Selective Hydrogenation Of Soybean Oil Research Articles

Characteristics and catalytic behavior of different platinum supported catalysts in the selective hydrogenation of soybean oil

Platinum (Pt) catalysts supported on TiO2, ZrO2, activated carbon, and multi-walled carbon nanotubes were prepared by the wet impregnation method. The characterization of the obtained catalysts was performed with XRD, ICP-AES, TEM and N2-adsorption. Their catalytic behavior during the selective hydrogenation of soybean oil was also studied. The results showed that compared with the commercial Raney Ni, all the platinum-catalysts exhibited better activity and lower selectivity towards trans isomer during the partial hydrogenation of soybean oil. Especially the Pt/ZrO2 catalyst had the lowest selectivity towards the formation of trans C18:1 isomers and stearic acid. The results also showed that the metal loading had little impact on the hydrogenation activity and selectivity. Meanwhile, the acid value of hydrogenated oil over platinum-catalysts was less than 1.0 (KOH)/(mg/g). The hydrogenated oil over platinum-catalyst indicated good melting characteristics and solid fat content. These results demonstrated that Pt/ZrO2 catalyst could be a good alternative of Raney Ni to reduce the formation of trans fatty acid and saturated fatty acid in hydrogenated soybean oil, and meanwhile ensure the physicochemical quality requirements of hydrogenated oils.

Ultrasound assisted selective catalytic transfer hydrogenation of soybean oil using 5% Pd/C as catalyst under ambient conditions in water

Catalytic transfer hydrogenation (CTH) is an alternative approach that does not require the use of potentially dangerous hydrogen gas. Pd/C is the most favoured catalyst for the selective hydrogenation of soybean oil yielding lower extent of formation of stearic acid and trans-isomer, which have adverse health effects. The present work deals with intensification of catalytic transfer hydrogenation of soybean oil in the presence of 5wt.% Pd/C using ultrasound under ambient reaction conditions. The effect of important operating parameters such as ultrasound power, temperature, type of hydrogen donor, catalyst loading and donor concentration on the progress of reaction has been investigated. It was established that the maximum extent of hydrogenation as indicated by reduction in iodine value from 135 to 95 was observed under optimized conditions of irradiation power as 100W, 22kHz frequency, 90% duty cycle, ammonium formate concentration of 0.32mol/50ml water and 2% (w/w) Pd/C loading at ambient temperature and pressure in the presence of water as solvent. The approach also offered excellent selectivity with much lower trans-isomer formation as compared to the conventional approach of high pressure hydrogenation. Overall, the work has successfully demonstrated process intensification benefits due to the use of ultrasound for the Pd/C catalyzed transfer hydrogenation of soybean oil.

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

AbstractThe 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 (DCu) 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 (DCu = 2 %). The oil hydrogenation activity on Cu(15)–Zn–Al (DCu = 9 %) was lower than on Cu/SiO2‐CH, while Cu(8)–Zn–Al (DCu = 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).

Catalytic Activity of Ruthenium Nanoparticles Supported on Carbon Nanotubes for Hydrogenation of Soybean Oil

AbstractRuthenium catalysts supported on multiwalled carbon nanotubes (MCNTs) with different loadings (1% wt, 3% wt, 5% wt) were prepared by reduction with H2 or NaBH4 for selective hydrogenation of soybean oil at 338 K and initial pressure of 1.066 MPa. These catalysts were characterized using transmission electron microscopy (TEM), X‐ray powder diffraction (XRD), N2 adsorption–desorption, and H2‐temperature programmed desorption (TPD) techniques. Ru particles were dispersed more homogeneously on the surface of the nanotubes after being reduced with H2 than with NaBH4. The catalysts with 3% and 5% Ru loadings had higher hydrogenation activity. The NaBH4‐reduced catalyst had higher cis‐isomer selectivity.

Studies in catalytic transfer hydrogenation of soybean oil using ammonium formate as donor over 5% Pd/C catalyst

Abstract The catalytic transfer hydrogenation (CTH) is a novel, alternative process for the selective hydrogenation of soybean oil due to the lower rate of formation of stearic acid and trans-isomer, which have an adverse health effects. Ruthenium and palladium supported catalysts were screened along with hydrogen donors during CTH process. The CTH of soybean oil was studied using aqueous ammonium formate solution over supported palladium catalyst. The method offered good selectivity in complete reduction of linolenic acid with a slight increase in stearic acid. The kinetics of CTH of soybean oil using ammonium formate as a hydrogen donor over 5% Pd/C catalyst was studied. The speed of agitation was sufficiently high enough to eliminate diffusional resistance. The CTH of soybean oil was described by pseudo-first order kinetic model. Runge–Kutta algorithm (RKS4) was used to determine the kinetic rate constants. The catalyst could be reused thrice without any adverse effect.

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

AbstractThe 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 (KLe/KLo=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).

Selective hydrogenation of soybean oil: XI. Trialkyl silane‐activated copper catalysts

AbstractAddition of triethyl silane to copper stearate resulted in an active heterogenous catalyst for the hydrogenation of soybean oil. The linolenate selectivity of this catalyst (KLe/KLo=2.4 to 3.9) was much lower than that obtained with copper chromite (8.4). Unlike copper‐chromite catalyst, triethyl silane‐activated copper formed stearate during hydrogenation. Both silica and alumina increased catalyst activity. Linolenate selectivity improved slightly in the presence of alumina.

Selective hydrogenation of soybean oil: X. Ultra high pressure and low pressure

AbstractSoybean oil was partially hydrogenated with copper‐chromite catalyst at 170 C and up to 30,000 psig hydrogen pressure. Catalyst activity increased with increase in pressure up to 15,000 psig. The linolenate selectivity (SLn) of the reaction remained essentially unchanged over 50–1000 psig pressure range. A SLn of 5.5 to 5.6 was achieved at 15,000 to 30,000 psig pressure range. This value is somewhat lower than the selectivity at 50–1000 psig, but much higher than that obtained with nickel catalysts. Geometric isomerization increased as pressure increased up to 200 psig; above this pressure, the percenttrans remained the same up to 500 psig.trans Isomer content decreased when the pressure was increased to 30,000 psig. cis,trans Isomerization of linoleate was greater at 1000 psig and 15,000 psig than at 50 psig. At 15,000 psig, part of the linoleate in soybean oil was hydrogenated directly without prior conjugation, whereas at low pressures, all of the double bonds first conjugate prior to hydrogenation. This difference in mechanism might explain the lower selectivities obtained at high pressures. Conjugated diene isomers were found in the products up to 200 psig. Above this pressure conjugated diene was not measurable. No significant differences were found in the double bond distribution oftrans monoenes even though the amount oftrans monoene formed decreased as pressure was increased to 30,000 psig.

Selective hydrogenation of soybean oil: IX. Effect of pressure in copper catalysis

AbstractSelective hydrogenation of soybean oil with copper catalyst at 50 psig or less is characterized as a relatively slow reaction requiring higher catalyst concentrations than the less selective but rapid nickel‐catalyzed reactions used in most commercial practice. Hydrogenations of soybean oil have been performed which included a high‐pressure scan (500, 1000, and 3000 psig), at selected temperatures (110, 130, 150, and 170 C), and at specific catalyst concentrations (0.05, 0.1, 0.2, and 0.4% copper). Selectivities, relative reaction rates, and geometric and positional isomerization have been determined as an evaluation of the effects of high pressure on the kinetics of the reaction. The experimental results indicate that an appropriate selection of pressure, temperature, and catalyst concentration can permit: (a) a significant increase in the rate of reaction while retaining the high linolenic acid selectivity of copper catalysts, (b) use of lower concentrations of copper catalyst while maintaining the higher reaction rate, and (c) elimination of conjugated diene as a measureable product in the hydrogenated oil.

Selective hydrogenation of soybean oil. VIII. Effect of method of preparation upon the activity of a copper‐silica catalyst

Abstract and SummaryA copper‐silica catalyst was prepared by adding copper nitrate solution to sodium silicate. The precipitated copper‐silica catalyst was washed, dried, and heat‐treated at high temperatures. The effect of preparational variables upon catalyst activity and selectivity for the hydrogenation of soybean oil was investigated. The optimum conditions were precipitation at 25 to 55 C, drying the catalyst by freeze drying, and heat treatment at 500 C. The catalyst obtained under these conditions is more than three times as active as a commercial copper‐chromite catalyst.

Selective hydrogenation of soybean oil: VII. Poisons and inhibitors for copper catalysts

AbstractHydrogenation rates for the catalytic reduction of soybean oil with a copper‐on‐silica catalyst increased when the oil was re‐refined and bleached in the laboratory. Purification of the re‐refined and bleached oil by passage through alumina further enhanced hydrogenation rates. Since these observations suggested that poisons were present in the oil, the effect of minor components of soybean oil upon the activity of copper catalysts was investigated. Free fatty acids, monoglycerides, β‐carotene, phosphoric acid, sodium soaps, phosphatides, glycerine, choline, ethanolamine, water, pheophytin, and pyrrole all reduced hydrogenation rates when added to the oil. Organic sulfur added to the oil was a more effective catalyst inhibitor than inorganic sulfur added to the gas. Catalyst activity was affected adversely when iron was added to the oil as a soap or when deposited on the catalyst during its preparation. Squalene, copper soaps, and carbon monoxide had no influence on the activity of the catalyst. Aging of soybean oil also had no effect. There was no significant change in either selectivity or formation oftrans or conjugated diene isomer when these additives were added to the oil.

Evaluatioil of Reversion Flavor for Isomerized Soybean Fatty Triglycerides

It has been observed tlint iso-linoleic acid in partially hydrogenated linseed and soybean oils is responsible for the development of characteristic hydrogenation flavor. In the present paper, authors investigated whether isomerized soybean fatty triglycerides caused the hydrogenation flavor. Three types of isomerized soybean fatty triglycerides were prepared as follows. 1) Trans isomerized soybean oil was prepared by treatment with nitrous acid. (trans isomer 61.5%) 2) Triglyceride which contained positional isomers was prepared by esterification of glycerine with hydrazine-reduced soybean fatty acid. (9, 15-iso-linoleic 1.4%) 3) Triglyceride which contained both trans and positional isomers was prepared by esterification of glycerine with hydrazine-reduced and trans-isomerized soybean fatty acid. Hydrogenated soybean oils having the I.V. of 116.2, 71.2 and 55.1, respectively, were also prepared by selective hydrogenation of soybean oil with nickel catalyst. Reversion flavor of isomerized and hydrogenated oil was evaluated organoleptically under the following conditions whether it contained hydrogenation flavor or not.1) Flavor evaluation was made during heating at 120°C. 2) Flavor evaluation was made after storage under diffused sun light for 10 days.It was found tlint hydrogenation flavor was detected only for hydrogenated soybean oil with L.V. of 116.2, 71.2 and 55.1, but not detected for other isomerized soybean fatty triglycerides. It was also postulated t hat t he precursor of hydrogenation flavor was not only iso-linoleic acid but also iso-oleic acid.

Selective hydrogenation of soybean oil. VI. Copper‐on‐silica gel catalysts

AbstractThe preparation of copper‐on‐silica gel catalysts containing 15% and 20% copper is described. These catalysts can be reused three times without appreciable loss of activity. Their activity compares favorably with the highly active 5% copper‐on‐silica gel catalyst previously reported. Higher copper catalysts are somewhat less selective for the reduction of linolenate in soybean oil than 5% copper‐on‐silica gel, but these copper catalysts have greater activity, better reuse characteristics, and selectivity comparable to commercial copper‐chromite catalysts.

Hydrogenation of triglycerides containing linolenic acids: II. Continuous hydrogenation of vegetable oils

AbstractIn this study continuous hydrogenation of neutral oils, especially the selective hydrogenation of soybean oil, is described. The reactor is a column divided by a series of plates into a number of reaction chambers. Oil with suspended catalyst and hydrogen enters the column at the bottom and flows concurrently with hydrogen through it. The pressure in the reactor will adjust itself, depending on the activity and concentration of the catalyst and throughput of oil. The ratio of gas volume in the reactor to volume of the oil is very low, so that the iodine value of the hydrogenated product can be controlled to within 1.5 iodine unit.

Selective hydrogenation of soybean oil: V. A Novel copper catalyst with excellent re‐use properties

AbstractA procedure for the preparation of highly active copper catalyst by chemisorption of copper‐ammonia complex on silica gel is described. This catalyst was highly selective towards the reduction of linolenate in soybean oil. The catalyst was re‐used four times with no loss in activity.

Pilot‐plant selective hydrogenation of soybean oil: Activation and evaluation of copper‐containing catalysts

AbstractIn pilot‐plant tests, the linolenate content of soybean oil was reduced to less than 1% without increasing the saturates, by hydrogenation to an IV of about 115 with an active copper‐chromite catalyst. The linolenate‐linoleate selectivity ratio (KLe/KLo) was from 9 to 12. Several commercial copper‐chromite catalysts were used in hydrogenation tests. The activities of four of five commercial catalysts tested were improved to various degrees by heating in air at 350 C (one was inactive both before and after heating). Examination by differential thermal analysis (DTA) of each catalyst, just as received and then after being heated at 350 C, demonstrated that heating greatly diminished or removed peak areas from the DTA curve. Studies made with one commerical copper‐chromium‐barium catalyst showed that heating the catalyst was also necessary to gain maximum linolenate‐linoleate selectivity in hydrogenating soybean oil.

Selective hydrogenation of soybean oil: IV. Fatty acid isomers formed with copper catalysts

AbstractTwo samples of soybean oil hydrogenated with copper‐containing catalysts at 170 and 200 C were analyzed for their natural and isomeric fatty acids. Methyl esters of the hydrogenated oils were separated into saturates, monoenes, dienes and trienes by countercurrent distribution between acetonitrile and pentane‐hexane. Monoenes were further separated intocis‐ andtrans‐isomers on a silver‐saturated resin column. Double bond location in these fractions was determined by a microozonolysis‐pyrolysis technique. The diene fraction was separated with an argentation countercurrent distribution method, and linoleate was identified by infrared, ozonolysis and alkaliisomerization data. The double bonds in thecis‐monoenes were located in the 9‐position almost exclusively. However, the double bonds in thetrans‐monoene were quite scattered with 10‐ and 11‐isomers predominating. About 86% to 92% of the dienes consisted of linoleate as measured by alkali isomerization. Other isomers identified as minor components includecis,trans andtrans, trans conjugated dienes and dienes whose double bonds are separated by more than one methylene group.

High oleic oils by selective hydrogenation of soybean oil

AbstractHigh 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.

Selective hydrogenation of soybean oil. 3. Copper-exchanged molecular sieves and other supported catalysts.

AbstractCopper‐chromium catalysts promote selective reduction of linolenyl groups in soybean oil. Since commercially available catalysts possess only moderate activity, more active catalysts were sought. Copper was dispersed on high‐surface‐area supports, such as silica, alumina, and molecular sieves. These catalysts had varying activities. Precipitation of copper on Cab‐O‐Sil, a pure form of silica with a large external surface area, gave the most active catalyst. Selectivity ratios (KLe/KLo) for the hydrogenation of soybean oil with these catalysts varied from 4 to 16; a copper‐on‐Cab‐O‐Sil catalyst exhibited the greatest selectivity. Improved selectivity and activity were observed when some supports were treated with hydrochloric acid. For example, with a copper‐on‐Celite catalyst, soybean oil was hydrogenated in 165 min and gave a selectivity ratio of 5.9. Hydrochloric acid treatment of Celite improved the selectivity to 9.9 and reduced hydrogenation time to 54 min. To ensure maximum activity of some of these catalysts, soybean oil should be more thoroughly bleached than is customarily done for nickel hydrogenation. A commercially refined and bleached soybean oil was hydrogenated with a copper‐on‐Cab‐O‐Sil catalyst in 18 min. The same oil, re‐refined in the laboratory, was reduced in 11.5 min and had the same selectivity ratio of 15.

Selective hydrogenation of soybean oil in the presence of copper catalysts

AbstractMany investigators associate the poor keeping properties of soybean oil with its linolenic acid content. On the other hand the high linoleic acid content is a desired property from a nutritional point of view. We have therefore developed a process for the preferential reduction of the linolenic acid content by selective hydrogenation. Conventional catalysts for the hydrogenation of fats have a rather low selectivity in this respect. When linolenic acid in soybean oil is hardened (e.g., with a nickel catalyst), most of the linoleic acid is converted into less unsaturated acids.It was found that linolenic acid is hydrogenated much more preferentially in the presence of copper catalysts than in that of nickel and other hydrogenation catalysts. At a linolenic acid content of 2%, soybean oil hardened with nickel catalyst contained about 28% linoleic acid, whereas with copper catalyst the hardened soybean oil contained 49% linoleic acid.By means of our process it is possible to manufacture a good keepable oil of, e.g., I.V. 115 and containing 1% linolenic acid and 46% linoleic acid. The storage stability of this product is comparable with that of sunflower‐seed oil. A liquid phase yield of 86% is obtained after winterization at 5C for 18 hr.The high selectivity for linolenate reduction of copper catalysts must be ascribed to the copper part of the catalyst. Investigations into the structure of the catalyst indicate that the active center consists of copper metal crystallites; whether these centers are promoted by the carrier or traces of other substances is under investigation.