The effect of fatty acid composition on the acrylation kinetics of epoxidized triacylglycerols

Epoxidized oils, epoxidized triacylglycerols, and epoxidized fatty acid methyl esters were made by reaction with performic acid formed in situ. The extent of epoxidation was ca. 95% for all of the epoxidized samples, as determined by ¹H nuclear magnetic resonance. The epoxidized samples were reacted with an excess of acrylic acid for different reaction times. The acrylation reaction was found to have a first-order dependence on the epoxide concentration for all oils, pure triacylglycerols, and fatty acid methyl esters. However, the rate constant of acrylation was found to depend on the composition of the epoxidized material. The acrylation rate constant for 9,10-epoxystearic acid was 96 L²/(mol²·min). The rate constant of acrylation for the epoxides on 9,10,12,13-diepoxystearic acid was 60 L²/(mol²·min). The acrylation rate constant for the epoxides on 9,10,12,13,15,16-triepoxystearic acid was 50 L²/(mol²·min). Thus, the rate constant of acrylation increased as the number of epoxides per fotty acid decreased. Multiple epoxides per fatty acid decrease the reactivity of the epoxides because of steric hindrance effects, and the oxonium ion, formed as an intermediate during the epoxyacrylic acid reaction, is stabilized by local epoxide groups. These results were used to derive an acrylation kinetic model that predicts rate constants from fatty acid distributions in the oil. The predictions of the model closely match the experimentally determined rate constants.     

Optimization of the chemoenzymatic epoxidation of soybean oil

The lipase Candida antarctica (Novozyme 435) immobilized on acrylic resin was used as an unconventional catalyst for in situ epoxidation of soybean oil. The reactions were carried out in toluene. The peracid used for converting TG double bonds to oxirane groups was formed by reaction of FFA and hydrogen peroxide. The reaction conditions were optimized by varying the lipase concentration, solvent concentration, molar ratio of hydrogen peroxide to double bond, oleic acid concentration, and reaction temperature. The kinetic study showed that 100% conversion of double bonds to epoxides can be obtained after 4 h. The addition of free acids was not required for the reaction to proceed to conversions exceeding 80%, presumably owing to generation of FFA by hydrolysis of soybean oil. The enzyme catalyst was found to deteriorate after repeated runs.     

Free radical meleation of soybean oil <Emphasis Type="Italic">via</Emphasis> a single-step process

In this study a new value-added product was developed from soybean oil for use as a chemical feedstock. The investigation and optimization of this work resulted in a fast and simple process to maleate soybean oil. An anhydride functionality was introduced into soybean oil through a free radical-initiated maleation. Two initiators were evaluated, 2,5-bis(tert-butylperoxy)2,5-dimethylhexane peroxide and di-tert-butyl peroxide. The effects of reaction time, initiator concentration, maleic anhydride concentration, and reaction temperature were investigated. The maleated soybean oil was characterized using acid value, iodine value, and FTIR spectroscopy. The acid value was directly related to the initial concentration of maleic anhydride, whereas the concentration and type of initiator had little effect on the acid value. The peroxide-initated functionalization of soybean oil with maleic anhydride in a closed vessel at elevated pressure and temperature was found to proceed by a Diels-Alder mechanism.     

Epoxidationen mit Peressigsäure V: Zur Kenntnis epoxidierter technischer Monoglyceride

Epoxidation with Peracetic Acid V: Epoxidised Technical Monoglycerides For the direct epoxidation of the technical monoglycerides with differently prepared peracetic acid, which is described for the first time, a number of monoglycerides as well as mixtures of linseed oil, esterified with different polybasic alcohols, were used. In all the cases, where a preprepared peracetic acid in acetic acid or especially in acetic acid ester was used, epoxide yields ranging from 84% to nearly 95% were obtained. Linseed oil monoglyceride, when treated by in-situ procedure with DOWEX-50 resin as an acidic catalyst also gave 84% yield of epoxides. The comparison of different epoxidations and the contents of the secondary products at the maximum level of epoxides, showed, that the reaction takes the most favourable course in homogeneous phase. Free glycerin had no effect on the yield of epoxides from glycerin monooleate.     

Aqueous-enzymatic extraction of plum kernel oil

An aqueous-enzymatic extraction process of plum kernel oil was investigated on a laboratory scale, varying several processing parameters, with main emphasis on the oil yield. Efficient recovery of oil was related to three operations: pretreatment, enzymatic reaction and separation of oil. Maximum oil yield of about 70% (estimated by the Soxhlet method) was obtained at an enzyme concentration of 0.5%, extraction temperature of 45°C, pH 4.5, treatment time of 1 h and dilution ratio of 1:4. The aqueous-enzymatic extraction did not have any determining effect on the fatty acid composition, tocopherol composition, iodine value and saponification value. The free fatty acid content was higher, while the phosphatide content and peroxide value were lower in the oil extracted by the aqueous-enzymatic process as compared to the Soxhlet extracted samples.     

过氧化氢一步法制备环氧亚麻油工艺

报道了亚麻油在以石油醚为溶剂、磷酸为催化剂的条件下,经甲酸、双氧水环氧化,一步合成增塑剂———环氧亚麻油的一种新方法。该法反应条件温和,操作方法简单,反应时间较短,而且产物各项指标均可达到增塑剂标准:环氧值>7.8,碘值<10,酸值<0.5。     

1H-NMR Characterization of Epoxides Derived from Polyunsaturated Fatty Acids

In recent years, ¹H NMR has been used to study epoxides in lipid oxidation and industrial processes, but the peak assignments reported for monoepoxides and diepoxides have been inconsistent. Lack of clear assignments for chemical shifts of epoxides derived from polyunsaturated fatty acids (PUFA) has also limited the use of ¹H NMR in detecting and quantifying these products during both oxidative degradation and industrial epoxidation. In this study, ¹H NMR was used to characterize the epoxides synthesized from trilinolein, trilinolenin, canola oil, and fish oils by reaction with formic acid and hydrogen peroxide. Assignments for epoxides derived from PUFA in canola oil and fish oil were between 2.90–3.23 ppm and 2.90–3.28 ppm, distinct from other chemical groups in these oils. Chemical shifts of epoxy groups moved downfield with an increasing number of epoxy groups in the fatty acid chain. Hence, peaks for diepoxides appeared at 3.00, 3.09, and 3.14 ppm and for triepoxides at 3.00, 3.16, and 3.21 ppm. Results also suggested that stereoisomers of diepoxides and triepoxides were formed during the epoxidation process under the conditions of this study. These new assignments for di‐ and tri‐epoxide stereoisomers were supported by GC–MS analysis of their methyl esters, H–H COSY experiments, and a re‐evaluation of several previous epoxide‐related studies.     

Direct hydroxylation of fats and derivatives with a hydrogen peroxide tungstic acid system

The direct preparation ofthreo-1,2-glycols without isolation of intermediates from oleic acid, methyl oleate, and oleyl alcohol by oxidation with a hydrogen peroxide (70%)-tungstic acid system at pH 0–1 and 45–55C without solvent has now been shown to be an efficient, high-yield reaction. Thethreo-isomers are formed from intermediate epoxides by in situ hydration with accompanying inversion. Preincorporation of about 2% of the glycol reaction product into oleic acid or methyl oleate speeds up the oxidation reactions markedly and adds to their control and reproducibility. With oleyl alcohol, addition of reaction product is not necessary. Castor and olive oils are also readily oxidized to almost complete elimination of unsaturation, but the products are only 50–60% 1,2-glycols, owing to intra- and intermolecular polyether information. Addition of reaction product is unnecessary with castor oil, but with olive oil the reaction rate is greatly accelerated by incorporation of 2% of reaction product. Preconditioning (5 hr) of the hydrogen peroxide with the tungstic acid permits slightly faster oxidation rates. Emulsions are also rapidly oxidized under appropriate conditions, but these systems are more complicated to prepare and work up than oxidation of the substrates directly. Tentative reaction mechanisms are proposed in which an inorganic polyperoxytungstic acid is the effective oxidizing agent and hydroxyl-containing species are important interfacial or complexing agents between the substrate and oxidant system. Presented in part at the AOCS Meeting in Philadelphia, October 1966. Present address: Warner-Lambert Research Institute, Morris Plains, N. J. Work completed in partial fulfillment of the requirements for the PhD degree.     

Kinetics of oxirane cleavage in epoxidized soybean oil

The kinetics of oxirane ring cleavage in epoxidized soybean oil have been studied using glacial acetic acid at 60, 70, 80 and 90°C. It was shown that the reaction can be successfully modelled as first order with respect to the epoxide concentration and second order with respect to acetic acid. The reaction velocity constant at 70°C was found to be 2 × 10⁻³ 1⁻³ hr⁻¹ mol⁻², the frequency factor, A, = 2.321 × 10⁷ hr⁻¹ and the energy of activation, E_a = 15.84 k cal mol⁻¹. The effects of the concentration of acetic acid and the temperature on the net yield of epoxides by in situ epoxidation were also studied on the basis of the predicted kinetic parameters of the reaction system.     

Long-term behavior of oil-based varnishes and paints I. Spectroscopic analysis of curing drying oils

The curing of drying oils at 60°C has been investigated by Fourier transform infrared spectroscopy and Fourier transform Raman analysis of linseed oil and poppyseed oil. In the first step, hydroperoxides are formed (broad vibration band centered around 3425 cm⁻¹) with concomitant conjugation and cis-trans isomerization of the double bonds (disappearance of cis bands at 3011 and 716 cm⁻¹, appearance of trans conjugated and trans nonconjugated bands at 987 and 970 cm⁻¹). The subsequent decomposition of hydroperoxides in the presence of oxygen leads to the formation of alcohols (nitrite band at 779 cm⁻¹ after nitrogen monoxide treatment), aldehydes (bands at 2810 and 2717 cm⁻¹ in gas phase), ketones (saturated and unsaturated at 1720 and 1698 cm⁻¹, respectively), carboxylic acids (saturated and unsaturated acid fluorides identified at 1843 and 1810 cm⁻¹ after SF₄ treatment), and peresters or γ-lactones (near 1770 cm⁻¹). A rapid decrease in the double-bond concentration is recorded when curing continues, and the formation of epoxides, characterized by a vibration band at 885 cm⁻¹, is observed. Thermolysis experiments have suggested the proposal of a reaction of addition of peroxyl radicals on the conjugated double bonds as a probable mechanism. This mechanism explains both the rapid disappearance of conjugated double bonds and the formation of epoxides as intermediate products observed in the initial step of curing.     

DSC and 13C-NMR studies of the imidazole-accelerated reaction between epoxides and phenols

The imidazole-accelerated reaction between epoxides and phenols has been studied through DSC and ¹³C-NMR of model compounds. The selectivity of the accelerator has been found to be strongly dependent on its concentration. If a low amount of accelerator is used, the reaction takes place almost exclusively through the addition of phenols to epoxides even if the latter are used in excess. However, a larger amount of accelerator will cause the secondary hydroxyls (produced by the main reaction) to react with the epoxides. In any case, the lower reactivity of the secondary hydroxyls prevents them from reacting to any significant extent as long as there are any phenols present. When polyfunctional resins are used, the effect of the selectivity of the reaction on the properties of the crosslinked network is very clear. If a low amount of accelerator is used (to promote only the epoxy–phenol reaction), the maximum glass transition temperature (T_g) occurs when the epoxides and phenols are stoichiometrically balanced, reaching 178°C. However, when an excess of epoxides over phenols is used, along with a larger amount of accelarator, the maximum T_g increases its value to 199°C.     

Characterization of cyclopropenoid acids in selected seed oils

Evidence is provided that sterculic and malvalic acids occur together in seed oils ofSterculia foetida, Hibiscus syriacus, andLavatera trimestris. Sterculia foetida oil contains 54.5% sterculic and 6.7% malvalic acids;Hibiscus syriacus oil contains 16.3% malvalic and 3.4% sterculic; andLavatera trimestris oil contains 7.7% malvalic and 0.6% sterculic acids.Hibiscus syriacus oil also contains 1.5% dihydrosterculic acid. The cyclopropenoid acids were characterized by hydrogenation in conjunction with gas-liquid chromatography and by oxidation to β-dioxo acids with subsequent cleavage with peracetic acid. Acetolysis of epoxides in the presence of cyclopropenes was effected by room temperature treatment with acetic acid-10% sulfuric acid (5∶2). This is a laboratory of the Northern Utilization Research and Development Division, Agricultural Research Service, U. S. Department of Agriculture.     

Concentration of ω-3 polyunsaturated fatty acids of marine oils using Candida cylindracea lipase: Optimization of reaction conditions

Production of ω-3 fatty acid concentrates from seal blubber oil (SBO) and menhaden oil (MHO) upon enzymatic hydrolysis by Candida cylindracea lipase was optimized. In this process, the content of total ω-3 fatty acids, Y ₁; eicosapentaenoic acid, Y ₂; and docosahexaenoic acid, Y ₃, in the final product was maximized. A three-factor central composite rotatable design was used to study the effect of enzyme concentration (X ₁), reaction time (X ₂), and reaction temperature (X ₃). Second-order polynomial regression models for Y ₁, Y ₂, and Y ₃ were employed to generate response surfaces. After hydrolysis, a maximum of 54.3% total ω-3 fatty acids was obtained from SBO at an enzyme concentration of 308 U/g oil, a reaction time of 40 h, and a reaction temperature of 37°C. Similarly, a maximum of 54.5% total ω-3 fatty acids was obtained from MHO at an enzyme concentration of 340 U/g oil, a reaction time of 45 h, and a reaction temperature of 38°C.     

Optimization of Cottonseed Oil Ethanolysis to Produce Biodiesel High in Gossypol Content

Transesterification of cottonseed oil was carried out using ethanol and potassium hydroxide (KOH). A central composite design with six center and six axial points was used to study the effect of catalyst concentration, molar ratio of ethanol to cottonseed oil and reaction temperature for percentage yield (% yield) and percentage initial absorbance (%A _385nm) of the biodiesel. Catalyst concentration and molar ratio of ethanol to cottonseed oil were the most significant variables affecting percentage conversion and %A _385nm. Maximum predicted % yield of 98% was obtained at a catalyst concentration of 1.07% (wt/wt) and ethanol to cottonseed oil molar ratio of 20:1 at reaction temperature of 25 °C. Maximum predicted %A _385nm of more than 80% was obtained at 0.5% (wt/wt) catalyst concentration and molar ratio of 3:1 at 25 °C. The response surfaces that described % yield and %A _385nm were inversely related. Gossypol concentration (% wt), oxidative stability and %A _385nm of biodiesel were found to be highly correlated with each other. Hence, color %A _385nm is a measure of the amount of pigments present in biodiesel fuels that have not yet been subjected to autoxidation. High gossypol concentration also corresponds to a fuel with high oxidative stability. The fatty acid ethyl esters (FAEE) produced from cottonseed oil had superior oxidative stability to fatty acid methyl esters (FAME) produced from cottonseed oil.     

Formation of α-Tocopherolquinone and α-Tocopherolquinone Epoxides in Plant Oil

The antioxidative activity of α-tocopherol in oil is necessary for the inhibition of lipid peroxidation. If no regeneration of antioxidants is possible in foods, oxidation products are formed to a measurable extent. The aim of this study was to investigate oxidation products of α-tocopherol in plant oil. The oxidation of α-tocopherol in plant oil leads to α-tocopherolquinone and to two epoxides (α-tocopherolquinone-2,3-epoxide, α-tocopherolquinone-5,6-epoxide). These three reaction products were identified and quantified in plant oil. The 2,3-epoxide is formed at lower temperatures (90°C) whereas at high temperatures (180–220°C) only the 5,6-epoxide appears. The kinetics show that the 5,6-epoxide is produced as long as α-tocopherol is present. With longer reaction times the concentration of the 5,6-epoxide starts to decrease. α-Tocopherolquinone is found at substantially lower concentrations.     

Preparation of fatty amide polyols <Emphasis Type="Italic">via</Emphasis> epoxidation of vegetable oil amides by oat seed peroxygenase

Prior work has shown that oat (Avena sativa) seeds are a rich source of peroxygenase, an enzyme that promotes the oxidation of carbon-carbon double bonds to form epoxides. Ground and defatted oat seeds were used as a low-cost source of peroxygenase. A systematic study of the epoxidation of i-butyl amides from linseed oil was conducted. Hexane was used as the primary component of the reaction media to eliminate the need for extraction. We found that the addition of a small amount of buffered water containing Tween 20 enhanced the epoxidation activity when using t-butyl hydroperoxide and cumene hydroperoxide as oxidants. This activity could be further enhanced by the addition of isopropyl ether. Conditions for larger-scale reactions were developed and applied to amides prepared from linseed, soybean, and canola oils. Because of enzymatic selectivity, the epoxidation of adjacent double bonds was low, and monoepoxides from the amides of oleate and linoleate predominated; the diepoxide, N-i-butyl-9,10–15,16-diepoxy-12(Z)-octadecenamide, was obtained from the amide of linolenate. The enzymatically epoxidized amides from the oils were hydrolyzed in dilute acid, and the distribution of the various classes of polyols was determined. Reflecting the high proportion of starting monoepoxides, saturated diols and diols with one double bond were the major polyols obtained from soybean and canola oils. Because linseed oil contains a high proportion of linolenate, polyols obtained from the epoxides of this oil had a major amount of the tetrol, N-i-butyl-9,10,15,16-tetrahydroxy-12(Z)-octadecenamide. In contrast, the components of polyols obtained from the hydrolysis of commercial epoxide preparations of soybean and linseed methyl esters followed by amide formation were primarily saturated diols and furan derivatives resulting from the presence of adjacent epoxide groups in these preparations.     

Enzymatic fat hydrolysis and synthesis

The hydrolysis of tallow, coconut oil and olive oil, by lipase fromCandida rugosa, was studied. The reaction approximates a firstorder kinetics model. Its rate is unaffected by temperature in the range of 26–46 C. Olive oil is more rapidly hydrolyzed compared to tallow and coconut oil. Hydrolysis is adversely affected by hydrocarbon solvents and a nonionic surfactant. Since amounts of fatty acids produced are almost directly proportional to the logarithms of reaction time and enzyme concentration, this relationship provides a simple means of determining these parameters for a desired extent of hydrolysis. All three substrates can be hydrolyzed, almost quantitatively, within 72 hr. Lipase fromAspergillus niger performs similarly. The lipase fromRhizopus arrhizus gives a slow hydrolysis rate because of its specificity for the acyl groups attached to the α-hydroxyl groups of glycerol. Esterification of glycerol with fatty acid was studied with the lipase fromC. rugosa andA. niger. All expected five glycerides are formed at an early stage of the reaction. Removal of water and use of excess fatty acid reverse the reaction towards esterification. However, esterification beyond a 70% triglyceride content is slow.     

The electrocatalytic hydrogenation of soybean oil

Soybean oil has been hydrogenated electrocatalytically at a moderate temperature, without an external supply of pressurized H₂ gas. In the electrocatalytic reaction scheme, atomic hydrogen is produced on an active Raney nickel powder cathode surface by the electrochemical reduction of water molecules from the electrolytic solution. Adsorbed hydrogen then reacts with an oil’s triglycerides to form a hydrogenated product. Experiments were carried out at 70°C with a flow-through electrochemical reactor operating in a batch recycle mode. The reaction medium was a two-phase mixture of soybean oil in a water/t-butanol solvent containing tetraethylammoniump-toluenesulfonate as the supporting electrolyte. In all experiments the reaction was allowed to continue for sufficient time to synthesize a brush hydrogenation product. The effects of oil content, applied current, solvent composition, and supporting electrolyte concentration on the efficiency of hydrogen addition to the oil and on the chemical properties of the hydrogenated oil product were determined. The electrohydrogenated oil is characterized by a high stearic acid content and a low percentage of totaltrans isomers, as compared to that produced in a traditional hydrogenation process.     

Parameter optimization for the enzymatic hydrolysis of sunflower oil in high-pressure reactors

This study is concerned with the hydrolysis of sunflower oil in the presence of lipase preparation Lipolase 100T (Aspergillus niger lipase). Supercritical carbon dioxide was used as a solvent for this reaction. In a high-pressure stirred tank reactor operated in a batch mode, the effects of various process parameters (temperature, pressure, enzyme/substrate ratio, pH, and oil/buffer ratio) were investigated to determine the optimal reaction rate and conversion for the hydrolysis process. The optimal concentration of lipase was 0.0714 g/mL of CO₂-free reaction mixture, and the highest conversions of oleic acid (0.193 g/g of oil phase) and linoleic acid (0.586 g/g of oil phase) were obtained at 50°C, 200 bar, pH=7, and an oil/buffer ratio of 1∶1 (w/w).     

Selective hydrolysis of borage oil with Candida rugosa lipase: Two factors affecting the reaction

A 46% γ-linolenic acid (GLA)-containing oil was produced by selective hydrolysis of borage oil (GLA content, 22%) at 35°C for 15 h in a mixture containing 50% water and 20 units (U)/g reaction mixture of Candida rugosa lipase. The GLA content was not raised over 46%, even though the hydrolysis extent was increased by extending the reaction time and by using a larger amount of the lipase. However, 49% GLA-containing oil was produced by hydrolysis in a reaction mixture with 90% water. This result suggested that free fatty acids (FFA) that accumulated in the mixture affected the apparent fatty acid specificity of the lipase in the selective hydrolysis and interfered with the increase of the GLA content. To investigate the kinetics of the selective hydrolysis in a mixture without FFA, glycerides containing 22, 35, and 46% GLA were hydrolyzed with Candida lipase. The result showed that the hydrolysis rate decreased with increasing GLA content of glycerides, but that the release rate of GLA did not change. Thus, it was found that the apparent fatty acid specificity of the lipase in the selective hydrolysis was also affected by glyceride structure. When 46% GLA-containing oil was hydrolyzed at 35°C for 15 h in a mixture containing 50% water and 20 U/g of the lipase, GLA content in glycerides was raised to 54% at 20% hydrolysis. Furthermore, GLA content in glycerides was raised to 59% when the hydrolysis extent reached 60% using 200 U/g of the lipase. These results showed that repeated hydrolysis was effective to produce the higher concentration of GLA oil. Because film distillation was found to be extremely effective for separating FFA and glycerides, large-scale hydrolysis of borage oil was attempted. As a result, 1.5 kg of 56% GLA-containing oil was obtained from 7 kg borage oil by repeated reaction.