Classifications

• • C—CHEMISTRY; METALLURGY
  • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
  • C11C—FATTY ACIDS FROM FATS, OILS OR WAXES; CANDLES; FATS, OILS OR FATTY ACIDS BY CHEMICAL MODIFICATION OF FATS, OILS, OR FATTY ACIDS OBTAINED THEREFROM
  • C11C3/00—Fats, oils, or fatty acids by chemical modification of fats, oils, or fatty acids obtained therefrom
  • C11C3/12—Fats, oils, or fatty acids by chemical modification of fats, oils, or fatty acids obtained therefrom by hydrogenation

Definitions

• the present invention relates to a hydrogenation process for unsaturated glyceride oil, in particular to a hydrogenation process for direct, selective and partial hydrogenation of unsaturated glyceride oil with optionally concomitant cis/trans isomerization of the glyceride oil.
• the hydrogenated or hardened oils obtained are specifically used for the production of margarines and shortenings.
• the process is particularly useful for the hardening of vegetable oils which contain per kg oil less than 60 mg phosphorus (denoted as 60 ppm P) in the form of phosphatides.
• Crude glyceride oils are normally subjected to a so-called degumming treatment in order to remove phosphatides from the glyceride oil.
• degumming treatment water is added to the crude glyceride oil to hydrate the phosphatides which are subsequently removed by for instance centrifugal separation. Since The resulting degummed oil often still contains unacceptably high levels of "non-hydratable" phosphatides, which may interfere with subsequent oil processing including hydrogenation. Therefore the water-degumming treatment is normally followed by a chemical treatment with acid and/or alkali in order to remove the residual phosphatides and to neutralize the free fatty acids. This subsequent treatment is often called alkali refining. The soapstock formed is separated from the neutralized oil. During further refining the oil may be bleached resulting in a neutralized bleached oil containing 0-5 ppm P. If desired, the oil is subsequently hydrogenated.
• a deodorizing treatment is a usual last step of refining.
• US-A-4,049,686 discloses a degumming method in which crude or water-degummed oil is treated with a concentrated acid, such as citric acid, and residual phosphorus level can be brought down to within the range of 20-50 mg P/kg oil.
• This degumming method is a so-called super-degumming method.
• a refining process sequence which does not involve an alkali treatment and the subsequent removal of soapstock is often referred to as "physical refining", and is highly desirable in terms of avoiding pollution, processing simplicity and yield.
• the phosphatide level should be brought down to a phosphorus content of 4 ppm or less, preferably 2-3 ppm phosphorus or less in order to avoid an inhibition of the hydrogenation catalyst used and/or an interference with the removal of the catalyst by filtration after the hydrogenation.
• Almost no inhibition of the hydrogenation catalyst occurs with oils containing no more than 4 ppm phosphorus. It has been disclosed in JAOCS, July 1989, 66 , no. 7, page 1002-1009, that so called totally degummed oils, having a very low phosphorus content (lower than 10 ppm, generally 4-7 ppm P), can be successivefully hydrogenated even when the usual prior neutralization treatment is omitted.
• US-A-4,857,237 discloses a process for refining oil, in which an effective aqueous substance is used so that after hydrogenation using a nickel catalyst, subsequently residual nickel may be removed by filtration.
• This aqueous substance such as water, steam or a diluted aqueous acid, may be added prior, during or after hydrogenation. Improved filtration results are obtained because of the agglomeration of finely divided nickel catalyst particles.
• the amount of aqueous substance added is dependent on the water content of the glyceride oil used.
• US-A-4,179,454 discloses a two-step process for providing completely hydrogenated fatty acids.
• crude or unrefined glyceride oil is subjected to a catalytic hydrogenation, and in a second step the hydrogenated glyceride oil obtained is split into hydrogenated fatty acids and glycerine.
• the crude glyceride oil Prior to the hydrogenation the crude glyceride oil may be subjected to a cumbersome degumming process, such as a treatment using water, boric acid, sodium chloride and the like, in order to decrease the phosphatide content of the crude oil.
• the oil may be dried, and alternatively, a preferred catalyst system comprising two types of catalysts may be used in order to obtain completely hydrogenated fatty acids.
• the object of the invention is to provide a hydrogenation process for not pre-refined oils containing up to 60 ppm P.
• the hydrogenation treatment is carried out in substantial absence of water, so that the precipitation of phosphatides is avoided. Precipitation is avoided when the water content is less than 0.2% by weight. Good results are obtained with a water content of 0.005-0.15% by weight. If the phosphorus content is so low that precipitation is not likely, even in the presence of moisture, it still is advantageous to hydrogenate under dry conditions because the adverse effect of water on the catalyst is avoided. If the moisture content of the available oil is 0.2% by weight or higher, it can be dried in the usual way, e.g. by heating it at a temperature over 100°C, preferably 120-140°C. The moisture content can be further decreased by sparging the oil with an inert gas, for example nitrogen. Especially when using fixed bed hydrogenation where the catalyst should be spared as much as possible a very low moisture content is desired.
• Performing the hydrogenation treatment according to the invention at such a low water content involves also a positive control of the dryness of the hydrogen which is used in the hydrogenation treatment in up to a 70-fold excess over the oil volume.
• Suitable dry hydrogen comprises hydrogen produced in the so-called pressure-swing process.
• the positive control of the hydrogen dryness includes further that, when hydrogen is recycled, contact of hydrogen with water is avoided. This means, that in safety locks water may not be used.
• Hydrogen pressure generally is 0.1-10 bar. On account of a higher solubility of hydrogen in dry oil the speed of hydrogenation is increased.
• the hydrogenated glyceride oil is used in the production of margarines and shortenings. A minimum level of unsaturation therefore is recommended. Preferably not more than 50% of the initially available double bonds in the fatty acid units of the glyceride oil will be saturated. However, superior products are obtained when not more than 70% of the initially available double bonds are saturated.
• the temperature during the hydrogenation treatment may be 90-220°C, generally is above 120°C, but preferably is within the range of 150-220°C. At that temperatures there is no substantial adverse effect on the hydrogenation by the phosphatides still present in the glyceride oil.
• the hydrogenation catalyst is chosen from catalysts known in the art, and preferably is a partially de-activated nickel catalyst, such as a sulfur poisoned nickel catalyst.
• the nickel content generally is 15-25%.
• Suitable partially de-activated catalysts are disclosed in EP-A-0,246,366.
• the catalyst preferably comprises a mixture of fresh catalyst and recycled catalyst.
• the recycling value that is the ratio of the amount of recycled catalyst over the amount of fresh catalyst, is larger than 5, more preferably within the range of 7-15. Recycling of the catalyst is desired not only for economic reasons, but also because a recycled catalyst enables a more selective hydrogenation.
• An effect of selective hydrogenation is that the hardened oil contains not more than one stearic acid group.
• the amount of nickel catalyst used for an effective hydrogenation is 0.03-0.8 kg nickel/ton glyceride oil, but lower amounts of 0.05-0.15 kg nickel/ton glyceride oil are attainable with good result.
• the figures for catalyst consumption recycling of the catalyst has been taken into account. Therefore the figures reflect the amount of catalyst which has to be replenished to maintain catalytic activity.
• the starting oil should have less than 60, preferably less than 40 ppm P. Optimal results are obtained if the starting glyceride oil comprises 15-40 mg P/kg, more preferably 18-35 mg P/kg.
• the hydrogenated oil, freed from catalyst may be subjected to steam distillation or stripping in order to remove free fatty acids still present in the oil.
• the process of the invention is equally applicable to the hydrogenation of phosphatides containing fatty acids. Inhibition of the catalyst is prevented when the moisture content of the reaction mixture is positively controlled. The moisture content is not allowed to rise above the lowest concentration where phosphatides separate at the hydrogenation temperature.
• Super-degummed sunflower oil (18-25 mg P/kg), super-degummed bean oil (30 mg P/kg) and super-degummed rape oil (23-32 mg P/kg and having a water content of 0.1 wt.%) have been subjected to a direct hydrogenation process according to the invention at a hydrogenation temperature of 120°/190°C.
• Nickel catalyst containing 15% nickel (C-cat obtained from Unimills, Zwijndrecht, the Netherlands), was used in an amount of 0.42 and 0.53 kg catalyst/ton oil, respectively, corresponding with 0.06-0.08 kg nickel/ton oil.
• the recirculation value was 12 and 10, respectively.
• the moisture content was controlled at 0.1 wt% of the mixture under hydrogenation.

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• Chemical Kinetics & Catalysis (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Wood Science & Technology (AREA)
• Organic Chemistry (AREA)
• Fats And Perfumes (AREA)
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Citations (2)

• 1992
  • 1992-09-11 EP EP92202763A patent/EP0534524A2/fr not_active Withdrawn
  • 1992-09-23 AT AT189592A patent/AT398430B/de not_active IP Right Cessation

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