Competitive hydrogenation rates of isomeric methyl octadecenoates

Hydrogenation rates of isomeric methyl octadecenoates were compared by reducing mixtures containing a small weight of one radioactively labeled isomer and a much larger weight of another unlabeled isomer. As hydrogenation proceeded, samples were removed for analysis by a gas chromatograph, coupled with an ionization chamber so that mass peaks measured reduction of the unlabeled isomer and radioactive peaks of the labeled isomer. The ratio of hydrogenation rates best fitting these data was calculated with a digital computer. Reductions were made at atmospheric pressure generally with either nickel at 140C or platinum at 50C. A few were made with palladium at 50C. Methyl oleate hydrogenated more rapidly than methyl elaidate and thecis-15-isomer more rapidly than oleate. Other variations among the positionalcis isomers investigated were small. Presented at the AOCS Meeting, San Francisco, April 1969.     

Equivalent chain lengths of methyl octadecadienoates and octadecatrienoates

Equivalent chain lengths (ECL) have been determined for a number of methyl octadecadienoates and octadecatrienoates with different stationary phases, including Apiezon L, polyphenyl ether, diethylene glycol succinate, XF 1150, 100% cyanoethyl silicone and tetracyanoethylated pentaerythritol. ECL values for unconjugated esters are slightly larger than calculated by adding the ECL increments over stearate found for octadecenoates with the same position and configuration of double bonds. In general, differences are greater for methylene-interrupted double bonds and fortrans double bonds. They are greater for more polar columns. Average corrections can be added so that calculated ECL values agree well with the determined values. ECL increases with polarity of the stationary phase. The relative ECL pattern on different stationary phases changes little with position of double bonds in the isomers, but it is affected by double bond configuration. For esters with the same double bond positions isomers withtrans double bonds tend to have lower ECL values thancis on polar stationary phases and higher ECL values on nonpolar. ECL’s of conjugated octadecadienoates are always higher than unconjugated and increase in the ordercis,cis; mono-trans; andtrans,trans. Presented at the AOCS Meeting, Chicago, September 1970.     

The geometric isomers of conjugated octadecadienoates from dehydrated methyl ricinoleate

The dehydration of methyl ricinoleate by heatingin vacuo in the presence of KHSO₄ resulted in the formation of the following conjugated octadecadienoates expressed as a percentage of the final product:cis, trans (trans, cis), 14.3;cis, cis, 11.2;trans, trans, 7.3. The isomers contained the double bonds predominantly in the 9,11 position but the possible presence of traces of 8,10 and other conjugated isomers is not excluded. Using urea “inclusion” fractionation and low temp crystallization from acetone methyl,cis-9,cis-11-octadecadienoate was isolated. The methyl esters of commercially dehydrated castor oil fatty acids on the other hand, contained the following percentages of conjugated octadecadienoate isomers:cis, trans (trans, cis), 20.3;cis, cis, 8.0;trans, trans, 5.4. From these mixtures conc ofcis, trans (trans, cis)- andtrans, trans-octadecadienoates were prepared by fractional distillation and low temp crystallization. It was found that the conjugated octadecadienoates consisted of mixtures of positional isomers with double bonds mainly in the 8,10 and 9,11 positions with lesser amounts in the 7,9 and 10,12 positions.     

The determination of conjugatedcis-trans andtrans-trans methyl octadecadienoates by infrared spectrometry

Summary Pure conjugated methylcis-trans andtrans-trans octadecadienoates have been prepared and used to develop a method for the determination of these compounds by infrared spectrometry.Cis-trans compounds alone or in the presence oftrans-trans conjugation may be determined directly by the absorption at 10.55 μ. In the absence ofcis-trans isomers conjugatedtrans-trans octadienoates may be determined directly from the absorption at 10.11 μ. When both types of compounds are present however, a correction must be applied for the contribution of thecis-trans isomers to the 10.11 μ absorption of thetrans-trans material. A report of work done under contract with the U. S. Department of Agriculture and authorized by the Research and Marketing Act. The contract was supervised by the Northern Utilization Research and Development Division of the Agricultural Research Service, Peoria, Ill. This research was supported also by The Hormel Foundation.     

Study on the effect of antioxidants in the autoxidation of methyl nonconjugated octadecadienoates

Many studies have been published on the effect of antioxidants on unsaturated fatty acid esters but the differences of the effects of antioxidants on geometric isomers have never been investigated. In this study, methylcis-9,cis-12-octadecadienoate and itstrans isomer methyltrans-9,trans-12-octadecadienoate were used as methyl nonconjugated dienoates, and BHA, BHT, PG, NDGA, 4,4′-dihydroxy-3,5,3′,5′-tetratert-butyl diphenyl methane, L-thyroxine sodium salt,a-tocopherol and sesamol were used, as antioxidants. The differences of the effects of antioxidants on both geometric isomers were investigated by determining the induction period using the weighing method. Also determined were the infrared and ultraviolet spectra, peroxide values, conjugated diene contents, isolatedtrans double bond contents and molecular weights for the controls and the samples containing antioxidants. Thecis,cis isomer was more easily autoxidized and had a shorter induction period than thetrans,trans form. By the end of the induction period, no isolatedtrans double bond forms in thecis,cis isomer, but a considerable amount of isolatedtrans double bond decreased in thetrans,trans isomer. In general, the effects of antioxidants, except NDGA, on thecis,cis isomer were larger than thetrans,trans form.     

Autoxidation of methyl linoleate. Separation and analysis of isomeric mixtures of methyl linoleate hydroperoxides and methyl hydroxylinoleates

The mixture of conjugated diene hydroperoxide isomers obtained from autoxidation of methyl linoleate was separated by high performance liquid chromatography (HPLC). Four major isomers were obtained from adsorption chromatography and identified as the 9 and 13 positional isomers having thetrans-trans andcis-trans configurations. The latter geometrical isomers have thetrans double bond adjacent to the hydroperoxide group. The hydroxy compounds (methyl hydroxylinoleates) obtained from the hydroperoxides by NaBH₄ reduction were similarly separated but with improved resolution. This is the first instance of the complete separation of these compounds and provides a rapid method for their analysis. Unlike adsorption chromatography, reversed-phase chromatography separates the mixtures only according to the geometrical isomerism of the double bonds and not according to the position of the hydroxy or hydroperoxide function.     

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%...     

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.     

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.     

Gas chromatographic equivalent chain lengths of isomeric methyl octadecenoates and octadecynoates

Equivalent chain lengths (ECL) have been determined for methylcis-5-, 6-, 8-, 9-, 10-, 11-, 12-, 15-;trans-2-, 3-, 5-, 6-, 8-, 9-, 10-, 11-, 12-, 15-; and 17-octadecenoates and for methyl 5-, 6-, 8-, 9-, 10-, 11-, 12- and 15-octadecynoates on diethylene glycol succinate, polyphenyl ether and 100% β-cyanoethylmethylsiloxane capillary columns. Although the levels of ECL values differed, the patterns were similar for the different substrates. For methyl octadecenoates, except for 2-isomers, ECL generally increased with distance of double bond from the ester group but changed little from the 6 to the 10 position. Differences were smaller among isomerictrans esters than amongcis. In methyl octadecynoates there was a greater and more regular increase of ECL occurred as the triple bond moved away from the ester group. Presented at the AOCS Meeting, San Francisco, April 1969 No. Utiliz. Res. Dev. Div., ARS, USDA     

苯甲酸甲酯气相原位加氢制苯甲醛

提出了苯甲酸甲酯气相原位加氢制苯甲醛的路线。在常压固定床反应器上研究了浸渍法制备的Cu-MnO/γ-Al₂O₃双功能催化剂催化苯甲酸甲酯气相原位加氢制苯甲醛的反应性能,考察了催化剂的组成、反应温度、进样速率、酯/醇/水摩尔比等因素对苯甲酸甲酯转化率和苯甲醛选择性的影响。在优化的反应条件（苯甲酸甲酯/甲醇/水摩尔比为0.5/40/40、反应温度为420℃、进样速率为0.1 ml•min^-1）下,苯甲醛选择性可达到88.5%,苯甲酸甲酯的转化率为79.6%,且Cu-MnO/γ-Al₂O₃催化剂具有较好的稳定性。根据产物分布提出了苯甲酸甲酯原位加氢的反应机理。该反应体系不需要外部供应氢气,避免了氢气的生产和运输,简化了反应工艺。     

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.     

Comparative rates of oxidation of isomeric linolenic acids and their esters

Conclusion 1. The maximum velocities of oxygen absorption as measured by the Warburg-Barcroft respirometer at 40° and expressed as mols 0₂/mol substance/100 minutes was found for a series of octadecatrienoic acids and their esters to be as follows:alpha-eleostearic acid, 2.68;beta-eleostearic acid, 1.02; pseudo-eleostearic acid, 0.64; methyl pseudo-eleostearate, 0.42; alpha-linolenic acid, 0.52; ethyl linolenate, 0.24. 2. The data showed the effect of spatial configuration as well as type of unsaturation and functional grouping on the oxidation reaction. 3. The apparently pure fatty compounds were found to have induction periods, pointing to the autocatalytic nature of the oxidation reaction. This work was aided by grants from the National Livestock and Meat Board, the Hormel Foundation, and the Graduate School of the University of Minnesota. Presented before the Chicago convention of the American Oil Chemists’ Society on October 2, 1940.     

Separation and spectral data of the six isomeric ozonides from methyl oleate

The structures of the products obtained on ozonation of methyl oleate have been re-examined. The assignments for the six isomeric ozonides of methyl oleate have been made by¹H and¹³C nuclear magnetic resonance (NMR), which were consistent with the retention times observed in high-performance liquid chromatography; the assignments were confirmed by mass and infrared spectroscopy. Two triplets for the ozonide ring protons of thecis andtrans isomers in the normal (MOO1) and the two cross ozonides (MOO1 and MOO3) can be resolved by 400 MHz NMR. For MOO1 and MOO3, where the two ring carbons are equivalent, two peaks for the ring carbons of each cross ozonides are resolved in the¹³C NMR spectra, one for thecis and one for thetrans isomer. For MOO2, four peaks for the ring carbons are resolved in the¹³C NMR spectra, two for thecis and two for thetrans isomer.     

Mass transfer resistances in the palladium-catalyzed hydrogenation of methyl linoleate

The hydrogenation of methyl linoleate to methyl oleate and methyl stearate was studied in a 6-inch stirred batch reactor at 121°C and 45 psia. Several particle size fractions of a 1 per cent Pd-carbon catalyst were used to help separate the gas absorption resistance, the external mass transfer resistance, and the internal resistance to pore diffusion and reaction. Corrected to the same concentration of hydrogen, the initial rate of reaction for linoleate was 30 times that for oleate. This difference in reactivity and stronger adsorption of linoleate account for the high selectivity of 50–80.     

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.     

Partial hydrogenation of fatty acid methyl esters at supercritical conditions

Under supercritical or near-critical conditions propane is a very good solvent for both lipids and hydrogen. Thus, it is possible to generate an essentially homogeneous phase, in which the transport resistances for the hydrogen are eliminated. Therefore, the hydrogen concentration at the catalyst surface can be greatly increased, resulting in extremely high reaction rates and products having low trans fatty acid contents. In this study we present results from hydrogenation of rapeseed fatty acid methyl esters under near-critical and supercritical conditions. Temperature, residence time, hydrogen pressure, and catalyst life were varied systematically, using a statistical experimental design, in order to elucidate reaction rate and trans fatty acid formation as functions of the above variables. The experiments were carried out in a microscale fixed-bed reactor, using a 3% Pd-on-aminopolysiloxane catalyst. At 92 °C, a hydrogen pressure of 4 bar, and a residence time of 40 ms we obtained a trans content of 3.8 ± 1.7% at a iodine value of 70. Our results support the findings from traditional processes that at a constant iodine value (IV) the trans content decreases with decreasing temperature, increasing pH₂, and increasing residence time. The reaction rate at our best conditions was roughly 500 times higher than in traditional batch hydrogenation.     

Reaction rates of simultaneous dehydration and hydrogenation of castor oil

The reaction rates of simultaneous dehydration and hydrogenation of castor oil to make tallow-like hard fat were calculated through a simplified procedure which makes use of a new variable derived from the incremental change in hydrodxyl value and iodine value.