Empirical modeling of soybean oil hydrogenation

Empirical hydrogenation models were generated from statistically designed laboratory experiments. These models, consisting of a set of polynomial equations, relate the operating variables of soybean oil hydrogenation to properties of the reaction and of the fat produced. These properties include reaction rate,trans-isomer content and melting point. Operating variables included in the models were temperature, hydrogen pressure, catalyst concentration, agitation rate and iodine value. The effects of catalyst concentration and agitation rate were found to be significant in determiningtrans-isomer content, which in turn influences the melting characteristics of the hydrogenated oil. Pressures above 30 psig were found to have little effect ontrans-isomer content, although pressure was very important in determining reaction rate. Reaction temperature was observed as the most important factor in determining thetrans-isomer content for a given iodine value. Generally, 50 to 60%trans isomer content is predicted by the model for the iodine value range and operating conditions used in this study. Thus, these predictive models can assist in scaling up hydrogenation processes and in determining the optimum operating parameters for running commercial hydrogenation. Presented at the AOCS Meeting, Chicago, May 1983.     

Supported gold catalysis in the hydrogenation of canola oil

The catalytic activity of gold supported on silica orγ-alumina has been studied in the hydrogenation of canola oil. In the hydrogenation of butadiene and pentene using these catalysts, high stability, low yield oftrans-isomers and high monoene selectivity have been reported in the literature. Catalysts containing 1% and 5% Au w/w on porous silica andγ-alumina were active in hydrogenating canola oil in the range of 150 to 250 C and 3550 to 5620 kPa. The activity level of these catalysts was about 30 times lower than that shown by the standard AOCS Ni catalyst based on the concentration of metal (g Au/L oil). Up to 91% monoene content was obtained using these catalysts in comparison with a maximum of 73% for the AOCS standard Ni catalysts. Gold catalysts can be recovered easily by filtration and reused several times without a decrease in activity. The hydrogenated oil was nearly colorless. No gold was detectable in the oil. Contrary to claims in the patent literature, the gold catalyst produces higher concentrations oftrans-isomers than does nickel. However, using gold catalysts the complete reduction of linolenic acid in canola oil can be achieved at a lowertrans-isomer content in the products than that obtained by using the AOCS standard nickel catalyst.     

Analysis and monitoring oftrans-isomerization by IR attenuated total reflectance spectrophotometry

Attenuated total reflectance for IR determination oftrans-isomers in fats appears to have distinct advantages over procedures currently used. The AOCS standard method CD 14-61 requires weighing and quantitative dilution of a sample with carbon disulfide before spectrophotometric analysis at 10.3 μm. In contrast, according to the attenuated total reflectance analytical procedure, one neither weighs nor dilutes but merely fills the cell with oil and reads at 10.3 μm. In addition to analyses fortrans-isomers in liquid oils, margarines and shortenings, attenuated total reflectance enables one to monitortrans-development continuously during hydrogenation. The presence of catalyst in unfiltered hydrogenated oils does not interfere with attenuated total reflectance measurements in contrast to classical transmission measurements. Unfiltered oil from the hydrogenator can be circulated through the attenuated total reflectance cell to recordtrans-isomerization during the reaction. ARS, USDA.     

Behavior of hydrogenation catalysts. I. Hydrogenation of soybean oil with palladium

A statistical method for evaluation of catalysts was used to determine the behavior of palladium catalyst for soybean oil hydrogenation. Empirical models were developed that predict the rate,trans-isomer formation, and selectivity over a range of practical reaction conditions. Two target iodine value (IV) ranges were studied: one range for a liquid salad oil and the other for a margarine basestock. Although palladium has very high activity, it offered no special advantage intrans-isomer formation or selectivity. Palladium can substitute for nickel catalyst, at greatly reduced temperature and catalyst concentrations, for production of salad oil or margarine basestock from soybean oil. Presented at the AOCS meeting, Chicago, May 1983.     

Isomerization during hydrogenation of soap: II. Potassium elaidate and potassium linoleate

Potassium elaidate in slightly alkaline solution was hydrogenated for up to 7 hr with 1.5% of Rufert nickel catalyst at 150 C and 20 kg/sq cm pressure. Potassium linoleate was similarly hydrogenated with 1.0% catalyst for 7 hr, and the hydrogenation continued for another 7 hr after addition of 0.5% fresh catalyst. Periodic samples from each were analyzed for component acids. The positional isomers in thecis andtrans monoenes, isolated by preparative argentation thin layer (TLC) or column chromatography, were estimated after oxidation to dicarboxylic acids. Some diene fractions were isolated for further examination. In potassium elaidate hydrogenation,cis monoenes were initially produced in considerable amounts, but to a lesser extent thereafter. Positional isomers were similarly distributed in bothcis andtrans monoenes after prolonged hydrogenation. In the hydrogenation of potassium linoleate, a drop in iodine value (IV) of 60 units occurred in the first hour, and 38% oftrans monoenes (in which the 10- and 11-monoenes constitute 32% each) were formed. The IV then fell only slowly, and up to 38% ofcis monoene (mostly 9- and 12-isomers) was formed. Addition of fresh catalyst caused a major shift ofcis monoenes totrans forms. The diene fraction was mostly nonconjugated material with the first double bond at the 9, 8 and 10-positions. Minor amounts of conjugated dienes were present as well as a dimeric product.     

Industrial hydrogenation of cottonseed oil: A compositional study

Intermediate samples during a typical plant hydrogenation of cottonseed oil for vanaspati (shortening) manufacture have been examined for their fatty acid composition by gas-liquid chromatography andtrans isomers content by infrared spectrophotometry. In the initial stages, hydrogenation of linoleate proceeds almost exclusively in preference to that of oleate. During this period,trans isomers are also formed at a rapid rate. It has been proposed that this high selectivity and hightrans isomer formation are linked to the formation of conjugated diene from linoleate as a first step in the hydrogenation. It has been found that a linear relationship exists between the linoleate content and thetrans isomers content or the^k10.38 μ values of the glycerides. The practical utility of this plot is that it can be employed as a guide to arrest the process at any desired linoleate level.     

Selective hydrogenation of the cyclopropene acid groups in cottonseed oil

The cyclopropene acid groups in cottonseed oil can be modified by a light hydrogenation which will not produce large amounts oftrans isomers or lower the iodine value to a significant extent. Optimum conditions, as indicated by this investigation, are 105-115C, 20 psig hydrogen pressure, 0.1% electrolytic nickel as catalyst, and a low hydrogen-dispersion rate. Under milder conditions of hydrogenation the elimination of the cyclopropenes was accompanied by a lower formation oftrans isomers and a lower hydrogenation of noncyclopropenes, but the time required increased. In one hydrogenation carried out with commercial nickel catalyst, the 0.4% of malvalic acid groups in the cottonseed oil was hydrogenated completely whereas the iodine value was reduced by only 1.7 units and only 2.1% oftrans isomers was formed. AVinterization of cottonseed oils which had been hydrogenated to the point of eliminating their response to the Halphen test and in which only small amounts of saturated acid groups andtrans isomers had been formed gave yields equal to or better than those of the original oil. Hydrogénation actually increased the ease of winterization. 2 So. Utiliz. Ees. Dev. Div, ARS, USDA.     

Heterogeneous catalytic hydrogenation of canola oil using palladium

The hydrogenation of canola oil was studied using palladium black as a potential catalyst for producing partially hydrogenated fats with lowtrans-isomer content. Pressure (150\s-750 psig) appeared to have the largest effect ontrans-isomer formation. At 750 psig, 90 C and 560 ppm metal concentration, a maximum of 18.7%trans isomers was obtained at IV 53. A nickel catalyst produces about 50%rans isomers at the same IV. For palladium black, the linolenate and linoleate selectivities were 1.2 and 2.7, respectively. The maximum level oftrans isomers observed ranged from 18.7% to 42.8% (150 psig). Temperature (30\s-90 C) and catalyst concentration (80\s-560 ppm) affected the reaction rate with little effect ontrans-isomer formation and selectivities. At 250 psig and 50 C, supported palladium (5% Pd/C) appeared to be twice as active as palladium black. At 560 ppm Pd, 5% Pd/C produced 30.2%trans (IV 67.5), versus 19.0%trans for palladium black (IV 68.9). Respective linoleate selectivities were 15 and 6.6, while linolenate selectivities were approximately unity. Analysis of the oil samples by neutron activation showedapproximately a 1 ppm, Pdresidue after filtration.     

Catalysts for selective hydrogenation of soybean oil.1 II. Commercial catalysts

A survey of commercial hydrogenation catalysts demonstrated the higher selectivity (S_L= 2.4\s-2.7) of certain platinum, palladium and rhodium catalysts for hydrogenating linolenic components in soybean oil. Nickel catalysts generally showed selectivities below S_L=2.0 although skeletal nickel achieved higher values.Trans-isomers were in the range 7.8\s-15.4% for the above noble metal catalysts. Nickel catalysts provide a lesser degree of isomerization, 5.2\s-7.4% oftrans-isomers for the most selective catalysts. Presented at the AOCS Meeting at Toronto, 1962.     

Production of Low-trans Fatty Acids Edible Oil by Electrochemical Hydrogenation in a Diaphragm Reactor Under Controlled Conditions

Electrochemical hydrogenation is a novel, alternative process for selective hydrogenation of vegetable oils, because of its high extent of hydrogenation and low trans-isomer formation. Electrochemical hydrogenation of soybean oil in a diaphragm reactor with a formate ion concentration of 0.4 mol/l at pH 5.0 under moderate temperature conditions using a current density of 10 mA/cm² was investigated to identify the critical conditions affecting the selective hydrogenation reaction and the resulting fatty acid profile. The optimum composition was an oil-to-formate solution ratio of 0.3 (w/w), 2?C3 g EDDAB in 100 g soybean oil, and 0.8% Pd?CC catalyst loading. The electrochemical hydrogenation reaction of soybean oil was described by first-order kinetics, and the kinetic rate constants and reaction selectivity were determined accordingly. Re-use of the Pd?CC catalyst up to five times was found to be acceptable. A comprehensive evaluation revealed that the most significant conditions affecting the extent of hydrogenation and the trans fatty acids content of final products were operating temperature, pH of the formate solution, and catalyst loading.     

Hydrogenation practice

This paper deals with such topics as the changes in the molecular dimensions of a triglyceride during hydrogenation and the effect of catalyst structure on selectivity and filterability and the effect of sulfur on activity and isomerization, the prevention of aromatics formation during hydrogenation of highly unsaturated oils, explanation and prevention of green coloration of oil, the effect of phosphatides on selectivity andtrans-isomer formation. Heat saving equipment and process control are discussed.     

Selective homogeneous hydrogenation of triunsaturated fats catalyzed by tricarbonyl chromium complexes

The need for a selective catalyst to hydrogenate linolenate in soybean oil has prompted our continuing study of various model triunsaturated fats. Hydrogenation of methylβ-eleostearate (methyltrans,trans,trans-9,11,13-octadecatrienoate) with Cr(CO)₃ complexes yielded diene products expected from 1,4-addition (trans-9,cis-12- andcis-10,trans-13-octadecadienoates). Withα-eleostearate (cis,trans,trans-9,11,13-octadecatrienoate), stereoselective 1,4-reduction of thetrans,trans-diene portion yielded linoleate (cis,cis-9,12-octadecadienoate). However,cis,trans-1,4-dienes were also formed from the apparent isomerization ofα- toβ-eleostearate. Hydrogenation of methyl linolenate (methylcis,cis,cis-9,12,15-octadecatrienoate) produced a mixture of isomeric dienes and monoenes attributed to conjugation occurring as an intermediate step. The hydrogenation ofα-eleostearin in tung oil was more stereoselective in forming thecis,cis-diene than the corresponding methyl ester. Hydrogenation of linseed oil yielded a mixture of dienes and monoenes containing 7%trans unsaturation. We have suggested how the mechanism of stereoselective hydrogenation with Cr(CO)₃ catalysts can be applied to the problem of selective hydrogenation of linolenate in soybean oil. No. Market. Nutr. Res. Div., ARS, USDA.     

Cocoa butter-like fats from fractionated cottonseed oil: I. preparation

The manufacture of salad oil from cottonseed oil can produce a byproduct stearine fraction consisting essentially of 1-palmito and 1,3-dipalmito triglycerides of oleic and linoleic acids and having an iodine value of ca. 72. Hydrogenation of this fraction to an iodine value of ca. 28–42, under conditions simultaneously selective and conducive to a low rate oftrans-isomer formation, yielded a product that could readily be fractionated to produce over 60% of a cocoa butter-like fat. The conditions of fractionation influenced the yield and properties. Fractionation was most easily accomplished by tempering the solidified hydrogenation product and leaching with a petroleum naphtha or acetone. ARS, USDA.     

Content of trans-fatty acids in edible margarines

Fatty acid composition, including trans-isomers, was determined for four types of imported margarines consumed by the Bulgarian population. The results were compared with data obtained from a Bulgarian edible margarine produced under German license. Fatty acid composition and trans-isomer content were determined by gas chromatography of fatty acid methyl esters on a packed and capillary column, respectively. The total contents of trans-isomers of oleic and linoleic acid were within the ranges of 1.9–8.0% and 0.4–1.4%, respectively. The Bulgarian margarine contained similar quantities of trans-isomers.     

Dimorphotheca sinuata lipoxygenase: Formation of 13-L-hydroperoxy-cis-9,trans-11-octadecadienoic acid from linoleic acid

Lipoxygenase (EC 1.13.1.13) from the seed ofDimorphotheca sinuata oxidized linoleic acid to predominantly 13-L-hydroperoxy-cis-9,trans-11-octadecadienoic acid. When the reaction proceeded at pH 6.9, the 13-hydroperoxide was the only isomer detected; but at pH 5.1, the 13-isomer was 92% of the total, the remaining 8% being the 9-hydroperoxide. At both pH's small amounts of hydroxyoctadecadienoic acid accumulated during the reaction. This acid from the pH 6.9 reaction was analyzed as 13-hydroxy-cis,trans-octadecadienoic. The postulate advanced by many workers that dimorphecolic acid, 9-D-hydroxy-trans-10,trans-12-octadecadienoic acid, is biosynthesized via a lipoxygenase product was not proved. Although the product specificity ofD. sinuata lipoxygenase is like that of lipoxygenase type 1 from soybeans, its inactivity at pH 9 demonstrated that it is a novel enzyme. ARS, USDA.     

Effect of some isothiocyanates on the hydrogenation of canola oil

Sulfur compounds were added to refined and bleached canola oil before hydrogenation in the form of allyl, heptyl and 2-phenethyl isothiocyanates, and the effects on hydrogenation rate, solid fat content and percentagetrans fatty acids were determined. The poisoning effect was most pronounced with allyl isothiocyanate and least with phenethyl isothiocyanate. As the amount of added sulfur increased, the hydrogenation rate decreased. Of the three isothiocyanates used, allyl isothiocyanate caused formation of larger amounts oftrans isomers. An increased sulfur level in the oil resulted in increased solid fat content andtrans isomer level. Allyl isothiocyanate also caused formation of larger amounts of solid fat than other isothiocyanates at all levels of sulfur addition.     

Reactivity of fatty acids in the different positions of the triglycerides during hydrogenation of canola oil

Canola oil was hydrogenated under selective and nonselective conditions. After various hydrogenation times, the triglycerides were hydrolyzed by pancreatic lipase and the monoglycerides separated by TLC. Triglycerides and monoglycerides were analyzed for fatty acid composition andtrans isomer content. The reaction rate in the 2- and 1,3-positions of the glycerides was identical and of first order kinetics. Since the 2-position of the canola oil contained higher levels of 18:2 acids, the rate of change was greater than in the 1,3-positions. There were indications of a slightly lower rate oftrans formation in the 2-position during nonselective hydrogenation. Linoleate selectivities for the 2- and 1,3-positions were determined.     

Positional isomers formed during the hydrogenation of cottonseed oil

Summary A commercial cottonseed oil was hydrogenated under nonselective, normal, and selective conditions. The operating variables used were within the ranges of those ordinarily found in large-scale operations. For each run samples were withdrawn at iodine values of approximately 75, 62, and 48; and these samples were analyzed for the position of the donble bonds, content oftrans isomers, and content of linoleins. Double bonds were found in the 6 through 14 positions of the monounsaturated fatty acid groups resulting from the hydrogenations. On the basis of the percentage distribution of the double bonds, there appeared to be no marked tendency for the linoleoyl group to form 9- or 12-isomers of the oleoyl group. In the early stages of the selective hydrogenation the rate at which double bonds shifted from the 9-position was greater than the rate at which double bonds were hydrogenated. The conditions of hydrogenation did not have a marked effect on the distribution of the double bonds at iodine values of about 62 and 48. The conditions of hydrogenation did have a marked effect on the percentage oftrans bonds. At an iodine value of approximately 75 the content oftrans bonds, expressed as weight percentage of trielaidin, was 9.4 for the nonselective hydrogenation and 27.3 for the selective hydrogenation while at an iodine value of approximately 48 these values increased to 21.6 and 37.7, respectively. Presented at the 48th Annual Meeting. American Oil Chemists' Society, New Orleans, La., April 29–May 1, 1957. One of the laboratories of the Southern Utilization Research and Development Division, Agricultural Research Service, U. S. Department of Agriculture.     

The chemistry of polymerized oils. V. The autoxidation of methyl linoleate

1. The geometrical forms obtained during autoxidation of methyl linoleate at ordinary temperatures are largely conjugatedcis-trans andtrans-trans as shown by previous workers; there is a possibility that conjugatedcis-cis forms are also produced. 2. Thetrans-trans molecules arise partly, at least, by thermal rearrangement of already formedcis-trans peroxide. 3. Some proportion, at least, of thecis-trans molecules have theirtrans double bonds nearest to the hydroperoxide group. 4. A partial separation of the geometrical forms can be accomplished by reversed phase partition chromatography both on methyl linoleate hydroperoxides and on the corresponding mixed hydroxy compounds; isolation of thetrans-trans forms can be accomplished in the latter case by urea complex fractionation. 5. No position isomers except the known 9- and 13-isomers have been positively identified; there is a possibility that very minor amounts of the 2-isomer are formed; the 9- and 13-isomers are present in about equal amounts; the 11-isomer was not detected by the methods applied. 6. Various ways in which the linoleate autoxidation problem might be advanced further are suggested.     

Selectivity and isomerization during partial hydrogenation of cottonseed oil and methyl oleate: Effect of operating variables

Results are now available for hydrogenation of cottonseed oil and methyl oleate in which sufficient agitation was provided to eliminate mass transfer resistances from the catalyst surface. The ratio of thetrans-to-cis isomers of oleic acid groups approaches 2.0 even at high pressures and high degrees of agitation. The rates of hydrogenation for bothcis andtrans isomers and for positional isomers are all essentially identical. A reaction scheme has been devised that is consistent with extensive experimental data, and the method of evaluating the relative reaction rate constants for each step is outlined. Using these rates constants, selectivity can be quantitatively evaluated.