Ketonization of fatty methyl esters over Sn−Ce−Rh−O catalyst

A mixture of methyl esters of fatty acids obtained by transterification of nonerucic rape oil was ketonized. The starting material, diluted with methanol, was converted at atmospheric pressure over a catalyst that contained Sn, Ce, and Rh oxides in a molar ratio of 90:9:1. At a temperature of 385°C ketones were obtained with a total yield of 63% at the 96% conversion of starting material. The reported experiments prove that catalysts other than iron that are active in ketonization of primary alcohols can be successfully used in ketonization of esters of fatty acids. The kind of diluent used plays a crucial role in the conversion.     

Formation of long chain ketones over an iron catalyst

Primary aliphatic alcohols, aldehydes, esters, carboxylic acids, and their anhydrides undergo a transformation to ketones with high yield and selectivity. The reactions proceed in a continuous way in the gas phase over an iron catalyst. This revised version was published online in August 2006 with corrections to the Cover Date.     

Glycerolysis of fats and methyl esters

The glycerolysis of methyl esters and triglycerides with crude glycerol, a coproduct from the transesterification of triglycerides, was studied. Three procedures were followed for this conversion. The first procedure was a one-step glycerolysis with methyl esters. The second procedure was a two-step process. This procedure involved an initial partial glycerolysis with methyl esters, followed by fat glycerolysis. The third procedure was a simultaneous glycerolysis with methyl esters and triglycerides. In the glycerolysis with methyl esters, the removal of methanol is vital to the production of mono- and diglycerides. Methanol was removed either by drawing vacuum on the reactor or by stripping methanol out by means of an inert carrier gas (nitrogen). Different molar ratios of methyl esters to glycerol were tested in the first two processes. At low concentration of methyl esters, total conversion of methyl esters to mono- and diglycerides was achieved. As the concentration of methyl esters was increased, the conversion of methyl esters to mono- and diglycerides was decreased. Furthermore, the ratio of mono- to diglycerides was also higher at lower concentrations of methyl esters. The conversion of triglycerides in the two-step process with crude glycerol was similar to a one-step fat glycerolysis with pure glycerol. The composition of different components and the ratio of mono- to diglycerides were also comparable.     

<Emphasis Type="Italic">In situ</Emphasis> alkaline transesterification: An effective method for the production of fatty acid esters from vegetable oils

The production of simple alkyl FA esters by direct alkali-catalyzed in situ transesterification of the acylglycerols (AG) in soybeans was examined. Initial experiments demonstrated that the lipid in commercially produced soy flakes was readily transesterified during agitation at 60°C in sealed containers of alcoholic NaOH. Methyl, ethyl, and isopropyl alcohols readily participated in the reaction, suggesting that the phenomenon is a general one. Statistical experimental design methods and response surface regression analysis were used to optimize reaction conditions, using methanol as alcohol. At 60°C, the highest yields of methyl ester with minimal contamination by FFA and AG were predicted at a molar ratio of methanol/AG/NaOH of 226∶1∶1.6 with an approximately 8-h incubation. An increase in the amount of methanol, coupled with a reduced alkali concentration, also gave high ester yields with low FFA and AG contamination. The reaction also proceeded well at 23°C (room temperature), giving higher predicted ester yields than at 60°C. At room temperature, maximal esterification was predicted at a molar ratio of 543∶1∶2.0 for methanol/AG/NaOH, again in 8 h. Of the lipid in soy flakes, 95% was removed under such conditions. The amount of FAME recovered after in situ transesterification corresponded to 84% of this solubilized lipid. Given the 95% removal of lipid from the soy flakes and an 84% efficiency of conversion of this solubilized lipid to FAME, one calculates an overall transesterification efficiency of 80%. The FAME fraction contained only 0.72% (mass basis) FFA and no AG. Of the glycerol released by transesterification, 93% was located in the alcoholic ester phase and 75 was on the post-transesterification flakes.     

Production of mixed methyl/ethyl esters from waste fish oil through transesterification with mixed methanol/ethanol system

Biodiesel (mixed fatty acid methyl/ethyl esters) was prepared from waste fish oil through base-catalyzed transesterification with mixed methanol/ethanol system. Effect of methanol/ethanol (% v/v), type and concentration of the catalyst, mixed alcohols to oil molar ratio, the reaction temperature, and the reaction time on the biodiesel yield was optimized. Maximum biodiesel yield (97.30?wt%) was produced by implementing 1:1 methanol/ethanol (v/v), 1.0?wt% KOH, 6:1 mixed alcohols to oil molar ratio, 40°C reaction temperature, and 30?min of reaction time. Conversion of the waste fish oil to mixed methyl/ethyl esters was confirmed by ¹H NMR spectroscopy. Fuel properties of the resulting biodiesel in addition to its blends with petrodiesel were in good agreement with specifications of ASTM D6751 and ASTM D7467, respectively. Therefore, it was concluded that using mixed alcohol system for biodiesel production could reduce the production cost through reducing conditions required for maximum conversion.     

从废弃油脂生物柴油中分离不饱和脂肪酸甲酯

以废弃油脂制生物柴油为原料,以95%醇为溶剂,采用尿素包合法提取不饱和脂肪酸甲酯,为生物柴油联产具有高附加值化工产品打下基础.重点考察了尿素用量、溶剂用量、包合时间和包合温度对不饱和脂肪酸甲酯分离效果的影响.结果表明,尿素包合法从生物柴油中分离不饱和脂肪酸甲酯的适宜工艺条件为:尿素,生物柴油质量比为1.4～1.7,溶剂/生物柴油质量比为4.6～6.0,包合温度为10℃,包合时间为18 h.在适宜条件下,不饱和脂肪酸甲酯含量可达93.5%,收率可达55.8%.     

Synthesis of Biodiesel from Soybean Oil using Heterogeneous KF/ZnO Catalyst

Biodiesel was produced by transesterification of soybean oil with methanol using ZnO loaded with KF as a solid base catalyst. It was found that the catalyst with 15 wt.% KF loading and calcined at 873 K showed the optimum activity. XRD, IR and Hammett indicator method were employed for the catalyst characterization. The results showed the activity of the catalysts was correlated with their basicity. The influence of various reaction variables on the conversion was also discussed.     

预酯化-酯交换法利用餐饮废油脂制备生物柴油

以高酸值餐饮废油脂和乙醇为原料,采用预酯化-酯交换法制备生物柴油。第一步为预酯化反应,控制反应温度为70℃,最佳条件为:催化剂加入量为4%,反应时间为90min,带水剂加入量为10%,乙醇加入量控制在醇酸摩尔比为6∶1,可使油脂酸值降至4mg KOH·g-1以下,满足酯交换反应要求。第二步为酯交换反应,最佳条件是:醇油摩尔比为8∶1,碱性催化剂加入量为0.8%,反应温度为70℃,反应时间为30min。本方法具有反应时间短、转化率高,反应条件温和,清洁环保等优点。     

Kinetics of transesterification of palm-based methyl esters with trimethylolpropane

Kinetics of transesterification of palm-based methyl esters (POME) with trimethylolpropane (TMP) to polyol esters was investigated. A kinetic model of reaction was obtained by assuming a series of irreversible elementary reactions at various temperatures. The reaction rate constants were determined under limited conditions. The optimal ratios for k ₂/k ₁ and k ₃/k ₁ were 0.70–0.80 and 0.21–0.25, respectively. Both palm oil methyl esters (PPOME) and palm-kernel oil methyl esters (PKOME) were reacted with TMP by using sodium methoxide as catalyst. The POME-to-TMP molar ratio and catalyst weight percentage were held constant at 10∶1 and 0.4%, respectively. The effects of temperature (70–110°C) and raw materials (PKOME and PPOME) were investigated and found to have a significant impact on the reaction kinetics. When using a large excess of POME and continual withdrawal of methanol via vacuum, the reaction reached completion in less than 20 min at 80°C. After removal of unreacted POME, the final product contained apprximately 98 wt% triesters.     

制备活性炭负载K2CO3用于催化餐饮废油合成生物柴油

以K₂CO₃为催化剂,工业碱木质素(KL)为活性炭(AC)前体,在管式电阻炉中经一步共混活化(K₂CO₃/KL质量比为0.6、活化温度800℃、N₂流量100cm³/min、活化时间2h)制备K₂CO₃/AC固体碱催化剂,用于餐饮废油与甲醇的酯交换反应合成生物柴油。对制备的固体碱催化剂进行了X-射线衍射(XRD)、BET表面积及扫描电镜(SEM)表征。考察了反应温度、催化剂用量、反应时间、醇油摩尔比等因素对餐饮废油转化为生物柴油产率的影响。结果表明当反应时间2h、反应温度60℃、醇油摩尔比15:1、催化剂为原料油质量的3.0%时,生物柴油最大产率为87.5%。考查了催化剂的循环利用效果,结果表明催化剂能循环利用3次,第3次利用时生物柴油的产率仍达到80.7%。     

Simple, high-efficiency synthesis of fatty acid methyl esters from soapstock

We report a simple method that efficiently esterifies the fatty acids in soapstock, an inexpensive, lipid-rich by-product of edible oil production. The process involves (i) alkaline hydrolysis of all lipid-linked fatty acid ester bonds and (ii) acid-catalyzed esterification of the resulting fatty acid sodium salts. Step (i) completely saponified all glycerides and phosphoglycerides in the soapstock. Following water removal, the resulting free fatty acid sodium salts were rapidly and quantitatively converted to fatty acid methyl esters (FAME) by incubation with methanol and sulfuric acid at 35°C and ambient pressure. Minimum molar reactant ratios for full esterification were fatty acids/methanol/sulfuric acid of 1∶30∶5. The esterification reaction was substantially complete within 10 min and was not inhibited by residual water contents up to ca. 10% in the saponified soapstock. The product FAME contained >99% fatty acid esters, 0% triglycerides, <0.05% diglycerides, <0.1% monoglycerides, and <0.8% free fatty acids. Free fatty acid levels were further reduced by washing with dilute sodium hydroxide. Free and total glycerol were <0.01 and <0.015%, respectively. The water content was <0.04%. These values meet the current specifications for biodiesel, a renewable substitute for petroleum-derived diesel fuel. The identities and proportions of fatty acid esters in the FAME reflected the fatty acid content of soybean lipids. Solids formed during the reaction contained 69.1% ash and 0.8% protein. Their sodium content indicated that sodium sulfate was the prime inorganic component. Carbohydrate was the predominant organic constituent of the solid.     

Enzymatic transesterification of sunflower oil in an aqueous-oil biphasic system

A biphasic oil-aqueous system for FAME production by enzymatic catalysis was studied. The transesterification of sunflower oil with methanol was catalyzed by free or immobilized lipases from Rhizomucor miehei (Palatase 20 000 L) and Humicola insolens (Lipozyme TL 100 L). The effects of protein amount, temperature, pH, and molar ratio of methanol to sunflower oil on the enzymatic reaction using free lipase were evaluated; the best results were obtained with H. insolens, at pH 5, 40°C, and 36.8 mg of protein. By using this lipase immobilized in Hypol^® 2002 (64. 8 mg of protein) at a 6∶1 methanol/oil molar ratio and a 2∶1 volumetric oil/water phase ratio, an ester content of 96.1% and a conversion of 91.2% were achieved. The immobilized lipase could be reused, although a 30% reduction in conversion efficiency was observed after four uses.     

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.     

Pseudomonas sp. lipase-catalyzed synthesis of geranyl esters by transesterification

Pseudomonas sp. lipase was immobilized by adsorption onto five supports and tested for its ability to synthesize geranyl esters by transesterification using short-chain triacylglycerols as acyl donors. Reaction mixtures were prepared in 2 mL ofn-hexane, 0.1 M geraniol, 0.03M triacylglycerol, and 200 units of lipase, and incubated at 30°C and 200 rpm for 24 h. Overall, glass beads were the best support. Geranyl acetate and caproate performed best with Duolite (77.5 and 95.3%, respectively). Geranyl butyrate and caprylate performed best with polyvinylpyrrolidone, (80.2 and 95.5%, respectively). Values for nonimmobilized enzyme also were obtained. Immobilization improved yields, with geranyl caproate exhibiting best results.     

Use of dolomite catalyst in biodiesel production via transesterification of waste cooking oil in oscillatory baffled reactor

Biodiesel has recently gained popularity due to its environmental issues and the fact that it is generated from renewable resources. However, the cost of the synthesis of biodiesel is the major impediment to commercialization. The utilization of leftover cooking oils as raw material, the adaptation of a continuous transesterification process, and the use of cheap catalysts are the major possibilities for investigating the cost of biodiesel. In this work, a dolomite catalyst was prepared from natural dolomite rocks and used for the evaluation of continuous transesterification of biodiesel from oleic acid as a model compound of waste cooking oil (WCO). The dolomite catalyst was prepared by activation under vacuum at a surface area of 34.5 m²/g. The characterization tests showed good thermal stability of the catalyst and evolution of the CaO and MgO compounds at high concentrations. A kinetic study was conducted to obtain kinetic parameters of catalytic transesterification of the WCO. The kinetic experiments were carried out at 298–333 K, and residence time up to 80 min. The results presented that the catalytic transesterification is the first-order reaction, and the activation energy was 43 kJ/mol. The oscillatory baffled reactor (OBR) was used to evaluate the dolomite catalyst for the continuous production of biodiesel via transesterification. The evaluation study was conducted at a methanol: oil mole ratio of 6:1 and the effect of different operation variables on oleic acid conversion to biodiesel was studied. These variables were temperature (323, 333, and 343 K), residence times (5–40 min), the amplitude of oscillation (2–8 mm), and frequency of oscillation (1, 2, 3, 4, and 4.3 Hz). The results showed an outstanding performance and stable activity of the dolomite catalyst as a conversion of 96% was obtained at 333 K, 4.3 Hz, 8 mm amplitude, and 40 min residence time.     

Application of Indirect Enzymatic Method for Determinations of 2-/3-MCPD-Es and Gly-Es in Foods Containing fats and Oils

Because of the potential health risks, fatty acid esters of 3‐chloro‐1,2‐propanediol (3‐MCPD‐Es), 2‐chloro‐1,3‐propanediol (2‐MCPD‐Es) and glycidol (Gly‐Es) in foods are drawing the attention of public health authorities. To assess applicability of the rapid indirect method developed earlier by using a Candida rugosa lipase for the analyses of refined fats and oils was applied to the analyses of various foods. Mayonnaise, vegetable oil margarine and fat spread could be analyzed with the hydrolysis condition of 30 min at room temperature. Analyses of 3‐MCPD‐Es in margarines and fat spreads containing milk fat could be analyzed by increasing the hydrolysis temperature to 40 °C. The results in a mayonnaise, four fat spreads and five margarines analyzed by the enzymatic method were 0.10–0.98 mg/kg for 3‐MCPD, 0.05–0.41 mg/kg for 2‐MCPD and 0.15–0.59 mg/kg for Gly, and correlated well with the results obtained by AOCS Cd 29a with Cd 30–15 with slopes of 0.99–1.13, and R²s of 0.87–0.99. Further, by adding a simple fat extraction step using a solvent mix at 60 °C, foods high in protein and carbohydrate, such as infant formulas, could also be successfully analyzed with >90 % recovery in 1 day. Because the enzymatic method requires only 30 min for hydrolysis, the method is considered suitable for routine analyses of 2‐/3‐MCPD‐Es and Gly‐Es in foods.     

Remarks on official methods employing boron trifluoride in the preparation of methyl esters of the fatty acids of fish oils

Some “official methods” for preparing methyl esters of the fatty acids from oils or fats may be referred to by users as the boron trifluoride (BF₃) method and invariably have two stages. The first stage, brief treatment with alkali [commonly NaOH in methanol (MeOH), sometimes NaOCH₃] and heat has been popularly described as a saponification step for over 30 yr. In fact, the disappearance of visible fat or oil is mostly transesterification, which can be accomplished in a few minutes under mild conditions. Free fatty acids (FFA) originally present, or produced by saponification, are not converted to methyl esters at this stage. The second stage, heating in BF₃-MeOH, has in practice been as short as 2 min. It can convert all FFA to methyl esters, but this step requires at least 30 min. Examples from the recent literature illustrate the necessity of extending the time for BF₃-MeOH transesterification of lipids or oils and methylation of FFA. No alkali transesterification is needed. Presented in part at the 88th Annual Meeting of the American Oil Chemists’ Society, Seattle, WA, May 1997.     

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.     

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。