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.     

Two-step homogeneous conjugation and hydrogenation of methyl esters of unsaturated fatty acids

A new approach to the selective hydrogenation of unsaturated fatty acids is suggested. It consists of a two step process. The first is a selective conjugation of the double bonds, while the second consists of the hydrogenation reaction using a catalyst which is specific to conjugated systems. Potassiumt-butoxide was used as a conjugation catalyst and its activity and selectivity were tested at various concentrations, different molar ratios of catalyst to oil, and in various solvents. Phenanthrene chromium tricarbonyl was used as the hydrogenation catalyst and its activity tested at various concentrations, temperatures and in various solvents. UN Expert, Physical Organic Chemist.     

Selective conjugation of soybean esters to increase hydrogenation selectivity

Polyunsaturated fatty acid methyl esters of soybean oil (MeSBO) were selectively conjugated as a means of increasing the linolenate selectivity of various homogeneous and heterogeneous hydrogenation catalysts. Kinetics of the conjugation reaction in various solvents indicated that linolenate conjugated 5–8 times faster than linoleate. Selective conjugation of MeSBO with potassiumt-butoxide in dipolar solvents resulted in an increase in linolenate hydrogenation selectivity to 7–8 with Ni and Pd heterogeneous catalysts, and to 7–10 with homogeneous and heterogeneous chromium carbonyl catalysts.Trans-unsaturation in the hydrogenated products was only 1–3% with the chromium carbonyl catalysts, in contrast to 30–39% with the heterogeneous metal catalysts. Triglycerides were readily converted to partial glycerides andt-butyl esters with the potassiumt-butoxide reagent. Presented at the AOCS North Central Section Symposium, March 1980.     

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.     

High oleic oils by selective hydrogenation of soybean oil

High oleic (monoene) oils were obtained from soybean oil by selective hydrogenation with copper catalysts. A mixture of nickel and copper chromite catalyst had activity suitable for producing the high monoene oils. A new catalyst (copper-on-Cab-O-Sil) prepared in the Laboratory was more active than commercial copper catalysts. Hydrogenated oils contained 61–72% monoenoic and 14–24% dienoic acids, and there was essentially no increase in stearic acid. Thetrans-isomer content of these oils varied between 17% to 32%. Double bonds in the monoene were distributed along the molecule from C₆ to C₁₅, but were located preferentially in the C₉ position for thecis-monoene and in the C₁₀ and C₁₁ positions for thetrans-monoene. When the iodine value of these high monoene oils was about 90–95, they remained liquid above 28 C. Citric acid treatment reduced the copper content of hydrogenated oils to a level that was comparable to that of the original soybean oil. Presented at the AOCS Meeting, Chicago, October 1967. Food and Agricultural Organization representative from Rumania. No. Utiliz. Res. Dev. Div., ARS, USDA.     

The thermal cracking of soybean/canola oils and their methyl esters

Triacyl glycerides (TGs) are naturally occurring oils produced by a significant variety of crops, microorganisms (bacteria and algae), and animals (certain fats). The diversity and prevalence of the sources of these compounds suggest that they may serve as an attractive alternative to crude oil as the feedstock for the production of transportation fuels and certain industrial chemicals — organic compounds with carbon chain lengths in the range of C₇ to C₁₅. In the present study a series of batch thermal cracking reactions was performed using soybean oil and canola oil under reaction conditions leading towards attractive yields of potentially valuable (as fuels and/or chemicals) shorter chain products. An attractive yield of alkanes and fatty acids (from oil cracking) or esters (from biodiesel) was obtained. From a parametric study reaction temperature, followed by residence time, was found to have the most significant effect. Significantly, cracking under increased pressures in a hydrogen atmosphere did not improve the yields of desirable species.     

Bromination of methyl esters of soybean fat acids and methyl linoleate with N-bromosuccinimide

1. The reaction of N-bromosuccinimide with methyl esters of soybean fat acids and with methyl linoleate has been investigated, and the influence of changes in the conditions of reaction has been studied.
2. The reaction of brominated methyl esters of soybean fat acids with sodium methoxide produced both methoxylated products and a dimer-like substance.
3. The reaction of brominated methyl esters of soybean fat acids with sodium cyanide and cuprous cyanide did not result in significant replacement of bromine with the cyano group.

     

The hydrogenation of soybean oil

Journal of the American Oil Chemists' Society - 1     

Cr(CO)3-complexed,silica-bonded polyphenylsiloxane as a stereoselective catalyst for hydrogenation of sorbate and soybean methyl esters

A silica-bonded complex was prepared by reacting polyphenylsiloxane with silylated Chromosorb and then with Cr(CO)₆. This complex catalyzed stereoselective hydrogenation of sorbate tocis-3-hexenoate. Soybean methyl esters were hydrogenated at 210 C in cyclohexane to form products high incis unsaturation. The recovered catalyst could be recycled once with methyl sorbate. IR showed decreased Cr(CO)₃ in the recovered catalysts, and the hydrogenation products contained inactive Cr.     

多不饱和脂肪酸及其酯的选择性加氢研究进展

尽管部分加氢是提高多不饱和脂肪酸及其酯性能的一种有效方式,但加氢过程中反式异构体的生成会影响油脂的品质,因此,对油脂加氢反应中如何减少反式异构体生成的研究具有一定的意义。首先,介绍了多不饱和脂肪酸及其酯加氢机理及反式异构体生成的原理。然后,综述了加氢方式、加氢催化剂(包括活性组分、助剂、载体及催化剂制备方法)对反式异构体生成影响的研究新进展。最后,对影响反式异构体生成的规律进行总结,进而提出了多不饱和脂肪酸及其酯加氢过程中以减少反式异构体生成为目的的措施。     

Evaluation of partially hydrogenated methyl esters of soybean oil as biodiesel

Biodiesel, an alternative fuel derived from vegetable oils or animal fats, continues to undergo rapid worldwide growth. Specifications mandating biodiesel quality, most notably in Europe (EN 14214) and the USA (ASTM D6751), have emerged that limit feedstock choice in the production of biodiesel fuel. For instance, EN 14214 contains a specification for iodine value (IV; 120 g I₂/100 g maximum) that eliminates soybean oil as a potential feedstock, as it generally has an IV >120. Therefore, partially hydrogenated soybean oil methyl esters (PHSME; IV = 116) were evaluated as biodiesel by measuring a number of fuel properties, such as oxidative stability, low‐temperature performance, lubricity, kinematic viscosity, and specific gravity. Compared to soybean oil methyl esters (SME), PHSME were found to have superior oxidative stability, similar specific gravity, but inferior low‐temperature performance, kinematic viscosity, and lubricity. The kinematic viscosity and lubricity of PHSME, however, were within the prescribed US and European limits. There is no universal value for low‐temperature performance in biodiesel specifications, but PHSME have superior cold flow behavior when compared to other alternative feedstock fuels, such as palm oil, tallow and grease methyl esters. The production of PHSME from refined soybean oil would increase biodiesel production costs by US$ 0.04/L (US$ 0.15/gal) in comparison to SME. In summary, PHSME are within both the European and American standards for all properties measured in this study and deserve consideration as a potential biodiesel fuel.     

Selective hydrogenation of soybean oil: XII. Trialkyl aluminum-copper stearate homogeneous catalysts

The reaction of copper stearate with triethylaluminum (TEAL) formed a soluble catalyst that promoted the selective hydrogenation of the linolenyl groups in soybean oil. This homogeneous catalyst was more active than copper-chromite. The activity was enhanced by the addition of silica, alumina or titania. Ethyl alcohol accelerated the hydrogenation when it was added in small amounts and retarded hydrogenation when increased amounts were added. More active and, in some cases, more selective catalysts were formed when TEAL was replaced by trialkylaluminum compounds containing longer chain length in the alkyl groups. Among other organometallics tested, diethylmagnesium and diisobutylaluminum ethoxide formed catalysts with activity comparable to heterogeneous catalysts (K_Le/K_Lo=2.8~5.2) was less than that obtained with copper-chromite (12~14), but greater than that of commercially used nickel catalysts (2). Isomerization, as measured by the percentage oftrans isomers formed, was similar to that of heterogeneous copper catalysts (%trans/ΔIV=0.6~0.7). Presented at the AOCS meeting in New Orleans, May 1981.     

Hydrogenation of methyl sorbate and soybean esters with polymer-bound metal catalysts

New polymer-bound hydrogenation catalysts were made by complexing PdCl₂, RhCl₃·3H₂O, or NiCl₂ with anthranilic acid anchored to chloromethylated polystyrene. The Pd(II) and Ni(II) polymers were reduced to the corresponding Pd(O) and Ni(O) catalysts with NaBH₄. In the hydrogenation of methyl sorbate, these polymer catalysts were highly selective for the formation of methyl 2-hexenoate. The diene to monoene selectivity decreased in the order: Pd(II), Pd(O), Rh(I), Ni(II), Ni(O). Kinetic studies support 1,2-reduction of the Δ4 double bond of sorbate as the main path of hydrogenation. In the hydrogenation of soybean esters, the Pd(II) polymer catalysts proved superior because they were more active than the Ni(II) polymers and produced lesstrans unsaturation than the Rh(I) polymers. Hydrogenation with Pd(II) polymers at 50~100 C and 50 to 100 psi H₂ decreased the linolenate content below 3% and increasedtrans unsaturation to 10~26%. The linolenate to linoleate selectivity ranged from 1.6 to 3.2. Reaction parameters were analyzed statistically to optimize hydrogenation. Recycling through 2 or 3 hydrogenations of soybean esters was demonstrated with the Pd(II) polymers. In comparison with commercial Pd-on-alumina, the Pd(II) polymers were less active and as selective in the hydrogenation of soybean esters but more selective in the hydrogenation of methyl sorbate. Presented at ISF-AOCS Meeting, New York, April 1980.     

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.     

Displacement of the double bonds during hydrogenation of unsaturated fatty acid methyl esters

Summary The displacement of the double bond of several unsaturated fatty acid methyl esters during hydrogenation with a nickel-kieselguhr catalyst at 180°C. was investigated. The analysis of the dicarboxylic acids (obtained by oxidation of the reaction products with KMnO₄ in acetic acid solution) by means of partition chromatography enabled a reliable semiquantitative determination of the position isomers formed. During hydrogenation of methyl esters of oleic, elaidic, petroselinic, and linoleic acid formation of large amounts of position isomers was proved to occur. Migration of the double bonds in both directions took place but was in all cases strongly pronounced in a direction opposite the ester group. The place and configuration (cis or trans) of the double bonds in the starting material apparently were of little importance in this respect. It follows that hydrogenation of fatty acid esters leads to products which are far more complicated, as is generally known. This is especially of importance with respect to the application of hydrogenated fatty oils in the food industries.     

Efficacy of myricetin as an antioxidant in methyl esters of soybean oil

The antioxidant activity of myricetin, a natural flavonol found in fruits and vegetables, was determined in soybean oil methyl esters (SME) and compared with α‐tocopherol and tert‐butylhydroquinone (TBHQ) over a 90‐day period employing EN 14112, acid value, and kinematic viscosity methods. Myricetin had greater antioxidant activity than α‐tocopherol, but was inferior to TBHQ. Synergism was observed between myricetin and TBHQ, but antagonism between α‐tocopherol and either myricetin or TBHQ was discovered. A binary mixture of myricetin and TBHQ at 1000 ppm (1:1) was the most effective treatment investigated at inhibiting oxidation of SME. Myricetin was not completely soluble in SME at 1000 ppm, suggesting that 500 ppm is a more appropriate treatment level. Pro‐oxidant activity of α‐tocopherol was observed when added to SME obtained from crude soybean oil, but antioxidant behavior was observed in distilled SME. Addition of α‐tocopherol to methyl esters initially free of antioxidants revealed that 600–700 ppm was the optimum concentration for antioxidant activity. Acid value and kinematic viscosity remained within prescribed specifications after 90 days, despite failure of a number of samples with regard to EN 14112, suggesting that these parameters are insufficient as sole indicators of oxidation stability.     

亚临界相脂肪酸甲酯加氢制备脂肪醇

以Cu - Zn为催化剂,在正己烷亚临界状态下以脂肪酸甲酯为原料加氢制备脂肪醇.考察了正己烷用量、温度、氢气与原料油体积比对反应的影响,并对Cu - Zn催化剂和Cu - Cr催化剂的催化活性进行了比较.结果表明,在系统压力6.0 MPa,反应温度250℃,空速0.8h-1,正己烷与脂肪酸甲酯体积比7∶1,氢气与原料油体积比250∶1的条件下脂肪酸甲脂转化率为99.5％,脂肪醇选择性为99.6％,Cu - Zn催化剂的催化活性和选择性均优于Cu - Cr催化剂.     

Transfer hydrogenation and transfer hydrogenolysis: XII. Selective hydrogenation of fatty acid methyl esters by various hydrogen donors

The selective hydrogenation of methyl linoleate was studied using various organic compounds as hydrogen sources in the presence of homogeneous and metallic palladium catalysts. Complete selectivity to monoenes and relatively little formation of isolatedtrans double bonds were realized by the hydrogen transfer from L-ascorbic acid at 47% conversion of starting material to hydrogenation products. The hydrogenation bytrans-1,2-cyclohexanediol catalyzed by RuH₂(PPh₃)₄ also showed rather high selectivity tocis-monoenes. In the reaction catalyzed by RuH₂(PPh₃)₄, also showed rather high selectivity tocis-monoenes. In the reaction catalyzed by RuH₂(PPh₃)₄, the presence of these hydroxy compounds increased the isomerization of methyl elaidate tocis-monoenes.     

Intrinsic selectivities and yields in the catalytic hydrogenation of polyenoic fatty acid methyl esters

Precise values of the intrinsic selectivities and yields for the hydrogenation products of methyl linolenate (Ln) and methyl linoleate (L) obtained under carefully controlled conditions using a commercial Ni catalyst are presented and analyzed in detail. The existence of a preferential adsorption of Ln and a significant co-hydrogenation of its double bonds are confirmed as being the dominant features under typical vegetable oil processing conditions. It is shown that the values of the selectivities that are obtained from the classical consecutive reactions network account for the intrinsic selectivity of the catalyst only while hydrogenating feedstocks with moderate to low (<10%) contents of Ln. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional del Lltoral (U.N.L.)