Solvent Effects in Epoxidation of Fatty Acid Methyl Esters with Hydrogen Peroxide over TS-1 Catalyst

Kinetics and Catalysis - Solvent effects in epoxidation of fatty acid methyl esters (FAMEs) by hydrogen peroxide on a TS-1 heterogeneous catalyst is studied for the first time. It is found that the...     

Gas chromatography/mass spectrometry of oils and oil binders in paintings

A GC/MS procedure has been developed, optimized, and applied to characterization of oil binders in paintings. The procedure involves hydrolysis of lipids to fatty acids (FAs) and derivatization of FAs to fatty acid methyl esters (FAMEs) by a solution of sodium methanolate in methanol at an elevated temperature. FAMEs are analyzed by temperature-programed GC followed by full-scan MS. Old and dried samples are subjected to extraction of nonpolymerized FAMEs into dichloromethane prior to hydrolysis. The method provides a good repeatability of results and has been applied to the characterization of common plant oils used in paintings, to commercial oil and tempera paints, to model painting samples, and to samples taken from real paintings. The fresh oils and binders can readily be identified and characterized. The ratio of the methyl esters of palmitic and stearic acids can be used to characterize oil binders in old works of art.     

Production of biodiesel fuel by transesterification of rapeseed oil

Fatty acid methyl esters (FAMEs) show large potential applications as diesel substitutes, also known as biodiesel fuel. Biodiesel fuel as renewable energy is an alternative that can reduce energy dependence on petroleum as well as air pollution. Several processes for the production of biodiesel fuel have been developed. Transesterification processes under alkali catalysis with short-chain alcohols give high yields of methyl esters in short reaction times. We investigated transesterification of rapeseed oil to produce the FAMEs. Experimental reaction conditions were molar ratio of oil to alcohol, concentration of catalyst, type of catalyst, reaction time, and temperature. The conversion ratio of rapeseed oil was enhanced by the alcohol:oil mixing ratio and the reaction temperature.     

Trans-esterification of fatty acids from microorganisms and human blood serum by trimethylsulfonium hydroxide (TMSH) for GC analysis

Summary Trimethylsulfonium hydroxide (TMSH) can convert fatty acids into the corresponding fatty acid methyl esters (FAMEs) in a single step. These fatty acids may also be bound in biomolecules such as phospholipids and/or glycerides. Complex mixtures of saturated and unsaturated FAMEs which may contain hydroxy and cylopropyl groups are obtained by trans-esterification; they can easily be separated in most cases by capillary GC. When FAMEs are generated from different microorganisms e.g. bacteria the patterns of the chromatograms are characteristic. Examples of characteristic patterns of bacteria with different cell wall structures are shown. The described method of transesterification can also be applied directly to blood serum without sophisticated sample pretreatment. The profiles of the chromatograms match well those described in the literature obtained by other methods of trans-esterification or sample preparation.     

An empirical approach for estimating the equivalent chain length of fatty acid methyl esters in multistep temperature-programmed gas chromatography.

The equivalent chain length (ECL) has been widely accepted as an identification tool for fatty acid methyl esters (FAMEs). In this study, FAMEs from the seed oil of Chinese mustard (Brassica juncea) analyzed on a 0.25-mm-i.d. capillary column coated with an SA-WAX are used as an example for the calculation of the ECL in single-, two-, three-, and four-step temperature-programmed gas chromatography. The ECLs of unsaturated FAMEs tend to increase with temperature, and they agree well with those reported in the literature.     

Analysis of the Triglycerides and the Free and Derivatized Fatty Acids in Fish Oil by Capillary Electrochromatography

Capillary ElectroChromatography (CEC) on a fused silica capillary column (40 cm L × 100 μm i.d.) packed with 3 μm octadecylsilica (ODS) was evaluated for the analysis of the triglycerides and their fatty acids in fish oils, and more especially in the oil of Moroccan Sardinia pilchardus. The very high complexity of the lipids in fish oil is well illustrated by CEC with a nonaqueous mobile phase consisting of acetonitrile/isopropanol/n-hexane in the ratio 57/38/5 to which 50 mM ammonium acetate has been added. In order to unravel the complexity, the oil was hydrolyzed and the free fatty acids (FFAs), the methyl esters (FAMEs), and the phenacyl esters (FAPEs) were analyzed by CEC on the same column used for the analysis of the triglycerides. Isocratic elution was achieved with the mobile phase acetonitrile/50 mM MES pH 6 in ratio 9/1. The migration characteristics of FFAs, FAMEs, and FAPEs are compared. The analysis of FAPE derivatives has the advantage that quantification applying UV detection is possible and moreover that the number of double bonds in the fatty acid chains can be elucidated by measuring the UV abundance ratio 240/210 nm.     

Castor oil modified by epoxidation,transesterification, and acrylation processes: Spectroscopic characteristics

In the present study, castor oil (CO) was modified by epoxidation, transesterification, and acrylation processes. In situ epoxidation method was used to prepare epoxidized castor oil (ECO) in acetic acid with hydrogen peroxide in the presence of Seralite SRC-120 catalyst. Transesterified epoxidized castor oil was synthesized from the reaction of methanol in the presence of sodium methoxide catalyst. The acrylated epoxidized castor oil was synthesized from the reaction of ECO with acrylic acid containing hydroquinone. Chemical structures of modified CO were analyzed by Fourier transform infrared spectroscopy and proton nuclear magnetic resonance spectra analysis.     

Separation of cis/trans geometrical fatty acid isomers by silver-exchanged zeolite Y

The separation of cis and trans isomers is relevant for biological and nutritional applications, silver-exchanged zeolite Y was prepared and applied for the treatment of mixtures of cis and trans geometrical isomers of mono- and polyunsaturated fatty acid methyl esters (FAMEs). cis FAMEs were adsorbed into zeolite with a high degree of selectivity (cis/trans ratio in the range of 1.9-3.2). The effectiveness was due to the synergism of the π-complexation between the silver ion and the double bonds and the different FAME structures trapped into the zeolite cages. Some indication of the complex stabilities came from theoretical studies using unsaturated lipids. A prototype cartridge was also designed for application in the fractionation of cis/trans FAME mixtures.     

蓖麻油—甲基丙烯酸甲酯AB交联聚合物的研究

将蓖麻油与顺丁烯二酸酐反应,合成端乙烯基蓖麻油,再与甲基丙烯酸甲酯共聚,制得了组成不同的一系列AB交联聚合物,研究了它们的动态性能、力学性能和形态结构与组成的关系.     

Molecular Simulations of Fatty‐Acid Methyl Esters and Representative Biodiesel Mixtures

Despite the importance of fatty‐acid methyl esters (FAMEs) as key components of various green solvents, detergents, plasticizers, and biodiesels, our understanding of these systems at the molecular level is limited. An enhanced molecular‐level perspective of FAMEs will enable a detailed analysis of the polymorph and crystallization phenomena that adversely impact flow properties at low temperatures. Presented here, is the parameterization and validation of a charge‐modified generalized amber force field (GAFF) for eight common FAMEs and two representative biodiesel mixtures. Our simulations accurately reproduce available experimental data (e.g. densities and self‐diffusivity coefficients) and their trends, with respect to temperature and degree of unsaturation. Structural analyses from our simulations provide a more detailed picture of liquid‐phase molecular ordering in FAMEs and confirm recent experimental hypotheses. This study provides a firm foundation to initiate further studies into the mechanisms that drive crystallization phenomena at the molecular level.     

Analysis of biodiesel/petroleum diesel blends with comprehensive two-dimensional gas chromatography

Comprehensive two-dimensional gas chromatography (GCxGC) is used to analyze petroleum diesel, biodiesel, and biodiesel/petroleum diesel blends. The GCxGC instrument is assembled from a conventional gas chromatograph fitted with a simple, in-line fluidic modulator. A 5% phenyl polydimethylsiloxane primary column is coupled to a polyethylene glycol secondary column. This column combination generates chromatograms where the fatty acid methyl esters (FAMEs) found in biodiesel occupy a region that is also populated by numerous cyclic alkanes and monoaromatics found in petroleum. Fortunately, the intensities of the petroleum hydrocarbon peaks are far lower than the intensities of the FAME peaks, even for blends with low biodiesel content. This allows the FAMEs to be accurately quantitated by direct integration. The method is calibrated by analyzing standard mixtures of soybean biodiesel in petroleum diesel with concentrations ranging from 1 to 20% v/v. The resulting calibration curve displays excellent linearity. This curve is used to determine the concentration of a B20 biodiesel/petroleum diesel blend obtained from a local retailer. Excellent precision and accuracy are obtained.     

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.     

Toward new biosilicones: hydrosilylation of fish oil unsaturated fatty acid esters

Hydrosilylation of fatty acid methyl esters (FAMEs) were efficiently catalyzed by Speier's and Wilkinson's catalysts in the case of vinylic acid esters, but less efficiently in the case of ­non‐vinylic ones, which gave non‐regiospecific additions. In the latter case, initiation by radicals led to regiospecific reactions for oleic esters (C10‐silylation). This regiospecificity can be attributed to the higher stability of the C10‐silylated adduct and of the corresponding radical intermediate. Only regioselective addition was observed for linoleic esters (C13‐silylation ≈ 70%, C10 ≈ 20%, C9 ≈ 10%). Molecular modeling was used to examine the stability of the isomeric products and radicals. The new concept of radical initiation sequence has been successfully applied to FAMEs and then was extended to crude fish oil. Copyright © 2001 John Wiley & Sons, Ltd.     

Dimethyl carbonate as a novel methylating reagent for fatty acids in analytical pyrolysis

Dimethyl carbonate (DMC) was investigated as a mild, harmless and odorless reagent for pyrolytic methylation of fatty acids. Soybean oil was selected as test material for its high content of (poly)unsaturated fatty acids. Pyrolyses were performed at 500, 700 and 900 degrees C by means of a heated platinum filament pyrolyser on-line and off-line to the GC-MS apparatus. Methyl esters of palmitic, linoleic, oleic and stearic acid were formed as prominent products from off-line pyrolysis of soybean oil in the presence of DMC and zeolite 13X. Fatty acid methyl esters (FAMEs) were not observed at important levels in the absence of zeolite, while on-line Py-GC-MS experiments resulted principally in the formation of free fatty acids and hydrocarbons. The FAME profiles obtained from the DMC/zeolite off-line pyrolysis were compared to those resulting from tetramethylammonium hydroxide (TMAH) thermochemolysis and BF3-methanol procedure. The observed differences between pyrolysis and methanolysis methods were principally attributed to the thermal degradation of unsaturated fatty acids. The effectiveness of the DMC/zeolite pyrolytic methylation was further demonstrated by the analysis of tripalmitine and soybean seeds.     

Addition of an azido group to epoxidised fatty acid methyl esters of Jatropha curcas by epoxy cleavage

Azidohydrin was synthesized from the seed oil of Jatropha curcas by use of simple chemical reactions. This entailed first, transesterification of the seed oil of J. curcas to produce the fatty acid methyl esters, epoxidation of the fatty acid methyl esters to form the epoxides, then azidation of the epoxidised fatty acid methyl esters. The yield of the azidation reaction was 93.60 %, and the distribution of azide and alcohol functionality on the fatty acid was approximately random. The reactants and products were monitored and confirmed by FTIR and NMR spectroscopy.     

Features of Epoxidation of Fatty Acid Methyl Esters in a Bubble Reactor

Russian Journal of Applied Chemistry - The patterns of epoxidation of linoleic acid methyl ester in a mixture of methyl esters of sunflower oil fatty acids with atmospheric oxygen in a bubble...     

Preparation, characterization, and catalytic performance of a novel methyl-rich Ti-HMS mesoporous molecular sieve with high hydrophobicity

A novel methyl-rich Ti-containing hexagonal mesoporous silica (Ti-HMS) molecular sieve with high hydrophobicity has been prepared by a two-step method involving co-condensation followed by vapor-phase methyl grafting. The sample was characterized by XRD, N₂ adsorption, FTIR, UV-visible and ²⁹Si NMR spectroscopies, TG, ICP-AES, and hydrophilicity measurements, and its catalytic performance was evaluated using the epoxidation of cyclohexene as a probe reaction. The Ti-HMS material retains a typical mesoporous structure and compared with a co-condensed Ti-HMS prepared in a one-step method possesses more methyl groups and higher hydrophobicity, and also exhibits better catalytic activity and selectivity.     

An alternative approach for the estimation of equivalent temperature in gas chromatography

The temperature at which the isothermal retention time (tRiso) is equal to the temperature-programmed retention time (tRTPGC) or the isothermal retention index (Iiso) is equal to the temperature-programmed retention index (ITPGC) is defined as the equivalent temperature (Teq). The Teq of one-, two-, three-, and four-step temperature-programmed gas chromatography (TPGC) of unsaturated fatty acid methyl esters (FAMEs) from Chinese mustard seed oil is calculated. All of the tR values obtained at the Teq (tRTeq) are very close to the tRTPGC. The highest difference for each chromatogram is less than 0.5%. The slight deviation may partly arrive from the difficulty in setting the desired carrier gas flow rate. Also, good agreement among equivalent chain length values determined by different methods is observed, including the graphical method at the Teq. Therefore, it is speculated that the proposed method may facilitate the GC identification of FAMEs as well as other organic compounds in TPGC by using the available isothermal retention index database.     

新型高疏水性富含甲基Ti-HMS介孔分子筛的制备、表征和催化性能

通过共缩合和气相甲基接枝两步法制备了新型的高疏水性富含甲基的Ti-HMS介孔分子筛.采用X光衍射、N2吸附、红外光谱、硅核磁、热重、元素分析(原子发射光谱)、紫外可见光谱等手段和亲水性实验对样品进行表征,并用环己烯环氧化反应进行催化性能测试.结果表明,经过两步接枝甲基后,Ti-HMS仍保持典型的介孔结构特征,拥有较多的甲基含量和较高的疏水性,催化环己烯环氧化活性和选择性均比共缩合法(一步接枝法)Ti-HMS有所提高.     

12-磷钨杂多酸根柱撑水滑石合成及催化脂肪酸甲酯环氧化

研究了一种可用于脂肪酸甲酯环氧化的类水滑石催化剂. 采用共沉淀法合成类水滑石[Mg_1-xAl_x(OH)₂]^x+-(NO^3-)_x·mH₂O, 通过离子交换法制备出一种新的柱撑水滑石[Mg_1-x²⁺Al_x³⁺(OH)₂]^x+[PW₁₂O₄₀]_x/3^3- ·mH₂O化合物, 并由XRD,FT-IR, Raman, ICP和UV-Vis 进行了表征. 用制备的类水滑石应用于无羧酸环境下的催化脂肪酸甲酯环氧化反应, 结果表明, 柱撑水滑石较插层前转化率和选择性都有了明显的提高. 考察了反应温度、反应时间、催化剂重复使用等因素对环氧化反应的影响, 在60 ℃时反应16 h, 转化率和选择性分别达到56.1%和59.4%, 催化剂使用4 次后重复使用率仍高于90%. 对催化剂催化环氧化的机理进行了初步的探讨.