Hydrogenation of alkali-conjugated linoleate: Isomeric monoene profiles obtained with nickel,palladium and platinum catalysts

Alkali-conjugated linoleate (cis-9,trans-11- andtrans-10,cis-12-octadecadienoate) was hydrogenated with nickel, palladium and platinum catalysts. Thetrans andcis monoenes formed during reduction were isolated, and their double bond distribution was determined by reductive ozonolysis and gas liquid chromatography. About 44–69% of the monoenes were composed of δ¹⁰ and δ¹¹ trans monoene isomers, whereas the δ⁹ and δ¹² cis monoenes amounted to 20–26%. With nickel catalyst, composition of monoene isomers remained the same, even when the hydrogenation temperature was increased. The monoene isomer profiles between nickel and palladium catalysts were indistinguishable. Isomerization of monoenes with platinum catalyst was suppressed at 80 psi. The position of the double bonds in unreacted conjugated diene was always retained, except with nickel at both temperatures and with platinum at 150 C when a slight migration occurred. Geometrical isomerization totrans,trans-conjugated diene was observed in the unreacted diene with nickel (ca. 15% of diene) at both 100 C and 195 C, and with platinum (ca. 7% of diene) at 150 C. ARS, USDA.     

Deuteration of methyl linoleate with nickel,palladium, platinum and copper-chromite catalysts

Samples taken during deuteration of methyl linoleate with the title catalysts were separated into saturate, monoene and diene fractions. Monoenes were further separated intocis andtrans fractions. A comparison of the double bond distribution in monoenes with those from hydrogenation of alkaliconjugated linoleate indicated that up to 59% of the linoleate was reduced through a conjugated intermediate with nickel catalyst. The respective percentages for palladium and platinum catalysts were 51 and 23. Copper catalysts have previously been shown to reduce linoleate solely through conjugated intermediates. Copper-chromite catalyst showed infinite selectivity for the reduction of linoleate, because stearate did not form. The decreasing order of various catalysts for the selective reduction was copper-chromite>>>Ni at 195 C>Pd>Ni at 100 C>Pt. Computer simulation of platinum reduction indicated that ca. 20% of the linoleate was directly reduced to stearate through a shunt. Geometrical isomers of linoleate were formed during reduction with all catalysts except copper-chromite. Nickel catalyst formed bothtrans,trans- andcis,trans-isomers, as well as nonconjugatable dienes. These isomers were favored at the higher temperature and deuterium was incorporated into them. Palladium and platinum did not isomerize linoleate to nonconjugatable dienes. Because conjugated dienes are more reactive than linoleate, they were not found in appreciable amounts during reduction. Conjugated dienes were the only isomers formed with copper-chromite catalyst. Deuterium was found in these conjugated dienes, which were also extensively isomerized. As a result of isomerization and exchange during reduction of linoleate-as well as further exchange between deuterium and monoenes-a wide distribution of isotopic isomers in monoenes was found with nickel, palladium and platinum catalysts. Since isomerization of monoenes with copper-chromite is negligible, the isotopic distribution of monoenes must be due to exchange of intermediate conjugated dienes followed by addition. Presented at the AOCS Meeting, Ottawa, September 1972. ARS, USDA.     

Hydrogenation of linolenate. X. Comparison of products formed with platinum and nickel catalysts

One mole of hydrogen/mole of ester was added to methyl linolenate over a platinum catalyst at 20C and atmospheric pressure. The product was separated into trienoic, dienoic and monenoic esters by countercurrent distribution (CCD) with acetonitrile and hexane. Bach of these ester fractions was further separated by CCD with methanolic silver nitrate and hexane. Comparison with hydrogénations, in which a commercial nickel catalyst at 140C and atmos-pheric pressure was used, shows that with plati-num more stéarate is formed ; i.e., the platinum hydrogénation was less selective. Also, a smaller amt oftrans esters was formed with platinum, and there was less shift of double bonds from the original 9, 12 and 15 positions. Presented at AOCS Meeting, Atlanta, 1963. A laboratory of the No. Utiliz. Res. & Her. Div., ARS, USDA.     

Kinetics of hydrogenation of conjugated triene and diene with nickel,palladium, platinum and copper-chromite catalysts

A mixture of methyl linoleate and alkali-conjugated methyl linoleate was reduced with nickel, palladium, platinum and copper-chromite catalysts. The course of hydrogenation was followed by gas liquid chromatography of samples withdrawn at intervals. Relative rate constants of reactants and inermediates were calculated by a computer. Conjugated linoleate was 10–18 times more reactive than methyl linoleate with all catalysts except platinum, which showed no selectivity at 60 C. At 150 C conjugated diene reacted four times faster than methyl linoleate with platinum catalyst. A conjugated diene-to-stearate shunt was observed with palladium and platinum catalysts. When β-eleostearate was hydrogenated with the same catalysts, 50–97% of the triene was reduced directly to monoene with all catalysts except copper chromite, which selectively reduced conjugated triene to conjugated diene. On the basis of present kinetic data and previous knowledge about the mode of hydrogen addition to conjugated systems, a scheme has been proposed to account for the products formed during hydrogenation of methyl linolenate. ARS, USDA.     

Hydrogenation of linolenate. VI. Survey of commercial catalysts

A survey of commercially available hydrogenation catalysts has been made in a search for high-selectivity and low-isomerizing characteristics. Selectivity—the ratio of hydrogenation rates for linolenate to linoleate—was determined on a linoleate-linolenate equimixture under standardized conditions. Ratios of reaction rate constants for nickel catalysts at 140C ranged between 1.48 and 2.71; for palladium catalysts at 25C, 1.68 to 1.99; and for platinum catalysts at 25C, 1.33 to 1.61.Trans contents of ester mixtures reduced with these three metal catalysts ranged from 18.0 to 22.8, 16.7 to 20.5, and 6.3 to 8.4%, respectively. Although platinum catalysts produced the lowest isomerization, their selectivities were also low. Presented at Spring meeting, American Oil Chemists' Society, 1961. A laboratory of the Northern Utilization Research and Development Division. Agricultural Research Service, U.S.D.A.     

Hydrogenation of carbons catalyzed by nickel,platinum and rhodium

Catalytic hydrogenation of a carbon was investigated at a constant temperature. The reaction occurred in two stages as observed thermogravimetrically. For a nickel-catalyzed reaction at 540°C, about a half of active carbon was rapidly gasified to methane and the remaining carbon was gasified at a very slow rate. The activation energy for the latter reaction was estimated as 25 kcal/mole. When the carbon was partially oxidized to increase the concentration of surface functional groups, the methane formation in the first stage decreased. An X-ray study showed the formation of crystalline carbon during the course of the reaction. The presence of two stages is attributed to the presence of two components with different reactivities in carbon. The carbon gasified in the first stage may be an amorphous one, and a more crystalline fraction remains without reacting until the temperature is raised up to the reaction temperature for the second stage.     

Hydrogenation of natural oils with platinum metal group catalysts

Studies in the hydrogenation of natural oils with catalysts of the platinum metals group have been limited mainly to platinum and palladium with only scant attention to rhodium, ruthenium, iridium and osmium. This preference was dictated largely by economics, palladium being the only noble metal catalyst truly competitive on a usecoat basis with nickel in the hydrogenation of low-priced oils. This paper discusses the noble metal catalysts as a group, points out similarities and differences among the metals relevant to the hydrogenation of natural oils, and describes some of the practical applications of catalysis by palladium. One of 10 papers to be published from the Symposium “Hydrogenation”, presented at the AOCS Meeting, New Orleans, April 1970.     

Hydrogenation of heptaldehyde to heptyl alcohol with nickel catalysts

Hydrogenation of heptaldehyde to heptyl alcohol was studied with W2 Raney nickel catalyst, prepared in the laboratory, commercial Raney nickel catalyst and Rufert nickel catalyst by varying temperature, catalyst concentration, hydrogen pressure and reaction time. The products were analyzed by gas-liquid chromatography on SE-30 column. The optimum conditions found for quantitative conversion (99.6%) of heptaldehyde to heptyl alcohol were: temperature, 100°C, W2 Raney nickel catalyst concentration, 2% based on heptaldehyde (w/w), hydrogen pressure, 145 psig and reaction time, 1 h. IICT Communication No. 3085.     

Synthesis and characterization of triacylglycerols containing linoleate and linolenate

Triacylglycerols containing linoleate and linolenate found in vegetable oils were synthesized in gram quantities for oxidation studies. Two acylation methods were examined to convert diacylglycerols or monoacylglycerols to the desired triacylglycerols. Acylations with fatty acid and 1,1′-dicyclohexylcarbodiimide in the presence of 4-dimethylaminopyridine were more rapid, gave triacylglycerols of better isomeric purities and generally better overall yields than the acylations with acid chloride in pyridine. The functional and isomeric purity of the synthetic triacylglycerols were investigated by thin-layer and gas-liquid chromatography of the methyl esters, by lipase hydrolysis, and by¹³C NMR. Quantitative¹³C NMR provided a valuable tool to determine isomeric structures of the unsaturated triacylglycerols and complemented the lipase hydrolysis method. The triacylglycerols purified by dry column chromatography were obtained in the following respective percent yields, functional and isomeric purities: LLLn, 92.1, 99.4, 98.1; LLnLn, 91.7, 99.2, 97.4; LLnL, 84.2, 99.7, 98.9; and LnLLn 77.5, 97.8, 99.0 (where L=linoleoyl and Ln=linolenoyl glycerol residues). These synthetic triacylglycerols are valuable models to elucidate the interrelationship of unsaturated fatty acids on the oxidative stability of polyunraturated vegetable oils. Presented in part at the AOCS meeting in Phoenix, AZ in May 1988.     

Hydrogenation of linolenate. V. Procedure of evaluating hydrogenation catalysts for selectivity

Equations for determining the ratio of hydrogenation rates for linolenate and linoleate acyl groups are derived from kinetic theory. They are based upon the analysis for linolenate after absorption of 0.5 mole of hydrogen by an equal mixture of linoleate and linolenate. This method finds routine application in the evaluation of hydrogenation catalysts for selectivity. Presented at spring meeting, American Oil Chemists' Society, May 1–3, 1961, St. Louis, Mo. This is a laboratory of the Northern Utilization Research and Development Division, Agricultural Research Service, U. S. Department of Agriculture.     

Hydrogenation of soybean oil with copper catalysts containing small amounts of nickel catalysts

Reaction rates, linolenate/linoleate reaction selectivity,trans formation, and conjugated diene formation were determined for mixed commerical catalysts containing 0.5, 1, 2, 10, and 20 parts nickel catalyst (25% nickel) per 1000 parts copper chromite catalyst (ppt) and at catalyst concentrations in the oil of 1.0, 0.5, and 0.25%. The rate of hydrogenation increased as the amount of nickel increased. Addition of 0.5, 1, and 2 ppt nickel catalyst to copper chomite catalyst resulted in a small decrease in selectivity compared with straight copper chromite. When soybean oil was hydrogenated with these mixed catalysts sufficiently to reduce linolenate to 0, iodine values were 102–108 compared to 109–112 for straight copper chromite and to less than 80 for straight nickel. Presented at the AOCS Meeting, New Orleans April 1973. ARS, USDA.     

Catalytic dehydrogenation of propane on chromia,palladium and platinum supported catalysts

The dehydrogenation of propane to propylene over Cr₂O₃/Al₂O₃, Pd/Al₂O₃ and Pt/SiO₂ has been investigated in the temperature range 580–618°C. Runs were performed on propane, alone or in the presence of nitrogen (as a diluent), with complete analysis of the reaction products. The reaction was carried out in a fixed bed reactor at space velocities from 450–800 h^?1 which are close to industrial values and at pressures from 0.3 to 1 atm. A set of runs was made over a commercial chromia-alumina catalyst (10% Cr₂O₃) and over a promoted catalyst prepared in the laboratory by impregnation (16.8% Cr₂O₃ + 2% K₂O). The latter catalyst showed high selectivity and stability even when subjected to continuous cycles of dehydrogenation, regeneration and purging. Of the two noble metal supported catalysts used, reduced Pd/Al₂O₃ showed higher activity than Pt/SiO₂ at 618°C. The former catalyst gave a propylene yield of around 98% at 20% conversion level.     

Analysis of oleate,linoleate and linolenate hydroperoxides in oxidized ester mixtures

The hydroperoxides in oxidized mixtures of methyl oleate, linoleate and linolenate were analyzed by reducing the hydroperoxides to the corresponding hydroxyesters and separating the hydroxyesters from the unoxidized esters by thin layer chromatography (TLC). The hydroxyesters from linolenate were separated from the other hydroxyesters by TLC on silver ion plates. The hydroxyesters were converted to TMS-hydroxy derivatives. The TMS-hydroxyoleate and TMS-hydroxylinoleate were separated by gas chromatography (GC), and all the TMS-derivatives were quantified by GC. The relative rates of oxidation of methyl oleate, linoleate and linolenate in mixtures were ca. 1∶10.3∶21.6. The hydroperoxides formed in the oxidation of soybean and olive oils were similar before and after randomization and similar to corresponding methyl ester mixtures. Journal Paper No. J-9657 of the Iowa Agriculture and Home Economics Experiment Station, Ames. Project 2143.     

Synthesis and characterization of triacylglycerols containing linoleate and linolenate

The online version of the original article can be found at     

Hydrogenation of 1,2-indanedione over heterogeneous cinchonidine-modified platinum catalysts

Hydrogenation of the prochiral diketone, 1,2-indanedione was for the first time investigated using cinchonidine-modified Pt/Al₂O₃ as a catalyst. The influence of the reaction parameters on catalyst activity, regio- and enantioselectivity was studied revealing fully regioselective hydrogenation of the C(2)-keto group. Enantioselectivities of the (R)- versus (S)-2-hydroxy-1-indanone varied from low to moderate in favor of the (R)-enantiomer.

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Graphical abstract A systematic study of enantioselective hydrogenation of 1,2-indanedione – a new substrate for chirally modified heterogeneous catalysts – over cinchonidine modified Pt/Al₂O₃ is presented. The influence of the reaction parameters on activity, regio- and enantioselectivity was studied.

     

Selective hydrogenation with copper catalysts: I. Isolation and identification of isomers formed during hydrogenation of linolenate

Methyl linolenate was hydrogenated with 10% copper chromite catalyst at 150 C and atmospheric hydrogen pressure. The product was separated into monoene, diene and triene fractions by countercurrent distribution. These fractions were further separated into various geometrical isomers. The double bond location in the various fractions was determined by reductive ozonolysis. Double bonds in bothcis andtrans monoene fractions, as well as incis,trans andtrans,trans conjugated dienes, were extensively isomerized. A monoene containing vinylic unsaturation was one of the major products. The nonconjugated dienes were mostly dienes whose double bonds were widely separated. Results are explained on the basis of conjugation of the double bonds in linolenate followed by hydrogen addition. Presented in part at the symposium “Hydrogenation Process,” Division of Industrial Engineering Chemistry, 157th American Chemical Society Meeting, Minneapolis, April 1968. No. Utiliz. Res. Dev. Div., ARS, USDA.     

The hydrogenation of aromatics on catalysts having their platinum,ruthenium and palladium replaced with rhenium

Three alumina-supported catalysts containing 0.6% of the transition metals: platinum, ruthenium and palladium as well as combinations of each of these metals with rhenium have been studied for hydrogenating the aromatics present in a desulphurised white spirit fraction. The catalyst containing 0.6% Re, which represents complete replacement of the transition metal, appears to be completely inactive for the hydrogenation of aromatics. The relative activities of the catalysts containing 0.6% of the metals Pt, Ru and Pd at 100°C reaction temperature are of the order: 4.2:2.6:1, respectively, whereas for the 50/50 combinations of these metals with Re are of the order: 4.1:1.9:1, respectively, indicating that the replacement of Ru with Re may lower the hydrogenation activity of Ru by some 30%. The activation energies obtained for aromatic hydrogenation over the 0.6% Ru and Pd are, respectively, 6.17 and 8.83 kcal/mol, whereas they are 7.82 and 8.87 kcal/mol for the 50/50 replaced Ru and Pd catalysts, respectively with Re. On the other hand, the Pt-containing catalysts are too active to permit activation energy calculation.     

Hydrogenation of benzene on nickel catalysts promoted by ferroalloys

New industrial stationary catalysts, which are highly active, stable, and selective by cyclohexane and operate at temperatures of up to 140°C and pressures of up to 8 MPa, have been developed. The Ni-Al-FMo-grade catalyst developed by us is recommended for implementation in the production of cyclohexane from benzene.