Reactions of fatty materials with oxygen. XVIII. Catalytic hydrogenation of autoxidized methyl oleate and oleic acid. Preparation of monohydroxystearic acids

Summary Autoxidation of methyl oleate and oleic acid beyond the peak peroxide values followed by catalytic hydrogenation gave mixed monohydroxystearic acids in high yield. The complicated autoxidation mixture which contains peroxides, hydroxy, carbonyl, and oxirane compounds was simplified considerably in composition by this procedure. For complete reduction of the double bond, and the carbonyl and oxirane groups, hydrogenation was conducted at about 150° and 150 lbs.. Peroxides were reduced at room temperature. Catalysts used were palladium on carbon and Raney nickel. The selective reduction of peroxides in autoxidation mixtures has been studied by chemical and catalytic means. Peroxides were converted largely to carbonyl compounds rather than to the anticipated hydroxy compounds. Palladium-lead on calcium carbonate is an excellent catalyst for reducing peroxides with hydrogen. tert-Butyl hydroperoxide, 12- ketostearic acid, stearone,cis-9,10-epoxystearic acid and methyl oleate peroxide concentrate were employed as model substances in determining hydrogenation conditions. Paper XVII. is reference 5. Presented at the fall meeting of the American Oil Chemists' Society, Minneapolis, Minn., Oct. 11–13, 1954. A laboratory of the Eastern Utilization Research Branch, Agricultural Research Service, U. S. Department of Agriculture.     

Thermal degradation of single methyl oleate hydroperoxides obtained by photosensitized oxidation

A peroxidation mixture containing methyl 9- and 10-hydroperoxy-trans-octadecenoates (MOHP) was obtained by singlet oxygen oxidation of methyl oleate. The two hydroperoxides were collected by solid phase extraction and purified separately by high-performance liquid chromatography. Identification and single-isomer purity evaluations were carried out by comparing the chromatographic and gas chromatography-mass spectrometry parameters of the corresponding reduced hydroxy derivatives. Each purified MOHP was thermally degraded and new reaction mechanisms were proposed from the identification of the degradation products. Thermal rearrangement of each hydroperoxide isomer involved an allylic 3-carbon intermediate before further degradation steps. The two MOHP isomers obtained from singlet oxygen oxidation produced all eight hydroperoxide isomers by thermal degradation in the condensed phase at high temperature (200°C). This result supports the assumption of singlet oxygen as a promoter of the first steps of oxidation of food lipids and also reconsiders the Khan mechanism.     

Thermal degradation of single methyl oleate hydroperoxides obtained by Photosensitized oxidation

A peroxidation mixture containing methyl 9- and 10-hydroperoxy-trans-octadecenoates (MOHP) was obtained by singlet oxygen oxidation of methyl oleate. The two hydroperoxides were collected by solid phase extraction and purified separately by high-performance liquid chromatography. Identification and single-isomer purity evaluations were carried out by comparing the chromatographic and gas chromatography-mass spectrometry parameters of the corresponding reduced hydroxy derivatives. Each purified MOHP was thermally degraded and new reaction mechanisms were proposed from the identification of the degradation products. Thermal rearrangement of each hydroperoxide isomer involved an allylic 3-carbon intermediate before further degradation steps. The two MOHP isomers obtained from singlet oxygen oxidation produced all eight hydroperoxide isomers by thermal degradation in the condensed phase at high temperature (200°C). This result supports the assumption of singlet oxygen as a promoter of the first steps of oxidation of food lipids and also reconsiders the Khan mechanism.     

Shifting of the double bond in methyl oleate during hydrogenation

Summary The displacement of the double bond of methyl oleate during hydrogenation with a nickel-kieselguhr catalyst at 180°C. was investigated, particularly with respect to the analysis of dicarboxylic acids, obtained either by oxidation of the reaction products with KMnO₄ in acetic acid or by means of ozone. In the oxidation experiments with KMnO₄ a considerable degradation of lower molecular dicarboxylic acids occurs that makes a quantitative analysis of the isomerization phenomena uncertain. According to the ozonization experiments an equal migration of the double bond in both directions, toward and opposite the ester group, takes place.     

Isomerization phenomena during hydrogenation of methyl oleate and methyl elaidate over nickel-silica catalysts

Methyl oleate was hydrogenated at temperatures varying from 50–175 C over three nickel-silica catalysts of different pore-size distribution. Methyl elaidate was reduced over one of these catalysts at temperatures between 75–150 C. From the detailed double bond distributions information was obtained on transport phenomena in the pores of the catalyst. It was established that the migration of the double bond in methyl oleate proceeds with a stepwise mechanism, and evidence was obtained that the double bond in methyl elaidate migrates significantly faster than that in methyl oleate, while the rate of hydrogenation of these esters was equal. Thetrans-cis ratio of the geometrical isomers which are formed by double bond migration varies strongly during hydrogenation.     

油酸甲酯催化加氢制备生物烷烃的热力学分析

采用Benson基团贡献法对油酸甲酯加氢脱氧、加氢脱羰和加氢脱羧制备生物烷烃的热力学进行了分析,计算了613~653 K温度区间内油酸甲酯加氢体系的反应热、反应熵变、反应Gibbs自由能变和标准平衡常数,在此基础上采用PRO/Ⅱ软件中的平衡反应器模型分析了温度对油酸甲酯加氢产物分布的影响并和实验数据进行了对比验证。结果表明,油酸甲酯加氢脱氧、加氢脱羧和加氢脱羰制备生物烷烃的反应均为放热反应,放热量依次递减,各反应在613~653 K范围内均能够自发进行且反应完全。升高温度能够提高平衡产物中油酸甲酯加氢脱羰/羧产物的选择性,降低温度则有利于加氢脱氧产物的选择性,加氢脱氧与脱羰/羧产物选择性的比例随温度从613 K升高到653 K相应从1.92降低到0.56,与实验测得的反应数据变化趋势吻合。     

Thermal decomposition of methyl oleate hydroperoxides and identification of volatile components by gas chromatography-mass spectrometry

The role of methyl oleate hydroperoxides as precursors of volatile compounds was investigated by thermal decomposition in the injector port of a gas chromatograph attached to a computerized mass spectrometer. The major volatile compounds identified correspond to those formed from triolein heated in air at 192 C.     

乙醇酸甲酯催化加氢制备乙二醇

在微型固定床反应器上,以乙醇酸甲酯为原料,使用Cu-Cr催化剂,催化加氢制备了乙二醇.考察了氢酯摩尔比、反应温度、反应压力、床层空速对反应的影响,并对加氢催化剂的活性进行了XRD的评价.结果显示最佳反应条件为:氢酯摩尔比40:1、反应温度210℃、反应压力3.5MPa,床层空速0.4h-1时,乙醇酸甲酯的转化率达94%...     

Vapor-Phase hydrogenation of methyl oleate in the presence of a supported nickel catalyst

The reaction order with respect-to hydrogen was found to be higher than unity and increased with increasing temperature in the vapor-phase hydrogenation of methyl oleate in the presence of a supported nickel catalyst. These findings may be of certain interest in understanding the role that hydrogen plays in fat hydrogenation selectivity. Two reaction mechanisms were discussed to explain the high reaction order. The two reaction models were shown to give the same rate equation.     

The oxidation of methyl oleate. II. A reaction between methyl hydroperoxido oleate and oleic acid

Oleic acid is intermolecularly oxidized by methyl hydroperoxido leate at 90°C, through the addition of oxygen at the olefinic bond with the formation of opexy and dihydroxy compounds. Only the lowmelting isomeric form of dihydroxystearic acid could be isolated from the reaction mixture. The oxidation of olefinic linkages by hydroperoxides appears to account, at least in part, for the observed reduction of unsaturation in autoxidizing fats. One of the laboratories of the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, U. S. Department of Agriculture.     

Volatile compounds from thermally oxidized methyl oleate

Thermal oxidation of methyl oleate was studied over a range of temperatures from 50 C to 150 C for periods of time up to 30 min. Degradation was quantitatively followed by gas liquid chromatography (GLC) and liquid scintillation counting of the products of methyl oleate-U-¹⁴C heated under a stream of compressed air. Heptane, octane, 2-decanone, benzene,o-xylene, methyl hexanoate, methyl heptanoate and methyl octanoate were identified by GLC and mass spectrometry. Mass spectral evidence also was obtained for methyl pimelaldehydate, methyl suberaldehydate and methyl azelaaldehydate. Organic synthesis confirmed the identity of methyl azelaaldehydate. Most of the products formed suggested that autoxidation was responsible for the degradation occurring at the temperatures employed in this study. Paper No. 2628 from the Oregon Agricultural Experiment Station.     

Conjugated dienes and trienes from methyl oleate and methyl linoleate

Methyl oleate and methyl linoleate were converted to conjugated dienes and trienes, respectively, by selecting and modifying the conventional procedures usually applied to the generation and characterization of fatty hydroperoxides. Conditions have been studied in the laboratory for: (a) the optimum production of hydroperoxides with a minimum of by-products, (b) the effective separation and concentration of the resulting hydroperoxide, (c) the economic reduction of the hydroperoxide mixture, (d) simple dehydration of the reduced product, and, (e) recovery of the resulting polyene-rich material. If the processing sequence is halted after the reduction step, the resulting product,is a mixture of allylic hydroxy monoene or diene methyl esters. Our investigations have been extended to include studies on the methyl esters of commercial oleic acid and the mixture of methyl esters resulting from alcoholysis of lard oil. Products containing 20–25% conjugated diene and lesser proportions of conjugated triene were obtained. Presented at the AOCS Meeting, Houston, April 1965. E. Utiliz, Res. Dev. Div., ARS, USDA.     

Structure of hydroperoxides obtained from autoxidized methyl linoleate

Summary A sample of debromination methyl linoleate has been autoxidized to a peroxide value of 671 m.e./kg. at approximately 0°C. in the dark. An essentially pure concentrate of methyl octadecadienoate monohy-droperoxide was quantitatively separated; infrared and ultraviolet spectral studies were made on the peroxide concentrate and on the corresponding hydroxyl derivative obtained by reducing the peroxides with stannous chloride. The infrared data showed no conjugated peroxides having geometric configurations other than cis, trans; the same data also showed that the peroxide concentrate contained at least 90% conjugated cis,trans forms. Calculations based on ultraviolet spectrophotometric methods also indicated that the peroxides were at least 90% conjugated. The remaining 10% of the sample is most likely nonconjugated diene hydroperoxide. Since analogous cis, cis conjugated dienes have not been isolated and their infrared and ultraviolet properties are unknown, their presence here in small amounts is possible. Ultraviolet and infrared spectra of the reduced compounds conform closely to those of the peroxides except for reduction in the intensity of the OH bond at 2.88 μ. The infrared absorption spectra of the C−H structure and carbonyl groups of an essentially pure conjugated cis, trans methyl octadecadienoate monohydroperoxide were recorded, using a LiF prism. The infrared absorption spectra of the C−H strucfraction isolated from methyl linoleate autoxidized in the dark at 24°C. indicated that appreciable amounts of conjugated trans, trans hydroperoxides were present, in addition to those of the cis, trans type. It is possible that the conjugated cis, trans isomers were formed originally but were labile at the higher temperature and in the presence of catalysts (e.g., peroxides) were transformed to the thermodynamically more stable conjugated trans, trans isomer. This work was supported in part by a contract between the Office of Naval Research, Department of the Navy, and the University of Minnesota. Hormel Institute publication No. 81, and paper No. 133, Journal Series, General Mills Research Laboratories.     

Isomerization during hydrogenation of soap. I. Potassium oleate

Potassium oleate in slightly alkaline solution was hydrogenated for up to 7 hr with Rufert nickel catalyst at 150C and 20 kg/sq cm pressure. With 1% catalyst, the iodine value dropped by 12 units in the first hour, and only slightly thereafter. With 2% catalyst there was a drop of 24 units in iodine value in the first hour, a steady state for the next 3 hr, and a second sharp drop of 30 units prior to the seventh hour. Samples of fat hydrogenated over 1% catalyst for 3 hr and 7 hr respectively were analyzed by gas-liquid chromatography, thecis andtrans monoenes were separated by argentation thin-layer chromatography, and the positional isomers in each were determined by oxidation of the total fraction to dicarboxylic acids, which were then estimated by GLC. Apart from double-bond saturation during the first 3 hr of hydrogenation, extensive double-bond migration yielded 23.5% oftrans 8- to 13-monoene, accompanied by small amounts only of positionalcis monoenes other than the starting material. After 7 hr of hydrogenation, extensivecis tocis isomerization occurs, accompanied by lesscis totrans shift; thecis:trans ratio for each monoene consequently tended toward 1:1. The results are explained on the sorption mechanism of hydrogenation and suggest that soap hydrogenation, involving catalyst poisoning, may represent a magnified version of normal fat hydrogenation.     

The oxidation of methyl oleate I. The preparation,properties and reactions of methyl hydroperoxido oleate

Summary Low temperature fractional crystallization from acetone has been applied to the separation of methyl hydroperoxido oleate in 85 to 90 percent purity from partially oxidized methyl oleate. The hydroperoxido ester was subjected to hydrogenation, oxidative fission, and reduction with hydrogen iodide. Certain characteristics of the original hydroperoxide and its reaction products have been described. The results obtained lend definite support to the view that the first oxidation product of methyl oleate is a mixture of 8- and 11-hydroperoxido octadecenoic acids, at least under the conditions employed,i.e., oxidation under the influence of ultraviolet light or reaction temperatures up to 60° C. The spectral absorption of methyl hydroperoxido oleate and some derived products was determined. The hydroperoxide group was shown to have no characteristic absorption in the ultraviolet region. The reactions of the peroxide with alkali, hydroxylamine, lead tetraacetate, and α-tocopherol have been described and discussed. Presented before the 37th Annual Meeting of the American Oil Chemists' Society, New Orieans, Luisiana, May 15–17, 1946. One of the laboratories of the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, U. S. Department of Agriculture.     

Modification of vegetable oils. XI. The formation of trans isomers during the hydrogenation of methyl oleate and triolein

Summary 1. During the hydrogenation of methyl oleate, trans isomers are formed at a very rapid rate. As much as 38% of trans isomers formed while the first 10% of methyl stearte was formed. 2. The rate of formation of trans isomers in methyl oleate undergoing hydrogenation is increased by increasing the temperature, increasing the catalyst concentration, and decreasing the degree of dispersion of the hydrogen. 3. The hydrogenation of methyl oleate always resulted in the establishment of an equilibrium between cis and trans isomers, and irrespective of the conditions employed the concentration of trans isomers was always 67%, calculated on the basis of total unsaturated constituents. 4. It is concluded that all of the iso-oleic acids formed during the hydrogenation of methyl oleate adsorb hydrogen at the same rate as oleic acid and are adsorbed and desorbed from the nickel catalyst with equal ease. 5. Trans isomers are formed at a slightly lower rate during the hydrogenation of triolein than in the case of methyl oleate. 6. Partial hydrogenation of triolein also results in the establishment of an equilibrium between cis and trans isomers of oleic acid but at values of less than 67% of trans constituents (based on the total unsaturated constituents) observed with methyl oleate. The equilibrium concentration was found to vary with the conditions of hydrogenation and was found to be 62% at 200°C. and 57% at 175°C. Report of study made under the Research and Marketing Act of 1946. Presented at the 24th Fall Meeting of the American Oil Chemists’ Society, San Francisco, Calif., Sept. 26–28, 1950. One of the laboratories of the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, U. S. Department of Agriculture.     

甲醇体系电镀污泥衍生磁性多金属材料催化糠醛加氢转化

以电镀行业废弃物电镀污泥为前体合成磁性多金属催化材料,考察其在甲醇供氢体系生物基糠醛加氢转化制备糠醇和2-甲基呋喃的催化性能。通过X射线衍射(XRD)、液氮吸脱附、NH₃程序升温脱附(NH₃-TPD)、扫描电镜(SEM)等手段对煅烧后电镀污泥进行表征,并研究了煅烧温度和各反应工艺条件对甲醇供氢体系糠醛转化的影响。结果表明,电镀污泥衍生磁性多金属材料均具有强酸性位点和部分介孔结构,以铜组分为主的催化活性中心在反应过程中部分被还原为零价,有助于促进甲醇重整产氢和糠醛加氢转化;以700℃煅烧的电镀污泥为催化剂,在240℃反应2 h以上,糠醛几乎完全转化,产物中糠醇和2-甲基呋喃最高收率(摩尔分数)分别为70.9%和31.9%,反应过程副产物以2-呋喃甲基甲醚和2-(二甲氧基甲基)呋喃为主。此外,基于甲醇重整产氢、铜镍组分原位还原以及糠醛加氢反应之间的耦合作用,推测出甲醇体系电镀污泥衍生磁性多金属材料催化糠醛加氢转化可能的反应机制。     

甲醇体系电镀污泥衍生磁性多金属材料催化糠醛加氢转化

以电镀行业废弃物电镀污泥为前体合成磁性多金属催化材料,考察其在甲醇供氢体系生物基糠醛加氢转化制备糠醇和2-甲基呋喃的催化性能。通过X射线衍射(XRD)、液氮吸脱附、NH₃程序升温脱附(NH₃-TPD)、扫描电镜(SEM)等手段对煅烧后电镀污泥进行表征,并研究了煅烧温度和各反应工艺条件对甲醇供氢体系糠醛转化的影响。结果表明,电镀污泥衍生磁性多金属材料均具有强酸性位点和部分介孔结构,以铜组分为主的催化活性中心在反应过程中部分被还原为零价,有助于促进甲醇重整产氢和糠醛加氢转化;以700℃煅烧的电镀污泥为催化剂,在240℃反应2 h以上,糠醛几乎完全转化,产物中糠醇和2-甲基呋喃最高收率(摩尔分数)分别为70.9%和31.9%,反应过程副产物以2-呋喃甲基甲醚和2-(二甲氧基甲基)呋喃为主。此外,基于甲醇重整产氢、铜镍组分原位还原以及糠醛加氢反应之间的耦合作用,推测出甲醇体系电镀污泥衍生磁性多金属材料催化糠醛加氢转化可能的反应机制。     

Catalytic hydrogenation of soybean oil methyl esters and some related compounds

Mixtures of platinum complexes and tin(II) chloride are effective homogeneous catalysts for the hydrogenation of soybean oil methyl ester, reducing it to the monoene stage only. Hydrogenation and isomerization reactions have been examined under various conditions, using a solvent consisting of 60% benzene and 40% methanol. The extent of hydrogenation depends upon the temperature (90C>60C>30C) but not upon the pressure (1075 psi as compared with 525 psi). It almost stops after 3 hr, although one double bond remains in the molecule. After hydrogenation with a catalyst consisting of a mixture of dichloro-bis-triphenylphosphine-platinum(II) and tin(II) chloride, soybean oil methyl ester shows an increase in monoene, a decrease in diene and triene, and formation of conjugatedcis-trans andtrans-trans dienes, but no increase in stearate. Similarly, methyl oleate and methyl linoleate were converted to trans monoene, but not to stearate. Hydrogenations with mixtures of tetrachloroplatinum(II) ion or hexachloro-platinum(IV) ion and tin(II) chloride were similar to those described above but they form some stearate. Several other metal ions were studied as replacements for tin. None of them were effective.