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1.
Electrocatalytic hydrogenation of phenol in aqueous solutions at a Raney nickel electrode in the presence of cationic surfactants 总被引:1,自引:0,他引:1
The electrocatalytic hydrogenation (ECH) of phenol at a Raney nickel cathode was studied in aqueous solutions. At 30 °C, without surfactants, cyclohexanol was obtained with low or medium yields. The best results were observed in alkaline solutions (pH 9). At pH 2 the efficiency of the hydrogenation reaction is significantly improved by low amounts of didodecyldimethylammonium bromide (DDAB). This surfactant effect is studied in relation to the substrate and hydrogen adsorption phenomena. 相似文献
2.
Continuous hydrogenation of soybean oil with a stationary copper catalyst bed was performed at 110–180 C, 30–75 psig hydrogen
and Iiquid hourly spaced velocities (LHSV) of 0.25–0.6 cc/hr/cc catalyst. In contrast to batch, continuous hydrogenation was
achieved at a lower temperature with no need to postfilter the product. The soybean oil products from the continuous and batch
processes hydrogenated to 0% triene were similar in fatty acid composition,trans content of 29% and linolenate selectivity of 5.
Biometrician, North Central Region, Agricultural Research Service, U.S. Department of Agriculture, stationed at the Northern
Regional Research Center, Peoria, IL 61604. 相似文献
3.
S. Koritala K. J. Moulton Sr. E. N. Frankel 《Journal of the American Oil Chemists' Society》1984,61(9):1470-1471
Soybean oil was hydrogenated continuously in the presence of nickel catalysts. The iodine value of the products was varied
by changing the oil flow rate and temperature of the reaction. Sulfur-promoted nickel catalyst increased the selectivity for
linolenate hydrogenation, but formed much higher proportions oftrans isomers. Linoleate selectivity improved with temperature with both nickel and sulfur-promoted nickel catalysts, buttrans isomerization also increased. The feasibility of this continuous reactor system was demonstrated as a practical means to
prepare hydrogenated stocks of desired composition and physical characteristics at high throughput. 相似文献
4.
Current efficiency for soybean oil hydrogenation in a solid polymer electrolyte reactor 总被引:4,自引:0,他引:4
Soybean oil has been hydrogenated electrocatalytically in a solid polymer electrolyte (SPE) reactor, similar to that in H2/O2 fuel cells, with water as the anode feed and source of hydrogen. The key component of the reactor was a membrane electrode assembly (MEA), composed of a precious metal-black cathode, a RuO2 powder anode, and a Nafion® 117 cation-exchange membrane. The SPE reactor was operated in a batch recycle mode at 60°C and one atmosphere pressure using a commercial-grade soybean oil as the cathode feed. Various factors that might affect the oil hydrogenation current efficiency were investigated, including the type of cathode catalyst, catalyst loading, the cathode catalyst binder loading, current density, and reactant flow rate. The current efficiency ordering of different cathode catalysts was found to be Pd>Pt>Rh>Ru>Ir. Oil hydrogenation current efficiencies with a Pd-black cathode decreased with increasing current density and ranged from about 70% at 0.050Acm–2 to 25% at 0.490Acm–2. Current pulsing for frequencies in the range of 0.25–60Hz had no effect on current efficiencies. The optimum cathode catalyst loading for both Pd and Pt was 2.0mgcm–2. Soybean oil hydrogenation current efficiencies were unaffected by Nafion® and PTFE cathode catalyst binders, as long as the total binder content was 30wt% (based on the dry catalyst weight). When the oil feed flow rate was increased from 80to 300mlmin–1, the oil hydrogenation current efficiency at 0.100Acm–2 increased from 60% to 70%. A high (70%) current efficiency was achieved at 80mlmin–1 by inserting a nickel screen turbulence promoter into the oil stream. 相似文献
5.
The electrocatalytic hydrogenation (ECH) of 2,6-dimethylphenol and 2-tert-butylphenol was performed at RaNi cathodes in aqueous buffers containing various amounts of didodecyldimethylammonium bromide (DDAB). Without surfactant, 2,6-dimethylcyclohexanol, 2-tert-butylcyclohexanone and 2-tert-butylcyclohexanol were obtained, at 65 °C, with very low yields. The surfactant effect on the yields, the selectivity of the reaction and the diastereoisomeric composition of alkylcyclohexanols produced was studied in acidic and basic solutions in relation to the substrate adsorption. At pH 9 the efficiency of the hydrogenation reaction was significantly improved by low amounts of DDAB, which led to an increase of the alkylcyclohexanols formation. In particular, cis-2-tert-butylcyclohexanol was obtained with a high diastereoselectivity. 相似文献
6.
B. MAHDAVI A. LAFRANCE A. MARTEL J. LESSARD H. ME´NARD L. BROSSARD 《Journal of Applied Electrochemistry》1997,27(5):605-611
The electrocatalytic hydrogenolysis (ECH) of lignin model compounds has been investigated under galvanostatic control at Raney nickel electrodes in aqueous ethanol. The influence of current density, concentration of substrate and temperature on the efficiency of the carbon–oxygen bond hydrogenolysis was studied with benzyl phenyl ether and the optimum conditions leading to its total conversion were found. The effect, on the current efficiency, of replacing the phenyl group by an alkyl group (e.g. benzyl methyl ether) and of substituting hydrogens on aromatic rings by methoxy groups was investigated using the optimum electrolysis conditions. The electrocatalytic hydrogenolysis of -phenoxyethylbenzene and -phenoxyacetophenone, representatives of two other kinds of carbon–oxygen linkage in lignin, was also carried out. 相似文献
7.
The activities of several commercial nickel catalysts were determined by measuring their activation energies. Among these
catalysts, G95E, Resan 22, Nysosel 222 and 325, all with low activation energy, were more active than DM3 and G95H, which
had higher activation energy. However, the less active catalysts increased the linoleate selectivity of soybean oil during
hydrogenation. The yields of bothtrans isomers and winterized oil were higher for the more selectively hydrogenated oil catalyzed by the less active catalysts.
In the sensory evaluation, the fractionated solid fat that contained moretrans isomers was lower in flavor scores than the fractionated liquid oil after hydrogenation and winterization of soybean oil. 相似文献
8.
9.
Hydrogenation of soybean oil by nickel/silica catalysts in a rotating packed disk reactor 总被引:1,自引:0,他引:1
Sun Choia Young Sung Ghima Ho Nam Change J. S. Rhee 《Journal of the American Oil Chemists' Society》1986,63(10):1351-1355
Hydrogenation of soybean oil was carried out by nickel/ silica catalysts in a newly developed rotating packed disk reactor
(RPDR). The rotation of a catalyst-filled disk facilitated hydrogen transfer into the liquid phase and mixing in the reactor,
resulting in an improved threephase reaction. Performance of RPDR in a batch operation was studied by varying temperature,
pressure, nickel concentration in the oil, and disk rotating speed. The overall reaction rate increased with these variables,
but the selectivity of linoleic acid was high when the hydrogen transfer controlled the reaction on the catalyst. 相似文献
10.
K. J. Moulton S. Koritala E. N. Frankel 《Journal of the American Oil Chemists' Society》1983,60(7):1257-1258
The rate of hydrogenation of soybean oil with either copper chromite or nickel catalysts increased more than a hundredfold with the aid of ultrasonication. In a continuous reaction system, the selectivity with copper catalyst for linolenate reduction was somewhat lower when ultrasonic energy was applied than when not applied. With ultrasonic energy, 87% hydrogenation of linolenate in soybean oil was obtained in 9 sec at 115 psig H2 with 1% copper chromite at 181 C and 77% linolenate hydrogenation with 0.025% nickel. Without ultrasonic energy, only 59% linolenate hydrogenation was obtained in 240 sec with copper chromite at 198 C and 500 psig H2 and 68% linolenate hydrogenation in 480 sec with nickel at 200 C and 115 psig H2. This innovation may offer an important advantage in increasing the activity of commercial catalysts, particularly copper chromite, for fats and oil hydrogenation. 相似文献
11.
Journal of the American Oil Chemists' Society - 1 相似文献
12.
I. Garibaym 《Journal of the American Oil Chemists' Society》1981,58(3):201-203
Soybean oil differs from other oils in linolenic acid content. This causes variations in processing. Hydrogenation of soybean
oil depends on catalyst selectivity, hydrogenation conditions and the final product desired. Oil, hydrogen and catalyst must
meet certain conditions in order to attain successful hydrogenation. Batch equipment and processing are described. 相似文献
13.
H. V. Tümer R. O. Feuge E. R. Cousins 《Journal of the American Oil Chemists' Society》1964,41(3):212-214
The degree of activity of Raney nickel catalysts in the hydrogenation of triglycerides has been found to vary considerably with and to depend upon unknown factors in the original alloy. Highly active preparations of Raney nickel rapidly lost their activity when stored in absolute ethanol due to the formation of acetaldehyde. Loss of activity was associated with the amount of residual aluminum in the catalyst. The nickel was found to dissolve to some extent in the acetal-dehyde-ethanol solution. Catalysts deactivated by acetaldehyde could be reactivated to a greater degree of activity than that possessed originally by treating with acetic acid. The activity of the original Raney nickel catalyst was preserved to a greater extent by storage in dioxane instead of ethanol. 相似文献
14.
Catalytic transfer hydrogenation of soybean oil 总被引:4,自引:0,他引:4
The catalytic transfer hydrogenation of soybean oil by various hydrogen donors and solvents with palladium-oncarbon catalyst
was investigated in batch and continuous modes. The choice of reaction conditions, donor and catalyst allowed the manufacture
of partially hydrogenated oils or semi-solid fats with controlled fatty acid contents, iodine value, melting point and solid
content index. The level of “iso” forms of fatty acids was similar to, and average initial selectivity was higher than that
obtained with gaseous hydrogenation under pressure with a catalyst of the same type. The best results were obtained in aqueous
solution with sodium formate as hydrogen donor at 60°C. 相似文献
15.
Empirical modeling of soybean oil hydrogenation 总被引:2,自引:0,他引:2
Empirical hydrogenation models were generated from statistically designed laboratory experiments. These models, consisting
of a set of polynomial equations, relate the operating variables of soybean oil hydrogenation to properties of the reaction
and of the fat produced. These properties include reaction rate,trans-isomer content and melting point. Operating variables included in the models were temperature, hydrogen pressure, catalyst
concentration, agitation rate and iodine value.
The effects of catalyst concentration and agitation rate were found to be significant in determiningtrans-isomer content, which in turn influences the melting characteristics of the hydrogenated oil. Pressures above 30 psig were
found to have little effect ontrans-isomer content, although pressure was very important in determining reaction rate. Reaction temperature was observed as the
most important factor in determining thetrans-isomer content for a given iodine value. Generally, 50 to 60%trans isomer content is predicted by the model for the iodine value range and operating conditions used in this study. Thus, these
predictive models can assist in scaling up hydrogenation processes and in determining the optimum operating parameters for
running commercial hydrogenation.
Presented at the AOCS Meeting, Chicago, May 1983. 相似文献
16.
The electrocatalytic hydrogenation of soybean oil 总被引:2,自引:0,他引:2
Soybean oil has been hydrogenated electrocatalytically at a moderate temperature, without an external supply of pressurized
H2 gas. In the electrocatalytic reaction scheme, atomic hydrogen is produced on an active Raney nickel powder cathode surface
by the electrochemical reduction of water molecules from the electrolytic solution. Adsorbed hydrogen then reacts with an
oil’s triglycerides to form a hydrogenated product. Experiments were carried out at 70°C with a flow-through electrochemical
reactor operating in a batch recycle mode. The reaction medium was a two-phase mixture of soybean oil in a water/t-butanol
solvent containing tetraethylammoniump-toluenesulfonate as the supporting electrolyte. In all experiments the reaction was allowed to continue for sufficient time
to synthesize a brush hydrogenation product. The effects of oil content, applied current, solvent composition, and supporting
electrolyte concentration on the efficiency of hydrogen addition to the oil and on the chemical properties of the hydrogenated
oil product were determined. The electrohydrogenated oil is characterized by a high stearic acid content and a low percentage
of totaltrans isomers, as compared to that produced in a traditional hydrogenation process. 相似文献
17.
Kanchan Mondal 《Chemical engineering science》2003,58(12):2643-2656
In this study, formate ion was used as a shuttle for transferring hydrogen to the surface of a hydrogenation catalyst (7% Ni/SiO2), where the soybean oil was reduced in such a way that the production of deleterious trans fatty acid was greatly reduced. The formate ion was regenerated at the cathode and thus acted as a mediator for the hydrogenation process. The effect of temperature, pH, and applied potential (current) on the fatty acid profile of the hydrogenated soybean oil was determined. The effects of oil and catalyst loadings on the final product quality were also determined. The application of a current density of resulted in hydrogenated product with desired fatty acid composition. Kinetic studies were also performed for experiments conducted at constant potential conditions. A model that assumes: (i) the rate of regeneration of formate from its oxidized form (bicarbonate ion) is limited by the mass transport effects, and (ii) second-order elementary reaction rate expression was developed to describe the hydrogenation reaction was developed and tested. A good correlation between the model predictions and experimental data was observed. 相似文献
18.
Palladium- catalyzed hydrogenation of soybean oil 总被引:1,自引:0,他引:1
M. M. Ahmad T. M. Priestley J. M. Winterbottom 《Journal of the American Oil Chemists' Society》1979,56(5):571-577
The hydrogenation of soybean oil has been studied using charcoal-supported palladium catalysts at hydrogen pressures between
ambient and 70 psig and at temperatures between 80 C and 160 C in three types of stirred reactor. The catalysts employed were
1-10% w/w Pd supported on charcoal and represented differing metal placement on the support. The structure of the catalysts
was confirmed by metal surface area measurements, transmission electron microscopy (TEM) and electron spectroscopy for chemical
analysis (ESCA). Comparative studies also were carried out under similar conditions using samples of commercial nickel catalysts.
Palladium catalysts with the metal placed on the exterior of the charcoal support were the most active and selective at ambient
pressure, and although palladium catalysts with metal placed within the charcoal pore system became the most active at higher
hydrogen pressures, only the former type of catalyst retained high selec-tivity over the whole temperature and pressure range.
Palladium catalysts gave rise to moretrans- acids than nickel, particularly under conditions normally em-ployed with the latter, but if diffusion limitation was avoided, especially
at lower temperatures, palladium gave lower quantities oftrans- acid than nickel. In addition, the selectivity of a well designed palladium catalyst was superior to that of nickel and its activity
was 15-20 times greater. It is concluded that if palladium is deposited on the exterior of the charcoal so that it is accessible
to the triglyceride molecules, then its selectivity and activity is superior to that of nickel, even at low temperatures,
at which nickel is inactive. This underlines the importance of choosing the correct preparative route to give optimum metal
placement, and it is suggested that when previous studies have indicated that palladium is unselective for fat hardening,
it is likely that the metal was not dispersed on the exterior surface of the support. Furthermore, whereas nickel is best
used under diffusion-controlled conditions because its selectivity is better in the latter situation palladium should be used
under diffusion-free conditions, which implies that very careful attention should be paid to the reactor design. 相似文献
19.
Ewa Szukalska 《European Journal of Lipid Science and Technology》2000,102(12):739-745
Phospholipids (PL) are one of the compounds which poison nickel catalysts during the hydrogenation process. It was affirmed that even trace amounts of PL (5—10 ppm P) cause a decrease in catalyst activity. Quantities over 50 ppm P almost totally inhibit the reaction. In bleached oils used for hydrogenation, PL exist as native compounds as well as products of their transformation. In the present work, the effect of native phospholipids, lysophospholipids (LPL) and phosphatidic acids (PA) on the kinetics and chemistry of soybean oil hydrogenation was investigated. It was found that PA were more toxic to nickel catalysts than LPL and native PL. Fine‐grained catalyst was more active and resistant to the poisoning effect of phospholipids than moderate‐grained catalyst. No changes in the oil hydrogenation chemistry were observed in the presence or absence of PL; thus, linoleic and linolenic selectivity and specific isomerization did not undergo any change. 相似文献
20.
Catalytic transfer hydrogenation of 7-ketolithocholic acid to ursodeoxycholic acid with Raney nickel
Ursodeoxycholic acid was produced by the stereoselective reduction of 7-ketolithocholic acid. This hydrogenation reaction was catalyzed by the T-1 Raney nickel and potassium borohydride was used as hydrogen donor instead of inflammable hydrogen gas. Potassium tert-butoxide was introduced to improve yield of ursodeoxycholic acid from about 70% to a maximum of 94% by inducing the stereoselectivity on hydroxyl group at 40 °C and atmospheric pressure. Reduction reaction conditions such as amount of reactants, temperature and stirring speed were optimized. The whole process is safe and low-cost. Eventually, the product, ursodeoxycholic acid was characterized by IR, 1H NMR and 13C NMR spectra. 相似文献