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.     

苯乙炔选择性加氢催化剂的研究进展

对各种苯乙炔选择性加氢催化剂的开发研究情况进行了详细介绍。由于负载型钯催化剂和镍催化剂在加氢反应领域应用广泛,本文对这两种催化剂进行了重点介绍。阐述了各种催化剂的性能、使用条件、存在的主要问题、失活原因以及改进措施。提出今后对苯乙炔选择性加氢催化剂的改进应以高空速、适当提高操作温度、改善对原料的适应性等为目标。     

HYDRODEMETALLATION CATALYST DEACTIVATION—EFFECT OF METALS ACCUMULATION ON HYDROGENATION AND HYDROGENOLYSIS ACTIVITIES

The deactivation of hydrodemetallation catalyst was investigated in diffusion-free conditions using a model oil system. The hydrodemetallation activity of a CoMo/γ-alumina catalyst was studied using nickel or vanadyl etioporphyrins as model compounds and the hydrodesulfurization and hydrogenation activity using dibenzothiophene and naphthalene. The experiments were carried out over sulfided catalysts at 320°C and 4.83 MPa total pressure. The catalyst activity for nickel etioporphyrin hydrodemetallation was maintained at least up to 50% metal loading. The hydrogenolysis activity decreased with increasing nickel and vanadium on the catalyst but the hydrogenation activity increased. The changes in activity were attributed to the different activities of the various sulfide phases present in the catalyst system.     

Influence of various catalyst poisons and other impurities on fatty acid hydrogenation

The effect of various impurities which reduce the activity of nickel catalysts during fatty acid hydrogenation has been studied. It is here proposed to divide the compounds which negatively influence the nickel-based fatty acid hydrogenation process into three categories, namely, catalyst poisons, inhibitors and deactivators, each group acting according to a different mechanis. The deleterious effect of typical catalyst poisons, such as S, N, P or Cl, is more or less independent of the chemical nature of the individual organic compounds containing these elements. There is good correlation between these element contents and the required nickel catalyst loading level. Other typical impurities present in technical fatty acids, such as oxidized fatty acids, soaps and water, also diminish the catalyst activity considerably. A number of experiments were designed to study the influence of various pretreatments of fatty acids on the catalyst loading levels needed for hydrogenation. In view of the high cost of nickel catalysts, considerable savings can be obtained by pretreatment of fatty acids prior to hydrogenation. Such pretreatment steps may include sulfuric acid washing, application of spent catalysts, and/or distillation. The most economical method will depend on local circumstances.     

Deactivation of fixed-bed nickel hydrogenation catalysts by sulfur

A series of fixed-bed nickel hydrogenation catalysts was tested in the dearomatization of hydrocarbon solvents. The mechanism of catalyst deactivation by aromatic sulfur compounds was studied in high-pressure micro-flow equipment by variation of the experimental conditions and the sulfur content of the feed. It is concluded that catalyst deactivation proceeds under mild but realistic conditions through formation of a surface sulfide which blocks the active surface. The rate of the disappearance of the active sites is a first-order process with rate constant 1.0 × 10⁻³ (ppm S)⁻¹ h⁻¹. Under more severe conditions, more sulfide layers are formed, but bulk Ni₃S₂ was not observed even after full deactivation of the catalysts. The poisoning of the active sites in the latter case is no longer a first-order process. Consequently, under the circumstances investigated, the sulfur resistance of nickel catalysts is determined by the nickel surface area per unit weight of catalyst.     

Catalytic behavior of ruthenium in soybean oil hydrogenation

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 (k_c) 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.     

Hydrogenation of cyclopropenoid fatty acids occurring in cottonseed oil

The hydrogenation of cyclopropenoid acids and their relative reactivities during hydrogenation as compared to linoleic and oleic acids were examined. Pure methyl sterculate and purifiedSterculia foetida oil and its methyl esters, which have a cyclopropene content more than 60 times that of cottonseed oil, were used for the hydrogenation experiments. Nickel, palladium and platinum catalysts were used. The effect of temperature and type of catalyst were demonstrated in a series of hydrogenation experiments of safflower andS. foetida oil mixtures, and methyl oleate and methyl dihydrosterculate mixtures. Partial hydrogenation of methyl sterculate formed as many as twenty compounds in addition to the cyclopropenoid derivatives. Most of these compounds were monounsaturated. The cyclopropene group hydrogenated very readily compared to the 9,12-diene system in linoleate. The cyclopropane group obtained by hydrogenating the cyclopropenoid acids group was quite resistant to further attack by hydrogen and nickel catalyst had little effect. With palladium catalyst, a temperature of 180 C was necessary for the reaction to go to completion. Platinum in acetic acid was a good system for hydrogenolysis of the cyclopropane group at 80 C. Retired.     

Deep desulfurization of diesel fuels: kinetic modeling of model compounds in trickle-bed

Five catalysts with different hydrodesulfurization (HDS) and hydrogenation activity were tested in HDS of fresh crude heavy atmospheric gas oil (HAGO) (1.33 wt% S), two partially hydrotreated HAGO (1100 and 115 ppm S) and two model compounds, dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (DMDBT), dissolved in model solvents and HAGO. Aromatic compounds in the liquid decreased significantly the HDS rate of 4,6-DMDBT, especially for catalysts with high hydrogenation activity. H₂S displayed a similar inhibition effect with all catalysts. These effects were extremely pronounced in HAGO where the DBT HDS rate decreased by a factor of 10 while 4,6-DMDBT – of 20 relative to paraffinic solvent. The feasibility of using a highly active hydrogenation catalyst for deep HDS of HAGO is diminished by the strong impact of aromatics.     

Partial hydrogenation of polyunsaturated fatty materials

For many applications involving the use of polyunsaturated triglycerides such as soybean oil, a liquid product having an improved stability to oxidation is required. The partial hydrogenation of soybean oil into a liquid product containing less oxidizable materials can be achieved with selective nickel catalysts. A soybean oil containing ca. 5% solid matter at 10 C, 1% linolenic acid and 0.5% conjugated dienes is obtained with a nickel/titanium oxide catalyst or with nickel-zirconium oxide/kieselguhr catalyst treated wity fatty amines such as lauric or coco primary amines. In the frame of this work, ca. 100 heterogenous Ni catalysts have been tested under standard operating conditions for the partial hydrogenation of soybean oil.     

Hydrogenation of soybean oil with copper catalysts containing small amounts of nickel catalysts

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.     

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.     

Reaction of cyclopropene esters with hydrogenation catalysts

Methyl esters of stereulic and malvalic acids were heated under nitrogen in the presence of various hydrogenation catalysts, and the effect on the cyclopropene moiety was established. Similar tests were conducted with cottonseed oil, which contains glycerides of sterculic and malvalic acids. Palladium catalysts, and some palladium compounds which were tested, readily gave cyclopropene-free products, while nickel and platinum catalysts did not. Palladium catalysts freshly activated with hydrogen were not as active as those freed of adsorbed hydrogen. The catalysts could be reused. Heating cottonseed oil (0.73% cyclopropenes, calculated as trimalvalin) with 0.02% palladium, as a 10% palladium-on-carbon catalyst, gave a cyclopropene-free oil after 2 hr at 150 C. The treated oil was unaltered in appearance, and the noncyclopropene components were unaffected. Heating methyl sterculate with palladium catalyst produced a mixture of unsaturated condensation products and a number of unsaturated monoesters of practically unchanged molecular weight. The palladium treatment was shown to cleave the cyclopropene ring and produce methyl and methylene substituted fatty acid groups. Presented at the AOCS-AACC Joint Meeting, Washington, D.C., April 1968.     

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.     

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.     

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.     

Stationary catalysts for the continuous hydrogenation of fats

Hydrogenation characteristics of a wide variety of stationary catalysts were studied with an aim to explore their possible use in the continuous hydrogenation of fats. Refined soybean oil was hydrogenated continuously in a vertical flow-through reactor over a fixed bed of catalyst. Catalysts investigated were pelleted products containing Raney nickel, reduced nickel, reduced palladium, and copper chromite, as well as granulated alloys of the Raney type, such as Ni-Al, Cu-Al, Pd-Al, and Cu-Cr-Al, which were activated with alkali. These catalysts offered a wide choice of activity, selectivity, and ability to form geometrical isomers. Pelleted copper chromite and granular Raney copper-chromium were found to be highly selective toward the linolenate moiety of soybean oil, whereas pelleted palladium on carrier, as well as granular Raney nickel, Raney copper, and Raney palladium, though moderately selective, exhibited very high activity even at relatively low temperatures. A unique feature of most of the stationary catalysts was the remarkably high rate of hydrogenation. With most catalysts, the iodine value of soybean oil was reduced by 40–60 units within a reaction period of 2–4 min. The hydrogenated fat was practically free of catalyst particles.     

Continuous slurry hydrogenation of soybean oil with nickel catalysts

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.     

Copper-hydrogenated soybean and linseed oils: Composition,organoleptic quality and oxidative stability

Copper and nickel hydrogenations give a wide distribution of double bonds in the monoene fraction from both reduced soybean and linseed oils. With copper catalysts, high pressure hydrogenation reduces the extent of this double bond distribution when compared with low pressure hydrogenation. With nickel catalysts, some Δ17-octadecenoate is formed but less than with a copper catalyst. In room odor evaluations, copper-hydrogenated soybean (CuHSB) oil gave higher scores and lower fishy responses than nickel-hydrogenated soybean oil after both had been exposed to fluorescent light. A mixture of CuHSB oil (33%) and peanut oil received room odor scores equal to or better than peanut oil alone, whether light exposed or not. Although hydrogenated products with remarkable stability to oxidation were obtained by copper hydrogenation of linseed oil, these oils have lower organoleptic stability when compared to nickel-hydrogenated, winterized soybean oil.     

Novel mesoporous aluminosilicate supported palladium-rhodium catalysts for diesel upgrading: II. Catalytic activity and improvement of industrial diesel feedstocks

Bimetallic PdRh catalysts (molar ratio Pd/Rh = 1 and 2) were prepared by impregnation of a mesoporous aluminosilicate (molar ratio Si/Al = 10 and 20). These materials are destined to be used in industrial processes aiming to improve diesel quality by hydrogenation and ring-opening of aromatic components. The four catalysts were examined for their activity in hydrogenation of naphthalene and tetralin model feedstocks, at 6 MPa, including in the presence of sulfur containing compounds. The capacity of one of these catalysts to improve the quality of hydrogenated industrial light cycle oil containing ≤50 wt ppm of sulfur was evaluated in a pilot plant. In these industrial conditions, the catalyst has a higher catalytic activity at lower temperature than a reference state of-the-art catalyst, giving a seven-point improvement of the cetane number at 280–300 °C and with formation of less than 10% of non-selective cracking products.     

油脂氢化三元金属催化剂制备及性能研究

在相同的加氢条件下,对自制Cu-Ni-Cr三元金属催化剂与Cu-Ni二元金属催化剂和进口单元镍催化剂的加氢性能进行了比较。结果表明,三元金属催化剂的活性高于二元金属催化剂,选择性高于单元金属催化剂。关于氢化油的固体脂肪指数,多元催化剂和单元催化剂的性能接近。