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
  • C11C3/003—Fats, oils, or fatty acids by chemical modification of fats, oils, or fatty acids obtained therefrom by esterification of fatty acids with alcohols
• • 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
  • C11C3/04—Fats, oils, or fatty acids by chemical modification of fats, oils, or fatty acids obtained therefrom by esterification of fats or fatty oils

Definitions

• the invention relates to an improved process for the preparation of esters of fatty acids or fatty acid mixtures and lower monofunctional alcohols by catalytic transesterification of fatty acid glycerides with the lower monofunctional alcohols in the presence of basic catalysts.
• Suitable lower monohydric alcohols in particular the corresponding C1- 4 alcohols are suitable, in practice, belongs to the methanol important technical significance.
• Fatty acid glycerides in the sense of the teaching according to the invention are corresponding triglycerides or any partial esters of fatty acids or fatty acid mixtures and glycerin. Of particular importance here are the triglycerides and, above all, fats and / or oils of native origin which can be converted into fatty acid methyl esters in a simple manner by the process according to the invention.
• Fatty acid methyl esters are of great technical importance as a starting material for the production of fatty alcohols and other oleochemical products such as ester sulfates, fatty acid alkanolamides and soaps.
• the industrial production of fatty acid methyl esters takes place predominantly by catalytic transesterification (alcoholysis) of fatty acid triglyceride mixtures as they are present in the fats and oils of vegetable and / or animal origin.
• Native fats and oils almost always contain considerable amounts of free fatty acids, whereby the respective value - depending on the origin of the material and its history - can fluctuate in a wide range and is almost always above 3% by weight.
• Such pre-esterification of acidic fatty acid glycerides can be carried out in several ways. For example, it is possible to work in the presence of alkaline catalysts from 240 ° C. and 20 bar (Ullmann, Encyclopedia of Industrial Chemistry, 4th edition, volume 11, 1976, page 432). However, this type of pre-esterification with methanol again requires the use of expensive reactors ahead. It is also known to esterify the free fatty acids in oil with added monofunctional lower alcohols, especially methanol, in a homogeneous phase by means of acid catalysis, for example using p-toluenesulfonic acid as a catalyst. However, the subsequent removal of the catalyst with simultaneous removal of water by washing the pre-esterified oil with methanol is then required.
• the teaching of the present invention is based on the fact that fatty acid glycerides are reacted with lower monofunctional alcohols, in particular with methanol, with basic catalysis without problems under mild reaction conditions, in particular at ambient pressure, low temperatures and low use of methanol to give the corresponding alkyl esters and free glycerol can and that there are still sufficient practical possibilities for implementation for the preconditions set here - low contents of the feedstock in free fatty acids and water.
• the inventors have set themselves the task of modifying this base-catalyzed transesterification of the fatty acid glycerides with monofunctional alcohols, in particular methanol, in such a way that solids which are practically insoluble in the starting material or reaction mixture are used as catalysts - and thus with heterogeneous catalysis. It is obvious that considerable simplifications are obtained in this way, in particular when the catalyst is separated from the reaction mixture.
• the object of the invention is based on the surprising discovery that solid sodium carbonate Na 2 C0 3 and / or sodium N A HCO 3 are suitable as heterogeneous solid catalysts, the desired alcoholytic cleavage of fatty acid glycerides among the previously known per se mild conditions of particularly low pressures and catalyze temperatures effectively.
• the invention relates in a first embodiment to the use of solid sodium carbonate and / or sodium bicarbonate as heterogeneous solid catalysts in the transesterification of deacidified and anhydrous fatty acid glycerides with lower monofunctional alcohols to give fatty acid alkyl esters and glycerol.
• the invention relates to a process for the catalytic transesterification of fatty acid glycerides with lower monofunctional alcohols by reacting an essentially acid-free and anhydrous glyceride starting material with the monofunctional alcohol and preferably subsequently separating the released glycerol.
• the new process is characterized in that solid sodium carbonate and / or solid sodium bicarbonate is used as a heterogeneous solid catalyst.
• the process is carried out under energy and cost-saving conditions in such a way that the reaction of the fatty acid glyceride feedstock is carried out in the range of normal pressure and at only moderately elevated temperatures, which in particular do not substantially exceed the range of about 100.degree.
• the process temperature in the transesterification is preferably in the range of the boiling point of the alkanol used. Since work is carried out at normal pressure or only slightly elevated pressures, the reaction temperature for the transesterification of the glycerides with methanol is usually in the range from about 60 to 75 ° C., preferably in the range from about 65 to 70 ° C.
• Suitable fatty acid glycerides are in particular appropriately pretreated (deacidified) fats and / or oils of vegetable and / or animal origin. They are subjected to the transesterification with lower alkanols, preferably having 1 to 4 carbon atoms. Methanol is preferably used as the lower alkanol.
• the glyceride feed should have an acid number of at most about 1, preferably acid numbers of at most about 0.7, and it may be particularly expedient to work with acid numbers in the range of about 0.5 or less.
• the water content of the glyceride feed should be as low as possible; in particular it is not more than about 0.8% by weight, and it is preferred to work under practically anhydrous conditions. Deacidified and anhydrous glyceride feed material can easily be obtained as a reaction product of the upstream process stages described in the introduction - in particular as a product of a pre-esterification of the starting material.
• the reaction mixture is operated with weight ratios of alkanol - preferably methanol - to fatty acid glyceride in the range from 0.2 to 1: 1 and particularly preferably in the range from 0.2 to 0.5: 1.
• the heterogeneous Catalyzed transesterification can be carried out batchwise or continuously.
• the catalyst can be used either as a finer or coarser powder, in the form of chips or tablets or as an impregnation catalyst applied to a support material.
• the catalyst material can be arranged as a fixed bed, it is also possible to work with a moving bed of catalyst material, for example in stirred tanks, in a fluidized bed or fluidized bed in pulsation devices and the like. It is particularly expedient to carry out the heterogeneously catalyzed transesterification at normal pressure with low boiling point of the alcohol.
• the released glycerol is preferably separated from the reaction mixture by phase separation.
• it may be expedient to cool the reaction mixture or a partial stream branched off from the reaction mixture. It is advantageous to evaporate part of the monofunctional alcohol from the reaction mixture or from the branched-off partial stream of the reaction mixture before this cooling.
• the solubility of the released glycerol in the fatty acid ester / alcohol / oil phase is reduced and at the same time the density of the glycerol phase is increased, so that the resulting glycerol can be easily removed by phase separation.
• the alkanol drawn off from the reaction mixture in this way is preferably returned to the reactor in a circuit.
• the partial removal of the glycerol from the reaction mixture is carried out in such a way that when a partial stream is branched off, in particular continuously, from the By freeing it from the methanol and then separating free glycerol from the reactor, the methyl ester / oil phase returned to the reactor is a homogeneous liquid phase, ie that neither a separate methanol phase nor a phase consisting of free glycerol occurs in the returned liquid phase.
• a particularly preferred embodiment of the invention consists in first passing at least a partial stream of the reactant mixture through an evaporator in which the free alkanol present is evaporated at least partially in the continuous process.
• the liquid phase is then cooled to temperatures below 50 ° C., in particular to temperatures in the range from 30 to 40 ° C., whereupon the heavier glycerol phase is separated and discharged by phase separation, while part of the lighter ester phase is recycled into the transesterification as a recycle stream the evaporated alkanol portion and fresh reactants are fed in simultaneously.
• the transesterification is carried out in several stages in a reactor cascade.
• the process according to the invention is particularly suitable as an important process step in the processing of natural in particular unpurified fats and / or oils such as coconut oil, palm kernel oil, soybean oil, tallow and the like. It is not necessary to clean these raw materials from the naturally contained sludge and mucilage.
• the natural starting material is first subjected to pre-esterification as described at the beginning.
• Particularly suitable here is the process carried out with solid cation exchange resins in accordance with the applicant's older German patent application P 35 01 761.9 (D 6972; "Process for the Pre-Esterification of Free Fatty Acids in Crude Fats and / or Oils").
• the material obtained in this preliminary stage with acid numbers preferably below 0.7 contains, in addition to methanol, the excess from the pre-esterification also water components which can be partially or completely expelled as a mixture.
• the process according to the invention By eliminating the water of reaction from the pre-esterification, there is a feedstock for the process according to the invention which can be subjected directly to the transesterification in the sense of the invention.
• the previous separation of the sludge and mucilage is not necessary. It is brought about in the anyway necessary distillative treatment of the fatty acid methyl esters according to the invention.
• the proportion of bound glycerol in the methyl ester phase after the glycerol separation was approximately 0.5% by weight. The values were reproducible over several days without changing the catalyst.

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• Chemical & Material Sciences (AREA)
• General Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Wood Science & Technology (AREA)
• Organic Chemistry (AREA)
• Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)
• Fats And Perfumes (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Catalysts (AREA)

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Citations (3)

• 1985
  • 1985-04-29 DE DE19853515403 patent/DE3515403A1/de not_active Withdrawn
• 1986
  • 1986-04-10 GB GB08608680A patent/GB2174697B/en not_active Expired
  • 1986-04-21 EP EP86105506A patent/EP0200982B1/fr not_active Expired
  • 1986-04-21 AT AT86105506T patent/ATE39947T1/de not_active IP Right Cessation
  • 1986-04-21 DE DE8686105506T patent/DE3661737D1/de not_active Expired
  • 1986-04-28 PH PH33709A patent/PH23503A/en unknown
  • 1986-04-28 BR BR8601882A patent/BR8601882A/pt unknown
  • 1986-04-30 JP JP61100818A patent/JPS61254255A/ja active Pending

Patent Citations (3)

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