Transfer hydrogenation and transfer hydrogenolysis: XII. Selective hydrogenation of fatty acid methyl esters by various hydrogen donors

The selective hydrogenation of methyl linoleate was studied using various organic compounds as hydrogen sources in the presence of homogeneous and metallic palladium catalysts. Complete selectivity to monoenes and relatively little formation of isolatedtrans double bonds were realized by the hydrogen transfer from L-ascorbic acid at 47% conversion of starting material to hydrogenation products. The hydrogenation bytrans-1,2-cyclohexanediol catalyzed by RuH₂(PPh₃)₄ also showed rather high selectivity tocis-monoenes. In the reaction catalyzed by RuH₂(PPh₃)₄, also showed rather high selectivity tocis-monoenes. In the reaction catalyzed by RuH₂(PPh₃)₄, the presence of these hydroxy compounds increased the isomerization of methyl elaidate tocis-monoenes.     

Mass transfer resistances in the palladium-catalyzed hydrogenation of methyl linoleate

The hydrogenation of methyl linoleate to methyl oleate and methyl stearate was studied in a 6-inch stirred batch reactor at 121°C and 45 psia. Several particle size fractions of a 1 per cent Pd-carbon catalyst were used to help separate the gas absorption resistance, the external mass transfer resistance, and the internal resistance to pore diffusion and reaction. Corrected to the same concentration of hydrogen, the initial rate of reaction for linoleate was 30 times that for oleate. This difference in reactivity and stronger adsorption of linoleate account for the high selectivity of 50–80.     

Autoxidation of methyl linoleate. Separation and analysis of isomeric mixtures of methyl linoleate hydroperoxides and methyl hydroxylinoleates

The mixture of conjugated diene hydroperoxide isomers obtained from autoxidation of methyl linoleate was separated by high performance liquid chromatography (HPLC). Four major isomers were obtained from adsorption chromatography and identified as the 9 and 13 positional isomers having thetrans-trans andcis-trans configurations. The latter geometrical isomers have thetrans double bond adjacent to the hydroperoxide group. The hydroxy compounds (methyl hydroxylinoleates) obtained from the hydroperoxides by NaBH₄ reduction were similarly separated but with improved resolution. This is the first instance of the complete separation of these compounds and provides a rapid method for their analysis. Unlike adsorption chromatography, reversed-phase chromatography separates the mixtures only according to the geometrical isomerism of the double bonds and not according to the position of the hydroxy or hydroperoxide function.     

Positional isomers formed during the hydrogenation of methyl linoleate under various conditions

Journal of the American Oil Chemists' Society -     

Vapor-Phase hydrogenation of methyl linoleate in the presence of a supported copper catalyst

Methyl linoleate was hydrogenated in the vapor phase in the presence of a copper-on-alpha alumina catalyst. The kinetics of the reaction could be formulated with a Eley-Rideal mechanism including the reaction between chemisorbed methyl ester and hydrogen in the gas phase. The absorption coefficients in the rate equation were based on separately performed adsorption studies recently reported.     

The role of hydrogen in the selectivity of vapor-Phase hydrogenation of methyl linoleate

Methyl linoleate was hydrogenated in the vapor phase in the presence of a nickel on alpha-alumina catalyst. A reaction mechanism was proposed to explain the fact that the selectivity is influenced by the hydrogen pressure. A rate equation was derived based on the mechanism and the rate constant was evaluated from kinetic experiments. The adsorption coefficients in the rate equation were based on separately performed adsorption studies recently published.     

Mn/Ti-Zr复合氧化物催化苯甲酸甲酯选择性加氢

以五水合硝酸锆和钛酸四丁酯为原料,采用共沉淀法制备Ti-Zr-O氧化物载体,采用浸渍法制备了Mn/Ti-Zr催化剂;采用XRD、N2物理吸-脱附、H2-TPR、NH3-TPD和TG对Mn/Ti-Zr催化剂进行了表征,并考察了催化剂组成、结构和反应条件对苯甲酸甲酯(MB)加氢性能的影响,以及催化剂的长周期稳定性、失活和再...     

Mn/Ti-Zr复合氧化物催化苯甲酸甲酯选择性加氢

以硝酸锆和钛酸四丁酯为原料,采用共沉淀法制备Ti-Zr-O氧化物载体,采用浸渍法制备了Mn/Ti-Zr催化剂;采用XRD、N2物理吸附、H2-TPR、NH3-TPD和TG-DTA对Mn/Ti-Zr催化剂进行了表征,并考察了催化剂组成、结构和反应条件对苯甲酸甲酯（MB）加氢性能的影响,以及催化剂的长周期稳定性、失活和再生行为。结果表明：TiO2含量和Mn负载量分别为12% 和8% （二者均以Ti-Zr-O氧化物的质量为基准,下同）时制备的Mn/Ti-Zr催化剂性能最优,该催化剂在θ = 390 ℃, p = 1.0 MPa,n(H2)∶n(MB) = 9∶1和重时空速（WHSV）= 0.5 h-1的优化条件能够实现98.0% 的苯甲酸甲酯转化率和89.7%的苯甲醛和苯甲醇选择性;苯甲酸甲酯加氢反应的活性和选择性分别与Mn/Ti-Zr表面MnOx物种的氧化还原性和催化剂的酸性密切相关。此外,Mn/Ti-Zr催化剂具有良好的结构稳定性,在反应1000 h后仅因积碳而丧失11% 的活性,且轻微失活的催化剂可以通过焙烧恢复其初始活性和选择性。     

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

The 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.     

Ca对Ni基催化剂上丙酮加氢制备异丙醇性能的影响

以ZSM-5为载体制备了Ni-Ca/ZSM-5催化剂,考察了其对丙酮气相加氢制备异丙醇性能的影响,并考察了不同反应温度及催化剂焙烧温度对催化性能的影响。通过XPS、NH_3-TPD、XRD、SEM、N2吸附/脱附等表征手段对催化剂进行了详细的研究。结果表明,Ni-Ca/ZSM-5对丙酮加氢反应具有较高的催化活性,最佳反应温度为130℃,最佳焙烧温度为450℃。     

Mucor sp.JX23发酵液生物催化肉桂醛选择加氢制肉桂醇

研究了Mucor sp. JX23发酵液直接生物催化肉桂醛选择加氢制肉桂醇的反应,并考察了肉桂醛质量浓度、反应pH值、温度、时间等因素对反应转化率和选择性的影响。结果表明,Mucor sp. JX23发酵液的最适催化条件为：肉桂醛质量浓度3 g/L,反应体系的初始pH = 6.0,28℃反应70h。在此条件下,肉桂醛的转化率为82.9%,肉桂醇的选择性为90.4%。     

Ca对Ni基催化剂上丙酮加氢制备异丙醇性能的影响

以ZSM-5为载体制备了Ni-Ca/ZSM-5催化剂,考察了其对丙酮气相加氢制备异丙醇性能的影响,并考察了不同反应温度及催化剂焙烧温度对催化性能的影响。通过XPS、NH_3-TPD、XRD、SEM、N2吸附/脱附等表征手段对催化剂进行了详细的研究。结果表明,Ni-Ca/ZSM-5对丙酮加氢反应具有较高的催化活性,最佳反应温度为130℃,最佳焙烧温度为450℃。     

亚临界相脂肪酸甲酯加氢制备脂肪醇

以Cu - Zn为催化剂,在正己烷亚临界状态下以脂肪酸甲酯为原料加氢制备脂肪醇.考察了正己烷用量、温度、氢气与原料油体积比对反应的影响,并对Cu - Zn催化剂和Cu - Cr催化剂的催化活性进行了比较.结果表明,在系统压力6.0 MPa,反应温度250℃,空速0.8h-1,正己烷与脂肪酸甲酯体积比7∶1,氢气与原料油体积比250∶1的条件下脂肪酸甲脂转化率为99.5％,脂肪醇选择性为99.6％,Cu - Zn催化剂的催化活性和选择性均优于Cu - Cr催化剂.     

Catalytic transfer hydrogenation/hydrogenolysis of guaiacol to cyclohexane over bimetallic RuRe/C catalysts

The hydrodeoxygenation of lignin monomer guaiacol via catalytic transfer hydrogenation was studied with 2-propanol as a hydrogen donor and Ru-based catalysts. Guaiacol was mainly converted into a partially deoxygenated product, cyclohexanol (> 70% selectivity), over Ru/C catalysts with the hydrogen produced in-situ from 2-propanol. An addition of Re to Ru/C catalysts significantly enhanced the rate of C—O hydrogenolysis, resulting in the complete deoxygenation to cyclohexane (~ 60% selectivity). The remarkable deoxygenation ability of the bimetallic RuRe/C catalyst is attributed to its bifunctional characteristic, by which Ru catalyzes the hydrogenation-hydrogenolysis of guaiacol and Re provides acid sites to promote cyclohexane production via hydrogenolysis.     

Selective hydrogenation of soybean oil: X. Ultra high pressure and low pressure1

Soybean 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 (S_Ln) of the reaction remained essentially unchanged over 50–1000 psig pressure range. A S_Ln 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. 1 Presented at the AOCS meeting, San Francisco, May 1979.     

Autoxidation of methyl linoleate initiated by the ozonide of allylbenzene

Allylbenzene ozonide (ABO), a model for polyunsaturated fatty acid (PUFA) ozonides, initiates the autoxidation of methyl linoleate (18∶2 ME) at 37°C under 760 torr of oxygen. This process is inhibited by d-α-tocopherol (α-T) and 2,6-di-ert-butyl-4-methylphenol (BHT). The autoxidation was followed by the appearance of conjugated diene (CD), as well as by oxygen-uptake. The rates of autoxidation are proportional to the square root of ABO concentration, implying that the usual free radical autoxidation rate law is obeyed. Activation parameters for the thermal decomposition of ABO were determined under N₂ in the presence of radical scavengers and found to be E_a=28.2 ±0.3 kcal mol⁻¹ and log A=13.6±0.2; k_d (37°C) is calculated to be (5.1±0.3)×10⁻⁷ sec⁻¹. Autoxidation data are also reported for ozonides of 18∶2 ME and methyl oleate (18∶1 ME).     

Bleaching of vegetable oils. II. Conversions of methyl oleate and linoleate

Methyl oleate and linoleate were treated with 10% acid activated clay at 90–100 C for 1–50 hr with and without admission of air. Positional and geometric isomers of fatty acid esters were found. Polar compounds were detected having one or more functional groups with respect to the starting esters. Preparative thin layer chromatography and gas liquid chromatography were used in isolating the compounds, while IR, NMR, mass spectroscopy, and gas liquid chromatography analysis were employed for identification. The unsaturation of the isolated isomers was present at carbon atoms 5–11. The polar compounds were, among others, 9- and 10-keto octadecanoic methyl esters, isomeric keto octadecenoic methyl esters, isomeric epoxy octadecanoic methyl esters, 9- and 10-hydroxy octadecanoic methyl esters, and some mono methyl ester dicarbonic acids. It may be concluded that geometric, as well as positional, isomerization occurs and that small amounts of compounds with one or more functional groups are formed when unsaturated fatty acids were treated with acid-activated clay.     

Isomerization during hydrogenation of soap: II. Potassium elaidate and potassium linoleate

Potassium elaidate in slightly alkaline solution was hydrogenated for up to 7 hr with 1.5% of Rufert nickel catalyst at 150 C and 20 kg/sq cm pressure. Potassium linoleate was similarly hydrogenated with 1.0% catalyst for 7 hr, and the hydrogenation continued for another 7 hr after addition of 0.5% fresh catalyst. Periodic samples from each were analyzed for component acids. The positional isomers in thecis andtrans monoenes, isolated by preparative argentation thin layer (TLC) or column chromatography, were estimated after oxidation to dicarboxylic acids. Some diene fractions were isolated for further examination. In potassium elaidate hydrogenation,cis monoenes were initially produced in considerable amounts, but to a lesser extent thereafter. Positional isomers were similarly distributed in bothcis andtrans monoenes after prolonged hydrogenation. In the hydrogenation of potassium linoleate, a drop in iodine value (IV) of 60 units occurred in the first hour, and 38% oftrans monoenes (in which the 10- and 11-monoenes constitute 32% each) were formed. The IV then fell only slowly, and up to 38% ofcis monoene (mostly 9- and 12-isomers) was formed. Addition of fresh catalyst caused a major shift ofcis monoenes totrans forms. The diene fraction was mostly nonconjugated material with the first double bond at the 9, 8 and 10-positions. Minor amounts of conjugated dienes were present as well as a dimeric product.     

Hydrogen sulfide adducts of methyl oleate and linoleate

Sulfur compounds derived from photochemical addition of hydrogen sulfide to methyl oleate and linoleate were separated by preparative gas chromatography. The major compounds were investigated by NMR, mass and IR spectroscopy and by elemental analysis. The primary product of the methyl oleate reaction was methyl 9(10)-mercaptostearate. Gas chromatograms of the product from methyl linoleate showed four principal peaks. From mass spectra and NMR data, we identified methyl 9-(2-pentyl-1-thiolan-5-yl)nonanoate, methyl 8-(2-hexyl-1-thiolan-5-yl)octanoate and methyl 9-(3-hexyl-1,2-dithiolan-5-yl)nonanoate. Evidence for the formation of methyl mercapto-octadecenoates and methyl dimercaptostearates was also obtained. ARS, USDA.