共查询到20条相似文献,搜索用时 15 毫秒
1.
S. Koritala K. J. Moulton Sr. J. P. Friedrich E. N. Frankel W. F. Kwolek 《Journal of the American Oil Chemists' Society》1984,61(5):909-913
Selective hydrogenation of soybean oil to reduce linolenic acid is accomplished better with copper than with nickel catalysts.
However, the low activity of copper catalysts at low pressure and the high cost of batch equipment for high-pressure hydrogenation
has precluded their commercial use so far. To evaluate continuous systems as an alternative, soybean oil was hydrogenated
in a 120 ft × 1/8 in. tubular reactor with copper catalyst. A series of hydrogenations were performed according to a statistical
design by varying processing conditions: oil flow (0.5 L/hr, 1.0 L/hr and 2.0 L/hr), reaction temperature (180 C and 200 C),
hydrogen pressure (1,100 psig and 4,500 psig) and catalyst concentration (0.5% and 1.0%). An iodine value (IV) drop of 8–43
units was observed in the products whereas selectivity varied between 7 and 9. Isomerization was comparable to that observed
with a batch reactor. Analysis of variance for isomerization indicated interaction between catalyst concentration and hydrogen
pressure and between catalyst concentration and temperature. The influence of pressure on linolenate selectivity was different
for different temperatures and pressure. Hydrogenation rate was significantly affected by pressure, temperature and catalyst
concentration. 相似文献
2.
S. Koritala J. P. Friedrich T. L. Mounts 《Journal of the American Oil Chemists' Society》1980,57(1):1-5
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 (SLn) of the reaction remained essentially unchanged over 50–1000 psig pressure range. A SLn 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. 相似文献
3.
A survey of commercial hydrogenation catalysts demonstrated the higher selectivity (SL= 2.4\s-2.7) of certain platinum, palladium and rhodium catalysts for hydrogenating linolenic components in soybean oil. Nickel
catalysts generally showed selectivities below SL=2.0 although skeletal nickel achieved higher values.Trans-isomers were in the range 7.8\s-15.4% for the above noble metal catalysts. Nickel catalysts provide a lesser degree of isomerization,
5.2\s-7.4% oftrans-isomers for the most selective catalysts.
Presented at the AOCS Meeting at Toronto, 1962. 相似文献
4.
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
5.
N. Hsu L. L. Diosady W. F. Graydon L. J. Rubin 《Journal of the American Oil Chemists' Society》1986,63(8):1036-1042
The hydrogenation of canola oil was studied using palladium black as a potential catalyst for producing partially hydrogenated fats with lowtrans-isomer content. Pressure (150\s-750 psig) appeared to have the largest effect ontrans-isomer formation. At 750 psig, 90 C and 560 ppm metal concentration, a maximum of 18.7%trans isomers was obtained at IV 53. A nickel catalyst produces about 50%rans isomers at the same IV. For palladium black, the linolenate and linoleate selectivities were 1.2 and 2.7, respectively. The maximum level oftrans isomers observed ranged from 18.7% to 42.8% (150 psig). Temperature (30\s-90 C) and catalyst concentration (80\s-560 ppm) affected the reaction rate with little effect ontrans-isomer formation and selectivities. At 250 psig and 50 C, supported palladium (5% Pd/C) appeared to be twice as active as palladium black. At 560 ppm Pd, 5% Pd/C produced 30.2%trans (IV 67.5), versus 19.0%trans for palladium black (IV 68.9). Respective linoleate selectivities were 15 and 6.6, while linolenate selectivities were approximately unity. Analysis of the oil samples by neutron activation showedapproximately a 1 ppm, Pdresidue after filtration. 相似文献
6.
T. L. Mounts S. Koritala J. P. Friedrich H. J. Dutton 《Journal of the American Oil Chemists' Society》1978,55(4):402-406
Selective hydrogenation of soybean oil with copper catalyst at 50 psig or less is characterized as a relatively slow reaction requiring higher catalyst concentrations than the less selective but rapid nickel-catalyzed reactions used in most commercial practice. Hydrogenations of soybean oil have been performed which included a high-pressure scan (500, 1000, and 3000 psig), at selected temperatures (110, 130, 150, and 170 C), and at specific catalyst concentrations (0.05, 0.1, 0.2, and 0.4% copper). Selectivities, relative reaction rates, and geometric and positional isomerization have been determined as an evaluation of the effects of high pressure on the kinetics of the reaction. The experimental results indicate that an appropriate selection of pressure, temperature, and catalyst concentration can permit: (a) a significant increase in the rate of reaction while retaining the high linolenic acid selectivity of copper catalysts, (b) use of lower concentrations of copper catalyst while maintaining the higher reaction rate, and (c) elimination of conjugated diene as a measureable product in the hydrogenated oil. 相似文献
7.
Palladium supported on alumina was used to hydrogenate soybean and canola oil. Previous literature reports indicated that
palladium forms moretrans isomers than nickel. At 750 psig, 50 ppm palladium, and at 70 C, only 9.4%trans were formed when canola oil was hydrogenated to IV 74. In general, high pressure and low temperature favored lowtrans formation with no appreciable loss in catalyst activity. The effect of pressure, temperature and catalyst concentration on
reaction rate,trans formation and selectivity is presented. A survey of various catalyst supports is discussed. Apparent activation energies
of 6.3 to 8.9 kcal/mol were obtained; they are in good agreement with values reported in the literature. 相似文献
8.
We have compared a nickel with a copper catalyst in the formation of some geometrical and positional isomers during the partial
hydrogenation of trilinolein. The copper catalyst was found to produce fewer diene isomers than the nickel catalyst at a comparable
iodine value. The copper catalyst produced more monoene isomers however, than did the nickel, particularlytrans monoenes. The distribution of the monoene isomers appeared to obey an equilibrium relationship with each other, independent
of both iodine value and reaction conditions. We have presented additional evidence to postulate that copper catalysts hydrogenate
polyenoic acids by first conjugating the acids. The selectivity of copper catalysts for triene over diene is probably due
to the greater ease of conjugation of the triene. 相似文献
9.
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 相似文献
10.
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
11.
M. Pilar Gonzlez-Marcos Jos I. Gutirrez-Ortiz Cristina Gonzlez-Ortiz De Elguea Jon I. Alvarez Juan R. Gonzlez-Velasco 《加拿大化工杂志》1998,76(5):927-935
Several nickel on silica catalysts, prepared by impregnation or precipitation/deposition, and a commercial catalyst were tested for activity and selectivity in the sunflower seed oil hydrogenation. An average turn-over frequency of 2.57 s?1 was found for the catalysts, assuming inaccessibility of nickel in pores smaller than 2 nm and a constant nickel surface concentration poisoned by the reaction mixture. After studying the mass-transfer steps, the effect of temperature (373-453 K) and pressure (101-608 kPa) on reaction rates in the kinetic regime was analyzed, and the corresponding apparent activation energies and reaction orders were obtained. Conclusions on the effect of temperature and pressure on the selectivity to the preferential hydrogenation of polyunsaturates (So) and to the formation of trans-isomers ((Strans)0) in the kinetic regime were derived from the results. Finally, a similar analysis was carried out when diffusion limitations were known to be present. 相似文献
12.
K. J. Moulton R. E. Beal E. L. Griffin 《Journal of the American Oil Chemists' Society》1973,50(11):450-454
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. 相似文献
13.
Soybean oil was partially hydrogenated at 170 and 200C with 0.5 and 0.1% copper-chromium catalysts, respectively. The reaction
proceeded selectively at both temperatures, although selectivity was better at the lower temperature. Both commercial and
laboratory-prepared catalysts reduced the linolenic acid to less than 1% and with selectivity ratios (KLe/KLo) ranging from 6 to 13. Since stearate did not increase, linoleate selectivity (KLo/KOl) was extremely high. About 80% or more of the original linoleic acid remained in the hydrogenated products as measured by
the alkali-isomerization method. More conjugated dienes were formed at 200 than at 170C. 相似文献
14.
K. J. Moulton Sr. S. Koritala K. Warner 《Journal of the American Oil Chemists' Society》1985,62(12):1698-1701
Soybean oil was partially hydrogenated in a continuous system with copper and nickel catalysts. The hydrogenated products
were evaluated for flavor and oxidative stability. Processing conditions were varied to produce oils of linolenate contents
between 0.4 and 2.7%, as follows: oil flow, 0.6–2.2 liters/hr; reaction temperature, 180–220 C; hydrogen pressure, 100–525
psig, and catalyst concentration, 0.5–1% copper catalyst or 0.1% nickel catalyst.Trans unsaturation varied from 8 to 20% with copper catalyst and from 15.0 to 27% with nickel catalyst. Linolenate selectivity
was 9 with copper catalyst and 2 with nickel catalyst. Flavor evaluation of finished oils containing 0.01% citric acid (CA),
appraised initially and after accelerated storage at 60 C, showed no significant difference between hydrogenated oils and
nonhydrogenated oil. However, peroxide values and oxidative stability showed that hydrogenated oils were more stable than
the unhydrogenated oil. CA+TBHQ (tertiary butylhydroquinone) significantly improved the oxidative stability of test oils over
oils with CA only, but flavor scores showed no improvement. Dimethylpolysiloxane (MS) had no effect on either flavor or oxidative
stability of the oils. 相似文献
15.
Fixed- Bed continuous hydrogenation of soybean oil with palladium- Polymer supported catalysts 总被引:1,自引:0,他引:1
J. A. Heldal K. J. Moulton E. N. Fronkel 《Journal of the American Oil Chemists' Society》1989,66(7):979-982
To compare a continuous hydrogenation system with batch hydrogenation, soybean oil was treated with Pd and Ni catalysts in
a fixed-bed system under conditions that gave trickle flow. The influence of processing variables such as space velocity,
pressure, temperature and hydrogen flow on the selectivity, specific isomerization and the activity was investigated. Both
the Pd and Ni catalysts gave significantly lower specific isomerization(trans isomer per drop in Iodine Value) when compared to reported values for batch hydrogenation with similar type catalysts. The
linolenate and linoleate selectivities were also significantly lower. Heterogenized homogeneous Pd-on-polystyrene catalyst
gave lower specific isomerization formation and higher selectivity than carbon-supported Pd catalyst at same conditions. This
work indicates that Pd-on-styrene, Pd-on-carbon and extruded Ni catalysts, in fixed-bed continuous hydrogenation can produce
soybean oil of desirable composition after further optimization. 相似文献
16.
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
17.
Sambasi Varao Koritala E. Selke H. J. Dutton 《Journal of the American Oil Chemists' Society》1973,50(8):310-316
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. 相似文献
18.
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
19.
Two samples of soybean oil hydrogenated with copper-containing catalysts at 170 and 200 C were analyzed for their natural
and isomeric fatty acids. Methyl esters of the hydrogenated oils were separated into saturates, monoenes, dienes and trienes
by countercurrent distribution between acetonitrile and pentane-hexane. Monoenes were further separated intocis- andtrans-isomers on a silver-saturated resin column. Double bond location in these fractions was determined by a microozonolysis-pyrolysis
technique. The diene fraction was separated with an argentation countercurrent distribution method, and linoleate was identified
by infrared, ozonolysis and alkaliisomerization data. The double bonds in thecis-monoenes were located in the 9-position almost exclusively. However, the double bonds in thetrans-monoene were quite scattered with 10- and 11-isomers predominating. About 86% to 92% of the dienes consisted of linoleate
as measured by alkali isomerization. Other isomers identified as minor components includecis,trans andtrans, trans conjugated dienes and dienes whose double bonds are separated by more than one methylene group.
No. Utiliz. Res. Dev. Div., ARS, USDA. 相似文献
20.
Melih Cizmeci Anar Musavi Aziz Tekin Muammer Kayahan 《European Journal of Lipid Science and Technology》2009,111(6):607-611
Soybean oil was hydrogenated with a carbon‐supported ruthenium catalyst (Ru/C) at 165 °C, 2 bar H2 and 500 rpm stirring speed. Reaction rates, trans isomer formation, selectivity ratios and melting behaviors of the samples were monitored. No catalytic activity was found for the application of 10 ppm of the catalyst, and significant catalytic activity appeared at >50 ppm of active catalyst. The catalyst concentration had an effect on the reaction rate of hydrogenation, but the weight‐normalized reaction rate constant (kc) was almost independent of the catalyst concentration at lower iodine values. Ru/C generated considerable amounts of trans fatty acids (TFA), including high amounts of trans 18:2, and also stearic acid, due to its very non‐selective nature. The selectivity ratios were found to be low and varied between 1.12 and 4.32 during the reactions. On the other hand, because of the low selectivity, higher slip melting points and solid fat contents at high temperatures were obtained than those for nickel and palladium catalysts. Another different characteristic of this catalyst was the formation (max 1.67%) of conjugated linoleic acid (CLA) during hydrogenation. Besides, CLA formation in the early stages of the reactions did not change very much with the lower iodine values. 相似文献