Selective hydrogenation of soybean oil: XI. Trialkyl silane-activated copper catalysts

Addition of triethyl silane to copper stearate resulted in an active heterogenous catalyst for the hydrogenation of soybean oil. The linolenate selectivity of this catalyst (K_Le/K_Lo=2.4 to 3.9) was much lower than that obtained with copper chromite (8.4). Unlike copper-chromite catalyst, triethyl silane-activated copper formed stearate during hydrogenation. Both silica and alumina increased catalyst activity. Linolenate selectivity improved slightly in the presence of alumina.     

Hydrogenation of soybean oil with commercial copper-chromite and nickel catalysts: Winterization of low-linolenate oils

Soybean oil hydrogenated in the presence of copper-chromite catalysts to 3% linolenate and below requires winterization if it is to pass the cold test. Yields of winterized oil from soybean oil hydrogenated to several linolenate levels were therefore studied. Partially hydrogenated soybean oil was sampled and filtered at intervals during hydrogenation on a pilot plant scale with a commercial copper-chromite catalyst. Samples were then vacuum bleached and filtered to remove dissolved copper, held at 7 C for 48 hr and filtered to remove stearines. The filtered winter oils passed the standard 5.5 hr cold test. For soybean oil in which linolenate was reduced to 0.1% with a commercial copper-chromite catalyst or to 3.0% with a nickel catalyst yields of winter oil were about the same; 92% for a 5.5 hr cold test oil (winterized two days at 7 C) and 89% for a 20 hr cold test oil (winterized two days at 4 C). Presented at the AOCS Meeting, San Francisco, April 1969. No. Market. Nutr. Res. Div. ARS, USDA.     

Hydrogenation of soybean oil with copper-chromium catalyst: Preliminary plant-scale observations

Four commercial hydrogenations were carried out on 20,000 1b batches of soybean oil with 0.25, 0.5, and 1% fresh copper-chromite catalyst and 1% used catalyst. Hydrogenations proceeded smoothly at catalyst levels of 0.5 and 1%, but the reaction was slow at a 0.25% concentration. Kinetic, selectivity ratio \((K\frac{{Ln}}{{Lo}})\) and fatty acid compositional data were acquired during several of the hydrogenation runs. Nickel contamination, confirmed by analysis of used copper catalyst, lowered selectivity. Copper content of the oil rose during hydrogenation, but normal processing steps, particularly bleaching and winterization, removed it to below levels (0.01–0.02 ppm) detectable by direct atomic absorption spectroscopy. Both copper and chromium remaining in the oil after processing were concentrated by winterization in the stearine fraction. Organoleptic, oxidative, and room odor tests showed that oils of good stability can be produced on a commercial scale by copper hydrogenation and winterization. Information was gained regarding problems involved in the plant use of copper-chromite catalyst for hydrogenating soybean oil for edible purposes.     

Selective hydrogenation of soybean oil: XII. Trialkyl aluminum-copper stearate homogeneous catalysts

The reaction of copper stearate with triethylaluminum (TEAL) formed a soluble catalyst that promoted the selective hydrogenation of the linolenyl groups in soybean oil. This homogeneous catalyst was more active than copper-chromite. The activity was enhanced by the addition of silica, alumina or titania. Ethyl alcohol accelerated the hydrogenation when it was added in small amounts and retarded hydrogenation when increased amounts were added. More active and, in some cases, more selective catalysts were formed when TEAL was replaced by trialkylaluminum compounds containing longer chain length in the alkyl groups. Among other organometallics tested, diethylmagnesium and diisobutylaluminum ethoxide formed catalysts with activity comparable to heterogeneous catalysts (K_Le/K_Lo=2.8~5.2) was less than that obtained with copper-chromite (12~14), but greater than that of commercially used nickel catalysts (2). Isomerization, as measured by the percentage oftrans isomers formed, was similar to that of heterogeneous copper catalysts (%trans/ΔIV=0.6~0.7). Presented at the AOCS meeting in New Orleans, May 1981.     

Selective hydrogenation of soybean oil. III. Copper-exchanged molecular sieves and other supported catalysts

Copper-chromium catalysts promote selective reduction of linolenyl groups in soybean oil. Since commercially available catalysts possess only moderate activity, more active catalysts were sought. Copper was dispersed on high-surface-area supports, such as silica, alumina, and molecular sieves. These catalysts had varying activities. Precipitation of copper on Cab-O-Sil, a pure form of silica with a large external surface area, gave the most active catalyst. Selectivity ratios (K_Le/K_Lo) for the hydrogenation of soybean oil with these catalysts varied from 4 to 16; a copper-on-Cab-O-Sil catalyst exhibited the greatest selectivity. Improved selectivity and activity were observed when some supports were treated with hydrochloric acid. For example, with a copper-on-Celite catalyst, soybean oil was hydrogenated in 165 min and gave a selectivity ratio of 5.9. Hydrochloric acid treatment of Celite improved the selectivity to 9.9 and reduced hydrogenation time to 54 min. To ensure maximum activity of some of these catalysts, soybean oil should be more thoroughly bleached than is customarily done for nickel hydrogenation. A commercially refined and bleached soybean oil was hydrogenated with a copper-on-Cab-O-Sil catalyst in 18 min. The same oil, re-refined in the laboratory, was reduced in 11.5 min and had the same selectivity ratio of 15.     

Ultrasonic hydrogenation of soybean oil

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.     

Selective hydrogenation of soybean oil. VIII. Effect of method of preparation upon the activity of a copper-silica catalyst

A copper-silica catalyst was prepared by adding copper nitrate solution to sodium silicate. The precipitated copper-silica catalyst was washed, dried, and heat-treated at high temperatures. The effect of preparational variables upon catalyst activity and selectivity for the hydrogenation of soybean oil was investigated. The optimum conditions were precipitation at 25 to 55 C, drying the catalyst by freeze drying, and heat treatment at 500 C. The catalyst obtained under these conditions is more than three times as active as a commercial copper-chromite catalyst. Presented at the AOCS meeting May 1977 in New York.     

Evaluation of hydrogenation catalyst activity

The AOCS Recommended Practice for testing activity of hydroge-nation catalysts was used to compare activity and properties of a number of commercial catalysts with the AOCS standard catalyst. Four of five commercial catalysts tested were similar to the standard but one commercial catalyst was markedly more active and more selective. It also was very difficult to filter after hydrogenation. Selectivity of the catalysts in hydrogenation of soybean oil was determined from change in fatty acid composition. The most selective catalyst produced the highest level oftrans isomers and the highest dropping point. Solid fat contents measured after 30 and 40 min of hydrogenation time were determined by wide-line nuclear magnetic resonance. The Recommended Practice and standard catalyst were useful tools in evaluating activity and selectivity of hydrogenation catalysts.     

Removal of copper from hydrogenated soybean oil

Hydrogenation with a copper-chromite catalyst at 170 C, 30 psi, increased the copper content of a refined, bleached soybean oil from 0.02 to as much as 3.8 ppm. Removing residual copper from soybean oil is essential to the successful use of copper catalysts for selective hydrogenation. Various methods were examined to remove this copper, including alkali refining, bleaching, acid washing, citric acid treatment and cation-exchange resin treatment. Properly conducted, each of the methods except alkali refining gives 95% or higher removal of copper introduced during hydrogenation. Ion exchange appears to be the most economical, but addition of about 0.01% citric acid during deodorization may be needed to inactivate traces of unremoved copper. Soybean oil hydrogenated with a copper-chromite catalyst, bleached or treated with an ion-exchange resin and deodorized with 0.01% citric acid added had low AOM peroxide values and acceptable flavor scores after eight days at 60 C which indicate that removal of residual copper from the oil should be adequate for the production of stable oils low in linolenic acid content. Presented at AOCS Meeting, Chicago, October 1967.     

Selective hydrogenation of soybean oil. VI. Copper-on-silica gel catalysts

The preparation of copper-on-silica gel catalysts containing 15% and 20% copper is described. These catalysts can be reused three times without appreciable loss of activity. Their activity compares favorably with the highly active 5% copper-on-silica gel catalyst previously reported. Higher copper catalysts are somewhat less selective for the reduction of linolenate in soybean oil than 5% copper-on-silica gel, but these copper catalysts have greater activity, better reuse characteristics, and selectivity comparable to commercial copper-chromite catalysts. No. Mark. and Nutr. Res. Div., ARS, USDA.     

Continuous slurry hydrogenation of soybean oil with copper-chromite catalyst at high pressure

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.     

Catalysts for selective hydrogenation of soybean oil. I. An experimental method for evaluating selectivity

The undesirable flavor reversion properties of soybean oils may be counteracted by selective hydrogenation of the linolenate components. Screening of catalysts for this purpose was accomplished by a standardized laboratory hydrogenation of a refined, bleached soybean oil under atmospheric pressure. A mathematical derivation utilizes analytical chromatographic data to determine linolenate/linoleate reaction rates as a selectivity index S_L for a given catalyst. Presented at the AOCS Meeting, Toronto, 1962.     

Fixed- Bed continuous hydrogenation of soybean oil with palladium- Polymer supported catalysts

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.     

Behavior of hydrogenation catalysts. I. Hydrogenation of soybean oil with palladium

A statistical method for evaluation of catalysts was used to determine the behavior of palladium catalyst for soybean oil hydrogenation. Empirical models were developed that predict the rate,trans-isomer formation, and selectivity over a range of practical reaction conditions. Two target iodine value (IV) ranges were studied: one range for a liquid salad oil and the other for a margarine basestock. Although palladium has very high activity, it offered no special advantage intrans-isomer formation or selectivity. Palladium can substitute for nickel catalyst, at greatly reduced temperature and catalyst concentrations, for production of salad oil or margarine basestock from soybean oil. Presented at the AOCS meeting, Chicago, May 1983.     

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.     

Selective hydrogenation of soybean oil in the presence of copper catalysts

Many investigators associate the poor keeping properties of soybean oil with its linolenic acid content. On the other hand the high linoleic acid content is a desired property from a nutritional point of view. We have therefore developed a process for the preferential reduction of the linolenic acid content by selective hydrogenation. Conventional catalysts for the hydrogenation of fats have a rather low selectivity in this respect. When linolenic acid in soybean oil is hardened (e.g., with a nickel catalyst), most of the linoleic acid is converted into less unsaturated acids. It was found that linolenic acid is hydrogenated much more preferentially in the presence of copper catalysts than in that of nickel and other hydrogenation catalysts. At a linolenic acid content of 2%, soybean oil hardened with nickel catalyst contained about 28% linoleic acid, whereas with copper catalyst the hardened soybean oil contained 49% linoleic acid. By means of our process it is possible to manufacture a good keepable oil of, e.g., I.V. 115 and containing 1% linolenic acid and 46% linoleic acid. The storage stability of this product is comparable with that of sunflower-seed oil. A liquid phase yield of 86% is obtained after winterization at 5C for 18 hr. The high selectivity for linolenate reduction of copper catalysts must be ascribed to the copper part of the catalyst. Investigations into the structure of the catalyst indicate that the active center consists of copper metal crystallites; whether these centers are promoted by the carrier or traces of other substances is under investigation.     

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     

Selective hydrogenation of soybean oil. II. Copper-chromium catalysts

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 (K_Le/K_Lo) ranging from 6 to 13. Since stearate did not increase, linoleate selectivity (K_Lo/K_Ol) 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.     

Catalysts for selective hydrogenation of soybean oil.1 II. Commercial catalysts

A survey of commercial hydrogenation catalysts demonstrated the higher selectivity (S_L= 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 S_L=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.     

XRecent advances in canola oil hydrogenations

Rapeseed oil has been the source of edible oils in many parts of the world. In the last decade, Canadian plant breeders have developed new rapeseed cultivars which yield oil low in erucic acid and meal low in glucosinolates. These cultivars were named “canola” by the Canadian rapeseed industry. Literature on the hydrogenation characteristics of canola oil is limited; however, in recent years, several aspects of canola oil hydrogenations with commercial nickel catalysts have been reported including the formation ofrans-isomers, trisaturated glycerides and physical properties. In addition, as the methods for determination of sulfur compounds in canola oil developed, the effect of some isothiocyanates on the hydrogenation rate was further investigated to determine the relative catalyst poisoning ability of serveral of these sulfur compounds. However, during the last few years, most of the efforts were directed towards development of novel, selective and active catalysts for canola oil hydrogenations. These studies cover a wide range of homogeneous and heterogeneous catalysts including sulfur poisoned nickel, gold supported on silica, arene-Cr(CO)₃, RuCl₂(CO)₂(PPh₃)₂, palladium on carbon, palladium black and nickel and arene-Cr(CO)₃ mixtures. Effects of temperature, pressure, catalyst concentration and catalyst preparation procedure on the hydrogenation rate, selectivity, catalyst life and quality of the oil were examined and compared with that of commercial nickel catalysts. A brief discussion about continous hydrogenations of canola oil with commerical fixed bed catalysts is also included.