Phase and chemical equilibria in the transesterification reaction of vegetable oils with supercritical lower alcohols

Calculations of thermodynamic data are performed for fatty acid triglycerides, free fatty acids, and fatty acid methyl esters, participants of the transesterification reaction of vegetable oils that occurs in methanol. Using the obtained thermodynamic parameters, the phase diagrams for the reaction mixture are constructed, and the chemical equilibria of the esterification reaction of free fatty acids and the transesterification reaction of fatty acid triglycerides attained upon treatment with supercritical methanol are determined. Relying on our analysis of the obtained equilibria for the esterification reaction of fatty acids and the transesterification reaction of triglycerides attained upon treatment with lower alcohols, we select the optimum conditions for performing the reaction in practice.     

Phase equilibria modeling of biodiesel related mixtures using the GCA-EoS model

In this work, a group-contribution equation of state that takes into account association effects (GCA-EoS) is extended to model the phase behavior of fatty esters (biodiesel) in binary mixtures with glycerol, alcohols and water and ternary mixtures with glycerol and methanol. A new associating group (glycerol hydroxyl group: OH^Gly) was defined to take into consideration the association effects in the glycerol molecule. Self-association of methanol, water and glycerol and cross-association between methanol–glycerol, alcohol–ester, water–ester and glycerol–ester groups were considered. New pure-group, binary interaction and association parameters have been determined. The correlations and predictions of the model are found in acceptable agreement with selected experimental data reported in the literature.     

Fast identification of mycobacterium species by GC analysis with trimethylsulfonium hydroxide (TMSH) for transesterification

Trimethylsulfonium hydroxide (TMSH) reproducibly converts fatty acids bound in, e.g., biomolecules such as phospholipids and/or glycerides, into the corresponding fatty acid methyl esters (FAMEs). The transesterification can be performed at room temperature in a fast single step reaction. Surprisingly, secondary alcohols and mycolic acid cleavage products (MACPs) are also released from mycobacteria under these conditions. The complex reaction mixtures containing FAMEs, MACPs, and secondary alcohols can easily be separated by high resolution temperature-programmed capillary GC. Different species of mycobacteria give rise to characteristic chromatographic patterns and the amount of lipids from a single colony of mycobacteria is sufficient for reliable identification of the bacteria. The profiles of the chromatograms match well those obtained from other sample preparation techniques. The TMSH method of identification of mycobacteria from the patterns of the gas chromatograms is faster and more sensitive than conventional methods, which also involve transesterification. The identification of mycobacterial species by microbiological culture techniques is difficult to perform and requires several weeks.     

脂肪酸在超临界甲醇中的酯化反应研究

超临界甲醇中的酯化和酯交换反应是利用植物油、动物油或废油脂制备生物柴油的新工艺.它的最大特点是不需要添加催化剂,超临界甲醇既是反应媒介,又是反应物.     

Analysis of alcohols, as dimethylglycine esters, by electrospray ionization tandem mass spectrometry

Dimethylglycine (DMG) esters are new derivatives for the rapid, sensitive and selective analysis of primary and secondary alcohols, in complex mixtures, by electrospray ionization tandem mass spectrometry (ESI-MS/MS). Their development was inspired by the use of the complementary dimethylaminoethyl esters for the trace, rapid analysis of fatty acids. DMG esters are simply prepared by heating a dichloromethane solution of the imidazolide of dimethylglycine, containing triethylamine, and an alcohol. DMG esters of long-chain fatty alcohols, isoprenoidal alcohols and hydroxy-acids are analysed by electrospray ionization tandem mass spectrometry with a precursor ion of m/z 104 scan. Diols, glyceryl esters, glyceryl ethers and some sterols are analysed by a neutral loss of 103 Da scan. Trimethylglycine (TMG) ester iodides, prepared by alkylation of DMG esters with methyl iodide, are more sensitive derivatives for molecules containing secondary alcohol groups, such as cholesterol and gibberellic acid. They are analysed by a precursor ion of m/z 118 scan. DMG or TMG derivatives were shown to be at least comparable and sometimes an order of magnitude more sensitive than N-methylpyridyl ether derivatives for ESI-MS/MS analysis of the different classes of alcohols. Applications of these derivatives for the diagnosis of inherited disorders and the analysis of natural products are presented.     

Calculating the thermodynamic characteristics of the stepwise transesterification of simple triglycerides

Thermodynamic data for mono- and diglycerides of palmitic, oleic, and linoleic fatty acids participating in the stepwise transesterification reaction of the corresponding simple triglycerides in methanol are calculated. The obtained thermodynamic parameters allow us to calculate the chemical equilibrium and the equilibrium composition of the products of the stepwise transesterification reaction of fatty acid triglycerides with supercritical methanol.     

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.     

麻疯油转酯化产物的高效液相色谱分析

建立了高效液相色谱法同时测定麻疯油转酯化产物中4种主要脂肪酸甲酯的分析方法。样品经膜处理后用丙酮溶解,采用Hypersil ODS(C18)色谱柱进行分离。以乙腈为流动相进行等度洗脱,内标法定量,同时对色谱条件进行优化。结果表明,在优化的色谱条件下4种脂肪酸甲酯在10 min内得到良好的分离,标准曲线的线性相关系数均达到0.999以上,平均回收率为96%~98%,重现性相对标准偏差为7.2%~10.2%,重复性相对标准偏差为0.31%~2.02%。与气相色谱法相比,该方法具有较高的灵敏度,可用于麻疯油转酯化产物中脂肪酸甲酯含量的测定,为麻疯油转酯化反应制备生物柴油的定性定量分析提供了参考依据。     

Search for bioactive compounds from Cantharellus cibarius

Ground fruit bodies of Cantharellus cibarius (chanterelle) were extracted with dichloromethane and subjected to CC followed by preparative HPLC, which led to the isolation of glycerol 1,2- and 1,3-dilinoleates and glycerol tridehydrocrepenynate. Extraction of C. cibarius fruit bodies with ethanol or methanol afforded fatty acid ethyl or methyl esters as a result of esterification/transesterification reactions. Insecticidal activity of the isolated glycerides and esters was much lower than that of the crude extracts and chromatographic fractions suggesting a synergistic effect of some of the compounds present in the mixture.     

Pure short-chain glycerol fatty acid esters and glycerylic cyclocarbonic fatty acid esters as surface active and antimicrobial coagels protecting surfaces by promoting superhydrophilicity

Pure glycerol fatty acid esters and glycerylic cyclocarbonic fatty acid esters have an amphiphilic structure, giving these biomolecules a broad range of physico-chemical and biological properties. Physico-chemical properties depend on chain lengths, odd or even carbon numbers on the chain, and glyceryl or cyclocarbonic polar heads. The spectrum of melting-point values for these molecules is large. Surface-activity is very important and through determination of the critical aggregation concentration (CAC), some fatty-acid esters are considered as solvo-surfactant biomolecules. Coupling these self-aggregation and crystallization properties, superhydrophilic surfaces were obtained. An efficient durable water repellent coating of various metallic and polymeric surfaces was allowed. Moreover, these fatty acid esters promoting superhydrophilicity showed biological activity against Gram positive, Gram negative, and yeast-like micro-organisms. Such surfaces coated by self-assembled fatty acid esters in a stable coagel state present a novel solution to surface-contamination risks from pathogen proliferation.     

Development of heterogeneous catalysts for transesterification of triglycerides

This paper describes a preliminary work done towards the development of new metallic heterogeneous catalysts to be used in the transesterification reaction of triglycerides, which is of considerable interest in the production of biodiesel. Biodiesel is a mixture of mono-alkyl esters of fatty acids, and is currently manufactured by transesterification of triglycerides with methanol using NaOH or KOH as liquid base catalyst. Catalysts as such are corrosive to the equipment, and as these catalysts are present in the liquid phase, must be neutralized after the completion of the reaction, typically using HCl, thus producing salt streams. Moreover, due to the presence of free fatty acids, it reacts to form soaps as unwanted by-products, hence requiring more expensive separation processes. Therefore, there is a great need for the development of industrial processes for biodiesel production using solid acid catalysts. The key benefit of using solid acid catalysts is that no polluting by-products are formed, and the catalysts do not have to be removed since they do not mix with the biodiesel product.     

HPLC method for rapidly following biodiesel fuel transesterification reaction progress using a core-shell column

There are a wide and growing variety of feedstocks for biodiesel fuel. Most commonly, these feedstocks contain triglycerides which are transesterified into the fatty acid alkyl esters (FAAEs) which comprise biodiesel fuel. While the tranesterification reaction itself is simple, monitoring the reaction progress and reaction products is not. Gas chromatography-mass spectrometry is useful for assessing the FAAE products, but does not directly address either the tri-, di-, or monoglycerides present from incomplete transesterification or the free fatty acids which may also be present. Analysis of the biodiesel reaction mixture is complicated by the solubility and physical property differences among the components of the tranesterification reaction mixture. In this contribution, we present a simple, rapid HPLC method which allows for monitoring all of the main components in a biodiesel fuel transesterification reaction, with specific emphasis on the ability to monitor the reaction as a function of time. The utilization of a relatively new, core-shell stationary phase for the HPLC column allows for efficient separation of peaks with short elution times, saving both time and solvent.     

Clean synthesis of biodiesel over solid acid catalysts of sulfonated mesopolymers

FDU-15-SO₃H, a solid acid material prepared from the sulfonation of FDU-15 mesoporous polymer, has been demonstrated to serve as an efficient catalyst in the esterification of palmitic acid with methanol as well as in the transesterification of fatty acid-edible oil mixture. FDU-15-SO₃H achieved an acid conversion of 99.0% when the esterification was carried out at 343 K with a methanol/palmitic acid molar ratio of 6:1 and 5 wt% catalyst loading. It was capable of giving 99.0% yield of fatty acid methyl esters (FAME) when the transesterification of soybean oil was performed at 413 K and the methanol/oil weight ratio of 1:1. FDU-15-SO₃H was further applied to the transesterification/esterification of the oil mixtures with a varying ratio of soybean oil to palmitic acid, which simulated the feedstock with a high content of free fatty acids. The yield of FAME reached 95% for the oil mixtures containing 30 wt% palmitic acid. This indicated the sulfonated mesopolymer was a potential catalyst for clean synthesis of fuel alternative of biodiesel from the waste oil without further purification.     

Retention indices of glycerol esters

The retention indices of 27 mono-, di-, and trisubstituted esters of glycerol and C₁–C₆ carboxylic acids were determined on an OV-101 nonpolar phase in the temperature range 110–250°C. The dependence of the retention indices on temperature and the number of carbon atoms in the acid residue was linear for all compounds. The data obtained can be used for identifying glycerol esters in various mixtures and for predicting their thermodynamic properties.     

Chromatographic separation of diastereoisomeric esters-II Mandelates and lactates of 2-methylbutanol-1, 3-methylbutanol-2, pentanol-2 and hexanol-2

The racemic alcohols, 2-methylbutanol-l, 3-methylbutanol-2, pentanol-2 and hexanol-2 have been esterified with optically active mandelic or lactic acid, and the resultant mixtures of diastereoisomeric esters separated chromatographically with an optically inactive sulphonated polystyrene resin as the stationary phase and water or dilute aqueous sodium sulphate as the mobile phase. Lactate esters were more easily separated than mandelate esters. The Chromatographic separation of 26 mmole of (+/-)-3-methyl-2-butyl(+)-lactate and subsequent hydrolysis of the fractions containing only the ester of the (+)-alcohol yielded 1-2 mmole of pure 3-methyl-2-butanol.     

Determination of the Mono and Diethanolamides of Palmitic Acid and of Soybean Oil Fatty Acids by High Performance Liquid Chromatography

Abstract

HPLC separations and quantitative analyses are described for palmitic and soya monoethanolamides and diethanolamides synthesized from free fatty acids, methyl esters and triglycerides. Both reverse phase and adsorption techniques were employed, using a differential refractometer for detection. Starting materials and crude reaction products are analyzed without treatment or preliminary separations. The methods described are simple and rapid and can be used to monitor the course of condensation reactions as well as final products compositions. In some instances separation of homologous fatty acid alkanolamides was achieved, enabling comparison of the yields obtained from individual fatty acid precursors.     

Chemical equilibrium of transesterification reactions between mixed triglycerides and methanol

The chemical equilibrium of the transesterification reactions between methanol and mixed triglycerides containing radicals of palmitic, oleic, and linoleic fatty acids are studied. Based on the results of chemical equilibrium calculation, the behavior of the transesterification reaction of mixed triglycerides in the state of chemical equilibrium is predicted, both in the ideal approximation and with allowance for nonideality, in particular, in the region of supercritical state of the reaction mixture.     

Abnormal composition of commerical waxes revealed by supercritical fluid chromatography

Summary The analysis of natural waxes is a complicated process because they occur as complex mixtures. A study using supercritical fluid chromatography with packed columns made it possible to observe the behavior of each family of hydrocarbons, fatty esters, alcohols, acids and triglycerides. The latter were then separated according to their function type and alkyl chain lengths using octadecyl silica as stationary phase. With a polar modifier added to the supercritical fluid, it was possible to analyse certain waxes. Composition anomalies were observed which related to an overabundance of certain compounds which, in excess, are harmful to the quality of waxes intended for use in cosmetics.     

A review of chromatographic characterization techniques for biodiesel and biodiesel blends

This review surveys chromatographic technology that has been applied to the characterization of biodiesel and its blends. Typically, biodiesel consists of fatty acid methyl esters produced by transesterification of plant or animal derived triacylglycerols. Primary attention is given to the determination of trace impurities in biodiesel, such as methanol, glycerol, mono-, di-, and triacylglycerols, and sterol glucosides. The determination of the fatty acid methyl esters, trace impurities in biodiesel, and the determination of the biodiesel content of commercial blends of biodiesel in conventional diesel are also addressed.     

HPLC of fatty acid esters of mono- and polyhydric alcohols. Part 2: Preparative separation

This paper demonstrates how simply and rapidly fatty acid esters of mono- and polyhydric alcohols can be separated quantitatively in preparative quantities on Lobar® RP-8 packed columns. After the separation of unknown mixtures, the isolated esters are identified from spectroscopic data (IR/NMR) and, after saponification of the ester components (fatty acids and alcohols), from the retention times of gas and high-pressure liquid chromatographic separations. Thus, in particular, sparingly volatile or nonvolatile partial esters of polyhydric alcohols, as well as the long-chained full esters, can be determined qualitatively and quantitatively. The following fatty acid esters of mono- and polyhydric alcohols have been separated: the i-propylesters of the laurinic and myristinic acids, the i-butyl-, i-octyl- and i-octadecyl-esters of the palmitinic and stearic acids, the mono- and di-fatty acid esters of the 1,3-bis-(2-hydroxyethyl)-5,5-dimethylhydantoins, the mono-, di- and tri-esters of the trimethylalpropane and the full esters of the pentaerythrite.