Effect of some isothiocyanates on the hydrogenation of canola oil

Sulfur compounds were added to refined and bleached canola oil before hydrogenation in the form of allyl, heptyl and 2-phenethyl isothiocyanates, and the effects on hydrogenation rate, solid fat content and percentagetrans fatty acids were determined. The poisoning effect was most pronounced with allyl isothiocyanate and least with phenethyl isothiocyanate. As the amount of added sulfur increased, the hydrogenation rate decreased. Of the three isothiocyanates used, allyl isothiocyanate caused formation of larger amounts oftrans isomers. An increased sulfur level in the oil resulted in increased solid fat content andtrans isomer level. Allyl isothiocyanate also caused formation of larger amounts of solid fat than other isothiocyanates at all levels of sulfur addition.     

Removal of sulfur compounds from canola oil

The effect of a number of physical methods for the removal of sulfur compounds from canola oil was investigated. The methods tested included laboratory deodorization and use of catalyst and of bleaching earth. Nine temperature-time combinations were used for the deodorization. Bleaching earth had little effect on the removal of sulfur compounds from the oil. Other methods removed part of the sulfur. High temperature, longer time and high vacuum for deodorization facilitated the complete removal of volatile sulfur compounds. Treatment of oil with catalyst removed most of the volatile sulfur and part of the Raney nickel sulfur.     

Determination of total sulfur in canola oil

A rapid and sensitive chromatographic method for the determination of total sulfur in canola oil is described. All forms of sulfur in the oil are quantitatively converted to sulfate in an oxygen bomb. The sulfate is separated from other ions and measured using an ion chromatograph equipped with a conductivity detector. Standards containing different forms of sulfur were prepared and analyzed with this method. Recovery achieved on 11 compounds covering the concentration range from 9.3 to 143.5 mg/kg S ranged from 95.7% to 102.2%. The coefficient of variability of total sulfur in canola oils ranged from 1.0% to 2.9%. Values obtained on high sulfur content mustard oils when plotted vs the values determined by barium precipitation method showed a correlation coefficient of 0.997 and provided a slope of 1.0. This new method employing comparatively simple equipment requires less than 40 minutes for a complete analysis and is reliable for the determination of as little as 0.5 mg/kg S in canola oil.     

Heterogeneous catalytic hydrogenation of canola oil using palladium

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.     

Supported gold catalysis in the hydrogenation of canola oil

The catalytic activity of gold supported on silica orγ-alumina has been studied in the hydrogenation of canola oil. In the hydrogenation of butadiene and pentene using these catalysts, high stability, low yield oftrans-isomers and high monoene selectivity have been reported in the literature. Catalysts containing 1% and 5% Au w/w on porous silica andγ-alumina were active in hydrogenating canola oil in the range of 150 to 250 C and 3550 to 5620 kPa. The activity level of these catalysts was about 30 times lower than that shown by the standard AOCS Ni catalyst based on the concentration of metal (g Au/L oil). Up to 91% monoene content was obtained using these catalysts in comparison with a maximum of 73% for the AOCS standard Ni catalysts. Gold catalysts can be recovered easily by filtration and reused several times without a decrease in activity. The hydrogenated oil was nearly colorless. No gold was detectable in the oil. Contrary to claims in the patent literature, the gold catalyst produces higher concentrations oftrans-isomers than does nickel. However, using gold catalysts the complete reduction of linolenic acid in canola oil can be achieved at a lowertrans-isomer content in the products than that obtained by using the AOCS standard nickel catalyst.     

Determination of volatile sulfur compounds in canola oil

A simple and sensitive method for the quantitative determination of volatile isothiocyanates in canola oil has been developed. The method is based on the specific absorbance of isothiocyanates in the infrared region. The results obtained were confirmed by gas liquid chromatography using a flame photometric detector. The various volatile isothiocyanates isolated from the oil were allyl isothiocyanate, 3-butenyl isothiocyanate, 4-pentenyl isothiocyanate and 2-phenethyl isothiocyanate. Their identities were confirmed by mass spectroscopy and by retention times. The recoveries of sulfur from volatile sulfur compounds by this method ranged from 93.6% to 101.1% when compared to the amount determined by gas liquid chromatography. The coefficients of variability of volatile sulfur compounds in canola oils ranged from 1.7% to 3.2%. The sulfur content represented by the volatile sulfur compounds comprised 21.7% of the sulfur determined by the Raney nickel method for crude oil, 36.6% for refined oil and 22.7% for refined, bleached and deodorized oil.     

Reactivity of fatty acids in the different positions of the triglycerides during hydrogenation of canola oil

Canola oil was hydrogenated under selective and nonselective conditions. After various hydrogenation times, the triglycerides were hydrolyzed by pancreatic lipase and the monoglycerides separated by TLC. Triglycerides and monoglycerides were analyzed for fatty acid composition andtrans isomer content. The reaction rate in the 2- and 1,3-positions of the glycerides was identical and of first order kinetics. Since the 2-position of the canola oil contained higher levels of 18:2 acids, the rate of change was greater than in the 1,3-positions. There were indications of a slightly lower rate oftrans formation in the 2-position during nonselective hydrogenation. Linoleate selectivities for the 2- and 1,3-positions were determined.     

Homogeneous catalytic hydrogenation of canola oil using a ruthenium catalyst

Dichlorodicarbonylbis (triphenylphosphine) ruthenium (II), RuCl₂ (CO)₂ (PPh₃)₂, was investigated as a catalyst for edible oil hydrogenation in a preliminary screening of potential catalysts for producing partially hydrogenated fats with lowtrans-isomer content. Refined, bleached and deodorized canola oil was hydrogenated using 1.77 × 10⁻⁵ − 6.64 × 10⁻⁴ mol/kg-oil of ruthenium catalyst equivalent to 1.79 × 10⁻⁴ − 6.71 × 10⁻³ wt% Ru. The effects of temperature (50–180 C) and pressure (50–750 psig) on reaction rate,trans-isomer content and fatty acid composition were examined. The activities of RuCl₂ (CO)₂ (PPh₃)₂ and nickel (Nysel HK-4 and AOCS standard nickel catalyst) were compared on a molar basis. At 4.40 × 10⁻⁴ mol/kg-oil (0.0026 wt/Ni or 0.0044 wt% Ru), 140 C and 50 psig, the nickel catalysts were completely inactive, but the ruthenium catalyst produced an IV drop of 40 units in 60 min. At 110 C, 750 psig and 1.34 × 10⁻⁴ mol/kg-oil (1.35 × 10⁻³ wt% Ru), a hydrogenation rate of 0.89 ΔIV/min and a maximumtrans-isomer content of 10.4% (IV=45.0) was obtained with the ruthenium catalyst.     

Electrochemical hydrogenation of canola oil using a hydrogen transfer agent

A novel low-temperature process for the electrochemical hydrogenation of canola oil is described. An emulsion of oil and water containing formic acid and a nickel hydrogenation catalyst, placed in the cathode compartment of an electrolysis cell and subjected to an electrical current, underwent hydrogenation at temperatures as low as 45°C. At these low temperatures of hydrogenation, the trans FA content of the hydrogenated canola oil was very low as compared with that of the edible oils hydrogenated by commercial processes using high temperature and high partial pressure of hydrogen gas. Because of its adverse health effects, a high trans FA content in edbile oils is viewed as undesirable. In addition to the commercially available nickel supported on silica, amorphous nickelphosphorus alloys supported on a variety of substrates were also used. Amorphous alloys are generally very corrosion resistant because of the absence of grain boundaries. A mechanism for hydrogenation using the hydrogen transfer agent of formic acid and its continuous regeneration at the cathode was evoked to explain the experimental data.     

Trisaturates in the hydrogenation of canola oil with a commercial nickel catalyst

Refined and bleached Canola oil was hydrogenated with Pricat 9906 catalyst to an iodine value of 65 using various temperatures, pressures and catalyst concentrations. Hydrogenation with this catalyst resulted in great differences in SFI curves of fats with the same IV. Hydrogenation rate, dropping point, trisaturate content and linoleate selectivity were determined. All of the oils hydrogenated to IV 65 contained almost the same amount of solid fat at 20 C. For this reason, the crystal structure of the fats was examined by X-ray diffraction at 20 C. The catalyst was found to be non-selective. Increased selectivity can be obtained by careful temperature and pressure control. Reactivity also is temperature and pressure dependent. High trisaturate content increased instability by promoting formation of β crystals. The catalyst had excellent filterability characteristics.     

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.     

Hydrogenation of canola oil in the presence of nickel and the methyl benzoate-chrome carbonyl complex

Canola oil was hydrogenated using a mixture of homogeneous methyl benzoate-Cr(CO)₃ and heterogeneous nickel catalysts. The effect of the methyl benzoate-Cr(CO)₃_to-nickel ratio on the activity, specific isomerization index, linoleate and linolenate selectivities, and fatty acid composition was evaluated, and the results compared with those obtained with commercial nickel catalyst and methyl benzoate-Cr(CO)₃ used individually. At higher chromium-to-nickel ratios the activity of nickel was inhibited and the system behaved essentially like the pure chrome complex, while at low chromium-to-nickel ratios the characteristics of the nickel predominated. In a short transition zone relatively high reaction rates were obtained with significantly reducedtrans-isomer levels in the product. In a broader sense, it may be possible to combine a homogeneous and heterogeneous catalyst while retaining the advantages of both. We may thus be able to design catalyst systems for specific applications.     

Frying stability of canola oil in presence of pumpkin seed and olive oils

Frying performance of canola oil (CO) was investigated in the presence of 5, 10, and 15% levels of virgin olive oil (VOO) and pumpkin seed oil (PSO) during frying of potatoes at 180°C. Acid value, carbonyl value, total polar compounds content, and total tocopherols content of the oil samples were determined during the frying process. VOO and PSO addition improved the frying stability of the CO. Frying performance of the CO increased more in the presence of PSO than in the presence of the VOO. The PSO levels higher than 5% exerted pro‐oxidant effects, indicating the necessity of investigation at lower levels. The better antioxidative effect of PSO was attributed to its probably different phenolic composition.     

Positional isomers formed during the hydrogenation of cottonseed oil

Summary A commercial cottonseed oil was hydrogenated under nonselective, normal, and selective conditions. The operating variables used were within the ranges of those ordinarily found in large-scale operations. For each run samples were withdrawn at iodine values of approximately 75, 62, and 48; and these samples were analyzed for the position of the donble bonds, content oftrans isomers, and content of linoleins. Double bonds were found in the 6 through 14 positions of the monounsaturated fatty acid groups resulting from the hydrogenations. On the basis of the percentage distribution of the double bonds, there appeared to be no marked tendency for the linoleoyl group to form 9- or 12-isomers of the oleoyl group. In the early stages of the selective hydrogenation the rate at which double bonds shifted from the 9-position was greater than the rate at which double bonds were hydrogenated. The conditions of hydrogenation did not have a marked effect on the distribution of the double bonds at iodine values of about 62 and 48. The conditions of hydrogenation did have a marked effect on the percentage oftrans bonds. At an iodine value of approximately 75 the content oftrans bonds, expressed as weight percentage of trielaidin, was 9.4 for the nonselective hydrogenation and 27.3 for the selective hydrogenation while at an iodine value of approximately 48 these values increased to 21.6 and 37.7, respectively. Presented at the 48th Annual Meeting. American Oil Chemists' Society, New Orleans, La., April 29–May 1, 1957. One of the laboratories of the Southern Utilization Research and Development Division, Agricultural Research Service, U. S. Department of Agriculture.     

Evidence for the probable presence of sulfur-containing fatty acids as minor constituents in canola oil

Three isomeric epithio stearic acids have been concentrated as possible minor sulfur-bearing components of unprocessed canola oil. Chromatographic and mass spectral evidence is presented in support of these novel fatty acid structures, tentatively identified as isomeric 9, 12; 8, 11; and 7, 10 epithio stearic acids, each with a methyl substituent on the ring. Presented in part at the AOCS Canadian Section meeting in Guelph, Ontario, October 1986.     

Effect of agitation in the hydrogenation of castor oil

Castor oil was hydrogenated to evaluate the effect of agitation during hydrogenation. The turbine and propeller impellers were evaluated during hydrogenation of castor oil at various temperatures, pressures, and catalyst concentrations. The effect of impeller position in the agitator at definite oil depth was also evaluated. Hydrogenation of castor oil at 130°C, 2.0 kg/cm² hydrogen gas pressure with 0.5% Ni catalyst for 6 h while using two turbine impellers fitted in an agitator, one close to the reactor bottom and another at a height just below the top oil layer, revolving at 350 rpm, resulted in a product of a iodine value of 4.1, hydroxyl value of 156.4, and slip point of 84°C.     

Polymorphism of hydrogenated canola oil

The polymorphism of hydrogenated Canola oil was investigated using X-ray diffraction. The effects of hydrogenation conditions (selective: 200 C; 48 kPa hydrogen pressure, and nonselective: 160 C; 303 kPa) and degree of unsaturation on the transformation β′ → β are discussed. A densitometer was used to follow the changes in the relative density of the characteristic short spacings, in an attempt to present a semiquantitative measure of β′ « β transformation during storage. The samples studied were selectively and nonselectively hydrogenated Canola oils of iodine values (IV) 70 and 60, respectively. Among the 4 samples, the selectively hydrogenated sample with IV 70 was the most stable and the nonselectively hydrogenated sample with IV 60 the least stable.     

镍基芳烃加氢催化剂硫中毒的失活动力学

将某一时刻催化剂表面上活性中心数目与初始时刻活性中心数目之比定义为催化剂表观活性因子,并认为此活性因子包含在主催化反应速率系数的指前因子中。考虑活性中心在催化剂表面分布的不均匀性,在现有级数型失活动力学模型基础上,经推导得到表观活性因子的具体表达式及其极限式,该式在一般情况下为不可分。最后,结合之前报道的具有较高普适性的反应转化率方程式,得到催化反应转化率与运转时间的关系方程,并以Ni-B/SiO₂催化剂在噻吩存在下芳烃加氢反应为例加以验证。结果表明,所提出的失活动力学表达式可以较好地描述镍基催化剂硫中毒的行为,方程参量具有物理意义,方程可以较精确地拟合实验数据。     

Rapid extraction of canola oil

The simultaneous size reduction and solvent extraction of canola seeds were studied using a laboratory blender and a small, pilot-scale Szego mill. The laboratory tests established that over 95% of the oil may be removed from the seed in a single contact stage. The effects of contact time and solvent-to-seed ratio were investigated. The extraction equilibrium favored the extraction of the oil at higher solvent-to-seed ratios. In all cases the extraction reached some 90% of the equilibrium value after 3 min. Runs in the Szego mill, which is a unique orbitalmill developed by one of us (O. Trass), confirmed that solvent grinding is an efficient extraction technique. In this equipment, contact times as short as 30 sec give significant extraction, with the system approaching equilibrium in one minute. The Szego mill appears to be suitable for the rapid extraction of edible oil seeds such as rapeseed.