Catalytic behavior of palladium in the hydrogenation of edible oils

Palladium supported on alumina was used to hydrogenate soybean and canola oil. Previous literature reports indicated that palladium forms moretrans isomers than nickel. At 750 psig, 50 ppm palladium, and at 70 C, only 9.4%trans were formed when canola oil was hydrogenated to IV 74. In general, high pressure and low temperature favored lowtrans formation with no appreciable loss in catalyst activity. The effect of pressure, temperature and catalyst concentration on reaction rate,trans formation and selectivity is presented. A survey of various catalyst supports is discussed. Apparent activation energies of 6.3 to 8.9 kcal/mol were obtained; they are in good agreement with values reported in the literature.     

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.     

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.     

Reuse of copper catalyst in continuous hydrogenation

Continuous hydrogenation of soybean oil using copper catalyst can be improved economically by reusing the catalyst. A hydrogenated oil with an approximate iodine value drop of 25 was attained by regulating the conditions and size of the reactor. Catalyst was removed by centrifuge and recycled. Reaction products were evaluated to determine catalyst activity, linolenate selectivity andtrans formation. By adding 0.2–0.4% fresh catalyst each time, the activity was retained. Linolenate selectivity ranged from 6 to 11 andtrans formation, expressed as specific isomerization, ranged from 0.63 to 0.78.     

The effect of trans-isomers on the physical properties of hydrogenated oils

Data have been presented which indicate a positive relationship between thetrans-isomer content of a hydrogenated oil and the congeal point, Wiley melting-point, and solids index. It has also been shown that cottonseed oil and soybean oil undergo substantially the same type of reaction under identical hydrogenating conditions. This conclusion is based on the relationship oftrans-isomer formation to total reduction in unsaturation up to the point that equilibrium is reached and saturation of thetrans-isomers occurs. This equilibrium was noted at between 60–70 iodine value. The relationship oftrans-isomer formation to the total reduction in double bonds can be expressed as the hydrogenation index. This is a reliable indication of the type of reaction taking place up to the point where appreciable hydrogenation of thetrans-isomers occur.     

Laboratory-scale continuous hydrogenation: Effect of pressure

A laboratory-scale, high-pressure, continuous reactor was used to partially hydrogenate soybean oil with copper catalysts. Effects of pressure on the kinetics of the reaction were studied by conducting experiments in a central composite design. The interaction of pressure (75\s-200 psig) with the other independent variables of temperature (155\s-255 C) and copper concentration (0.15\s-1.85%) was evaluated. Dependent variables studied were linolenate selectivity and formation of trans isomers and conjugated dienes. in addition, effects of pressure up to 500 psig, use of experimental and commercial copper catalysts and comparison of continuous with high-pressure batch rections were investigated. Linolenate selectivity (8\s-10) and trans-isomer formation were not significantly affected by any of the independent variables. Conjugated dienes were eliminated as products of the reaction when pressure was above 200 psig. Experimental copper-silica catalyst gave a 1.6-fold increase in reaction rate over commercial copper catalysts. Presented at ISF-AOCS meeting, New York, April 1980.     

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.     

“Zerotrans” margarines: Preparation,structure, and properties of interesterified soybean oil-Soy trisaturate blends

The sodium methoxide-catalyzed random interesterification of liquid soybean oil-soy trisaturate blends was explored as a possible route to zerotrans margarine oils. Lipase hydrolysis of the rearranged fats showed that with 0.2% catalyst, interesterification is complete within 30 min at 75-80 C. The glyceride structures of natural and randomized soybean oil-soy trisaturate blends are presented, and relationships between their structure and physical properties are discussed. Organoleptic evaluations showed that randomization of the glyceride structure had no adverse effects on flavor and oxidative stability. Flavor evaluations made against a commercially hardened tub margarine oil showed that interesterified oil had comparable initial and aged flavor scores. X-ray diffraction studies demonstrated that randomized soybean oil-soy trisaturate blends possess the beta-prime crystal structure desirable for use in margarine production. Dilatometric data indicate that random interesterification of 20% by weight of soy trisaturate into the glyceride structure of soybean oil provides a product having a solid fat index suitable for use in a soft tub margarine. Presented at the AOCS Meeting, Chicago, September 1976.     

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.     

Hydrogenation of fatty oils with palladium catalysts. V. Products of the tall oil industry

Conditions were found for reducing tall oil distillate to an iodine number of 22 with a sufficiently small amount of palladium catalyst to make the process commereially feasible. The operating conditions were 200°C and 2,600 psi. Tall oil fatty acids were reduced with palladium and the concentration of linoleic acid,cis-oleic acid, saturated acid, andtrans isomers were determined as a function of iodine number. The five-platinum group metals (Pt, Pd, Ir, Rh, Ru) were compared as to activity, selectivity of partial hydrogenation, and tendeney to formtrans-isomers.     

Low-<Emphasis Type="Italic">trans</Emphasis> Shortening and Spread Fats Produced by Electrochemical Hydrogenation

Partially hydrogenated soybean oils (90–110 IV) were prepared by electrochemical hydrogenation at a palladium/cobalt or palladium/iron cathode, moderate temperature (70–90 °C) and atmospheric pressure. The trans fatty acid (TFA) contents of 90–110 IV products ranged from 6.4 to13.8% and the amounts of stearic acid ranged from 8.8 to 15.4% (the higher stearic acid contents indicated that some reaction selectivity had been lost). The solid fat values and melting point data indicated that electrochemical hydrogenation provides a route to low-trans spreads and baking shortenings. Shortenings produced by conventional hydrogenation contain 12–25% trans fatty acids and up to 37% saturates, whereas shortening fats produced electrochemically had reduced TFA and saturate content. Electrochemical hydrogenation is also a promising route to low-trans spread and liquid margarine oils. Compared to commercial margarine/spread oils containing 8–12% TFA, the use of electrochemical hydrogenation results in about 4% TFA. Names are necessary to report factually an available data: the USDA neither guarantees nor warrants the standard of the product, and the use of the name USDA implies no approval of the product to the exclusion of others that may also be suitable.     

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.     

Catalytic behavior of ruthenium in soybean oil hydrogenation

Soybean oil was hydrogenated with a carbon‐supported ruthenium catalyst (Ru/C) at 165 °C, 2 bar H₂ and 500 rpm stirring speed. Reaction rates, trans isomer formation, selectivity ratios and melting behaviors of the samples were monitored. No catalytic activity was found for the application of 10 ppm of the catalyst, and significant catalytic activity appeared at >50 ppm of active catalyst. The catalyst concentration had an effect on the reaction rate of hydrogenation, but the weight‐normalized reaction rate constant (k_c) was almost independent of the catalyst concentration at lower iodine values. Ru/C generated considerable amounts of trans fatty acids (TFA), including high amounts of trans 18:2, and also stearic acid, due to its very non‐selective nature. The selectivity ratios were found to be low and varied between 1.12 and 4.32 during the reactions. On the other hand, because of the low selectivity, higher slip melting points and solid fat contents at high temperatures were obtained than those for nickel and palladium catalysts. Another different characteristic of this catalyst was the formation (max 1.67%) of conjugated linoleic acid (CLA) during hydrogenation. Besides, CLA formation in the early stages of the reactions did not change very much with the lower iodine values.     

Rapeseed oil in a two-component margarine base stock

A two-component margarine base stock with liquid oil as one component allowed for a lowertrans fatty acid content and at the same time provided for a higher essential fatty acid level than a one-component base stock. Transesterification softened a two-component margarine base stock and resulted in a steeper solid fat index curve, but did allow for a lowertrans fatty acid level in a margarine base stock. The high content of erucic acid in rapeseed oil did not change the physical properties of a margarine base stock and provided a good hardstock when this oil was hydrogenated. The use of a hydrogenated rapeseed oil ensured interchangeability of liquid oils in blends and rearranged blends, also seemed superior to soybean hardstocks in this respect.     

Oxidative stability of soybean oil products obtained by regioselective chemical interesterification

Oxidative stability of products produced as potential margarine basestock from soybean oil and methyl stearate by a novel chemical regioselective interesterification was evaluated. The oxidative stability of the products was evaluated by peroxide formation and volatile analysis during storage in the dark with oxygen at 60°C for 72 h. The product obtained by regioselective interesterification resulted in the lowest peroxide formation and volatile concentration sample in comparison with soybean oil and the randomized product of the regioselective interesterified product. Regioselective interesterification of soybean oil with methyl stearate produced a product with increased oxidative stability. Presented at 84th American Oil Chemists’ Society Annual Meeting, April 26–30, 1993, Anaheim, California.     

Low trans-Fat Spreads and Shortenings from a Catalyst-Switching Strategy

Low trans fatty acid basestocks suitable for blending with liquid oils to make spreads and shortenings are prepared by using a two-step hydrogenation process. The first step uses a nickel catalyst to hydrogenate soybean, canola, high-oleic sunflower, and high-oleic safflower oils to a predetermined iodine value. At this point in the reaction, the second step commenced. Addition of a platinum catalyst at 80 °C and 73 psi hydrogen pressure allowed for hydrogenation to proceed to iodine values of 40–50. These products had 11–18% trans fatty acid content. These were then blended with soybean oil (5–50% basestock) to give products with bulk properties similar to commercial spreads and shortenings but with about one third the levels of trans fat. Names are necessary to report factually an available data: the USDA neither guarantees nor warrants the standard of the product, and the use of the name USDA implies no approval of the product to the exclusion of others that may also be suitable.     

Hydrogenation of soybean oil with copper catalysts containing small amounts of nickel catalysts

Reaction rates, linolenate/linoleate reaction selectivity,trans formation, and conjugated diene formation were determined for mixed commerical catalysts containing 0.5, 1, 2, 10, and 20 parts nickel catalyst (25% nickel) per 1000 parts copper chromite catalyst (ppt) and at catalyst concentrations in the oil of 1.0, 0.5, and 0.25%. The rate of hydrogenation increased as the amount of nickel increased. Addition of 0.5, 1, and 2 ppt nickel catalyst to copper chomite catalyst resulted in a small decrease in selectivity compared with straight copper chromite. When soybean oil was hydrogenated with these mixed catalysts sufficiently to reduce linolenate to 0, iodine values were 102–108 compared to 109–112 for straight copper chromite and to less than 80 for straight nickel. Presented at the AOCS Meeting, New Orleans April 1973. ARS, USDA.     

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.     

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.     

Fixed- Bed continuous hydrogenation of soybean oil with palladium- Polymer supported catalysts

To compare a continuous hydrogenation system with batch hydrogenation, soybean oil was treated with Pd and Ni catalysts in a fixed-bed system under conditions that gave trickle flow. The influence of processing variables such as space velocity, pressure, temperature and hydrogen flow on the selectivity, specific isomerization and the activity was investigated. Both the Pd and Ni catalysts gave significantly lower specific isomerization(trans isomer per drop in Iodine Value) when compared to reported values for batch hydrogenation with similar type catalysts. The linolenate and linoleate selectivities were also significantly lower. Heterogenized homogeneous Pd-on-polystyrene catalyst gave lower specific isomerization formation and higher selectivity than carbon-supported Pd catalyst at same conditions. This work indicates that Pd-on-styrene, Pd-on-carbon and extruded Ni catalysts, in fixed-bed continuous hydrogenation can produce soybean oil of desirable composition after further optimization.