Comparative Studies on the Epoxidation Techniques of Vegetable Oils

Concentrated hydrogen peroxide as well as stronger peracetic acid were prepared by simple methods. Commercial hydrogen peroxide (ca. 30%) was concentrated upto 60% by removing water slowly at low temperature and low pressure. Starting from 60% hydrogen peroxide, strong peracetic acid of 17.2% strength was obtained by a simple operation. Batch epoxidations of vegetable oils such as castor, safflower and linseed oils were carried out for different reaction periods from 2 to 10 hrs and the formation of oxirane oxygen was determined in order to study the effect of epoxidation time, catalyst employed and concentration of hydrogen peroxide as well as of preformed peracetic acid on the extent of epoxidation. The optimum conversions were obtained with 4 hrs reaction period at 50° C by the in situ epoxidation technique using 60% hydrogen peroxide and acid-form of Amberlite-120 resin (chemical grade) as catalyst; the mole ratio of the reactants was unsaturation : hydrogen peroxide : acetic acid (1 : 1.5 : 0.5).     

SIS的环氧化反应

研究了ＳＩＳ在甲苯溶剂中的环氧化反应,得到了甲苯溶剂中ＳＩＳ环氧化反应的适宜条件：ＳＩＳ溶液浓度为１５％,甲酸／过氧化氢（摩尔比）＝１．５：１,反应温度５０℃,反应时间２小时。所得产物的环氧含量为３．３５０ｍｏｌ／Ｋｇ。     

Kinetics of tungsten‐catalyzed sunflower oil epoxidation studied by 1H NMR

Sunflower oil (SO) is a renewable resource that can be epoxidized, and the epoxidized SO has potential uses as an environmentally friendly and reactive material in polymeric formulations, especially for polyvinyl chloride. SO was epoxidized with peracetic acid, which was either preformed or prepared in situ. In order to optimize the formation of oxirane rings, the epoxidation and the extent of the side reactions were studied at different temperatures. The peracetic acid was obtained by acidic catalysis in the presence of a cation‐exchange resin. The optimum conversions were obtained within a 4‐h reaction period at 55 °C by the in situ epoxidation technique. The epoxidation was also carried out with hydrogen peroxide in the presence of peroxotungstic acid complexed with lipophilic phosphorus‐based ligands. ¹H NMR was used to define the new indices Δ and Ω, which are the mean numbers of C=C double bonds and oxirane rings per fatty acid chain, respectively. This allowed monitoring of the reaction and quantification of the results. Peroxotungstic catalysts appeared less performing than peracids in the epoxidation of SO, but were found very efficient for the epoxidation of the SO methyl esters.     

Epoxidation of soybean oil in toluene with peroxoacetic and peroxoformic acids — kinetics and side reactions

The kinetics of the epoxidation of soybean oil and the extent of side reactions were studied at 40, 60, and 80 °C. Epoxidation was carried out in toluene with “in situ” formed peroxoacetic and peroxoformic acid and in the presence of an ion exchange resin as the catalyst. The reaction was found to be first‐order with respect to the double bond concentration. At higher temperatures and at higher conversions a deviation from the first‐order kinetics was observed. The rate constants for the epoxidation with peroxoacetic acid were 0.118 (h⁻¹) at 40 °C, 0.451 (h⁻¹) at 60 °C and 1.278 (h⁻¹) at 80 °C, while those for peroxoformic acid were 0.264, 0.734, and 1.250 (h⁻¹). The activation energy was found to be 54.7 kJ/mol for the epoxidation with peroxoacetic acid and 35.9 kJ/mol for that with peroxoformic acid. Three factors indicated that side reactions did not occur on a large scale: The absence of an OH band in the IR spectra, the formation of less than 2% of higher molecular weight products from gel permeation chromatography and the selectivity values between 0.9 and 1.     

Studies on the oxidation of phenols catalyzed by a copper(II)–Schiff base complex in aqueous solution under mild conditions

The catalytic oxidation of phenol with hydrogen peroxide using a synthetic copper(II)–Schiff base complex as catalyst has been investigated in phosphate buffer at pH 7 and 25 °C. In order to further investigate the reaction pathway, the catalytic oxidation of hydroquinone, p‐benzoquinone and catechol were also studied under the same conditions. These reactions were found to be pseudo‐first‐order with respect to the concentration of phenolic substances. The rate constants were also calculated. In the presence of catalyst, the kinetics and the HPLC analysis showed that for the first step phenol was oxidized to hydroquinone and catechol, and the catalyst easily promoted the formation of hydroquinone but not catechol, for the second step the dihydroxybenzenes were further oxidized to benzoquinone, and lastly short‐chain acids, including maleic acid and oxalic acid, were formed. The activity of the catalyst hardly decreased during the whole reaction. Addition of imidazole accelerated the oxidation of phenol. The catalytic decomposition of hydrogen peroxide using this catalyst was also investigated. Copyright © 2005 Society of Chemical Industry     

Influence of technological parameters on the epoxidation of 1‐butene‐3‐ol over titanium silicalite TS‐2 catalyst

BACKGROUND: The influence of technological parameters on the epoxidation of 1‐butene‐3‐ol (1B3O) over titanium silicalite TS‐2 catalyst has been investigated. Epoxidations were carried out using 30%(w/w) hydrogen peroxide at atmospheric pressure. The major product from the epoxidation of B3O was 1,2‐epoxybutane‐3‐ol, with many potential applications. RESULTS: The influence of temperature (20–60 °C), 1B3O/H₂O₂ molar ratio (1:1–5:1), methanol concentration (5–90%(w/w)), TS‐2 catalyst concentration (0.1–6.0%(w/w)) and reaction time (0.5–5.0 h) have been studied. CONCLUSION: The epoxidation process is most effective if conducted at a temperature of 20 °C, 1B3O/H₂O₂ molar ratio 1:1, methanol concentration (used as the solvent) 80%(w/w), catalyst concentration 5%(w/w) and reaction time 5 h. Copyright © 2009 Society of Chemical Industry     

Optimizing reaction parameters for the enzymatic synthesis of epoxidized oleic acid with oat seed peroxygenase

Peroxygenase is a plant enzyme that catalyzes the oxidation of a double bond to an epoxide in a stereospecific and enantiofacially selective manner. A microsomal fraction containing peroxygenase was prepared from oat (Avena sativa) seeds and the enzyme immobilized onto a hydrophobic membrane. The enzymatic activity of the immobilized preparation was assayed in 1 h by measuring epoxidation of sodium oleate (5 mg) in buffer-surfactant mixtures. The pH optimum of the reaction was 7.5 when t-butyl hydroperoxide was the oxidant and 5.5 when hydrogen peroxide was the oxidant. With t-butyl hydroperoxide as oxidant the immobilized enzyme showed increasing activity to 65°C. The temperature profile with hydrogen peroxide was flatter, although activity was also retained to 65°C. In 1 h reactions at 25°C at their respective optimal pH values, t-butyl hydroperoxide and hydrogen peroxide promoted epoxide formation at the same rate. Larger-scale reactions were conducted using a 20-fold increase in sodium oleate (to 100 mg). Reaction time was lengthened to 24 h. At optimized levels of t-butyl hydroperoxide 80% conversion to epoxide was achieved. With hydrogen peroxide only a 33% yield of epoxide was obtained, which indicates that hydrogen peroxide may deactivate peroxygenase.     

Kinetics and mechanism of homogeneous catalytic hydroxylation of maleic acid by hydrogen peroxide: III. Kinetics of the hydrolysis of cis‐epoxysuccinic acid

The objective of this work was to study the hydrolysis kinetics and also the character of the involvement of the epoxidation catalyst (Na₂WO₄ – sodium tungstate) on the hydrolysis of cis‐epoxysuccinic acid (the initial product in the hydroxylation reaction of maleic acid by hydrogen peroxide). The results obtained at 65 °C clearly revealed that the hydrolysis reaction exhibits a considerably low rate in the absence of a catalyst whilst the rate is significantly enhanced by the introduction of catalytic quantities of Na₂WO₄. The phenomenon of end‐product inhibition was observed in this study and the results obtained permitted the development of a kinetic model consistent with experimental observations. Analysis of the kinetic model shows that the reaction is first order with respect to the concentrations of the catalyst and the epoxide. However, tartaric acid has a strong inhibitive influence on the overall reaction rate. © 1999 Society of Chemical Industry     

A kinetic model for the enzyme-catalyzed self-epoxidation of oleic acid

This paper reports a kinetic model for the selfepoxidation of oleic acid with toluene as solvent and Novozym 435 (a commercially available preparation of immobilized Candida antarctica lipase) as catalyst at 30°C. The effects of various parameters on the conversion and rates of reaction were studied. Both the initial rate and the progress curve data were used to fit an ordered bi-bi model. At low temperatures, the rate of epoxidation was faster than the rate of deactivation of the enzyme by hydrogen peroxide.     

Hydrogen peroxide variables in increasing epoxidation efficiency

Summary Variations in quantity and concentration of hydrogen peroxide were studied in epoxidation of soybean oil by using the partially preformed peracetic acid epoxidation method. Use of a hydrogen peroxide/olefin mole ratio as low as 1.05/1 yields epoxidized soybean oil that meets the low iodine number and high epoxide content characteristics required for stabilizer-plasticizer use. Use of a hydrogen peroxide/olefin mole ratio as low as 0.50/1 results in more than 95% hydrogen peroxide utilization and yields epoxidized soybean oil containing more than two epoxide groups per molecule. Products of this type may be of interest for recently proposed applications in alkyd, polyester, and epoxy resins. Increasing the hydrogen peroxide concentration to 70% in epoxidation permits reduction of acetic acid usage to half that required when 50% hydrogen peroxide is used. Agitation control is also necessary for optimum results. A two-step epoxidation method can be used to avoid formation of potentially detonable mixtures in epoxidation with 70% hydrogen peroxide by the partially preformed peracetic acid method. Presented at the 32nd annual meeting, American Oil Chemists' Society, Chicago, Ill., October 20–22, 1958.     

ACETIC ACID AS AN OXYGEN CARRIER BETWEEN TWO PHASES FOR EPOXIDATION OF OLEIC ACID

Acetic acid was found to be an effective oxygen carrier for epoxidation of oleic acid. The reaction model of oleic acid epoxidation in the two-phase reaction system was systematically analyzed and the rate determining step was experimentally identified.

The results indicated that the rate of oxidation of the unsaturated acid was independent of the concentration of oleic acid and depended on the mixing rate and the rate of formation peracetic acid which in turn depended on the concentration of acetic acid, strength of acid catalyst and the oxygen source, hydrogen peroxide. In the region of reaction control, the rate equation of epoxidation was found to be

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where k = 2.98 × 10^-2 M^-2 min^-1 at temperature of 35^°C.     

磺酸功能化离子液体催化不饱和脂肪酸甲酯的环氧化研究

The epoxidation of unsaturated fatty acid methyl esters(FAMEs)by peroxyacetic acid generated in situ from hydrogen peroxide and acetic acid was studied in the presence of SO3H-functional Brnsted acidic ionic liquid (IL)[C3SO3HMIM][HSO4]as catalyst.The effects of hydrogen peroxide/ethylenic unsaturation ratio,acetic acid concentration,IL concentration,recycling of the IL catalyst,and temperature on the conversion to oxirane were studied.The kinetics and thermodynamics of unsaturated FAMEs epoxidation and the kinetics of oxirane cleavage of the epoxidized FAMEs by acetic acid were also studied.The conversion of ethylenic unsaturation group to oxirane, the reaction rate of the conversion to oxirane,and the rate of hydrolysis(oxirane cleavage)were higher by using the IL catalyst.     

Degradation of poly(vinyl alcohol) in strongly alkaline solutions of hydrogen peroxide

The action of hydrogen peroxide and sodium hydroxide independently as well as in combination together with stabilizer formulation–consisting of magnesium sulphate (5 g/L), ethylenediamine tetraacetic acid (2 g/L), gluconic acid (2 g/L), and nonionic/anionic wetting agent (1.5 g/L)–on poly(vinyl alcohol) (PVA) was investigated at 30°C and 95°C. The effect of sodium hydroxide (5–25 g/L) alone was to bring about an enhancement in the viscosity of PVA most probably due to gel formation. The latter was favored at higher sodium hydroxide concentrations and longer duration (30 min) of treatment. The opposite holds true when hydrogen peroxide (35% w/v) was used alone at concentrations ranging from 2 to 20 mL/L. The viscosity of PVA decreased as the hydrogen peroxide concentration increased. Nevertheless, hydrogen peroxide alone could not cause complete dissolution of PVA even at 95°C for 30 min. On the other hand, complete dissolution of PVA could be achieved under the influence of stabilized alkaline solutions of hydrogen peroxide at 95°C in less than 10 min. It was postulated that, under the conditions used, oxidation of PVA by hydrogen peroxide prevailed over gel formation under the influence of sodium hydroxide.     

Kinetics of in situ epoxidation of soybean oil in bulk catalyzed by ion exchange resin

The kinetics of the epoxidation of soybean oil in bulk by peracetic acid formed in situ, in the presence of an ion exchange resin as the catalyst, was studied. The proposed kinetic model takes into consideration two side reactions of the epoxy ring opening involving the formation of hydroxy acetate and hydroxyl groups as well as the reactions of the formation of the peracid and epoxy groups. The catalytic reaction of the peracetic acid formation was characterized by adsorption of only acetic acid and peracetic acid on the active catalyst sites, and irreversible surface reaction was the overall rate-determining step. Kinetic parameters were estimated by fitting experimental data using the Marquardt method. Good agreement between the calculated and experimental data indicated that the proposed kinetic model was correct. The effect of different reaction variables on epoxidation was also discussed. The conditions for obtaining optimal epoxide yield (91% conversion, 5.99% epoxide content in product) were found to be: 0.5 mole of glacial acetic acid and 1.1 mole of hydrogen peroxide (30% aqueous solution) per mole of ethylenic unsaturation, in the presence of 5 wt% of the ion exchange resin at 75°C, over the reaction period of 8 h.     

Epoxidation of allyl alcohol with hydrogen peroxide over titanium silicalite TS‐2 catalyst

The influence of the technological parameters on the course of the epoxidation of allyl alcohol with 30% H₂O₂ in the presence of titanium silicalite TS‐2 catalyst and methanol as a solvent was studied. The process was performed in an autoclave at the autogenic pressure. The influence of temperature in the range 20–120 °C, molar ratio of allyl alcohol/H₂O₂ (1:1–10:1), methanol concentration in the reaction mixture (10–80% w/w), catalyst TS‐2 concentration (0.1–2.0% w/w) and reaction time (1–8 h) were investigated. The functions describing the process were: selectivity of transformation to glycidocidol in relation to allyl alcohol consumed, selectivity of transformation to organic compounds in relation to hydrogen peroxide consumed, conversions of allyl alcohol and hydrogen peroxide. Copyright © 2007 Society of Chemical Industry     

Alumina‐Catalyzed Epoxidation with Hydrogen Peroxide: Recycling Experiments and Activity of Sol‐Gel Alumina

Commercial alumina looses some activity after the first epoxidation reaction of (S)‐limonene with hydrogen peroxide, but maintains a good activity and a very high selectivity in the subsequent three reactions. After this its activity is strongly reduced, probably due to structural modifications. Aluminas obtained by sol‐gel methods are normally less active than the commercial alumina. However, the use of monomeric aluminum sec‐butoxide and of oxalic acid to form stable alumina mesophases allows a very active alumina to be obtained, which catalyses the epoxidation of the less reactive cyclohexene with hydrogen peroxide in 98% yield. Close to 50% of the active oxygen is used up in the formation of molecular oxygen.     

The kinetics of epoxidation of trimethylolpropane ester

Kinetics pertaining epoxidation reaction of a palm oil‐based synthetic lubricant trimethylolpropane (TMP) ester were investigated. The epoxidation reaction of TMP ester was carried out utilizing peracetic acid generated by an in situ technique. The analysis of the reaction kinetics was performed within the low temperature (30, 50, and 60°C) and high temperature (70, 80, and 90°C) regions, owing to the nature of the reactions. The maximum conversion of the unsaturated carbon to oxirane ring was achieved in 1 h at high temperature region, while epoxidation of TMP esters took more than 4 h to reach the maximum conversion at the low temperature region. From the experimental data, the kinetics of epoxidation of TMP esters fitted well with both the second‐order and pseudo first‐order models. The rate constants for pseudo first‐order model increased from 0.0009 to 0.0055 by increasing temperature at the low temperature region, and from 0.0129 to 0.0209 within the high temperature region. The values of activation energies at low temperature and high temperature regions were found to be 69.4 and 53.3 kJ/mol, respectively.     

Characterisation of the Major Synthetic Products of the Reactions Between Butanone and Hydrogen Peroxide

The reactions between butanone and hydrogen peroxide, both catalysed and un‐catalysed, were investigated and spectral and sensitiveness data reported. The major product of the un‐catalysed reaction, 2‐hydroxy,2‐hydroperoxybutane, displayed a Figure of Insensitiveness (F of I) of 10, Temperature of Ignition (T of I) of 132 °C, and initiated when 128 N of frictional force or an electrostatic discharge (ESD) of 4.5 J was applied. Differential scanning calorimetric analyses revealed an onset of decomposition at 128 °C, peak maximum of 140 °C, and decomposition energy of 203 J g⁻¹. The major product of the cooled (5 °C) acid catalysed reaction between butanone and hydrogen peroxide, 2,2′‐dihydroperoxy‐2,2′‐dibutyl peroxide, displayed a F of I of<10, T of I of 110 °C and initiated upon application of 5 N of friction or a 0.45 J ESD. Calorimetry showed a melt at 38.3 °C, an onset of exothermic decomposition at 127 °C and the evolution of 1292 J g⁻¹. The major product of the raised temperature (20 °C) acid catalysed synthesis, 1,4,7‐trimethyl‐1,4,7‐triethyl‐1,4,7‐cyclononatriperoxane, displayed F of I of<10 and initiated upon application of 5 N of friction or a 0.45 J ESD. Calorimetry revealed an onset to melting at 28.9 °C, an onset to thermal decomposition at 128 °C, and decomposition energy of 1438 J g⁻¹.     

An efficient reaction protocol for the ruthenium‐catalysed epoxidation of methyl oleate

The transition metal catalysed epoxidation of methyl oleate 1 by hydrogen peroxide was investigated using Ru(acac)₃/dipicolinic acid as catalyst. Under optimised reaction conditions, the epoxidised methyl oleate 2 was obtained with a quantitative yield in short reaction time and under mild reaction conditions. Practical applications: Epoxidised fatty acids and their derivatives are produced by the Prilezhaev reaction and used in various applications in the chemical industry. Due to the known drawbacks of epoxidation with peroxy acids, such as hazardous handling of peracids in large quantities or the decrease of epoxide selectivity due to the formation of undesired by‐products in the acidic medium, the epoxidation of fatty acid derivatives using more convenient oxidants is still a subject of research interest. Herein, we present a simple procedure for the transition metal catalysed epoxidation of methyl oleate 1 by hydrogen peroxide in quantitative yields, and under mild reaction conditions, as a potential alternative for the production of epoxidised fatty acid derivatives.