental data for the latter region appear to be a good fit into a second-order kinetic mechanism. The reaction rate constants and the activation energies were determined for all the forward and reverse reactions.     

Effect of mixed alcohol reactants on ultrasonic alcoholysis of canola oil

The effect of ultrasonic irradiation energy was analyzed according to the kinds of alcohol in the ultrasonic alcoholysis. The ultrasonic irradiation energy density of ethanol (792.9 kJ/L) is higher than methanol (649.8 kJ/L). The optimum mixing ratio of canola oil, methanol and ethanol was proven as 1, 5 and 1, respectively. Also the optimum reaction conditions for the ultrasonic alcoholysis were a reaction temperature of 60 °C, ultrasonic irradiation power of 500 W, reaction time of 50 min, and alkaline catalyst (KOH) content of 0.6 wt.%. From these results, the optimum alcohol mixing ratio and the optimum process conditions were determined, with good quality biodiesel being manufactured.     

Alkali-catalyzed alcoholysis of crambe oil and camelina oil for the preparation of long-chain esters

The alcoholysis of crambe and camelina oils was carried out with oleyl alcohol, alcohols derived from crambe and camelina oils, and n-octanol using potassium hydroxide as catalyst to prepare alkyl esters. Conversions to alkyl esters were about 0% with oleyl alcohol, 20–45% with crambe and camelina alcohols, and 60% with n-octanol. The conversion to esters for crambe and camelina oil with oleyl alcohol and n-octanol increased with increasing molar excess of alcohol. Composition of the alkyl esters formed was as expected from the composition of the reaction partners. Presented as part of the doctoral thesis of Georg Steinke to the University of Münster, Münster, Germany.     

Lipase-catalyzed alcoholysis of crambe oil and camelina oil for the preparation of long-chain esters

Crambe oil and camelina oil were transesterified with oleyl alcohol, the alcohols derived from crambe and camelina oils, n-octanol or isopropanol using Novozym 435 (immobilized lipase B from Candida antarctica), Lipozyme IM (immobilized lipase from Rhizomucor miehei), and papaya (Carica papaya) latex lipase as biocatalysts. The highest conversions to alkyl esters were obtained with Novozym 435 (up to 95%) in most cases, whereas Lipozyme IM and papaya latex lipase gave lower (40 to 50%) conversions. The conversions with long-chain alcohols (oleyl alcohol, crambe alcohols, and camelina alcohols) were higher (40 to 95%) than with medium-chain n-octanol (30 to 85%). Isopropyl esters of crambe oil and camelina oil were obtained with rather low conversions using Novozym 435 (<40%) and Lipozyme IM (about 10%) as biocatalysts, whereas with papaya latex lipase no isopropyl esters were formed. The conversions of crambe oil and camelina oil to oleyl and n-octyl esters using Novozym 435 as biocatalyst were hardly affected by the ratio of the substrates, but with Lipozyme IM the conversions to alkyl esters distinctly increased with an excess of alcohol substrate Presented as part of the doctoral thesis of Georg Steinke to the University of Münster, Münster, Germany     

Exhaust emissions and fuel properties of partially hydrogenated soybean oil methyl esters blended with ultra low sulfur diesel fuel

Important fuel properties and emission characteristics of blends (20 vol.%) of soybean oil methyl esters (SME) and partially hydrogenated SME (PHSME) in ultra low sulfur diesel fuel (ULSD) were determined and compared with neat ULSD. The following changes were observed for B20 blends of SME and PHSME versus neat ULSD: improved lubricity, higher kinematic viscosity and cetane number, lower sulfur content, and inferior low-temperature properties and oxidative stability. With respect to exhaust emissions, B20 blends of PHSME and SME exhibited lower PM and CO emissions in comparison to those of neat ULSD. The PHSME blend also showed a significant reduction in THC emissions. Both SME and PHSME B20 blends yielded small increases in NO_x emissions. The reduction in double bond content of PHSME did not result in a statistically significant difference in NO_x emissions versus SME at the B20 blend level. The test engine consumed a greater amount of fuel operating on the SME and PHSME blends than on neat ULSD, but the increase was smaller for the PHSME blend.     

Biodiesel from an alkaline transesterification reaction of soybean oil using ultrasonic mixing

The feasibility of using ultrasonic mixing to obtain biodiesel from soybean oil was established. The alkaline transesterification reaction was studied at three levels of temperature and four alcohol-to-oil ratios. Excellent yields were obtained for all conditions. For example, at 40°C with ultrasonic agitation and a molar ratio of 6∶1 methanol/oil, the conversion to FAME was greater than 99.4% after about 15 min. For a 6∶1 methanol/oil ratio and a 25 to 60°C temperature range, a pseudo second-order kinetic model was confirmed for the hydrolysis of DG and TG. Reaction rate constants were three to five times higher than those reported in the literature for, mechanical agitation. We suspect that the observed mass transfer and kinetic rate enhancements were due to the increase in interfacial area and activity of the microscopic and macroscopic bubbles formed when ultrasonic waves of 20 kHz were applied to a two-phase reaction system.     

Preparation of glycol derivatives of partially hydrogenated soybean oil fatty acids and their potential as lubricants

Glycol diesters and mixtures of mono- and diesters have been prepared from methyl esters of partially hydrogenated soybean oil fatty acids and diethylene, dipropylene, neopentyl and triethylene glycols. The catalyst used in these reactions was a mixture of calcium acetate/barium acetate (3∶1, w/w). The reactions were carried out under nitrogen with 0.5% catalyst at temperatures in the range of 190–275°C. Borated esters of mixed mono- and diesters were prepared with 0.33 equivalent of boric acid per 1.0 equivalent hydroxyl group on the ester. Refractive indices, viscosities, and flash and fire points were determined for diesters, mixed mono- and diesters, and mixed diesters and borated esters. The viscosities, flash points and fire points indicate that these esters can be used as a component of lubricating oils. Wear-prevention characteristics of mixed diesters and borated esters indicated that they can be used as antifriction additives in lubricating oils. Lecture presented at the joint meeting of the International Society for Fat Research and the American Oil Chemists' Society in Toronto, May 10, 1992.     

Analysis of epoxidized soybean oil by gas chromatography

A fast and cost-effective procedure to quantitate epoxidized soybean oil by means of an external standard method is reported. This procedure is applicable to commercial epoxidized oils, polymer additive packages and polymers—polyvinyl chloride (PVC)—containing epoxidized oils. The epoxidized soybean oil is converted into fatty acid methyl esters with tetramethylammonium hydroxide, and analyzed by capillary gas chromatography with flame-ionization detection. In PVC samples, the epoxidized soybean oil was extracted with toluene and followed by derivatization prior to analysis. The methyl esters of monoepoxyoctadecanoic, diepoxyoctadecanoic and triepoxyoctadecanoic acid were separated with a short capillary column.     

Kinetics of palm oil transesterification in a batch reactor

Methyl esters were produced by transesterification of palm oil with methanol in the presence of a catalyst (KOH). The rate of transesterification in a batch reactor increased with temperature up to 60°C. Higher temperatures did not reduce the time to reach maximal conversion. The conversion of triglycerides (TG), diglycerides (DG), and monoglycerides (MG) appeared to be second order up to 30 min of reaction time. Reaction rate constants for TG, DG, and MG hydrolysis reactions were 0.018–0.191 (wt%·min)⁻¹, and were higher at higher temperatures and higher for the MG reaction than for TG hydrolysis. Activation energies were 14.7, 14.2, and 6.4 kcal/mol for the TG, DG, and MG hydrolysis reactions, respectively. The optimal catalyst concentration was 1% KOH.     

The pseudo-single-phase,base-catalyzed transmethylation of soybean oil

The base-catalyzed transmethylation of soybean oil has been studied under conditions whereby the reaction starts as a single phase, but later becomes two phases as glycerol separates. Methanol/oil molar ratios of 6∶1 were used at 23°C. The catalysts were sodium hydroxide (0.5, 1.0, and 2.0 wt%), potassium hydroxide (1.0 and 1.4 wt%), and sodium methoxide (0.5, 1.0, and 1.35 wt%), all concentrations being with respect to the oil. Oxolane (tetrahydrofuran) was used to form a single reaction phase. The reactions deviated from homogeneous kinetics as glycerol separated, taking with it most of the catalyst. When 1.0 wt% sodium hydroxide was used, the methyl ester content reached 97.5 wt% after 4 h, compared with 85–90 wt% in the two-phase reaction. Sodium hydroxide (1.0 wt%), sodium methoxide (1.35 wt%), and potassium hydroxide (1.4 wt%) gave similar results, presumably because the same number of moles was used. The ASTM biodiesel specification for chemically bound glycerol was achieved after only 3 min when 2.0 wt% sodium hydroxide was used. However, the standard was not achieved after 4 h when 1.0 wt% sodium hydroxide was used, the MG content being 1.1–1.6 wt%. The use of 2.0 wt% catalyst is commercially impractical.     

大豆油与甲醇酯交换反应体系的相平衡研究

生物柴油是一类清洁的可再生液体燃料,精炼植物油与甲醇酯交换是制备生物柴油的重要反应。针对目前难以准确获得酯交换反应体系的多组分相平衡组成等方面存在的问题,研究了间歇反应和连续逆流分离甘油等不同反应方式下大豆油与甲醇酯交换反应体系的多组分相平衡行为,并以三油酸甘油酯与甲醇酯交换为模型反应,采用UNIFAC和Modified UNIFAC模型进行了模拟计算。结果表明,在常压、60^oC反应条件下,在总组成偏离甲醇-甲酯二元组成的区域,UNIFAC和Modified UNIFAC模型准确计算了生物柴油酯交换反应体系的三元和四元相平衡组成。在甘油含量大于2.2%(质量)或转化率小于90%(质量)的酯交换反应中,计算值与实验值的平均偏差约为2%。酯交换反应相平衡的实验值和模型计算值表明,采用连续逆流方式分离甘油可以提高酯相中的甲醇含量,有利于传质和酯交换反应。这些结果为生物柴油工艺过程模拟、设备优化以及新技术开发提供了理论参考。     

Application of raman spectroscopy to monitor and quantify ethyl esters in soybean oil transesterification

Biodiesel (FA esters) has become very attractive as an alternative diesel fuel owing to its environmental benefits. Transesterification is the most usual and important method to make biodiesel from vegetable oils. This article investigates the potential for using Raman spectroscopy to monitor and quantify the transesterification of soybean oil to yield ethyl esters. The differences observed in the Raman spectra of soybean oil after transesterification were a peak at 2932 cm⁻¹ ( ), the displacement of the v _C=O band from 1748 to 1739 cm⁻¹, and the bands at 861 (v _R-C=O and v _C-C) and 372 cm⁻¹ (δ _CO-O-C). Uni- and multivariate analysis methods were used to build several analytical curves and then applied in known samples, treated as unknowns, to test their ability to predict concentrations. The best results were achieved by Raman/PLS calibration models (where PLS=partial least squares regression) using an internal normalization standard (v _=C-H band). The correlation coefficient (R ²) values so obtained were 0.9985 for calibration and 0.9977 for validation. Univariate regression analysis between biodiesel concentration and the increasing intensity of band or v _C=O displacement showed R ² values of 0.9983 and 0.9742, respectively. Although spectroscopic methods are less sensitive than chromatographic ones, the data obtained by spectroscopy can be correlated with other techniques, allowing biodiesel yield and quality to be quickly assessed.     

Transesterification of heated rapeseed oil for extending diesel fuel

Fatty acid methyl esters are well established as an alternative fuel called “biodiesel.” For economic reasons, used frying oil is an interesting alternative feedstock for biodiesel production. The chemical changes that occur during heating of rapeseed oil, especially the formation of polymers, were investigated. Heated rapeseed oil samples were transesterified with methanol and analyzed by size-exclusion chromatography. During heating, the amount of polymers in the starting oil increased up to 15 wt%, but only up to 5 wt% in the transesterified samples. So during transesterification, dimeric and trimeric triglycerides in the starting oil were mainly converted into monomeric and dimeric fatty acid methyl esters. The amount of polymeric fatty acid methyl esters had a negative influence on fuel characteristics. After 6 h of heating, the amount of Conradson carbon residue and after 16 h the viscosity exceeded that of the existing specifications for biodiesel. Therefore, the amount of polymers in waste oil is a good indicator for the suitability for biodiesel production. Presented in part at the 89th Annual Meeting, American Oil Chemists’ Society, Chicago, IL, May 1998.     

Synthesis of 2‐monoglycerides by alcoholysis of palm oil and tuna oil using immobilized lipases

Commercial immobilized lipases were used for the synthesis of 2‐monoglycerides (2‐MG) by alcoholysis of palm and tuna oils with ethanol in organic solvents. Several parameters were studied, i.e., the type of immobilized lipases, water activity, type of solvents and temperatures. The optimum conditions for alcoholysis of tuna oil were at a water activity of 0.43 and a temperature of 60 °C in methyl‐tert‐butyl ether for ～12 h. Although immobilized lipase preparations from Pseudomonas sp. and Candida antarctica fraction B are not 1, 3‐regiospecific enzymes, they were considered to be more suitable for the production of 2‐MG by the alcoholysis of tuna oil than the 1, 3‐regiospecific lipases (Lipozyme RM IM from Rhizomucor miehei and lipase D from Rhizopus delemar). With Pseudomonas sp. lipase a yield of up to 81% 2‐MG containing 80% PUFA (poly‐unsaturated fatty acids) from tuna oil was achieved. The optimum conditions for alcoholysis of palm oil were similar as these of tuna oil alcoholysis. However, lipase D immobilized on Accurel EP100 was used as catalyst at 40 °C with shorter reaction times (<12 h). This lead to a yield of ～60% 2‐MG containing 55.0‐55.7% oleic acid and 18.7‐21.0% linoleic acid.     

Quantification of soybean oil ethanolysis with <Superscript>1</Superscript>H NMR

In this study, proton NMR spectroscopy (200 MHz) was used for quantifying the content of ethyl esters in known mixtures of soybean oil and ethyl soyate (biodiesel). For this purpose, the peak areas of ester ethoxy and glycerol methylenic peaks in the region of 4.05–4.40 ppm were measured and a calibration plot of the respective peak areas vs. the known composition of the oil/ethyl ester mixtures was used. The transesterification values determined in this way were compared with viscosity and total glycerol determinations and a good correlation was obtained. Therefore, for routine analysis, the conversion (in %) of oil to ethyl esters was determined. The methodology presented in this work proved to be quicker and simpler than others reported in the literature, such as GC and/or HPLC.     

Equilibria in the alcoholysis reactions of terephthalic esters and chemical valorization of polyethyleneterephthalate waste. I. Equilibrium constants determination

The depolymerization of polyethyleneterephthalate (PET) by alcoholysis is an easy operation and gives interesting prospects for the valorization of wastes. The reactive species being composed of esters and alcohols, all possible alcoholysis reactions happen, whether wanted or not. Finally, a complex blend of many molecules follows. Practically, two great types of reactions occur: a reaction called “interchange,” and a reaction called “polycondensation.” We have determined the values of global equilibrium constants of those two types of reaction. The values of polycondensation equilibrium constants are close to those estimated from the “equireactivity” principle. We did not observe any particular behavior of monomer species. When reactants are the di‐ or mono‐propylene glycols, the molar proportion of these glycolic radicals is higher in the free glycols than in the polyester chains. Both proportions are similar, when diethylene glycol or 2‐ethylhexanol are used. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 329–340, 1999     

Acid-catalyzed alcoholysis ofVernonia galamensis oil

We have demonstrated the potential ofVernonia galamensis seed oil as a source of hydroxy alkoxy fatty esters. Reaction of the oil with various alcohols (methanol, ethanol, 1-propanol and 2-propanol), under acidic conditions, resulted in transesterification as well as epoxy ring opening in all cases. The major products, the hydroxy alkoxy fatty esters, constituted approximately 80% of the product mixtures, of which the 12-hydroxy-13-alkoxy isomers were the major constituents. These derivatives were isolated by solvent extraction and/or column chromatography to afford 78–80% of pure isomers. Alcoholysis with butanol resulted in a poor yield of the hydroxy butoxy esters. A discussion of the isolation and mass-spectrometric characterization of these new esters is provided.