Hydrogenation of unsaturated fatty acids to unsaturated fatty alcohols: I. Study of Cu and Cd oleates as catalysts

The catalyst system containing copper and cadmium oleates as used in selective hydrogenations was analyzed. The reddish brown reaction mixture as such and after precipitation by alcohol was subjected to polarographic, spectroscopic, x-ray and electron-microscopic analysis. The conclusion drawn was that the mixture is a heterogeneous system. From an electron micrograph it was observed that the average particle size is 48 Å. It was also possible to determine the mean degree of oxidation of copper in the precipitate, the results indicating that the copper is in its metallic state. Cadmium is present as cadmiumoleate, which stabilizes the copper colloid during the reaction.     

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.     

Hydrogenation of unsaturated fatty acids to unsaturated fatty alcohols: II. Kinetics and mechanism of the reaction using Cu and Cd oleates as catalysts

The kinetics and mechanism of the Cu and Cd-soap-catalyzed hydrogenation of oleic acid have been studied. The reaction is first order in Cd and H₂, and also first order in Cu if the double bond is completely preserved during reduction of the carboxyl group to the hydroxyl group. It will deviate from this order if the selectivity is lower owing to an increased Cu concentration. The reaction rate-determining step is independent of the Cd concentration. Its activation energy, of 13.4 kcal/mole, corresponds to that of the chemisorption of hydrogen on Cu. Unsaturated and saturated fatty acids of the same chain length have the same reaction rate. A decrease of the chain length causes a decrease in the reaction rate and in the final degree of conversion. Water and low molecular weight acids have an inhibitory effect on the reaction. A reaction mechanism is proposed which is based on the assumption that cadmium oleate plays a double role: it stabilizes the copper sol and is intermediate for the hydrogenation.     

Microbial production of rare unsaturated fatty acids and alcohols

Aeromonas hydrophila N‐6, isolated from a soil sample, converted vegetable oils to several rare unsaturated fatty acids and alcohols accumulated inside the cells as a wax ester form. A. hydrophila N‐6 effectively decreased fatty acid chain lengths, and converted rapeseed, safflower and linseed oils into 7‐16:1 and 5‐14:1 fatty acids, 7,10‐16:2 and 5,8‐14:2 fatty acids, and 7,10,13‐16:3 fatty acids, respectively. Furthermore, A. hydrophila N‐6 reduced the resulting fatty acids to rare unsaturated fatty alcohols, such as 7‐16:1, 5‐14:1, 9,12‐18:2, 7,10‐16:2, 9,12,15‐18:3 and 7,10,13‐16:3. Such unsaturated fatty acids and alcohols are rarely found in natural oils. Because decreasing fatty acid carbon chain lengths from the carboxyl end and reducing unsaturated fatty acids to unsaturated fatty alcohols in industrially applicable scale are both difficult reactions to accomplish by chemical means, we suggest that A. hydrophila N‐6 may facilitate the introduction of new bioprocesses for producing rare unsaturated fatty acids and alcohols, especially fatty alcohols with more than two double bonds.     

Aggregation of unsaturated long-chain fatty alcohols in nonaqueous systems

Aggregation and related phenomena in nonaqueous binary and ternary solutions containing unsaturated long-chain fatty alcohol amphiphiles have been studied. Six C₁₈ fatty alcohols were studied—oleyl alcohol (9Z-octadecen-1-ol), elaidyl alcohol (9E-octadecen-1-ol), linoleyl alcohol (9Z, 12Z-octadecadien-1-ol), elaidolinoleyl alcohol (9E, 12E-octadecadien-1-ol), linolenyl alcohol (9Z, 12Z, 15Z-octadecatrien-1-ol) and elaidolinolenyl alcohol (9E, 12E, 15E-octadecatrien-1-ol). Equivalent conductivity and photon correlation spectroscopy confirmed that unsaturated long-chain fatty alcohols form large and polydisperse aggregates in methanol. Critical micelle concentration (CMC) results showed that the degree of unsaturation and configuration of the double bonds in the fatty alcohol significantly influences aggregation. Aggregation of oleyl alcohol in a series of straight and branched medium-chainlength (C₃-C₈) alkanol solvents was studied. For shorter-chained alkanols (C₁-C₄), decreasing solvent dielectric constant decreases the CMC; however, for longer-chained alkanols (C₄-C₈), no significant effects occurred on the CMC. The effect of solubilized soybean oil on the viscosity of long-chain fatty alcohol/methanol solutions was also analyzed. Relative viscosity results were consistent with those expected for microemulsions. Although preliminary in nature, these results generally support the notion that soybean oil is solubilized by incorporation into large soybean oil-in-fatty alcohol aggregates in methanol solvent, resembling a nonaqueous detergentless microemulsion. Presented at the 67th Colloid and Surface Science Symposium, Toronto, Canada, June 20–23, 1993.     

Reduction of unsaturated fatty acids and fatty alcohols with diimide from hydroxylamine-ethyl acetate

Hydroxylamine has been recently found to react with ethyl acetate to generate diimide in situ. This reaction was used to reduce 10-undecenoic, oleic, linoleic, stearolic, concentrates of ricinoleic, cyclopentene and cyclopropene fatty acids (FA), dehydrated castor oil FA, 10-undecen-1-ol, oleyl alcohol and castor fatty alcohols. Unsaturated FA and their corresponding alcohols reacted in a similar manner. Terminally unsaturated, cyclopropene and cyclopentene FA were more reactive than oleic acid, which, in turn, was more reactive than hydroxymonoenoic acids. Conjugated dienoic FA reduced faster than nonconjugated dienoic acids. Partial hydrogenation using this reagent is particularly advantageous in determining geometry and the position of double bonds in the polyunsaturated FA, as it can be carried out in the absence of oxygen or oxidizing agents unlike hydrazine reductions.     

Hydrogenation of unsaturated fatty esters with copper-chromite catalyst: Kinetics,mechanism and isomerization

Hydrogenation of linolenate with copper chromite produced a large amount of conjugated diene and minor amounts of nonconjugatable dienes. The double bonds in conjugated dienes and monoenes were scrambled all along the chain. This product distribution can be explained if it is assumed that conjugation of the double bonds is followed by hydrogenation. In competitive hydrogenation, fatty esters with conjugated double bonds were reduced preferentially over fatty esters with methylene-interrupted double bonds. Isomerization of conjugated double bonds (geometric and positional) occurred more rapidly than reduction. Reduction of conjugated double bonds in the presence of deuterium resulted in a majority of the products containing no deuterium. Most of the added deuterium was incorporated into the unreacted material. Mechanisms are proposed to account for the products formed during the hydrogenation of linolenate, linoleate and their isomers. One of 10 papers to be published from the Symposium “Hydrogenation,” presented at the AOCS Meeting, New Orleans, April 1970. No. Utiliz. Res. Dev. Div., ARS, USDA.     

Studies in soap crystallization processes. Part III. Acid soap crystallization in the segregation of tall oil fatty acids

Tall oil fatty acids have been fractionated into 80–90% oleic acid, and 60–80% linoleic acid fractions, by precipitation of the oleic acid as acid soap from polar solvents. Sodium and potassium acid soaps are equally effective, but ammonium acid soaps require lower operating temperatures. The choice of solvent is not critical as regards degree of separation, but technically attractive filtration rates have been obtained only with methanol and acetone. Acidulation gives colorless oleic acid of very low rosin acid and unsaponifiable content, but with 5–10% of conjugated linoleic acid.     

The hydrogenation of fatty oils with palladium catalyst. III. Hydrogenation of fatty oils for shortening stock

Summary Palladium-on-carbon catalysts are exceedingly active for the hydrogenation of natural unsaturated oils when very mild conditions are used. Selectivity is usually good, andtrans content can be adequately controlled by the proper choice of conditions. In the range of operating variables used in this work,trans formation is lessened with increased agitation and pressure, decreased catalyst activity, decreased concentration of metal in oil and on carrier, and with decreased temperature. Some shortening stocks were obtained which have good physical properties, as expressed by their dilatometric curves.     

Manufacture of soap from fatty acids

Soap manufacture from fatty acids is a well established precess with some advantages over continuous saponification of neutral fats. These include:

1. Ability to use cheaper fats.
2. Easier glycerol recovery.
3. Better control over by-products.
4. Versatility-fatty acids can be used to make other derivatives than soaps.

     

Hydrogenation of fatty acids

Catalytic hydrogenation is a vital process for both the edible fats and oil and the industrial fatty chemical industries. The similarities and differences between the fat and oil and fatty acid hydrogenations in equipment, processing conditions, and catalysts employed are of some importance since both are used in the various operations. Generally, the catalytic hydrogenation of fatty acids is carried out in corrosion-resistant equipment (316SS), whereas for fats and oils while 316SS is desirable, 304SS or even black iron surffice. The speed of hydrogenation varies radically with the content of impurities in both fat and oil and fatty acid feedstocks. Especially detrimental for both hydrogenations are soap and sulfur contaminants, proteinaceous materials left in the oils from poor refining, etc. Fatty acids from vegetable oil soapstocks are especially difficult to hydrogenate. Soybean-acidulated soapstock must usually be double-distilled for good results; cottonseed soapstocks frequently triple-distilled in order that they can be hydrogenated below iodine values of 1. Fatty acid hydrogenation effectiveness is measured by achieveing a low iodine value as fast and as economically as possible. Variables that influence hydrogenation effectiveness are reactor design, hydrogen purity, feedstock quality, catalyst activity and operating conditions.     

Reactions of unsaturated fatty alcohols. XIII. copolymers of unsaturated fatty vinyl ethers and cyclic monomers

Conjugated linseed, conjugated soybean, and nonconjugated linseed vinyl ethers were copolymerized with various cyclic comonomers. The comonomers used were dihydroabietyl, cyclohexyl, 5-norbornene-2-methyl, di- and tetra-hydrodicyclopentadienyl vinyl ethers, and cyclo-and methylcyclo-pentadiene. All copolymers containing a cyclic comonomer gave baked films that are distinctly superior to unmodified drying oils or vinyl ether homopolymers in hardness and alkali resistance. Several of these copolymers air-dried overnight to moderately hard, wrinkle-free films. The improvement in hardness and alkali resistance may be caused by the steric effects of the cyclic comonomers. These hold the fatty side chains apart thus increasing the proportion of intermolecular to intramolecular crosslinking. Presented in part at the spring meeting, American Oil Chemists' Society, St. Louis, Mo., May 1–3, 1961. A laboratory of the Northern Utilization Research and Development Division, Agricultural Research Service, U.S.D.A.     

Hydrogenation of fatty acid methyl esters to fatty alcohols at supercritical conditions

Extremely rapid hydrogenation of fatty acid methyl esters (FAME) to fatty alcohols (FOH) occurs when the reaction is conducted in a substantially homogeneous supercritical phase, using propane as a solvent, over a solid catalyst. At these conditions, the limitations of hydrogen transport are eliminated. At temperatures above 240°C, complete conversion of the starting material was reached at residence times of 2 to 3 s, which is several orders of magnitude shorter than reported in the literature. Furthermore, formation of by-products, i.e., hydrocarbons, could be prevented by choosing the right process settings. Hydrogen concentration turned out to be the key parameter for achieving the above two goals. As a result of the supercritical conditions, we could control the hydrogen concentration at the catalyst surface independently of the other process parameters. When methylated rapeseed oil was used as a substrate, the hydrogenation catalyst was deactivated rapidly. However, by using methylated sunflower oil, a catalyst life similar to that obtained in industrial processes was achieved. Our results showed that the hydrogenation of FAME to FOH at supercritical conditions is a much more efficient method than any other published process.     

Reactions of unsaturated fatty alcohols. VI. Guerbet reaction of soybean and linseed alcohols

Summary Both soybean and linseed alcohols were heated with potassium hydroxide and boric anhydride at 300°C. for 3 to 4 hrs. Products obtained under these conditions contained no unreacted starting alcohol, and each one appeared to be a mixture of condensed alcohols with average molecular weights of 720–860. Infrared spectroscopic studies and chemical analyses indicate that little or no ethers, esters, or carbonyl compounds were present in the final product from either alcohol. Such reactions as thermal cross-linking of the unsaturated side chains probably account for higher molecular weight products than those obtained in the Guerbet reaction of stearyl alcohol. Condensed alcohols from soybean and linseed alcohol were esterified with acrylic, sorbic, maleic, and soybean fatty acids to yield products with low acid numbers. Preliminary experiments demonstrated that these alcohols and their esters showed promise as materials for protective coatings. Films from these alcohols and esters were cast from toluene containing a cobalt naphthenate drier and were baked at 150°C. for 1 hr. or at 200°C. for 20 min. All of the baked films were hard to moderately hard and showed good resistance to aqueous alkali and organic solvents. In general, films from soybean condensed alcohol and its esters were harder than those from linseed condensed alcohols, but the linseed films were superior in alkali and solvent resistance. A soybean fatty acid ester of soybean condensed alcohol air-dried to a soft film in 3 days. Presented at the 49th Annual Meeting, American Oil Chemists' Society, April 21–23, 1958, Memphis, Tenn.     

Hydroformylation of unsaturated fatty acids

When hydroformylation of unsaturated fatty materials is done with rhodium-triphenyl phosphine (or phosphite) catalysts, a number of advantages become apparent compared to cobalt carbonyl-catalyzed reactions. With rhodium, the reaction can be carried out (a) at pressures as low as 200 psi, (b) at each double bond location in a polyunsaturated fatty acid, and (c) in high yield and conversion. Solubilized catalyst can be recovered from distillation residue and readsorbed on spent catalyst support by thermal treatment in a rotary kiln. The reconstituted catalyst is more active than the original catalyst and can be recycled indefinitely at a relatively low cost. Recently developed supports for “homogeneous” catalysis may make catalyst recovery even more effective. Acetalation, oxidation with air to polycarboxylic acids and catalytic hydrogenation to hydroxymethyl compounds can be done easily and in high yield on mono-, di- and triformyl derivatives alike. Other reactions investigated for monoformyl fatty esters include reductive amination to form aminomethyl derivatives and Tollen’s condensation with formaldehyde to form geminal,bis-hydroxymethyl compounds. although the Northern Center has carried out some basic investigations on the hydroformylation reaction and on the chemistry of the hydroformylated products, there is a great deal more that can be done with regard to synthesis of new compounds and development of new applications.     

Reactions of unsaturated fatty alcohols. III. Viscosity and molecular weight studies on some vinyl ether polymers

Summary Molecular weights of the polymers of the vinyl ethers of stearyl, soybean, and linseed fatty alcohols were measured cryoscopically in cyclohexane at three different concentrations. Corrected number-average molecular weights were obtained by extrapolation to zero cocentration. For each family of polymers a series of preparations varying in degree of polymerization were studied with number-average molecular weights ranging from 1,500 to 15,000 or higher. Reduced viscosity measurements at 25°C. were made on benzene solutions of each polymer preparation at three different concentrations. Intrinsic viscosities were obtained by extrapolating to zero concentration. Intrinsic viscosities for the polymers range from 0.05 to 0.20. Logarithmic plots of molecular weightvs. intrinsic viscosity gave linear relationships for stearyl, soybean, and linseed polymers. Values forK′ anda in the equation of Mark and Houwink were obtained from these plots. Presented at fall meeting. American Oil Chemists' Society, September 23–26, 1956, Chicago, Ill.     

Production of fatty alcohols from fatty acids

Detergent-range alcohols from natural feedstock can be produced by high pressure hydrogenation of either methyl esters or fatty acids. The increasing quantities of fats and oils on the world market secure a reliable and economically priced material. Although fatty acid is an abundant worldwide commodity, most alcohol producers hydrogenate methyl esters, because direct hydrogenation of fatty acids is difficult as the catalyst is sensitive to acid attack. The process described here makes it possible to hydrogenate fatty acids directly to alcohols of high quality without prior esterification. The reaction takes place in the liquid phase over a fine-grained copper chromite slurry in a single reactor vessel. A special reactor design with an optimum arragement of the feeding nozzles causing an appropriate circulation of the reacting components inside the reactor facilitates the rapid “in situ” esterification reaction. This minimizes the free fatty acid concentration in the reactor to nearly zero. This results in a low consumption of catalyst. The most important advantages of the process are: direct feed of fatty acids of various origins, use of reasonably priced raw materials such as soapstock fatty acids and lower grade tallow acids, no process steps with methanol, and excellent economics. The process is industrially proven.     

Polymerization of unsaturated fatty acids

Summary A method is proposed for the preparation of polybasic fat acids or “dimer” acids directly from fatty acids which is readily adaptable to commercial use. The presence of moisture maintained in the reaction vessel by steam pressure substantially prevents decomposition and decarboxylation of the fatty acids. By this method a larger percentage of dibasic acids, as compared to tribasic acids, is produced than by the previously described methods. The method of high temperature polymerization of fatty acids in the presence of moisture is also used to remove polyunsaturated fatty acids from commercial oleic acid. Presented at 20th fall meeting, American Oil Chemists’ Society, Chicago, Ill., Oct. 30–Nov. 1, 1946.     

New method for hydroxylating long-chain unsaturated fatty acids,esters, alcohols,and hydrocarbons

Summary A new method for hydroxylating long-chain unsaturated compounds is described which involves addition of formic acid at its boiling point to the double bond followed by hydrolysis of the intermediate formate esters. The addition reaction proceeds slowly in the absence of catalysts, but strongly acidic substances, such as perchloric acid, sulfuric acid, and boron fluoride-acetic acid complex, speed up the addition tremendously. Monohydroxystearic acids can be prepared in good yield by addition of 90–100% formic acid to the double bond of oleic or elaidic acids, methyl oleate, or the unreacted olefinic material separated from the hydrolyzed reaction product of oleic acid with formic acid, followed by hydrolysis. Similarly prepared are dihydroxyoctadecanes from oleyl alcohol, monohydroxyoctadecenoic and dihydroxystearic acids from linoleic acid, monohydroxyhendecanoic acids (isolated as methyl esters) from 10-hendecenoic (undecylenic) acid, and secondary hexanols from 1-hexene. Triglycerides are readily formylated if a small amount of mutual cosolvent is employed. Acetic acid in the presence of acidic catalysts also adds to the double bond at its normal boiling point, but yields are lower than with formic acid. Presented at the Fall Meeting of the American Oil Chemists’ Society, Cincinnati, O., Oct. 20–22, 1952. One of the laboratories of the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, U. S. Department of Agriculture.