Hydrogenation Of Methyl Esters Research Articles

Evaluation of partially hydrogenated methyl esters of soybean oil as biodiesel

AbstractBiodiesel, an alternative fuel derived from vegetable oils or animal fats, continues to undergo rapid worldwide growth. Specifications mandating biodiesel quality, most notably in Europe (EN 14214) and the USA (ASTM D6751), have emerged that limit feedstock choice in the production of biodiesel fuel. For instance, EN 14214 contains a specification for iodine value (IV; 120 g I2/100 g maximum) that eliminates soybean oil as a potential feedstock, as it generally has an IV >120. Therefore, partially hydrogenated soybean oil methyl esters (PHSME; IV = 116) were evaluated as biodiesel by measuring a number of fuel properties, such as oxidative stability, low‐temperature performance, lubricity, kinematic viscosity, and specific gravity. Compared to soybean oil methyl esters (SME), PHSME were found to have superior oxidative stability, similar specific gravity, but inferior low‐temperature performance, kinematic viscosity, and lubricity. The kinematic viscosity and lubricity of PHSME, however, were within the prescribed US and European limits. There is no universal value for low‐temperature performance in biodiesel specifications, but PHSME have superior cold flow behavior when compared to other alternative feedstock fuels, such as palm oil, tallow and grease methyl esters. The production of PHSME from refined soybean oil would increase biodiesel production costs by US$ 0.04/L (US$ 0.15/gal) in comparison to SME. In summary, PHSME are within both the European and American standards for all properties measured in this study and deserve consideration as a potential biodiesel fuel.

Deactivation and coke formation on palladium and platinum catalysts in vegetable oil hydrogenation

AbstractDeactivation of palladium and platinum catalysts due to coke formation was studied during hydrogenation of methyl esters of sunflower oil. The supported metal catalysts were prepared by impregnating γ‐alumina with either palladium or platinum salts, and by impregnating α‐alumina with palladium salt. The catalysts were reused for several batch experiments. The Pd/γ‐Al2O3 catalyst lost more than 50% of its initial activity after four batch experiments, while the other catalysts did not deactivate. Samples of used catalysts were cleaned from remaining oil by repeated extractions with methanol, and the amount of coke formed on the catalysts was studied by temperature‐programmed oxidation. The deactivation of the catalyst is a function of both the metal and the support. The amount of coke increased on the Pd/γ‐Al2O3 catalyst with repeated use, but the amount of coke remained approximately constant for the Pt/γ‐Al2O3 catalyst. Virtually no coke was detected on the Pd/α‐Al2O3 catalyst. The formation of coke on Pd/α‐Al2O3 may be slower than on the Pd/γ‐Al2O3 owing to the carrier's smaller surface area and less acidic character. The absence of deactivation for the Pt/γ‐Al2O3 catalyst may be explained by slower formation of coke precursors on platinum compared to palladium.

Squalene in oils determined as squalane by gas—liquid chromatography after hydrogenation of methyl esters

AbstractLow levels (≤0.1%) of squalene were anticipated in oils from the blubber of the harp seal Phoca groenlandica. The traditional roule of saponification and analytical examination of the total unsaponifiables was unattractive. A method developed for squalene in olive oil, reportedly present in the range of 0.3–0.7%, was based on total conversion of the oil to methyl ester of fatty acids by alkali transesterification, followed by hydrogenation over Adam's catalyst (PtO2). The analysis of the fully saturated methyl esters and any squalane produced concurrently was by gas—liquid chromatography. This method was satisfactory for the small amounts, 0.03% or less, of squalene in seal oil and is also illustrated for olive oil. A flame‐ionization detector excessive response of approximately 25% was observed for all levels of squalene tested. The calculated factor of 1.22 should be applied to the peak area for squalane due to the higher response of hydrocarbons relative to the methyl esters of fatty acids and the system of oil components if reporting as fatty acids.

Fatty methyl ester hydrogenation to fatty alcohol: Reaction inhibition by glycerine and monoglyceride

AbstractThe present work demonstrates the rate‐limiting effect of varying levels of both glycerine and monoglyceride through a series of batch hydrogenations of fatty dodecyl methyl ester, using copper chromite as the catalyst. Reactions were carried out at 3000 psig H2, 280°C with catalyst levels varying between 1.25 and 1.80%. With increasing contaminant levels of glycerine (0.0, 0.1, 0.5, 5 wt%), conversion of fatty methyl ester to alcohol is correspondingly reduced (95, 89, 80, 2 wt%). On a molar basis of contaminant, monoglyceride equally reduces the conversion of methyl ester to alcohol. In both cases the latent appearance of fatty‐fatty ester results from the slower hydrogenation rate. Chemistry is proposed outlining the thermal decomposition of glycerine or glyceride to intermediate components (acetol and acrolein), leading to the generation of propanediols. Experimental studies indicate that diols effectively deactivate the copper chromite catalyst, limiting the rate of fatty methyl ester hydrogenation. Catalyst deactivation is not permanent, suggesting catalyst site blockage by physical adsorption of the polyhydroxyl components. The complete understanding of this interaction holds promise for the development of glycerine/monoglyceride‐insensitive catalysts. In addition, a brief overview of methyl ester hydrogenation inhibition effects of some heteroelements, water, and soap is presented.

Intrinsic Kinetics of 9-Monoenic Fatty Acid Methyl Ester Hydrogenation over Nickel-Based Catalysts

The monoenic fatty acid methyl ester hydrogenation and isomerization over a supported nickel catalyst was studied at 0.02 ≤ PH2 ≤ 0.50 MPa and 333 ≤ T ≤ 443 K. Batch hydrogenations at constant and variable hydrogen pressure were carried out to investigate the rate-determining steps. On the basis of the Horiuti−Polanyi mechanism, involving a half-hydrogenated surface intermediate, kinetic rate equations were systematically derived following the Langmuir−Hinshelwood−Hougen−Watson approach. Each set of rate equations was tested by means of a χ2 method on its ability to describe the experimental curves simultaneously. The χ2 was minimized by a stepwise optimization of model parameters. Furthermore, we used Bartlett's test to reduce the set of most-likely rate expressions. The statistically most significant model assumes the formation of the half-hydrogenated surface intermediate as the rate-determining step and an equilibrium associative hydrogen adsorption. The rate equations are RO = mc{[−( + Kisokiso)CO +...

Fatty methyl ester hydrogenation to fatty alcohol part I: Correlation between catalyst properties and activity/selectivity

AbstractFatty alcohols, derived from natural sources, are commercially produced by hydrogenation of fatty acids or methyl esters in slurry‐phase or fixed‐bed reactors. One slurry‐phase hydrogenation of methyl ester process flows methyl esters and powdered copper chromite catalyst into tubular reactors under high hydrogen pressure and elevated temperature. In the present investigation, slurry‐phase hydrogenations of C12 methyl ester were carried out in semi‐batch reactions at nonoptimal conditions (i.e., low hydrogen pressure and elevated temperature). These conditions were used to accentuate the host of side reactions that occur during the hydrogenation. Some 14 side reaction routes are outlined. As an extension of this study, copper chromite catalyst was produced under a number of varying calcination temperatures. Differences in catalytic activity and selectivity were determined by closely following side reaction products. Both activity and selectivity correlate well with the crystallinity of the copper chromite surface; they increase with decreasing crystallinity. The ability to follow the wide variety of side reactions may well provide an additional tool for the optimized design of hydrogenation catalysts.

Fatty methyl ester hydrogenation to fatty alcohol part II: Process issues

AbstractFatty alcohols are produced by hydrogenating fatty methyl esters in slurry phase in the presence of copper chromite catalyst at temperatures of 250–300°C and hydrogen pressures of 2000–3000 psi. The fatty methyl ester, catalyst, and hydrogen are fed to the reactor cocurrently. The product slurry is passed through gas‐liquid separators and then through a continuous filtration system for removal of the catalyst. A portion of the used catalyst in crude alcohol is recycled to the hydrogenator. The overall efficiency of the process depends upon the intrinsic activity, life, and filterability of the catalyst. The fatty alcohol producer therefore requires a catalyst with high activity, long life, and good separation properties. The main goal of the present laboratory investigation was to develop a superior copper chromite catalyst for the slurry‐phase process. Two copper chromite catalysts, prepared by different procedures, were tested for methyl ester hydrogenolysis activity, reusability, and filtration characteristics. The reaction was carried out in a batch autoclave at 280°C and 2000–3000 psi hydrogen pressure. The reaction rates were calculated by assuming a kinetic mechanism that was first‐order in methyl ester concentration. The catalyst with the narrower particle size distribution was 30% more active, filtered faster, and maintained activity for several more uses than the catalyst with the broader particle size distribution. X‐ray photoelectron spectroscopy data showed higher surface copper concentrations for the former catalyst.

Facile Preparation and Structural Determination of Monohydroxy Derivatives of Docosahexaenoic Acid (HDoHE) by α-Tocopherol-Directed Autoxidation

Polyunsaturated fatty acids are oxidized through both enzymatic and nonenzymatic reactions into hydroxy derivatives. With increasing interest in dietary manipulations through ingestion of the highly unsaturated fish oil fatty acids, eicosapentaenoic acid and docosahexaenoic acid (DHA), methods to measure their metabolism are required. In this study we report the simple and expedient α-tocopherol-directed autoxidative preparation of a series of monohydroxy derivatives of DHA to provide a relatively homogenous hydroxylation along each of the double bonds of the fatty substrate. Products were purified by high-performance liquid chromatography (HPLC) and their structures elucidated by the characteristic fragmentation pattern of the hydrogenated methyl ester trimethylsilyl ether derivatives by gas chromatography-mass spectrometry. Nine products were isolated in 20.2% yield overall, ranging from 1.55 to 4.14% yield of isolated compound. These were identified as 7, 8, 10, 11, 13, 14, 16, 17, and 20-HDoHEs (monohydroxydocosahexaenoic acids). Two of these products (14- and 17-HDoHE) could not be separated under the HPLC conditions used but were clearly distinguished using selected ion chromatography by their distinct mass spectral fragmentation. This method is highly suitable for the generation of standards to investigate the metabolism of DMA in tissues.

Formation of octadecadienoate dimers by soybean lipoxygenases

AbstractThe aim of this investigation was to determine whether the regioselectivity found for lipoxygenases in the formation of fatty acid hydroperoxides from linoleic acid is reflected in the formation of dimeric products in secondary reactions involving linoleic acid, product hydroperoxide and lipoxygenase. A method was therefore developed for the separation and identification of dimers formed by fusion of two linoleic acid radicals or a linoleic acid radical and linoleate. The method includes solid‐phase extraction, preparative separation of products by thin‐layer chromatography, derivatization to the corresponding fully hydrogenated methyl esters and capillary gas chromatography (GC) coupled with electron impact mass spectrometry. We present evidence that the formation of octadecadienoate dimers, during the secondary reaction of soybean lipoxygenase‐1 or lipoxygenase‐3, is a nonenzymic process that can be envisaged by nonspecific association of intermediate fatty acid radicals (L*) that have dissociated from the enzyme. We could show that the relative amounts of different octadecadienoate dimers formed remain unaltered, regard‐less of pH and type of soybean isoenzyme used. Quantitative analysis by GC showed that under the reaction conditions used, the formation of dimers branching at the 13‐position is preferred.

Remodeling of rat hepatocyte phospholipids by selective acyl turnover

Acyl turnover of rat hepatocyte phospholipids and triacylglycerols was assessed by incubating the cells in media containing 40% H2(18)O and measuring the time-dependent incorporation of 18O into ester carbonyls by gas chromatography-mass spectrometry of hydrogenated methyl esters. Incorporation of 18O into 22-carbon acyl groups was low in phosphatidylcholine, phosphatidylinositol, and phosphatidylserine, whereas in phosphatidylethanolamine, it was about the same as in the other acyl groups. Incorporation of 18O into individual molecular species of phosphatidylcholine and phosphatidylethanolamine was determined after phospholipase C hydrolysis, derivatization to dinitrobenzoates, and separation by high-performance liquid chromatography. In most molecular species, acyl groups at the sn-1 and sn-2 positions became 18O-labeled at drastically different rates, indicating remodeling through deacylation-reacylation. Molecular species expected to arise de novo from acylation of glycerophosphate exhibited similar rates of 18O incorporation at the sn-1 and sn-2 positions. The data suggest that hepatocyte phospholipids are continually synthesized, remodeled by deacylation-reacylation at specific turnover rates up to 10-15%/h, and degraded. This acyl turnover probably does not involve the majority of intracellular unesterified fatty acids whose 18O incorporation was found to be very low. In contrast, the oxygens of extracellular unesterified fatty acids were readily exchanged with the media. This exchange was enzyme-catalyzed, possibly by lipases released into the media from damaged cells. Incorporation of 18O into exogenously added fatty acids was also rapid and resulted in enhanced uptake of 18O-labeled fatty acids into cellular lipids, primarily triacylglycerols and phosphatidylcholine, without drastic change of the intracellular free fatty acid pool.

Differential turnover of phospholipid acyl groups in mouse peritoneal macrophages.

Phospholipid acyl turnover was assessed in mouse peritoneal exudate cells which consisted primarily of macrophages. The cells were incubated for up to 5 h in media containing 40% H218O, and uptake of 18O into ester carbonyls of phospholipids was determined by gas chromatography-mass spectrometry of hydrogenated methyl esters. The uptake was highest in choline phospholipids and phosphatidylinositol, less in ethanolamine phospholipids, and much less in phosphatidylserine. Acyl groups at the sn-1 and sn-2 positions of diacyl glycerophospholipids, including arachidonic and other long-chain polyunsaturated fatty acids, acquired 18O at about the same rate. Acyl groups of alkylacyl glycerophosphocholine exhibited lower rates of 18O uptake, and acyl groups of ethanolamine plasmalogens (alkenylacyl glycerophosphoethanolamines) acquired only minimal amounts of 18O within 5 h, indicating a low average acyl turnover via free fatty acids. Pulse experiments with exogenous 3H-labeled arachidonic acid supported the concept that acylation of alkenyl glycerophosphoethanolamine occurs by acyl transfer from other phospholipids rather than via free fatty acids and acyl-CoA. The 18O content of intracellular free fatty acids increased gradually over a 5-h period, whereas in extracellular free fatty acids it reached maximal 18O levels within the first hour. Arachidonate and other long-chain polyunsaturated fatty acids were found to participate readily in deacylation-reacylation reactions but were present only in trace amounts in the free fatty acid pools inside and outside the cells. We conclude that acyl turnover of macrophage phospholipids through hydrolysis and reacylation is rapid but tightly controlled so that appreciable concentrations of free arachidonic acid do not occur.

ChemInform Abstract: Hydrogenation of Unsaturated Fatty Acid Methyl Esters Using Decalin for Hydrogen Transfer.

A laboratory procedure was developed for hydrogenation of methyl esters of unsaturated fatty acids using decalin as a hydrogen-transfer agent and 10% Pd/C as catalyst. The esters of 10-undecenoic, oleic, elaidic, stearolic, linoleic, cycloaliphatic C21 di-, C22 tri- and C36 dicarboxylic acids, and a mixture of hydrnocarpic, chaulmoogric and gorlic acids were hydrogenated. Chromatographic and spectral analyses showed complete saturation. This procedure is simple, requiring no external source of hydrogen.

Gas chromatographic/mass spectrometric quantitative analysis of eicosanoids in human oesophageal mucosa.

In order to investigate the contribution of eicosanoids to human oesophageal functions and disorders (gastrooesophageal reflux, GOR and reflux oesophagitis, RO), we have used a selected ion monitoring gas chromatographic/mass spectrometric methodology to quantify the cyclooxygenase and lipoxygenase products biosynthesized in vitro by endoscopic mucosal biopsy specimens. Prostaglandins (PGs) were quantified as MEMOTMS derivatives and HETEs, as hydrogenated methyl ester of tert-butyldimethylsilyl) ether derivatives. PGE2, PGF2 alpha appeared as the major prostanoids, whereas 12HETE seemed to be the major lipoxygenase product. In the case of GOR or RO, biosynthesis of PGE2 was dramatically increased, while no change could be detected for 12HETE. PGE2 increase seems to be related to inflammatory reaction, in which its exact role remains unclear. Moreover, it cannot be excluded that PGE2 is a side product which might be protective to the oesophageal mucosa.

The acid‐catalyzed addition of alkoxyl groups to the olefinic double bonds of soybean oil

AbstractThe acid‐catalyzed reaction of soybean oil with the homologous series of straight‐chain alcohols: methyl, ethyl, n‐propyl, n‐butyl and n‐hexyl in a pressurized system yielded completely transesterified products and 18‐31% substituted alkyl ethers. Mass spectrometry of the hydrogenated methyl ester derivatives showed that the addition reaction occurred at one of three double bonds of the unsaturated fatty acids. The reaction with three secondary alcohols yielded only 0.1‐2.5% substituted alkyl ethers.

Hydrogenation of unsaturated fatty acid methyl esters using decalin for hydrogen transfer

AbstractA laboratory procedure was developed for hydrogenation of methyl esters of unsaturated fatty acids using decalin as a hydrogen‐transfer agent and 10% Pd/C as catalyst. The esters of 10‐undecenoic, oleic, elaidic, stearolic, linoleic, cycloaliphatic C21 di‐, C22 tri‐ and C36 dicarboxylic acids, and a mixture of hydrnocarpic, chaulmoogric and gorlic acids were hydrogenated. Chromatographic and spectral analyses showed complete saturation. This procedure is simple, requiring no external source of hydrogen.

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

AbstractThe 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.

Diastereoselective hydrogenation of methyl esters of trifluoroacetyldehydrophenylanalyl dipeptides and trifluoroacetyldehydrovalyl dipeptides

The stereoselectivity of hydrogenation of methyl esters of N-trifluoroacetyl dehydrodipeptides on a Ni-catalyst was determined by the structure of the C-terminal residue and the prochiral center. The S-configuration of the C-terminal amino acid leads to the formation of the R-configuration of a new center. The proline residue has the highest induction.

Cyclic fatty acid monomer formation in frying fats. I. Determination and structural study

AbstractThe formation of monomeric cyclic fatty acids was studied in a model system in which partially hydrogenated soybean oil (PHSO) was heated intermittently for 80 hr of simulated deep fat frying. Oil samples (fresh and heated) and their methyl esters were fractionated according to their molecular size using gel permeation chromatography (GPC). Oils and GPC fractions were analyzed for cyclic monomers by the following steps: (i) preparation of fatty acid methyl esters (FAME); (ii) microhydrogenation of FAME; (iii) urea fractionation of hydrogenated FAME; (iv) analysis by capillary gas liquid chromatography (GLC), and (v) structural characterization of cyclic monomer peaks by mass spectrometry (GC‐MS). Under simulated frying conditions the concentration of cyclic monomers increased from 736 ppm (0.07%) in fresh oil to 1803 ppm (0.18%) in heated oil. GC‐MS with capillary columns allowed the identification of several C18α‐disubstituted cyclohexane and cyclopentane isomers as hydrogenated methyl esters. Other noncyclic and contaminant compounds eluting within the expected GLC retention range of cyclic monomers also were identified in all the samples and GPC fractions.

Hydrogenation of methyl ester of Z-α-acetamidocinnamic acid catalysed by rhodium-phosphine carboxylates

The title reaction has been studied using the in situ catalysts prepared from [Rh(COD)Cl]2, [Rh(COD)OOCCH3]2 or Rh(COD) (acac) and a series of mono- and diphosphines. The use of (+)-N-acetylphenylalanine as a chiral carboxylato ligand gave catalytic systems with low asymmetric efficiency ( optical yields from 5 to 10%). Kinetics of the hydrogenation catalysed by [Rh(COD)OOCCH3]2 + (C6H5)2P(CH2)4P(C6H5)2 or P(n-C4H9)3 (Rh : P mol.ratio = 1 : 2) is reported.

Manufacture of fatty alcohols based on natural fats and oils

AbstractThe present worldwide capacity of fatty alcohols is ca. 1.0 million metric tons per year. About 60% of this capacity is based on petrochemical feedstocks, 40% on natural fats and oils. Three basic dominating commercial‐scale processes are used to manufacture fatty alcohols: the Ziegler process and the Oxo synthesis starting from petrochemical feedstocks, and the high‐pressure hydrogenation of natural fatty acids and esters. Basically, the high‐pressure hydrogenation can be used with triglycerides, fatty acids or fatty acid esters as feedstock. The direct hydrogenation of fats and oils has not been developed to a commercial‐scale process, mainly because it was not possible to prevent decomposition of the valuable byproduct glycerol. Conversion of fatty acids into fatty alcohols by catalytic hydrogenation without preesterification requires corrosion‐resistant materials of construction and acid‐resistant catalysts. Required reaction temperatures are higher, resulting in a higher hydrocarbon content. The majority of fatty alcohol plants based on natural fats and oils use methyl esters as feedstock. These can be made either by esterification of fatty acids or by‐transesterification of triglycerides. For catalytic high‐pressure hydrogenation of methyl esters to fatty alcohols, several process options have been developed. The bawic distinguishing feature is the catalyst application either in a fixed bed arrangement or suspended in the methyl ester feed.