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.     

Application of high vacuum fractional distillation to complex mixtures of methyl esters of polyunsaturated fatty acids

A technique for the high vacuum fractional distillation, with a spinning band column, of methyl esters of polyunsaturated fatty acids employing a carrier of long chain acetates is described. The carrier is used to facilitate the fractionation of minor components and minimize artifact formation in mixtures of methyl esters containing up to six double bonds. The technique is demonstrated on a standard mixture of methyl esters and applied to a concentrate of unsaturated methyl esters containing a large number of minor components as well as methyl docosahexaenoate.     

Acidity and corrosiveness of methyl esters of vegetable oils

Methyl esters of vegetable oils are considered to be a significant alternative diesel fuel obtainable from domestic renewable resources. The corrosive effects of methyl esters are discussed in connection with their neutralization number. The neutralization number as a qualitative parameter is irrelevant for fuels based on methyl esters if their acidity is caused by higher fatty acids rather than by mineral acids. If methyl esters are treated with ammonia, their neutralization number has no informative value either. Formally determined acidity corresponds to the decomposition of ammonia salts of higher fatty acids. An increased corrosion activity of methyl esters in mixture with water, which is important for storing methyl esters in storage tanks and tank trucks, is observed. Mixed fuels, based on blends of methyl esters with mineral oils, have equal corrosion characteristics. It is possible either to hamper the corrosion partially by neutralizing with ammonia or to remove it totally through the use of special additives.     

Preparation of malvalic and sterculic acid methyl esters from Bombax munguba and Sterculia foetida seed oils

A method has been developed for the preparation of highly pure malvalic (cis-8,9-methyleneheptadec-8-enoic) and sterculic (cis-9,10-methyleneoctadec-9-enoic) acid methyl esters starting from Bombax munguba and Sterculia foetida seed oils. The methyl esters of these oils were prepared by sodium methylate-catalyzed transmethylation followed by cooling (6°C) the hexane solution of crude methyl esters and separation of insoluble fatty acid methyl esters by centrifugation in the case of B. munguba and by column chromatography in the case of S. foetida. Subsequently, the saturated straight-chain fatty acid methyl esters were almost quantitatively removed by urea adduct formation. Finally, methyl malvalate and methyl sterculate were separated from the remaining unsaturated fatty acid methyl esters, in particular methyl oleate and methyl linoleate, by preparative high-performance liquid chromatography on C₁₈ reversed-phase using acetonitrile isocratically. Methyl malvalate and methyl sterculate were obtained with purities of 95–97 and 95–98%, respectively.     

Oxygen absorption of methyl esters of fat acids,and the effect of antioxidants

Summary The oxygen absorption of methyl linolenate, methyl linoleate, methyl oleate, methyl stearate, the distilled methyl esters of lard, and various mixtures of the four individual methyl esters were measured at 100° C. in the Barcroft-Warburg apparatus. Mixtures of methyl esters absorbed oxygen at a rate which could be approximately predicted from the rate of oxygen absorption of each component and the percentage of each present. The antioxidants nordihydroguaiaretic acid (NDGA), propyl gallate, benzylhydroquinone, α-tocopherol, and their synergistic combinations with citric acid, d-isoascorbyl palmitate, and lecithin were tested with the substrates methyl linoleate, methyl oleate, methyl stearate, and the distilled methyl esters of lard. Citric acid showed marked synergism with each antioxidant. The two most effective were the combinations of citric acid with nordihydroguaiaretic acid and with propyl gallate. One of the laboratories of the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, United States Department of Agriculture.     

Sources of Methyl Ester Yield Reduction in Methanolysis of Recycled Vegetable Oil

Recycled vegetable oil (RVO) is a relatively cheap raw material for biodiesel production, but biodiesel grade methyl ester yields from RVO were found to be considerably lower than those from pure plant oil. The present paper investigates sources of yield loss during methanolysis of RVOs with free fatty acids (FFA) contents of 0.4–3.3%, and makes suggestions for the improvement of methyl ester yields. Data presented here indicated that yield losses of methyl esters during methanolysis were due to triglyceride and methyl ester hydrolysis and to the dissolution of methyl esters in the glycerol phase. Hydrolysis of triglycerides and methyl esters seemed to be the only side reaction causing yield losses, and the amount of fatty acids from hydrolysis increased with concentration of the potassium hydroxide catalyst. Dissolution of methyl esters in the glycerol phase was probably caused by the detergent effect of potassium salts of fatty acids originating from FFA in the RVO and from triglyceride hydrolysis, and the amount of dissolved methyl esters increased with FFA content of the RVO. The FFA content of the RVO had no effect on hydrolysis, and the amount of triglycerides and methyl esters hydrolysed during methanolysis remained constant with increasing FFA content of the RVO.     

A continuous process for the conversion of vegetable oils into methyl esters of fatty acids

A continuous process for the transesterification of triglycerides to methyl esters was investigated in a pilot plant. The process was equipped with a motionless and a high-shear mixer. The experimental studies explored variations in the mixing intensity, stoichiometry, and catalyst concentration on the overall conversion. The combined as well as individual effect of mixers was examined. The developed process resulted in high conversions of vegetable oils into methyl esters. Conversion of triglycerides to methyl esters in excess of 98% was achieved. Larger excess amounts of alcohol favored higher conversions. The motionless and high-shear mixers each provided adequate mixing for the process. Higher catalyst concentrations resulted in higher conversions but increased the solubility of methyl esters in the glycerol layer. This reduced the amount of methyl esters separated by gravity settling. Presented in part at the Third Liquid Fuel Conference, Nashville, September 15–17, 1996.     

The effect of natural and synthetic antioxidants on the oxidative stability of palm diesel

Crude and distilled palm oil methyl esters conveniently known as palm diesel have been successfully evaluated as diesel substitute. Crude palm oil methyl esters are produced from transesterification of crude palm oil with minor components such as carotenes and vitamin E still intact and they are reddish in colour. The distilled palm oil methyl esters are obtained after the recovery of minor components (e.g. Carotenes and vitamin E) From the crude palm oil methyl esters. These valuable minor components are preferably to be recovered as they can be sold as value-added products before they are burnt together with the methyl esters as fuel. Although both possesses fuel characteristics which are comparable to those of petroleum diesel, crude palm oil methyl esters are found to exhibit better oxidative stability (rancimat induction period >25 h) than distilled palm oil methyl esters (about 3.5 h). It is attributed to the presence of vitamin E (about 600 ppm), a natural antioxidant in the former. While the distilled palm oil methyl esters contain practically no vitamin E (<50 ppm) and as a result, they exhibit poor oxidative stability. Thus, the crude palm oil methyl esters meet the european standard for biodiesel (EN 14214) which has set a minimum rancimat induction period of 6 h. In the present study, research was conducted to enhance the oxidative stability of distilled palm oil methyl esters in order to meet the aforementioned standard. Natural and synthetic antioxidants were used in the present study to investigate their effect on the oxidative stability of distilled palm oil methyl esters. It was found that both types of antioxidant showed beneficial effects in inhibiting the oxidation of distilled palm oil methyl esters. Comparatively, the synthetic antioxidants were found to be more effective than the natural antioxidants as lower dosage (17 times less) was needed to achieve the minimum rancimat induction period of 6 h.     

Determination of Oxidation of Methyl Ricinoleates

Ricinoleate esters have desirable properties as biolubricants, but their oxidative stability has been questioned. To systematically study the stability of ricinoleate ester and its derivative, methyl esters of castor oil were prepared and methyl ricinoleate was isolated by solvent partitioning. Methyl 12‐acetyl ricinoleate was synthesized from the methyl ricinoleate by interesterification with excess methyl acetate and was then purified by solvent partitioning. The rates of oxidation of methyl linoleate, methyl oleate and the two ricinoleate esters were measured by oxidation of lipid dispersed on glass beads under three temperatures (40–80 °C). The relative amounts of the unoxidized methyl esters were determined periodically by gas chromatography, and the peroxide value of the oils was also determined. The oxidation rates were determined as the peroxide value increase rate, as well as the ester disappearance rate, and the stability of the various esters was compared. Overall, methyl ricinoleate was much more oxidatively stable than methyl oleate at mildly elevated temperatures, and the acetylation of the hydroxyl group on the 12th carbon decreased the stability.     

Low-temperature properties of triglyceride-based diesel fuels: Transesterified methyl esters and petroleum middle distillate/ester blends

This work examines low-temperature properties of triglyceride-based alternate fuels for direct-injection compression-ignition engines. Methyl esters from transesterified soybean oil were studied as neat fuels and in blends with petroleum middle distillates (No. 1 or No. 2 diesel fuel). Admixed methyl esters composed of 5–30 vol% tallowate methyl esters in soyate methyl esters were also examined. Pour points, cloud points, and kinematic viscosities were measured; viscosities at cooler temperatures were studied to evaluate effects of sustained exposure. Low-temperature filterability studies were conducted in accordance with two standard methodologies. The North American standard was the low-temperature flow test (LTFT), and its European equivalent was the cold-filter plugging point (CFPP). With respect to cold-flow properties, blending methyl esters with middle distillates is limited to relatively low ester contents before the properties become preclusive. Under most conditions, cold-flow properties were not greatly affected by admixing the methyl esters with up to 30 vol% tallowate (before blending). Least squares analysis showed that both LTFT and CFPP of formulations containing at least 10 vol% methyl esters are linear functions of cloud point. In addition, statistical analysis of the LTFT data showed a strong 1:1 correlation between LTFT and CP. This result may prove crucial in efforts to improve low-temperature flow properties of alternate diesel fuels that contain methyl esters derived from triglycerides.     

A study of fatty acid methyl esters with epoxy or alkyne functionalities

Described are the physical and chemical properties of the methyl esters of two uncommon fatty acids: vernolic acid, containing an epoxy group, and crepenynic acid, containing a triple bond. The incorporation of an epoxy or alkyne group into the fatty acid structure is shown to greatly affect the properties compared to conventional unsaturated fatty acids. The methyl esters have been characterized and compared with ordinary fatty acid methyl esters (i.e., methyl oleate and linoleate) with respect to spectroscopic characterization [¹H nuclear magnetic resonance (NMR)], ¹³C NMR, and Fourier transform infrared), rheological properties, and oxidative reactivity (using chemiluminescence). Both methyl vernoleate and methyl crepenynate could successfully be produced by transesterification under basic conditions without reaction of the epoxy or alkyne groups. Rheological measurements showed that the methyl esters had a significantly lower viscosity compared to their triglyceride analogs. Smaller differences were seen when comparing the different methyl esters where methyl vernoleate had the highest viscosity due to the presence of the more polar oxirane group. Very large differences were found with respect to the oxidation rate of the different methyl esters. Methyl crepenynate was shown to oxidize extremely rapidly, whereas methyl vernoleate was very stable toward oxidation.     

Quality control of rapeseed oil methyl esters by determination of acyl conversion

A simple procedure for the evaluation of vegetable oil conversion to methyl esters of fatty acids has been developed. These methyl esters, prepared by the transesterification of vegetable oil with methanol, are used as alternative fuel for diesel engines. A method of gas-liquid chromatography (GLC) on packed columns is used to determine the conversion of acyls bound in acylglycerols to methyl esters. This procedure is based on comparison of the peak areas of methyl esters in fuel samples before and after reaction with an effective transesterification reagent, which will transform unreacted acylglycerols to methyl esters. A correlation between the bound glycerol content, determined by the thin-layer chromatography/flame-ionization detector method, and the acyl conversion, determined by GLC, is given. In acyl conversions to methyl esters over 96.0%, the bound glycerol content is less than 0.25% by weight.     

Studies on the fatty acid composition of crayfish lipids

The fatty acid composition of carcass and exoskeleton lipids was determined for the freshwater crayfishOrconectes rusticus. Lipid fractions were isolated by column and thin-layer chromatography. Fatty acid methyl esters and alcohol acetates were then prepared and analyzed by gas-liquid chromatography. Peak identities were established from retention time data for methyl esters, hydrogenated methyl esters, and saturated, monoene, diene, and polyene methyl esters separated as acetoxy-mercuri-methoxy derivatives. Minor component acids were estimated from their relative compositions in these fractions. Presented at the symposium honoring J. B. Brown, AOCS meeting in Chicago, 1964.     

Saturated keto esters from lesquerolic,dimorphecolic, and densipolic acids

Summary The naturally occurring, unsaturated, hydroxy fatty esters, methyl lesquerolate (methyl 14-hydroxy-cis-11-eicosenoate), methyl dimorphecolate (methyl 9-hydroxy-trans, trans-10,12-octadecadienoate), and methyl densipolate (methyl 12-hydroxy-cis,cis-9,15-octadecadienoate) have been converted to the corresponding saturated keto esters by tow routes. The unsaturated esters were subjected to a hydrogenation-dehydrogenation reaction in the presence of Raney nickel or their saturated derivatives were dehydrogenated by copper chromite catalysis. Yields of the keto esters are 65–82% in the nickel-catalyzed reactions, and 71–94% by copper chromite-catalyzed dehydrogenation. In the hydrogenation-dehydrogenation system the order of reactivity is: methyl lesquerolate>methyl dimorphecolate>methyl densipolate. Relationships between structure and reactivity of these compounds, methyl 12-hydroxystearate, and methyl ricinoleate are discussed. W. Utiliz. Res. Dev. Div., ARS, USDA.     

Cold flow properties of fuel mixtures containing biodiesel derived from animal fatty waste

The aims of the present study were to evaluate the cold temperature behavior of methyl esters of vegetable and animal origin and of their mixtures with fossil diesel fuel, as well as to investigate the effectiveness of different depressants. Various blends of rapeseed oil methyl esters, linseed oil methyl esters, pork lard methyl esters and fossil diesel fuel were prepared, and both cloud point and cold filter plugging point (CFPP) were analyzed. It was found that mixtures with CFPP values of –5 °C and lower may contain up to 25% of pork lard methyl esters; whereas the ratio of summer fossil diesel fuel and rapeseed oil methyl esters may vary over a wide range, i.e. such mixtures can be used in a diesel engine in the summer. In the transitory periods it is possible to use up to 20% animal and vegetable ester blends (3 : 7) with winter fossil diesel, whereas only up to 5% of esters can be added to the fuel used in winter. In order to improve the cold properties of rapeseed oil, pork lard and linseed oil methyl ester mixtures, various additives were tested. Depressant Viscoplex 10–35 with an optimal dose of 5000 mg/kg was found to be the most effective.     

Strukturaufklärung cyclischer Fettsäuremethylester IV: Über das Auftreten von ω-Phenylalkancarbonsäure-methylestern in cyclisiertem Holz- und Leinöl

Structure Elucidation of Methyl Esters of Cyclic Fatty Acids IV: Occurrence of Methyl Esters of ω-Phenyl Alkanoic Acids in Cyclised Tung and Linseed Oil Methyl esters of cyclic fatty acids (CFA-Me) obtained from alkali cyclised tung and linseed oil were oxidized by performic acid. A series of fractions containing methyl esters of various aromatic fatty acids were obtained by column chromatographic separation of the oxidation products. Whereas the initial fractions consisted of methyl esters of ω-(o-alkylphenyl)alkanoic acids (AFA-Me), the later fractions were found to contain a homologous series of unsubstituted ω-phenyl alkanoic esters. The main component in cyclised tung and linseed oil is the methyl ester of 9-phenyl nonanoic acid. The formation of methyl esters of aromatic fatty acids is discussed.     

Binary freezing point behavior of some saturated and unsaturated fatty acid methyl esters with methyl heptadecanoate

The binary freezing point behavior of methyl heptadecanoate with methyl laurate, methyl myristate, methyl palmitate, methyl stearate, methyl elaidate and methyl petroselaidate have been determined. Both stable and metastable polymorphic forms were observed. Methyl laurate formed a simple eutectic with a region of metastable equilibrium. Methyl myristate formed a simple eutectic of stable equilibrium and a solid solution of metastable equilibrium. Methyl palmitate exhibited a solid solution of metastable equilibrium terminating in a eutectic and a region of discontinuous stable equilibrium. Methyl stearate formed a solid solution of metastable wquilibrium and also continuous stable equilibrium which formed an incongruently melting molecular compound that terminated in a eutectic point. Methyl heptadecanonate with the unsaturated eighteen carbon atom acid methyl esters exhibited only simple eutectic points and a small region of metastable equilibrium. The binary freezing point behavior of the methyl esters in general resemble that of the corresponding ethyl esters. The limited results of mixtures of methyl esters of an odd carbon acid with unsaturated acids indicate an induced stabilizing effect caused by unsaturation in the carbon chain. So. Utiliz. Res. Dev. Div., ARS, USDA.     

Analysis of hydroxylated fatty acids from plant oils

A novel process has been described recently for the preparation of hydroxylated fatty acids (HOFA) and HOFA methyl esters from plant oils. HOFA methyl esters prepared from conventional and alternative plant oils were characterized by various chromatographic methods (thin-layer chromatography, high-performance liquid chromatography, and gas chromatography) and gas chromatography-mass spectrometry as well as¹H and¹³C nuclear magnetic resonance spectroscopy. HOFA methyl esters obtained fromEuphorbia lathyris seed oil, low-erucic acid rapeseed oil, and sunflower oil contain as major constituents methylthreo-9,10-dihydroxy octadecanoate (derived from oleic acid) and methyl dihydroxy tetrahydrofuran octadecanoates, e.g., methyl 9,12-dihydroxy-10,13-epoxy octadecanoates and methyl 10,13-dihydroxy-9,12-epoxy octadecanoates (derived from linoleic acid). Other constituents detected in the products include methyl esters of saturated fatty acids (not epoxidized/derivatized) and traces of methyl esters of epoxy fatty acids (not hydrolyzed). The products that contain high levels of monomeric HOFA may find wide application in a variety of technical products.     

Essential Amino Acid Methyl Esters: Major Sex Pheromone Components of the Cranberry White Grub, Phyllophaga anxia (Coleoptera: Scarabaeidae)

Chiral capillary gas chromatographic–electroantennographic detection (GC-EAD) analysis indicates that L-valine and L-isoleucine methyl esters are the major sex pheromone components released by females of the cranberry white grub, Phyllophaga anxia (LeConte). The GC retention times and GC-mass spectrometry of the two natural compounds were identical to those of authentic standards. Of five reproducible GC-EAD active components revealed with female volatiles, the L-valine and L-isoleucine methyl esters elicited the strongest male antennal responses. The ratio of L-valine and L-isoleucine methyl esters was determined to be 3:1 by analysis of pheromone gland extracts. Chirality was shown to be critical by GC-EAD, since only the L-form of these amino acid methyl esters elicited an EAD response. In field experiments conducted in Massachusetts, a synthetic 3:1 blend of L-valine and L-isoleucine methyl esters on a rubber septum was attractive to P. anxia males.     

Studies on castor oil. I. Fatty acid composition of castor oil

Summary Methyl esters of castor oil were prepared by saponifying the oil with potassium hydroxide in methanol, splitting the potassium soapsin situ with an excess of hydrochloric acid, and esterifying at room temperature. The esters had hydroxyl values comparable with those of the parent oils. The methyl esters were quantitatively resolved into hydroxy and nonhydroxy esters after reacting with succinic anhydride in toluene. The composition of castor oil was calculated from a) amount of nonhydroxy esters, b) methyl linoleate content of methyl esters determined spectro-photometrically, c) iodine value of the methyl esters determined by the Wijs method at 15–20°C., and d) iodine value of the nonhydroxy esters determined by the Woburn method. This composition was confirmed by the estimation of saturated acids in one sample and dihydroxystearic acid in all. Castor oil was readly hydrogenated with Raney nickel in alcohol at room temperature (30–33°C.) without any hydrogenolysis of the hydroxyl groups. Methyl dihydroxystearate content of the methyl esters of this hydrogenated oil was determined by reaction with 80–100% excess periodic acid at 15–20°C. Part of a thesis submitted for the Ph.D. degree to the University of Bombay.