Supercritical carbon dioxide fractionation of fish oil fatty acid ethyl esters

Fractionation of fish oil fatty acid ethyl esters was investigated with the aim of obtaining a lipid fraction enriched in ω-3 fatty acids and with a suitable EPA/DHA ratio. The results obtained highlight the possibility of modifying the original fatty acid ethyl esters concentration by optimizing the extraction conditions in terms of pressure, temperature, and supercritical carbon dioxide flow rate. Supercritical fluid fractionation (SFF) appears to be a useful processing technique for changing the composition of lipids in order to obtain high value functional products. The use of proper fractionation temperatures and pressures along the column influenced the solvent-to-feed ratio to obtain fractions with suitable composition for market requirements.     

Solubilities of six cottonseed oil fatty acid methyl esters in methanol

Solubilities of six cottonseed oil fatty acid methyl esters in metha-nol have been determined. The esters were: methyl oleate, methyl linoleate, methyl malvalate, methyl dihydromalvalate, methyl sterculate and methyl dihydrosterculate. The solubility/temperature data are presented in graphical and tabular form.     

Very long chain fatty acid methyl esters in transesterified palm oil

Some unidentified minor compounds have been observed in the residue from short-path distillation of transesterified palm oil that are not detected in the original palm oil. A method combining short-path distillation to enrich the unknowns with fractionation using solid-phase extraction is described. The fractionated components were identified using GC coupled with MS. The transesterified palm oil was found to contain methyl esters of up to C₃₂ carbon atoms. In the very long chain FAME with carbon numbers ≥20, both even and odd carbon numbers accounted for 0.26 wt%, with C₂₄ and C₂₆ being the major ones present in the residue after short-path distillation of transesterified palm oil.     

Separation of fatty acid methyl esters from tall oil by selective adsorption

Fatty acid methyl esters (FAME) and resin acids (RA) were separated from tall oil by selective adsorption. Commercial nonmodified molecular sieve 13X was used as adsorbent. The adsorption isotherms of fatty acids (FA), FAME, and RA on molecular sieve 13X at 25°C were determined using various solvents. The solvents were methanol, ethanol, isopropanol, acetone, benzene, hexane, isooctane, petroleum ether (40–60°C), and petroleum naphtha (80–180°C). With each solvent, FA and RA were adsorbed to a greater extent than FAME. Adsorption isotherms for RA and FAME in binary adsorption systems were also determined using petroleum ether, petroleum naphtha, benzene, and isopropanol. For each component in the binary adsorption, the equilibrium amounts are lower than the values for pure component adsorption. The adsorption of FAME decreased in the presence of RA markedly in petroleum ether and petroleum naphtha. This fact may be the indication of the phenomenon of selective adsorption. Separation was accomplished by adding a solution of esterified tall oil in solvents used in the binary adsorption systems, through a column packed with molecular sieve 13X. With petroleum naphtha, FAME and RA were recovered in yields of 93 and 94%, respectively, from esterified tall oil. Petroleum naphtha gave the best results. The effects of particle size of adsorbent and flow rate of solvent on the efficiency of the separation were also investigated in fixed-bed column studies. The particle size of adsorbent did not apparently alter the results. Changes in the particle size should not significantly change the number of available adsorption sites in a microporous molecular sieve.     

Combustion characteristics of fatty acid methyl esters derived from recycled cooking oil

The goal of this study is to find out the exhaust emissions differences produced by different kinds of fatty acid methyl esters (FAME) derived from used cooking oils and animal fats, as well as the importance of the purification step in exhaust emissions production. A total of 120 L of waste vegetable oil and 30 L of waste frying oil were collected and converted into three batches of FAME. There were two batches of FAME produced from waste vegetable oil (B01 and B02), and one batch of FAME produced by mixing 2% of waste frying oil with waste vegetable oil (B03). The FAMEs used in this study had higher density, kinematic viscosity, and flash point, but a lower gross heating value, when compared to the premium diesel. The B01 engine produced higher CO formation and the diesel-fuelled engine produced higher CO than the B02 and B03 did for engine speeds higher than 1400 rpm. Most of the FAME fuels produced higher CO₂ than the diesel fuel did. The FAME fuels emitted higher NO_x and PM, but lower SO₂, than the diesel fuel. C_nH_2n+2, diphenyl sulfone (C₁₂H₁₀O₂S), and diethyl phthalate (C₁₂H₁₄O₄) can be selected as the character index for the combustion of FAME.     

Solubility of fish oil fatty acid ethyl esters in suband supercritical carbon dioxide

Mutual solubilities and K-values of fish oil fatty acid ethyl esters, prepared from sand launce oil, and sub- and supercritical carbon dioxide have been measured in an apparatus originally designed for phase equilibrium, density and gasoil ratio measurements of reservoir fluids. The measurements were performed at pressures from 2 to 22 MPa at temperatures of 283.2, 313.2 and 343.2°K. Experimental temperatures, pressures, solubilities, K-values and densities are reported. The K-values of ethyl myristate, palmitate, oleate, eicosapentaenoate and docosahexaenoate are compared with published experimental binary and/or multicomponent data. Because both vapor and liquid solubilities are reported, such data are applicable in the design of supercritical extraction plants.     

Performance of sulfoxylated fatty acid methyl esters

Sulfoxidation of fatty acid methyl esters with SO₂, O₂, and ultraviolet light of appropriate wavelength has led to the synthesis of methyl esters sulfonates or sulfoxylates known as Φ-MES because of the possible random position of SO₃ group in the alkyl chain. This work describes experimental measurements of physical properties such as solubility and viscosity of sodium Φ-MES water solutions. Amphipathic properties such as surface tension, critical micelle concentration, wetting and foaming powers were measured as well and compared to linear alkylbenzene sodium sulfonate (LAS). Finally, stability to water hardness, dishwashing test, and detergency performance were evaluated. Expectedly, these products may be used as LAS partners either in heavy-duty powders or in hand dishwashing liquids. Experimental results on Φ-MES of varying carbon number indicate that C₁₆ is the optimal carbon chain length.     

Dilatometric investigations of fatty acid methyl esters

Summary The coefficients of expansion and melting dilations were measured for methyl palmitate, methyl stearate, methyl arachidate, methyl behenate, and methyl oleate. The dilatometric curve for the heating cycle of methyl palmitate and methyl stearate in the solid state was composed of a linear section to 49 degrees below the melting point, followed by a curvilinear section to the melting point. The heating and cooling cycle curves for methyl palmitate show the same volume change from −38°C. to 29°C., but the shape of the curves is different. The same relation holds for methyl stearate from −38°C. to 37.5°C. “After-contractions” were found in volume measurements within a few degrees of the melting point of both esters. Equilibrated points were found within 0.5 degrees of the final melting temperature of methyl stearate. A striking similarity exists between curves for variation of the dielectric constant with temperature for long chain linear molecules and the dilatometric data. Presented at the fall meeting, American Oil Chemists' Society, Mnneapolis, Minn., October 11, 1954. Issued as Paper No. 196 on the “Uses of Plant Products” and as N.R.C. No. 3671.     

Oxidative stability of soybean oil fatty acid methyl esters by oil stability index (OSI)

Biodiesel, an alternative diesel fuel derived from transesterification of vegetable oils or animal fats, is composed of saturated and unsaturated long-chain FA alkyl esters. During long-term storage, oxidation caused by contact with air (autoxidation) presents a legitimate concern with respect to monitoring and maintaining fuel quality. Extensive oxidative degradation may compromise quality by adversely affecting kinematic viscosity, acid value, or PV. This work examines the oil stability index (OSI) as a parameter for monitoring the oxidative stability of soybean oil FAME (SME). SME samples from five separate sources and with varying storage and handling histories were analyzed for OSI at 60°C using an oxidative stability instrument. Results showed that OSI may be used to measure relative oxidative stability of SME samples as well as to differentiate between samples from different producers. Although addition of α-tocopherol or TBHQ increased OSI, responses to these antioxidants varied with respect to SME sample. Variations in response to added antioxidant were attributed to aging and other effects that may have caused oxidative degradation in samples prior to acquisition for this study. Results showed that OSI was more sensitive than iodine value in detecting the effects of oxidative degradation in its early stages when monitoring SME during storage.     

脂肪酸乙酯合成工艺研究

研究了大豆油和乙醇进行酯交换反应合成脂肪酸乙酯的工艺。考察了催化剂类型、催化剂用量、n(醇)∶n(油)、反应温度以及反应时间对酯交换率的影响,结果表明最佳合成工艺条件为反应温度60℃,n(醇)∶n(油)=5∶1,w(NaOMe)=1.0%,反应时间4h,在此条件下,酯交换率可达到96.7%。     

Mutual solubilities of some fatty acid methyl esters

Mutual solubility data have been obtained for methyl esters of the predominant fatty acids in vegetable oils. Binary freezing point diagrams are presented for systems exhibiting regions of metastable equilibria. Simple eutectic systems were obtained for both saturated-unsaturated and unsaturated-unsaturated methyl ester binary mixtures.     

Nutritional and metabolic studies of noncyclic dimeric fatty acid methyl esters in the rat

Methyl esters of noncyclic dimeric fatty acids were prepared by fractionation of the crude product ob-tained by heating a mixture of methyl oleate and di-fert-butyl peroxide for 48 hr at 130 C in a high pressure reactor. Rats fed diets containing less than 1% of the noncyclic dimer methyl ester showed no significant difference in growth, feed efficiency, and liver size, from those fed nutritionally adequate diets. The¹⁴C-labeled dimer was also synthesized and administered to rats via gastric intubation. The results indicated that an average of 85% of the radioactivity was recoverable from the gastrointestinal tract and feces within 48 hr of administration and that such an amount was not absorbed by the rat. Within a 48 hr period ca. 5% of the¹⁴C was recovered in the expired CO₂ and about 1% in the urine. Prefeeding rats diets containing dimer did not appear to influence the metabolism of either dimer or methyl oleate.     

Phase diagrams of mixtures of ethyl palmitate with fatty acid ethyl esters

The cloud point is an important property of biodiesel, controlling its low temperature behaviour, especially the fluidity of the fuel. Although biodiesel is an interesting renewable energy source, data for the melting/cloud point of biodiesel or simple binary or ternary mixtures of fatty acid ethyl esters (FAEE) are still scarce in the literature, particularly for those involving ethyl esters. The phase diagrams of six binary mixtures of ethyl palmitate with saturated and unsaturated fatty acid ethyl esters were determined by Differential Scanning Calorimetry (DSC). The determined systems were successfully described employing the UNIQUAC model. The experimental data indicates that the cloud point is controlled by the fatty acid ethyl ester in the mixture with higher melting temperature.     

Enzymatic synthesis of wax esters from rapeseed fatty acid methyl esters and a fatty alcohol

Wax esters were transesterified from fatty acid methyl esters of rapeseed and a fatty alcohol (1-hexadecanol, 16:0). The amounts of both the substrates were fixed to 0.1 mmol and an immobilized enzyme, Lipozyme, was used as catalyst. The experiment was performed following a statistic central composite design with five variables. The enzyme/lipid ratio was varied between 0.3–0.9 of the substrate weight and the enzyme was equilibrated to different water activities varying from 0.11 to 0.44. A temperature range of 50–80°C was investigated and the reaction time lasted up to 40 min. A solvent, isooctane, constituted 0–30% of the substrate weight. The first experimental series was performed in small closed test tubes. In the second series the caps of the test tubes were off to evaporate the methanol produced during the reaction. The highest initial reaction rate was 9.6 g_{wax esters}/g_enzyme · h. It appeared when: the enzyme/lipid ratio was low, 0.3, the temperature was high, 80°C; no isooctane was present; and the water activity was below 0.11. The initial reaction rate was independent of the caps on the test tubes. With the large amount of enzyme the yield of wax esters was above 70% after 10 min in both experimental series. In the reaction with caps, the reaction reached equilibrium at 83% after 20 min at 80°C. However, without caps the continuous evaporation of methanol increased the equilibrium constantly, and after 40 min at 80°C a yield of 90% was reached.     

Oxidative stability and storage behavior of fatty acid methyl esters derived from used palm oil

Fatty acid alkyl esters, especially FAME, are the most commonly used liquid biofuel. Because biofuels are expected to be important alternative renewable energy sources in the near future, more studies on their stability against oxidation need to be addressed. Biofuel derived from vegetable oils is well researched, currently with more attention focused on the reuse of waste oil sources than on pure vegetable oil for such production. A method to convert used palm oil, i.e., used frying oil, and residual oil of spent bleaching earths (SPE) to their respective methyl esters has been established by the Malaysian Palm Oil Board. These methyl esters can be used as diesel substitute. However, the methyl esters obtained from used frying oil have a low induction period (3.42 h). In Europe, any methyl esters must have an induction period of at least 6 h in Rancimat stability to be usable as biodiesel, as required by European Biodiesel Standard (EN 14214). To meet this requirement, the used frying oil methyl esters (UFOME) obtained can be treated with different types of antioxidants, either synthetic or natural, at different treatment levels, such as vitamin E, 3-ert-butyl-4-hydroxyanisole (BHA), 2,6-di-tert-butyl-4-methyl-phenol (BHT), 2,5-di-tert-butyl hydroquinone (TBHQ), and n-propyl gallate (PG), to investigate their oxidative stability and storage behavior. The order of increasing antioxidant effectiveness with respect to the oxidative stability of UFOME is: vitamin E<BHT<TBHQ<BHA<PG. Because methyl esters derived from residual oil of SBE have an induction period of 14.6 h, their treatment with antioxidants is unnecessary.     

Eiution characteristics of fatty acid methyl esters on capillary columns

The elution characteristics of fatty acid methyl esters on support-coated and open tubular capillary columns were investigated using reference standards and natural mixtures of fatty acid methyl esters. Over an extended range of fatty acid methyl esters chain lengths (C-11–C-26), the plot of the log of the adjusted retention time, t′_R, vs. number of carbon atoms in the fatty acid chain was not linear, as has been previously assumed by many investigators. With support-coated open tubular columns and with diethylene glycol succinate as the stationary phase, the relationship between the log of the retention time and carbon number was best approximated by a second-order equation: log (t′_R)_x=α+β(CN_x)+γ(CN_x)² where α, β, and γ are the virial coefficients of the equation. In addition, for the longer fatty acid methyl esters, the plots all tended to converge. Hence, for data from capillary columns, especially over a wide range of carbon numbers, all tentative indications based upon linear log plots and parallel lines for different homologous series of fatty acid isomers should be viewed with caution. A method is presented for identifying peaks from capillary columns; it uses quadratic equations and three reference fatty acid methyl ester standards for each homologous series being studied.     

Cholesterol interference in analysis of fatty acid methyl esters

In the course of isolating and analyzing the fatty acid methyl esters (FAME) from steelhead trout (Salmo gairdneri) eggs and sac fry, a component was found on gas liquid chromatography to have a retention time longer than any characteristic polyunsaturated fatty acid previously encountered in trout. Subsequent purification and analysis demonstrated this component to be cholesterol. Thus, cholesterol and related compounds can interfere in the analysis of FAME when the methyl esters are prepared by transesterification.     

Mass spectra of acetylenic fatty acid methyl esters and derivatives

A series of isomeric methyl octadecynoates was analyzed by mass spectrometry; each isomer gave a unique spectrum. The characteristic ions were those resulting from a McLafferty rearrangement of the allenic sites or of the already-rearranged allenic sites. The acetylenic esters were also subjected to oxymercuration whereupon a carbonyl group was formed at either of the original actylenic carbon atoms providing two oxostearates. Further reaction with NaBH₄ formed hydroxy esters which, after silylation, gave diagnostic mass spectra indicative of the triple bond location. Applied to esters with both double and triple bonds, this procedure permitted differentiation between the two types of unsaturation. Methoxyl groups marked the original double bond locations and hydroxyls did so for triple bonds. Presented at the 48th Fall Meeting of the American Oil Chemists’ Society, Philadelphia, PA, September 29–October 2, 1974.     

Sulfoxidation of fatty acid methyl esters: Conversion and selectivity

In this work several batch sulfoxidation reactions of different fatty acid methyl esters, having chain lengths of C12 to C18, in the presence of SO₂, O₂, and ultraviolet light of 253 nm have been carried out. The average reaction conversion for each methyl ester has been calculated and the selectivity determined by liquid chromatography. The results indicate that conversion increases dramatically with the increase of carbon chain length, whereas selectivity to monosulfonate seems to increase slightly as the chain length increases.     

Efficient synthesis of fatty monoglyceride sulfates from fatty acids and fatty acid methyl esters

An efficient high yield synthesis of fatty monoglyceride sulfates from fatty acids or fatty acid methyl esters, glycerine and chlorosulfuric acid in chloroform using stoichiometric amounts of reagents was developed. Sodium coco monoglyceride sulfate was prepared in 79% yield with 93% purity from coco fatty acids. Similarly, sodium palm kernel monoglyceride sulfate in 57% yield and sodium palm monoglyceride sulfate in 71% yield were obtained from palm kernel fatty acid methyl esters and palm fatty acids, respectively. This new synthetic method produced better quality products with higher active ingredients and improved yields without having to use such cost prohibitive, high purity, fatty acid monoglycerides, and it reduced the undesirable aqueous sodium sulfate by-product by 60% over a current commercial process. The product’s composition and purity were confirmed by cationic titration, infrared and C-13 NMR spectroscopy.