Homogeneous catalytic hydrogenation of unsaturated fats: Group VIB metal carbonyl complexes

Carbonyl complexes of Cr, Mo and W have been studied as soluble catalysts for the hydrogenation of methyl sorbate and of methyl esters from soybean oil. With methyl sorbate, relative catalytic activity decreased in the approximate order: mesitylene-Mo(CO)₃, cycloheptatriene-Mo(CO)₃, cycloheptatriene-Cr(CO)₃, bicyclo (2,2,1) hepta-2,5-diene-Mo(CO)₄, chlorobenzene-Cr(CO)₃, methyl benzoate-Cr(CO)₃, mesitylene-W(CO)₃, benzene-Cr(CO)₃, toluene-Cr(CO)₃, mesitylene-Cr(CO)₃, and hexamethylbenzene-Cr(CO)₃. Order of catalytic activity was related to thermal stability of the complexes during hydrogenation. With mesitylene-M(CO)₃ complexes, selectivity varied in the order Cr>Mo>W. Under certain conditions the mesitylene complexes of W, Cr and Mo reduced methyl sorbate respectively to methyl 2-, 3-, and 4-hexenoates as main products. The more active and thermally stable Cr(CO)₃ complexes catalyzed effectively the hydrogenation of linoleate and linolenate in soybean oil esters with little or no stearate formation. The hydrogenated products formed with the benzoate complex at 165–175 C contained 50–67% monoene, 18–30% diene, 2–7% conjugated diene, and only 3–7%trans unsaturation. Linolenate-linoleate selectivity values varied from 3 to 5 and linoleate-oleate selectivity from 7 to 80. Monoene fractions had 40–50% of the double bond in the C-9 position; the rest of the unsaturation was distributed mainly between the C-10 and C-12 positions. Conjugation is apparently an intermediate step in the hydrogenation of linoleate and linolenate. The Cr(CO)₃ complexes are unique in catalyzing the hydrogenation of polyunsaturated fatty esters to monounsaturated fatty esters of lowtrans content. Presented at AOCS-AACC Joint Meeting, Washington, D.C. April, 1968. No. Utiliz. Res. Dev. Div., ARS, USDA.     

Homogeneous catalytic hydrogenation of unsaturated fats: Metal acetylacetonates

Hydrogenation of linseed and soybean methyl esters was achieved at 100–180C, 100–1000 psi H₂ and 0.05–0.25 moles catalyst per mole of ester. The relative activity of metal acetylacetonates in decreasing order was: nickel (III), cobalt (III), copper (II) and iron (III). Reduction occurred readily in methanol solution but only slowly in dimethylformamide and acetic acid. No reduction occurred in the absence of solvents. Soybean oil was also hydrogenated rapidly with nickel (III) acetylacetonate in methanol, but in this system the triglycerides were converted to methyl esters. Nickel (III) acetylacetonate was the most selective catalyst toward linolenate hydrogenation. Methyl linoleate and linolenate hydrogenated with nickel(III) acetylacetonate were fractionated into monoenes, dienes and trienes. Thecis monoenes separated in 62 to 68% yield had double bonds in the original position. The remainingtrans monoenes had extensively scattered unsaturation. The dienes and trienes showed no conjugation, but some of the double bonds in the dienes were not conjugatable with alkali. Little stearate was formed. Presented at AOCS meeting in Chicago, 1964 No. Util. Res. and Dev. Div. ARS, USDA     

Homogeneous catalytic hydrogenation of unsaturated fats: Iron Pentacarbonyl

Iron pentacarbonyl is an effective homogeneous catalyst for the reduction of polyunsaturated fats. Hydrogenation of soybean oil and its methyl esters has been achieved at 180C, hydrogen pressures of 100-1,000 psi, and 0.05–0.5 molar concentrations of catalyst. Analyses of partially reduced products show considerable isomerization of double bonds, reduction of linolenate and linoleate with little or no increase in stearate, and accumulation ofcis,trans- andtrans, trans-conjugated dienes, and isolatedtrans monoenes. The unreduced trienes include diene conjugated fatty esters. The nonconjugated dienes contain large amounts oftrans and nonalkali conjugatable unsaturation. Considerable scattering of double bonds is evident in different fractions between the C₄ and C₁₆ positions. Complex formation between iron carbonyl and unsaturated fats is also indicated. The course of the homogeneous hydrogenation catalyzed by iron pentacarbonyl appears similar to the heterogeneous catalytic reaction. Metal carbonyls are well known for their isomerizing effects and their ability to form stable complexes with olefins. These homogeneous complexes provide suitable model systems to study the mechanism of catalytic hydrogenation of fats.     

Homogeneous catalytic hydrogenation of polypentenamer

Summary A high degree of hydrogenation of a polypentenamer was achieved with a homogeneous catalyst based on a metal alkyl-transition metal complex . Essentially complete saturation of the polymer was achieved without significant changes in molecular weight or molecular weight distribution.Presently Senior Humboldt Fellow, Institut für Makromolekulare Chemie, Universität Freiburg, West-Germany     

Homogeneous catalytic hydrogenation of soybean oil: Palladium acetylacetonate

Soybean oil was hydrogenated with palladium acetylacetonate at 60–170 C, 150 psi hydrogen and 1–60 ppm palladium. The best linolenate selectivity (K_Le/K_Lo=3.5−3.7) was found at 80–120 C. At 120 C palladium acetylacetonate hydrogenated faster than the heterogeneous Pd-on-carbon catalyst.Trans isomerization with the homogeneous catalyst was much higher compared to Pd-on-carbon catalyst. The low activity of the palladium complex at low temperatures was improved with the addition of triethylaluminum. Among other metal acetylacetonates tested only nickel and chromium were mildly active, whereas cobalt and copper were devoid of catalyst activity.     

Homogeneous catalytic hydrogenation of sorbic acid with pentacyanocobaltate II

The homogeneous hydrogenation of sodium sorbate, with pentacyanocobaltate II used as the catalyst, was followed manometrically at room temperature and atmospheric hydrogen pressure. One mole of hydrogen was absorbed by one mole of sorbate. UV and IR analyses demonstrated the reduction of sorbate to hexenoate. Gas liquid chromatography (GLC) of hexenoate indicated 82, 17, and 1% yields of 2-,3-, and 4-hexenoates, respectively, with traces of sorbate. Increasing either the period of hydrogenation or the ratio of catalyst to sorbate, or both, did not cause the formation of caproate or change the ratio of the three isomers. Homogeneous catalytic hydrogenation in methanolic solutions showed higher selectivity since 2-hexenoate was present in 96% yield. To standardize GLC columns, hexenoic acid isomers were synthesized by the Knoevenagel condensation.Trans- 2- hexenoic andtrans- 3- hexe- noic acids were prepared in 75 and 85% yields by a condensation ofn-butanal and malonic acid in the presence of pyridine and triethanolamine, respectively.Trans- i- h.exea.oic acid was prepared in 70% yield by condensing diethyl malo-nate with crotyl bromide. Physical properties, including UV and IR spectra, were determined for the purified synthetic acids and methyl esters. Although the absolute specificity of attack at the 4,5-double bond of sorbic acid was not confirmed, the high degree of selectivity obtained does encourage further study of homogeneous catalysis on higher fatty acids.     

Homogeneous catalytic hydrogenation of canola oil using a ruthenium catalyst

Dichlorodicarbonylbis (triphenylphosphine) ruthenium (II), RuCl₂ (CO)₂ (PPh₃)₂, was investigated as a catalyst for edible oil hydrogenation in a preliminary screening of potential catalysts for producing partially hydrogenated fats with lowtrans-isomer content. Refined, bleached and deodorized canola oil was hydrogenated using 1.77 × 10⁻⁵ − 6.64 × 10⁻⁴ mol/kg-oil of ruthenium catalyst equivalent to 1.79 × 10⁻⁴ − 6.71 × 10⁻³ wt% Ru. The effects of temperature (50–180 C) and pressure (50–750 psig) on reaction rate,trans-isomer content and fatty acid composition were examined. The activities of RuCl₂ (CO)₂ (PPh₃)₂ and nickel (Nysel HK-4 and AOCS standard nickel catalyst) were compared on a molar basis. At 4.40 × 10⁻⁴ mol/kg-oil (0.0026 wt/Ni or 0.0044 wt% Ru), 140 C and 50 psig, the nickel catalysts were completely inactive, but the ruthenium catalyst produced an IV drop of 40 units in 60 min. At 110 C, 750 psig and 1.34 × 10⁻⁴ mol/kg-oil (1.35 × 10⁻³ wt% Ru), a hydrogenation rate of 0.89 ΔIV/min and a maximumtrans-isomer content of 10.4% (IV=45.0) was obtained with the ruthenium catalyst.     

Homogeneous catalytic metathesis of unsaturated fatty esters: New synthetic method for preparation of unsaturated mono-and dicarboxylic acids

The catalytic metathesis of unsaturated fatty esters is a new, versatile method for the synthesis of a variety of fatty derivatives and alkenes. Monounsaturated esters are converted into unsaturated dicarboxylic esters which might be important technologically for the production of new polyesters and polyamides, and for the synthesis of civetone-type perfumes. Metathesis of linoleate and linolenate leads to a variety of hydrocarbons and mono- and dicarboxylates of different unsaturation. Joint reactions of unsaturated esters and alkenes are a useful means for the synthesis of homologues of oleic acid and other fatty acids. Metathesis of unsaturated fatty oils (olive, soybean, linseed, etc.) leads to the formation of high molecular dicarboxylic acid glyceryl esters with improved drying properties.     

Homogeneous catalytic hydrogenation of hydroxyl‐terminated liquid nitrile rubber

It was difficult to obtain high degree of hydrogenation of hydroxyl‐terminated liquid nitrile rubber (HTBN) by using homogeneous noble metal catalyst because the hydroxyl (? OH) in HTBN was likely to cause catalyst poisoning. In this study, with hexamethyl disilylamine protecting ? OH, a good yields of hydrogenated HTBN was synthesized through the use of homogeneous metal catalyst. The effects of catalyst concentration, reaction time, hydrogen pressure, and temperature on the hydrogenation of HTBN were investigated and obtained the following optimum process parameter values: catalyst mass fraction of 0.8%, reaction time of 8 h, pressure of 1.6 MPa, and temperature of 100°C. Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy were used to characterize the hydrogenation product of the protected HTBN, indicating that under certain conditions a high degree of hydrogenation of HTBN can be achieved. Only the carbon–carbon double bonds (C?C), not the ? CN bonds, are subject to hydrogenation. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Homogeneous catalytic hydrogenation of natural rubber using RhCl(PPh3)3

Hydrogenation is an important method of chemical modification, which improves the physical, chemical, and thermal properties of diene elastomers. It is also a useful method for preparation of polymers with unusual monomer sequences. Natural rubber (NR) could be quantitatively hydrogenated to a strictly alternating ethylene-propylene copolymer using a homogeneous RhCl(PPh₃)₃ catalyst. The effect of concentration of rubber, catalyst and triphenyl phosphine, temperature, pressure, and solvent on the course of hydrogenation were evaluated. The thermal properties of the hydrogenated NR are compared with NR. © 1997 John Wiley & Sons, Inc. J. Appl Polym Sci 66: 1647–1652, 1997     

Brown-colored oxypolymers of unsaturated fats

Summary The oxypolymerization of unsaturated fat in the presence of protein and amino acid was studied to determine whether the active carbonyl-amine-browning reaction is a dominant mechanism for the formation of brown-colored polymers. A highly reactive system of menhaden oil-aqueous egg albumin emulsion was studied in greatest detail. Three types of studies: activation energy of formation of brown color, inhibition analysis of the mechanism leading to formation of brown color, and measures of amino acid reaction in the oxidizing unsaturated fats, all gave evidence that active carbonyl-amine browning was not a dominant mechanism. This research was supported by funds made available through the Saltonstall-Kennedy Act and administered by means of a collaborative agreement between the Fish and Wildlife Service and the University of California.     

Homogeneous catalytic hydrogenation of poly(styrene-co-butadiene) using a ruthenium based Wilkinson catalyst

Summary Poly(Styrene-co-butadiene) can be quantitatively hydrogenated using tris(triphenyl phosphine) ruthenium(II) chloride, RuCl₂(PPh₃)₃ as catalyst. The effect of temperature, pressure and catalyst concentration on both the rate and degree of hydrogenation have been studied. The hydrogenated elastomers have been characterized by IR, ¹H NMR and TGA.Ref. 1     

Alkyl-and arylsulfanyl-substituted unsaturated carbonyl compounds

A method for the synthesis of captodative sulfanyl enals, enones and enoates via nucleophilic vinylic substitution of corresponding halogen-bearing derivatives has been developed. The one-pot treatment of the haloenoates, haloenones or haloenals with thiols in the presence of organic base leads either to vicinal dithiosubstituted carbonyl-bearing compound or captodative systems with good to excellent yield. The major reaction direction strongly depends on the type of base used.     

Stationary catalysts for the continuous hydrogenation of fats

Hydrogenation characteristics of a wide variety of stationary catalysts were studied with an aim to explore their possible use in the continuous hydrogenation of fats. Refined soybean oil was hydrogenated continuously in a vertical flow-through reactor over a fixed bed of catalyst. Catalysts investigated were pelleted products containing Raney nickel, reduced nickel, reduced palladium, and copper chromite, as well as granulated alloys of the Raney type, such as Ni-Al, Cu-Al, Pd-Al, and Cu-Cr-Al, which were activated with alkali. These catalysts offered a wide choice of activity, selectivity, and ability to form geometrical isomers. Pelleted copper chromite and granular Raney copper-chromium were found to be highly selective toward the linolenate moiety of soybean oil, whereas pelleted palladium on carrier, as well as granular Raney nickel, Raney copper, and Raney palladium, though moderately selective, exhibited very high activity even at relatively low temperatures. A unique feature of most of the stationary catalysts was the remarkably high rate of hydrogenation. With most catalysts, the iodine value of soybean oil was reduced by 40–60 units within a reaction period of 2–4 min. The hydrogenated fat was practically free of catalyst particles.     

Homogeneous hydrogenation of dienes with rhodium complexes

Different Rh complex catalysts were compared for the hydrogenation of methyl sorbate and linoleate in the absence of solvents. At 100 C and 1 atm H₂ the following complexes, RhCl(Ph₃ P)₃ (Ph= phenyl), [RhClNBD]₂ (NBD=norbornadiene) and RhH(CO)(Ph₃P)₃, produced mainly methyltrans-2-hexenoate (34 to 56%). Their diene selectivity was not particularly high as they produced 14 to 41% methyl hexanoate. With RhCl(Ph₃ P)₃ constant ratios between rates of methyl sorbate disappearance and formation of methyltrans-2- andtrans-3-hexenoate indicate approximately the same activation energy for 1,2-addition of H₂ on the Δ4 double bond of methyl sorbate and for 1,4-addition to this substrate. In the hydrogenation of methyl linoleate with RhCl(Ph₃ P)₃, the kinetic curves were simulated by a scheme in which 1,2-reduction was more than twice as important as 1,4-addition of H₂ via conjugated diene intermediates. Although the complexes RhCl(CO)(Ph₃ P)₃ and [Rh(NBD)(diphos)]⁺PF₆ (diphos=diphosphine) were inactive in the hydrogenation of methyl sorbate, they catalyzed the hydrogenation of methyl linoleate at 100 C and 1 atm. Catalyst inhibition apparently was caused by stronger complex formation with methyl sorbate than with the conjugated dienes formed from methyl linoleate.     

Estimating carbonyl compounds in rancid fats and foods

Summary A convenient method for the quantitative determination of the carbonyl compounds in fats and oils is described. The procedure is based upon the formation of the 2,4-dinitrophenyl hydrazones of the carbonyl compounds in the presence of trichloroacetic acid catalyst and the colorimetric determination of the hydrazone compounds in alkaline solution. Standardizations are presented for the simultaneous determination of saturated and allenic carbonyl content from the absorbences at 430 and 460 mμ. Applications of these procedures to edible oils are described, and data are presented showing the carbonyl values in relation to other criteria of change. The problem of correlating changes in the carbonyl content of oils with flavor deterioration is now under investigation. This paper reports research undertaken at the Quartermaster Food and Container Institute for the Armed Forces and has been assigned No. 428 in the series of papers approved. The views or conclusions contained in this paper are those of the authors; they are not to be construed as necessarily reflecting the views or indorsement of the Department of Defense.     

Homogeneously catalysed hydrogenation of unsaturated fatty acids to unsaturated fatty alcohols

The use of copper and cadmium oxides or soaps as catalysts for the hydrogenation of unsaturated fatty acids to unsaturated fatty alcohols has been investigated. It is shown that copper soaps homogeneously activate hydrogen. When copper and cadmium oxides are used as catalysts, they react with the acid under formation of a homogeneous soap solution. A continuous reaction system for the preparation of unsaturated fatty alcohols by hydrogenation under the influence of copper and cadmium soaps is described.