Studies on the hydrogenation of alkenes and alkynes using silica coated polymer anchored palladium complexes

Palladium complexes of polyvinyl pyridine coated silica gel have been prepared and used as hydrogenation catalysts for alkenes and alkynes under ambient conditions. The kinetics of hydrogenation for a few substrates have been studied and a possible mechanism proposed. The kinetic and mechanistic aspects of the hydrogenation of the substrates, effect of additives on the rate of hydrogenation, selectivity of the catalyst and recycling efficiency of the catalyst are presented in this paper.     

Kinetics of the hydrogenation of fatty oils

Hydrogenation results for fatty oils were analyzed by using a nonlinear least squares method. The rate of the hydrogenation for diunsaturated fatty groups to monounsaturated groups and the rate of the geometrical isomerizations between monounsaturated groups were found to be half order with respect to hydrogen concentration, whereas the hydrogenation rate of monounsaturated groups was the first order. A detailed reaction mechanism is presented to explain the kinetic behavior.     

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.     

The hydrogenation of fatty oils with palladium catalysts. VI. Hydrogenation for margarine

Satisfactory margarine stocks have been made with a palladium on carbon catalyst in laboratory, pilot plant, and plant processing. The catalyst was shown to make a satisfactory product even when, on continued re-use, the ratio of oil to metal used reached 400,000 to 1.     

Reactors for hydrogenation of edible oils

Due to the characteristics of the hydrogenation of edible oil, by far the most common type of reactor has been the batch-type shurry hardener. Although continuous reactors offer several advantages compared to batch reactors, they are seldom used in the industry. This review paper describes the most commonly used full-scale reactors, both batch and continuous. Several different laboratory reactors are also described. The experimental results obtained from those reactors indicate that it is possible to achieve selectivites and reaction rates in a continuous reactor as high as in a slurry batch reactor.     

The hydrogenation of fatty oils with palladium catalyst. I. Hydrogenation of castor oil

Summary A good quality of castor wax was prepared in the laboratory at 100°C. and 45 p.s.i.g., using a modified palladium catalyst. The product obtained had an iodine value of 4, a hydroxy value of 145, and acid value of 1.8, and a capillary melting point of 86°.     

The hydrogenation of fatty oils with palladium catalyst. IV. Pilot-plant preparation of shortening stocks

Summary Shortening stocks obtained in the pilot plant differ slightly from those obtained in the laboratory under nominally the same conditions. Pilot-plant processing is easily controlled to give a commercially attractive shortening at a cost competitive with nickel. By repeated re-use 1 g. of 5% palladium on earbon catalyst will hydrogenate about 18 kg. of oil to a satisfactory product, and 1 g. of 2% palladium on carbon catalyst about 11 kg. of oil.     

Occurrence,detection, and prevention of cyclization during hydrogenation of fatty oils

It has been shown that, under certain extreme conditions during catalytic hydrogenation of materials containing polyunsaturated fatty acids, o-substituted benzene monocarboxylic acids (aromatic fatty acids = AFA) can be formed. Pure AFA were isolated from isomerized linseed oil, and their structure was elucidated from spectroscopic data. Final confirmation of the structure was obtained by direct synthesis. Quantitative determinations involved IR and NMR measurements of the urea non-adduct forming fraction. In this way as little as 0.01% AFA can be detected. To provide a greater operational latitude in technical processing without formation of these compounds, a two-stage modified hydrogenation process has been worked out.     

Partial hydrogenation of fatty acid methyl esters at supercritical conditions

Under supercritical or near-critical conditions propane is a very good solvent for both lipids and hydrogen. Thus, it is possible to generate an essentially homogeneous phase, in which the transport resistances for the hydrogen are eliminated. Therefore, the hydrogen concentration at the catalyst surface can be greatly increased, resulting in extremely high reaction rates and products having low trans fatty acid contents. In this study we present results from hydrogenation of rapeseed fatty acid methyl esters under near-critical and supercritical conditions. Temperature, residence time, hydrogen pressure, and catalyst life were varied systematically, using a statistical experimental design, in order to elucidate reaction rate and trans fatty acid formation as functions of the above variables. The experiments were carried out in a microscale fixed-bed reactor, using a 3% Pd-on-aminopolysiloxane catalyst. At 92 °C, a hydrogen pressure of 4 bar, and a residence time of 40 ms we obtained a trans content of 3.8 ± 1.7% at a iodine value of 70. Our results support the findings from traditional processes that at a constant iodine value (IV) the trans content decreases with decreasing temperature, increasing pH₂, and increasing residence time. The reaction rate at our best conditions was roughly 500 times higher than in traditional batch hydrogenation.     

Catalyst studies for hydrogenation of vegetable oils

Cottonseed and soybean oils were partially hydrogenated using various commercial nickel catalysts. Methods were investigated by which commercial catalysts can be changed with respect to the rate of reaction, selectivity ortrans-isomerization during hydrogenation of the oils. Catalysts which were treated with hydrogen sulfide produce considerably moretrans isomers but catalysts treated with air often cause higher selectivity ratios. Factors affecting the hydrogenation characteristics of a catalyst are discussed. Present Address: University of Cincinnati, Cincinnati, Ohio     

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.     

Improved ozonolysis method for analysis of total n−3 fatty acids during hydrogenation of fish oils

A rapid and precise method for determining the total amount of n−3 fatty acids in small samples of fish oil is presented. The oil is ozonized at −10°C in hexane solution, and the ozonides are subsequently reduced with triphenyl-phosphine at 40°C. The propanal formed is quantitated by capillary gas chromatography. The method was utilized to follow the industrial hydrogenation of a fish oil, and it was demonstrated that the n−3 double bonds were simultaneously reduced to one-sixth as the iodine value decreased to one-half.     

还原条件对镍/氧化铝油脂加氢催化剂的影响研究

采用沉淀法制备了镍/氧化铝催化剂前驱体,前驱体经焙烧、还原、包油成型制得镍/氧化铝油脂加氢催化剂。通过对催化剂进行TPR、氮吸附测定以及棕榈油加氢评价实验,考察了还原条件（还原温度、还原时间和氢气流速等）对催化剂孔结构和加氢活性的影响。结果表明,还原温度对催化剂孔结构和加氢活性影响最明显;催化剂前驱体最适宜的还原条件为还原温度500 ℃、还原时间3.0 h、氢气流速150 mL/min。在此条件下制备的催化剂用于棕榈油加氢反应,能够使每100 g棕榈油碘值由56.0 g降到0.81 g。     

Electrochemical hydrogenation of edible oils in a solid polymer electrolyte reactor. Sensory and compositional characteristics of low Trans soybean oils

Soybean oils were hydrogenated either electrochemically with Pd at 50 or 60°C to iodine values (IV) of 104 and 90 or commercially with Ni to iodine values of 94 and 68. To determine the composition and sensory characteristics, oils were evaluated for triacylglycerol (TAG) structure, stereospecific analysis, fatty acids, solid fat index, and odor attributes in room odor tests. Trans fatty acid contents were 17 and 43.5% for the commercially hydrogenated oils and 9.8% for both electrochemically hydrogenated products. Compositional analysis of the oils showed higher levels of stearic and linoleic acids in the electrochemically hydrogenated oils and higher oleic acid levels in the chemically hydrogenated products. TAG analysis confirmed these findings. Monoenes were the predominant species in the commercial oils, whereas dienes and saturates were predominant components of the electrochemically processed samples. Free fatty acid values and peroxide values were low in electrochemically hydrogenated oils, indicating no problems from hydrolysis or oxidation during hydrogenation. The solid fat index profile of a 15∶85 blend of electrochemically hydrogenated soybean oil (IV=90) with a liquid soybean oil was equivalent to that of a commercial stick margarine. In room odor evaluations of oils heated at frying temperature (190°C), chemically hydrogenated soybean oils showed strong intensities of an undesirable characteristic hydrogenation aroma (waxy, sweet, flowery, fruity, and/or crayon-like odors). However, the electrochemically hydrogenated samples showed only weak intensities of this odor, indicating that the hydrogenation aroma/flavor would be much less detectable in foods fried in the electrochemically hydrogenated soybean oils than in chemically hydrogenated soybean oils. Electrochemical hydrogenation produced deodorized oils with lower levels of trans fatty acids, compositions suitable for margarines, and lower intensity levels of off-odors, including hydrogenation aroma, when heated to 190°C than did commercially hydrogenated oil.     

Low trans hydrogenation of edible oils

Hydrogenation of edible oils is an important process in the food industry to produce fats and oils with desirable melting properties and an improved shelf life. However, beside the desired hydrogenation reaction trans fatty acids are formed as well. As several studies indicate a negative health effect of trans fatty acids, consumer demands will urge the food producers to lower the content of trans fatty acids in their products. This article describes the option to reduce the trans levels in the hydrogenation of an edible oil by changing process conditions and by applying alternative low trans heterogeneous catalysts.     

A second-order model for catalytic-transfer hydrogenation of edible oils

A second-order kinetic model for hydrogenation of fatty acids in series has been developed and analyzed. The model is applied to the data obtained for sodium formatecatalyzed hydrogenation of soybean, peanut, corn, and olive oils. There is good agreement between the experimental data and predicted values obtained from the model as evidenced by the analysis of r ² and F-test values. The effect of individual fatty acid composition of various edible oils on the rate of hydrogenation has been explained in view of the mathematical model developed. The individual rate constants seem to obey the Arrhenius rate law. The second-order kinetic analysis discussed is found to be suitable for mathematically describing hydrogenation of vegetable oils by hydrogen donors as compared to the traditional first-order kinetic analysis     

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.     

Principles and catalysts for hydrogenation of fats and oils

Hydrogenation of vegetable oils has been practiced since the discovery by Normann some 75 years ago and is the major chemical process in the fat and oil industry. Hydrogenation changes a liquid oil to a semisolid fat which has more utility and better flavor stability. The reaction is not a simple saturation of double bonds with hydrogen, but is an extremely complex series of reactions that result in a myriad of products. By control of the reaction conditions, pressure, temperature, agitation, and catalyst type and concentration, the desired product may be obtained. The use of new equipment and methods has produced some understanding of the hydrogenation reactions. This knowledge has allowed the production of better, more consistent products designed for use by the consumer.     

Industrial applications for animal fatty oils

Some of the animal fats that are by-products of the meat packing industry can become a valuable commodity for certain other portions of our nation’s economy. This paper reviews the types of raw materials used, as well as the manufacturing techniques employed to manufacture these by-products into useful animal oils. The industrial uses for these oils include, not only petroleum and metal processing, but also the chemical and pharmaceutical industries. These oils also can be reacted chemically to produce various extreme pressure additives for the petroleum industry. In some areas it is even replacing the oil from the sperm whale whose use has been banned within the U.S. One of 12 papers presented in the Symposium “Novel Uses of Agricultural Oils” at the AOCS Spring Meeting, New Orleans, April 1973.