High Oleic and Low <Emphasis Type="Italic">Trans</Emphasis> Fatty Acid Formation by an Electrochemical Process

Electrochemical hydrogenation employing a mediator of formate/formic acid resulted in partial hydrogenation of vegetable and soybean oil at 20–40 °C and ambient pressure when palladium supported on alumina was employed as a catalyst. An oleic acid content of 48% with a corresponding iodine value of 81 for the vegetable oil hydrogenated at 20 °C was obtained. The total trans fatty acid content and especially the 18:1 trans fatty acid were found to increase with the reaction temperature and time. Nonetheless, relatively low total trans and 18:1 trans fatty acid (7 and 3.8%, respectively) contents were found when the vegetable oil was partially hydrogenated to achieve an iodine value of 112.     

Comparison of Soybean and Cottonseed Oils upon Hydrogenation with Nickel,Palladium and Platinum Catalysts

There is current interest in reducing the trans fatty acids (TFA) in hydrogenated vegetable oils because consumption of foods high in TFA has been linked to increased serum cholesterol content. In the interest of understanding the TFA levels, hydrogenation was carried out in this work on soybean oil and cottonseed oil at two pressures (2 and 5 bar) and 100 °C using commercially available Ni, Pd, and Pt catalysts. The TFA levels and the fatty acid profiles were analyzed by gas chromatography. The iodine value of interest is ~70 for all-purpose shortening and 95–110 for pourable oil applications. In all cases, higher hydrogen pressures produced lower levels of TFA. In the range of 70–95 iodine values for the hydrogenated products, the Pt catalyst gave the least TFA, followed closely by Ni, and then Pd, for both oils. For all three catalysts at 2- and 5-bar pressures and 70–95 iodine values, cottonseed oil contained noticeably less TFA than soybean oil; this is probably because cottonseed oil contains a lower total amount of olefin-containing fatty acids relative to soybean oil. Approximate kinetic modeling was also done on the hydrogenation data that provided additional confirmation of data consistency.     

Mediator-assisted electrochemical hydrogenation of soybean oil

In this study, formate ion was used as a shuttle for transferring hydrogen to the surface of a hydrogenation catalyst (7% Ni/SiO₂), where the soybean oil was reduced in such a way that the production of deleterious trans fatty acid was greatly reduced. The formate ion was regenerated at the cathode and thus acted as a mediator for the hydrogenation process. The effect of temperature, pH, and applied potential (current) on the fatty acid profile of the hydrogenated soybean oil was determined. The effects of oil and catalyst loadings on the final product quality were also determined. The application of a current density of resulted in hydrogenated product with desired fatty acid composition. Kinetic studies were also performed for experiments conducted at constant potential conditions. A model that assumes: (i) the rate of regeneration of formate from its oxidized form (bicarbonate ion) is limited by the mass transport effects, and (ii) second-order elementary reaction rate expression was developed to describe the hydrogenation reaction was developed and tested. A good correlation between the model predictions and experimental data was observed.     

Production of Low Acid Value Edible Oil with Reduced TFAs by Electrochemical Hydrogenation in a Diaphragm Reactor

A new diaphragm electrochemical system was devised and tested for hydrogenation of soybean oil under moderate processing temperature and atmospheric pressure. With proper loading of the catalyst Pd-C, the reactor was operated successfully for 6 h and yielded hydrogenated soybean oil containing 8.62% TFAs with an IV of 88.86 g I₂/100 g oil and an AV of 0.7 mg KOH/g oil. The low AV (acid value) of the hydrogenated oil, indicative of the oxidization tendency of the oil, is highly desirable from the industrial application standpoint. The low specific isomerization index was reached with 0.4 mol/L of formate ions at pH 5.0 under 60 °C using a constant applied current density (10 mA/cm²)_. The extent of hydrogenation was found to increase with increasing current density, formate ion concentration, reaction temperature, catalyst loading, and speed of agitation. It was characterized that the extent of hydrogenation under low pH (2.0–5.0) was controlled by the regeneration of formate ion, whereas under high pH (6.0–10.0) the hydrogenation was influenced strongly by the formate ion stability.     

Catalytic transfer hydrogenation of soybean oil methyl ester using inorganic formic acid salts as donors

The hydrogenation of soybean oil methyl esters using aqueous formic acid salts solutions and heterogeneous palladium-on-carbon catalyst was investigated. Complete hydrogenation of the methyl ester was achieved by mixing a concentrated aqueous alkali formate solution with the methyl ester at 80 C in the presence of the catalyst (0.2–0.4% Pd). At the initial stages of the reaction, the selectivity was significantly higher than conventional hydrogenation (hydrogenation under pressure) performed with the same catalyste.Cis-trans isomerization was similar to the behavior of conventional techniques.     

Catalytic Activity of a Thermoregulated, Phase-Separable Pd(II)-perfluoroalkylphthalocyanine Complex in an Organic/Fluorous Biphasic System: Hydrogenation of Olefins

A fluoroalkene-soluble tetrakis[heptadecafluorononyl]-substituted Pd(II)-phthalocyanine complex has been studied for olefin (styrene, 1-octene, trans-2-octene and cyclohexene) hydrogenation with molecular hydrogen in an organic/fluorous biphasic system [n-hexane/perfluoromethylcyclohexane (PFMCH)]. The palladium complex was found to be an active catalyst for styrene (100% conversion, TON = 634) and 1-octene (92%, TON = 596) at 80 °C and 15 bar of H₂ after 6 h of reaction time. The catalyst was recycled in nine consecutive reactions for the hydrogenation of styrene without the loss of activity or metal contamination.     

Catalytic transfer hydrogenation of soybean oil

The catalytic transfer hydrogenation of soybean oil by various hydrogen donors and solvents with palladium-oncarbon catalyst was investigated in batch and continuous modes. The choice of reaction conditions, donor and catalyst allowed the manufacture of partially hydrogenated oils or semi-solid fats with controlled fatty acid contents, iodine value, melting point and solid content index. The level of “iso” forms of fatty acids was similar to, and average initial selectivity was higher than that obtained with gaseous hydrogenation under pressure with a catalyst of the same type. The best results were obtained in aqueous solution with sodium formate as hydrogen donor at 60°C.     

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.     

Kinetics of catalytic transfer hydrogenation of soybean oil

The catalytic transfer hydrogenation of soybean oil was studied by using various concentrations of sodium formate solutions, an emulsifier and paladium on a carbon catalyst. Sodium formate concentration and addition of the emuldifier significantly affect the reaction rate because of their influence on the liquid/liquid interface. Under conditions in which diffusion effects are eliminated, all reactions carried out in diluted sodium formate solution obey first-order kinetics with respect to fatty acids. This allows control over the hydrogenation process of soybean oil, needed to obtain partially hydrogenated oil containing about 1% linolenic acid and a relatively high level of linoleic acid with no increase in the stearic acid concentration.     

Electrochemical hydrogenation of edible oils in a solid polymer electrolyte reactor. Sensory and compositional characteristics of low Trans soybean oils

Soybean oils were hydrogenated either electrochemically with Pd at 50 or 60°C to iodine values (IV) of 104 and 90 or commercially with Ni to iodine values of 94 and 68. To determine the composition and sensory characteristics, oils were evaluated for triacylglycerol (TAG) structure, stereospecific analysis, fatty acids, solid fat index, and odor attributes in room odor tests. Trans fatty acid contents were 17 and 43.5% for the commercially hydrogenated oils and 9.8% for both electrochemically hydrogenated products. Compositional analysis of the oils showed higher levels of stearic and linoleic acids in the electrochemically hydrogenated oils and higher oleic acid levels in the chemically hydrogenated products. TAG analysis confirmed these findings. Monoenes were the predominant species in the commercial oils, whereas dienes and saturates were predominant components of the electrochemically processed samples. Free fatty acid values and peroxide values were low in electrochemically hydrogenated oils, indicating no problems from hydrolysis or oxidation during hydrogenation. The solid fat index profile of a 15∶85 blend of electrochemically hydrogenated soybean oil (IV=90) with a liquid soybean oil was equivalent to that of a commercial stick margarine. In room odor evaluations of oils heated at frying temperature (190°C), chemically hydrogenated soybean oils showed strong intensities of an undesirable characteristic hydrogenation aroma (waxy, sweet, flowery, fruity, and/or crayon-like odors). However, the electrochemically hydrogenated samples showed only weak intensities of this odor, indicating that the hydrogenation aroma/flavor would be much less detectable in foods fried in the electrochemically hydrogenated soybean oils than in chemically hydrogenated soybean oils. Electrochemical hydrogenation produced deodorized oils with lower levels of trans fatty acids, compositions suitable for margarines, and lower intensity levels of off-odors, including hydrogenation aroma, when heated to 190°C than did commercially hydrogenated oil.     

The electrochemical hydrogenation of edible oils in a solid polymer electrolyte reactor. II. Hydrogenation selectivity studies

Soybean oil has been hydrogenated electrochemically in a solid polymer electrolyte (SPE) reactor at 60°C and 1 atm pressure. These experiments focused on identifying cathode designs and reactor operation conditions that improved fatty acid hydrogenation selectivities. Increasing oil mass transfer into and out of the Pd-black cathode catalyst layer (by increasing the porosity of the cathode carbon paper/cloth backing material, increasing the oil feed flow rate, and inserting a turbulence promoter into the oil feed flow channel) decreased the concentrations of stearic acid and linolenic acid in oil products [for example, an iodine value (IV) 98 oil contained 12.2% C_18:0 and 2.3% C_18:3]. When a second metal (Ni, Cd, Zn, Pb, Cr, Fe, Ag, Cu, or Co) was electrodeposited on a Pd-black powder cathode, substantial increases in the linolenate, linoleate, and oleate selectivities were observed. For example, a Pd/Co cathode was used to synthesize an IV 113 soybean oil with 5.3% stearic acid and 2.3% linolenic acid. The trans isomer content of soybean oil products was in the range of 6–9.5% (corresponding to specific isomerization indices of 0.15–0.40, depending on the product IV) and did not increase significantly for high fatty acid hydrogenation selectivity conditions.     

Hydrogenation of vegetable oils using mixtures of supercritical carbon dioxide and hydrogen

Hydrogenation of vegetable oils under supercritical conditions can involve a homogeneous one-phase system, or alternatively two supercritical components in the presence of a condensed phase consisting of oil and a solid catalyst. The former operation is usually conducted in flow reactors while the latter mode is more amenable to stirred, batch-reactor technology. Although many advantages have been cited for the one-phase hydrogenation of oils or oleochemicals using supercritical carbon dioxide or propane, its ultimate productivity is limited by the oil solubility in the supercritical fluid phase as well as unconventional conditions that affect the hydrogenation. In this study, a dead-end reactor has been utilized in conjunction with a head-space consisting of either a binary fluid phase consisting of varying amounts of carbon dioxide mixed with hydrogen or neat hydrogen for comparison purposes. Reaction pressures up to 2000 psi and temperatures in the range of 120–140°C have been utilized with a conventional nickel catalyst to hydrogenate soybean oil. Depending on the chosen reaction conditions, a wide variety of end products can be produced having different iodine values, percentage trans fatty acid content, and dropping points or solid fat indices. Although addition of carbon dioxide to the fluid phase containing hydrogen retards the overall reaction rate in most of the studied cases, the majority of products have low trans fatty acid content, consistent with a nonselective mode of hydrogenation.     

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.     

Hydrogenation of Edible Oils: a Model Involving Competitive Adsorption of Reactants

A model involving competitive adsorption of reactants for hydrogenation of fatty acids was developed and analyzed. The model was established based on data obtained from catalytic transfer hydrogenation of peanut, corn, and soybean oils and soybean lecithin with aqueous sodium formate solution as the hydrogen donor and palladium on carbon as the catalyst. The predicted values based on the model agreed well with the experimental data as indicated by the r ² and F test values. The rate of formate consumption, which decreased with time and the initial amount of formic acid versus the iodine value, was explained with regards to the mathematical model developed. Adsorption of reactants on the catalyst surface followed by a chemical reaction including participation of the fatty acid, formate and water were considered in this model.     

<Emphasis Type="Italic">cis</Emphasis>-, <Emphasis Type="Italic">trans</Emphasis>- and Saturated Fatty Acids in Selected Hydrogenated and Refined Vegetable Oils in the Indian Market

The fatty acid composition of 27 samples of commercial hydrogenated vegetable oils and 23 samples of refined oils such as sunflower oil, rice bran oil, soybean oil and RBD palmolein marketed in India were analyzed. Total cis, trans unsaturated fatty acids (TFA) and saturated fatty acids (SFA) were determined. Out of the 27 hydrogenated fats, 11 % had TFA about 1 % where as 11 % had more than 5 % TFA with an average value of about 13.1 %. The 18:1 trans isomers, elaidic acid was the major trans contributor found to have an average value of about 10.8 % among the fats. The unsaturated fatty acids like cis-oleic acid, linoleic acid and α-linolenic acid were in the range of 21.8–40.2, 1.9–12.2, 0.0–0.7 % respectively. Out of the samples, eight fats had fatty acid profiles of low TFA (less than 10 %) and high polyunsaturated fatty acids (PUFA) such as linoleic and α-linolenic acid. They had a maximum TFA content of 7.3 % and PUFA of 11.7 %. Among the samples of refined oils, rice bran oil (5.8 %) and sunflower oil (4.4 %) had the maximum TFA content. RBD palmolein and rice bran oils had maximum saturated fatty acids content of 45.1 and 24.4 % respectively. RBD palmolein had a high monounsaturated fatty acids (MUFA) content of about 43.4 %, sunflower oil had a high linoleic acid content of about 56.1 % and soybean oil had a high α-linolenic acid content of about 5.3 %.     

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.     

Selective Hydrogenation of Soybean Oil on Copper Catalysts as a Tool Towards Improved Bioproducts

The liquid-phase soybean oil hydrogenation was studied on silica-supported Cu and ternary Cu–Zn–Al catalysts. Cu/SiO₂ samples were prepared by incipient-wetness impregnation (Cu/SiO₂-Imp) and chemisorption-hydrolysis (Cu/SiO₂-CH), while two Cu–Zn–Al mixed oxides containing 8 (Cu(8)–Zn–Al) and 15?% Cu (Cu(15)–Zn–Al), respectively, were prepared by coprecipitation. Copper dispersion (D _Cu) was 23?% on Cu/SiO₂-CH, and this sample showed a high activity for soybean oil hydrogenation; in contrast, Cu/SiO₂-Imp was inactive, probably because Cu was poorly dispersed (D _Cu?=?2?%). The oil hydrogenation activity on Cu(15)–Zn–Al (D _Cu?=?9?%) was lower than on Cu/SiO₂-CH, while Cu(8)–Zn–Al (D _Cu?=?23?%) was inactive. Citral hydrogenation used as a test reaction showed that the intrinsic Cu⁰ activity was not significantly changed by the kind of support or the catalyst preparation method. These latter results suggested that the observed differences in soybean oil hydrogenation may be explained as changes in accessibility of the triglyceride molecules to Cu active sites. In ternary Cu–Zn–Al samples, access to catalytic sites was hampered by the narrower pore structure of the catalyst. Copper exhibited unique properties for obtaining proper lubricants from soybean oil hydrogenation because selectively hydrogenated unsaturated linolenic (C18:3) and linoleic (C18:2) fatty acids to unsaturated oleic acid (C18:1) without forming saturated stearic acid (C18:0).     

Effect of Metal Type on Partial Hydrogenation of Rapeseed Oil-Derived FAME

Supported SiO₂ catalysts were studied for the partial hydrogenation of rapeseed oil-derived fatty acid methyl esters (FAME) for improving its oxidative stability. The effect of metal type: Pt, Pd, and Ni, on catalytic activity and cis–trans selectivity was investigated. Hydrogenation activity was studied in terms of turn over frequency (TOF) of C18:3, C18:2, C18:1, and C18:0 FAME. The highest TOF of C18:3, C18:2, and C18:1 was found for Pd catalyst. However, C18:0 TOF of Pt is higher than that of the Pd catalyst. The higher in C18:0 TOF can explain the low selectivity towards trans-monounsaturated FAME of the Pt catalyst, which is due to the subsequent hydrogenation of the intermediate trans-monounsaturated to saturated FAME. On the other hand, Ni showed the lowest TOFs when compared with the Pt and Pd catalysts.     

Selective hydrogenation of sunflower seed oil in a three-phase catalytic membrane reactor

Continuous hydrogenation of sunflower seed oil has been carried out in a novel three-phase catalytic membrane hydrogenation reactor. The membrane reactor consisted of a membrane impregnated with Pd as the active catalyst, which provided a catalytic interface between the gas phase (H₂) and the oil. Hydrogenations were carried out at different pressures, temperatures, and selectivities, and the formation of trans isomers was monitored during the hydrogenation runs. For the three-phase catalytic membrane reactor, interfacial transport resistances and intraparticle diffusion limitations did not influence the hydrogenation reaction. Hydrogenation runs under kinetically controlled conditions showed that oleic and elaidic acid were not hydrogenated in the presence of linoleic acid. Initial formation of stearic acid was caused by direct conversion of linoleic acid into stearic acid by a shunt reaction. Furthermore, high selectivities led to high trans levels, which is in accordance with the many published data on hydrogenation of vegetable oils in slurry reactors. Finally, the catalytic membrane showed severe catalyst deactivation. Only partial recovery of the catalyst activity was possible.     

Conversion of Triglycerides to Hydrocarbons Over Supported Metal Catalysts

The deoxygenation of triglycerides (tristearin, triolein and soybean oil) under nitrogen atmosphere was investigated over 20 wt% Ni/C, 5 wt% Pd/C and 1 wt% Pt/C catalysts. Use of the Ni catalyst resulted in near quantitative conversion of the triglyceride in each case, high yields of linear C5 to C17 alkanes and alkenes being obtained. Oxygen was rejected as CO and CO₂, while small amounts of light alkanes (C1–C4) and H₂ were also formed. ¹³C NMR spectroscopic analysis of the liquid product from soybean oil deoxygenation at intermediate reaction times suggested that one pathway for triglyceride deoxygenation involves liberation of fatty acids via C–O bond scission and concomitant H transfer, followed by elimination of CO₂ from the acids in a later step. Compared to Ni, catalysts containing Pd or Pt supported on activated carbon showed lower activity for both triglyceride deoxygenation and for cracking of the fatty acid chains.