Fast formation of high-purity methyl esters from vegetable oils

Experiments have confirmed that the base-catalyzed methanolysis of vegetable oils occurs much slower than butanolysis because of the two liquid phases initially present in the former reaction. For the same reason, second-order kinetics are not followed. The use of a cosolvent such as tetrahydrofuran or methyl tertiary butyl ether speeds up methanolysis considerably. However, like one-phase butanolysis, one-phase methanolysis initially exhibits a rapid formation of ester, but then slows drastically. Experiments show that the half-life of the hydroxide catalyst is too long to explain the sudden slowing of the reaction. Similarly, lower rate constants for the methylation of the mono- and diglycerides are not a reasonable explanation. Instead the cause has been identified as the fall in polarity which results from the mixing of the nonpolar oil with the methanol. This lowers the effectiveness of both hydroxide and alkoxide catalysts. Increasing the methanol/oil molar ratio to 27 in the one-phase system raises the polarity such that the methyl ester content of the ester product exceeds 99.4 wt% in 7 min. This has obvious implications for the size of new methyl ester plants as well as the capacity of existing facilities.     

Fast formation of high-purity methyl esters from vegetable oils

Experiments have confirmed that the base-catalyzed methanolysis of vegetable oils occurs much slower than butanolysis because of the two liquid phases initially present in the former reaction. For the same reason, second-order kinetics are not followed. The use of a cosolvent such as tetrahydrofuran or methyl tertiary butyl ether speeds up methanolysis considerably. However, like one-phase butanolysis, one-phase methanolysis initially exhibits a rapid formation of ester, but then slows drastically. Experiments show that the half-life of the hydroxide catalyst is too long to explain the sudden slowing of the reaction. Similarly, lower rate constants for the methylation of the mono- and diglycerides are not a reasonable explanation. Instead the cause has been identified as the fall in polarity which results from the mixing of the nonpolar oil with the methanol. This lowers the effectiveness of both hydroxide and alkoxide catalysts. Increasing the methanol/oil molar ratio to 27 in the one-phase system raises the polarity such that the methyl ester content of the ester product exceeds 99.4 wt% in 7 min. This has obvious implications for the size of new methyl ester plants as well as the capacity of existing facilities.     

Quantitative studies on methyl ketone formation in butteroil: Effect of temperature

A quantitative study of the effect of various heat treatments on methyl ketone formation in butteroil was conducted. Methyl ketone formation was found to follow first-order reaction kinetics. The energy of activation was calculated to be approximately 26.55 kcal/mole. The ketones were formed in a fairly constant molar ratio approximating to the following C₁₅,2∶C₁₃,1∶C₁₁,1∶C₉,1∶C₇,2∶C₅,1. The temperature-time conditions had little or no effect on the ratio.     

Storage effect in the quality of different methyl esters and blends with diesel

Storage stability is an important aspect in the commercialization of biodiesel. Due to the chemical structure of methyl ester, long-term storage may lead to the degradation of fuel properties that can make it difficult to meet the EN 14214 Standard.This paper examines the degradation of several biofuels (sunflower methyl esters, used cooking oil methyl esters and blends with commercial diesel) under different storage conditions over a 6-month period. The storage conditions simulated real-life conditions by using similar temperatures to those found in commercial tanks, with little air turnover and in the absence of light. Extreme temperature conditions were also studied to determine if this variable has an effect on storage stability. Opaque glass or stainless steel storage containers were used to check the interaction between metal and biofuel.The results show that temperature plays an important role in the degradation of methyl esters. On the other hand, stainless steel was found to be a suitable material for the commercial storage tanks as the effect of this material on stability was almost negligible. The blends with commercial diesel performed better in long-term storage. This was probably due to the effect of the ester dilution and the presence of additives in commercial diesel.     

The occurrence of methyl methoxystearate isomers in the methyl esters prepared from sheep perinephric fat

A fraction has been isolated from sheep perinephric fat and identified by techniques which included mass and infrared spectrometry, as a mixture of the 8 to 14-methoxyoctadecanoic acid isomers. It is postulated that these isomers are artifacts produced by rigorous esterification with methanol and concentrated H₂SO₄ of a large sample of sheep perinephric fatty acids which are presumed to have contained trace amounts of constituent hydroxy fatty acids. It is estimated that these methoxystearic acid isomers represented approximately 0.08% of the total weight of fatty acids.     

The effect of aliphatic esters on the formation and degradation behavior of PLGA-based in situ forming system

The purpose of this study was to investigate the effect of three aliphatic esters, ethyl heptanoate, methyl heptanoate, and ethyl nonanoate on the in vitro degradation behavior of in situ forming systems. In situ forming implants based on 33% (w/w) poly (lactide-co-glycolide) (PLGA)/57% (w/w) N-methyl-2-pyrrolidone (NMP)/10% (w/w) esters were prepared after injection of the final formulation in phosphate buffer solution (pH 7.4, 0.2 M) at 37 °C. The influence of additives on the implants formation, morphology, and also on their in vitro degradation behaviors over a period of 45 days was investigated. The degraded matrices were evaluated to determine morphological analysis by SEM and ¹H-NMR study. The solution of degradation medium was studied to indicate NMP removal and altering acidity. The results showed that the additives generated a high porous structure and caused the fast phase inversion. However, the ¹H-NMR spectra indicated that ester additives remained in the matrices during degradation periods. The results of the acidity study showed that the degradation rates in the matrices containing esters were higher than the control matrix. In addition, it is shown that esters with lower molecular weight have affected the polymer degradation more efficiently than higher molecular weight esters.     

The selective homogeneous hydrogenation of soybean methyl esters

Soybean methyl esters are homogeneously, selectively hydrogenated in the presence of a variety of catalysts, of which [Pt(Pph₃)₂Cl₂]+SnCl₂·2H₂O and [MoCl₂(CO)₃(Pph₃)₂]+SnCl₂·2H₂O are typical. Many variations can be made in these catalysts without destroying their selectivity. All of the catalysts bring about isomerization of the substrate molecules. The role of the solvent and the mechanism of the reaction are discussed. One of 10 papers to be published from the Symposium “Hydrogenation”, presented at the AOCS Meeting, New Orleans, April 1970.     

The effect of hot surface temperature on diesel fuel deposit formation

The aim of this study is to investigate fuel deposits by using the hot surface deposition test (HSDT). In this test, diesel fuel droplets were repeatedly impinged to the hot surface and deposits were developed on it. The hot surface temperature affected the deposit formation. Different hot surface temperature showed different droplet-surface interaction, evaporation lifetime and wet/dry condition where various deposit development features resulted. The hot surface temperatures that located near MEP (maximum evaporation rate point) temperature have potential to reduce the deposit formation on the hot surface. The deposition within nucleate heat transfer boiling regime (lower than the MEP temperature) caused greater deposit accumulation on the hot surface compared to the deposition within transition heat transfer boiling regime (near the MEP temperature). Less total amount of deposit that was described as slow deposit development, resulted under non-overlapping impingement and dry deposit condition. Under the overlapping impingement and wet deposit condition, it caused the accumulation of greater total amount of deposit compared to the non-overlapping and dry deposit condition.     

The effect of citrate esters as plasticizers on the thermal and mechanical properties of poly(methyl methacrylate)

Plasticizers play a key role in the formulation of polymers and in determining their physical properties and processability. This study examines the effects of citrate esters, triethylcitrate, and triacetine as plasticizers on the thermal and mechanical properties of poly(methyl methacrylate). The samples were characterized by differential scanning calorimetry, dynamical mechanical analysis, and mechanical testing under different plasticizer contents. Both citrate esters proved to be effective as plasticizers, DSC data for the triacetine additive fits with Fox equation. Microstructure and relaxation properties were studied by dynamic mechanical analysis where loss modulus shows clearly that absorbed plasticizer shifts the α‐transition to lower temperature and β‐relaxations associated to ester side groups are unchanged even up to 30 wt % plasticizer. Mechanical properties were evaluated with an Instron testing machine. Both additives produced (1) an initial plasticization, with a decrease in tensile strength and modulus; (2) an antiplasticization, reflected as an increase in tensile strength; and modulus and (3) a final plasticization, with a notable decrease in tensile strength and modulus and an increase in elongation where a 35 wt % of triethylcitrate added to the poly(methyl methacrylate) increased in 200% its elongation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

The effect of free fatty acid on the reactivity of copper-based catalysts for the hydrogenolysis of fatty acid methyl esters

In the synthesis of fatty alcohols by hydrogenolysis of fatty acid methyl esters, small amounts of free fatty acids in the feed negatively affect the reactivity of copper-silica based catalysts. The effect of the acid was investigated in relation to the production of water, the nature of the inhibiting species, and the degree of reduction of the catalyst. Inhibition is reversible and not due to catalyst deactivation. Water is not the inhibiting species. Furthermore, formation of copper and zinc soaps was excluded. Lauric acid in the methyl ester feed reacts preferentially, but at a lower rate than the ester. Inhibition most likely stems from a preferential adsorption of the acid at the active sites of the catalyst. The consequences for practical applications are discussed.     

A rapid low temperature method for preparation of methyl esters of fatty acids

A rapid method for preparation of methyl esters of fatty acids in lipids has been accomplished by forming the sulfuric acid complex of the lipid in ethyl ether at the temp of a dry ice-acetone bath. Decomposition of the complex with methanol results in direct formation of methyl esters of the fatty acids. A comparison was made of gas liquid chromatography (GLC) analysis of fatty acid composition of several fats using methyl esters prepared by this and by two other methods. Results of this comparison reveal that the method is not only rapid but provides complete reaction with no apparent changes in the fatty acids. Mich. Agr. Exp. Sta. Pub. No. 3503. Presented at the AOCS meeting in Chicago, 1964.     

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.     

The amplified distillation of methyl esters of fatty acids

Summary Amplified distillation is a useful technique for the quantitative analysis of mixtures of fatty acid esters, especially for the detection and estimation of minor components and for the analysis of small samples. The amplified distillation of free fatty acids is largely limited to qualitative work on account of the formation of azeotropes with mineral oils. Presented before the 1945 Fall Meeting of the American Oil Chemists' Society, Chicago, Ill.     

The effect of fatty acid methyl esters on the curing performance and final properties of thermally cured solvent-borne coil coatings

The solvent content of a thermally cured coil-coating paint may be reduced by introducing a reactive diluent derived from a vegetable oil and thereby producing a coating partly based on a renewable resource. A reactive diluent acts as a solvent in the liquid paint, lowering the viscosity, and is then incorporated into the film during cure. In the present study, rape seed methyl ester (RME) has been evaluated as reactive diluent in a thermally cured hydroxyl-functional polyester/melamine system. RME has suitable diluting properties and functionality to be incorporated into the dry coating. Dynamic mechanical analysis of free standing films shows that the final film properties are affected by presence of reactive diluent, oven temperature, choice of co-solvent, and flash-off period.     

Hydrogenation of methyl linolenate. I. The formation of methyl isolinoleate on the hydrogenation of methyl linolenate

Summary A highly purified sample of methyl linoleate was prepared from linolenic acid obtained by debromination of hexabromostearic acid. The methyl linolenate was hydrogenated to varying degrees of saturation, using palladium on barium sulfate as the catalyst. Ethyl acetate was used as the solvent and all hydrogenations were conducted at room temperature and atmospheric pressure. The hydrogenated samples were analyzed for their fatty acid composition (as methyl esters). The relative reactivities of the various polyunsaturated acids towards hydrogenation were calculated and may be represented by the following whole numbers: oleic (including isooleic) acid, 1; isolinoleic acid, 5; linoleic, 27; linolenic, 27. A procedure was outlined for effecting a concentration of an isolinoleic acid (methyl ester) by low temperature crystallization. The fraction isolated contained 95.8% methyl isolinoleate. Contribution No. 798 from the Department of Chemistry, University of Pittsburgh.     

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.     

Continuous production of palm methyl esters

A system for continuous transesterification of palm oil was developed using a continuous stirred-tank reactor (CSTR) and pumps for continuous delivery of oil and catalyst and for continuous removal of product. Potassium hydroxide was used as the catalyst, the methanol-to-oil molar ratio was 6∶1, and reaction temperature was 60°C. The yield of methyl esters increased from 58.8% of theoretical yield at a residence time of 40 min to 97.3% at a residence time of 60 min. However, higher residence times decreased the production rate. During long-term continuous operation, the CSTR displayed steady state conditions in terms of product profile and methyl ester concentration. This process has good potential in the manufacture of biodiesel.