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
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E50/00—Technologies for the production of fuel of non-fossil origin
  • Y02E50/10—Biofuels, e.g. bio-diesel

Definitions

• the invention relates to a method for obtaining
• Fatty acid esters from fat and / or oil of biological origin by transesterification Fatty acid esters from fat and / or oil of biological origin by transesterification.
• Transesterification reactions per se are known and represent a commercially important class of industrial organic reactions.
• an ester is converted into another ester by exchanging the acid groups or by exchanging the alcoholic groups.
• alcoholysis also alkanolysis
• the alcohol is added in excess in order to obtain a high yield of the desired ester.
• alkyl esters in particular methyl esters
• alcoholysis of vegetable oils e.g. rapeseed oil
• the transesterification is an equilibrium reaction, which is usually already triggered by mixing the reactants. However, the reaction is so slow that for commercial
• Fats and oils of biological origin mainly consist of glycerides (mono-, di- and triglycerides).
• the glycerin component can be substituted by low molecular weight monohydric alcohols.
• the Bradshaw method (described in US Pat. Nos. 2,271,619 and 2,360,844) is often used for this purpose.
• the reaction is carried out in an open container, which may consist of ordinary carbon steel.
• the fat or oil must be dry (anhydrous), clean and above all neutral, ie the content of free fatty acids must be negligibly low (acid number not higher than 1.5).
• the starting product is heated to approximately 80 ° C., then commercially available, anhydrous methanol (99.7% by weight), which contains 0.1 to 0.5% by weight of sodium hydroxide or potassium hydroxide in solution, is added in excess (approximately that 1.2 to 1.6 times the stoichiometric amount). After the alcohol has been added, the mixture is stirred for a few minutes and then left to stand. The glycerin begins to settle immediately. Since it is practically free of water and much heavier than the other liquids, it settles easily and forms a layer on the bottom of the container. The reaction of an oil with methanol to methyl ester is usually 98% complete after one hour.
• the bottom layer contains no less than 90% of the glycerin originally present in the fat.
• the top layer is composed of methyl esters, unreacted alcohol and alkali, the remaining glycerin, and a very small amount of soap. These various impurities are removed from the esters by repeated washing with small ones
• the method is advantageous because methyl or ethyl esters can be obtained directly from the fat without an intermediate step, the reaction temperature is low, and no equipment made of special corrosion-resistant material is required.
• the methyl esters obtained are then used in a continuous process to produce anhydrous soap.
• the esters are saponified at low temperature by sodium hydroxide and potassium hydroxide, and the readily volatile methanol released in the process is recovered.
• Toyama et. al. (Y.Toyama, T.Tsuchiya and T.Ishikava, J.Soc.Chem.Ind. Japan, 36 [1933] 230-232 B) showed that the equilibrium between methanol or ethanol and fats in the presence of sodium hydroxide within room temperature of two hours is reached. In order to convert the reaction to monoester until the fat has completely converted, the released glycerol must be removed.
• US Pat. No. 2,383,614 describes a process for the continuous alcoholysis of fat, in which a partial esterification of the fat or oil is carried out, optionally in several steps, and the glycerol is also separated in several steps.
• US Patent 2,383,580 after the reaction is complete first the catalyst used is inhibited by neutralizing the reaction mixture, then the excess alcohol is removed by distillation. The remaining reaction mixture is distilled in vacuo. The condensate separates into a glycerol and a fatty acid alkyl ester layer.
• the free fatty acids are first reacted with short-chain alcohols in the presence of acidic catalysts to give the corresponding esters in a two-stage process.
• the glycerides are then transesterified in the presence of alkali with the separation of glycerol.
• German patent application DE 34 21 217 AI describes a process for the preparation of fatty acid esters of short-chain primary and secondary alcohols having 1 to 5 carbon atoms by transesterification of glycerides.
• a stream of the gaseous alcohol is passed through the liquid glycerides at temperatures between 230 and 270 ° C.
• the product mixture of glycerin and fatty acid alkyl ester is discharged from the reaction zone with this stream, which is then separated.
• alkali is dissolved in the liquid glycerides of the reaction vessel.
• DAMP 4-dimethylaminopyridine
• TBD 1, 5,7-triazabicyclo [4.4.0] dec-5-ene
• TMD 1, 1, 3, 3-tetramethyl-guanidine
• TMG 1, 1, 2, 3, 3, -pentabutylguanidine
• PBG 1, 3-diphenylguanidine
• guanidines offer in the transesterification of fats and oils of biological origin are that they can be heterogenized on organic polymers and thus lead to heterogeneous catalysis.
• Schuchardt et. al. investigated cellulose, polystyrene / divinylbenzene, and polyurethanes with regard to their suitability as a carrier material for guanidines.
• the heterogenization of guanidines on organic polymers and their use in the transesterification of vegetable oils are described in Brazilian Patent 8202429 (1984, inventors U. Schuchardt and OC Lopes).
• the Guani dines bound to gel-like poly (styrene / divinylbenzene) or cellulose showed a slightly reduced activity compared to the catalytic reaction in a homogeneous phase. However, they allow the same high sales after extended reaction times. Although less active than their homogeneous analogues, all polymer-containing guanidines could be reused in several successive reaction cycles. However, a loss of activity was observed, and a decrease in activity was observed after only 9 reaction cycles. This decrease in activity after repeated use was mainly caused by the slow leaching of the anchored base out of the polymers.
• fats and oils of biological origin always also contain free fatty acids with which the conventionally used catalysts (in particular alkali metal oxides or alkali metal alcoholates) are incompatible or only poorly compatible. Free fatty acids that are present in the starting product must therefore be removed to residual concentrations of 0.1% by weight or less before the transesterification, in particular if alkaline catalysts are to be used. If the starting product contains a lot of free fatty acids, chemical deacidification is too expensive and it becomes then usually deacidified by steam stripping at 240 ° C to 260 ° C. The high temperature requires a corresponding amount of energy.
• the conventionally used catalysts in particular alkali metal oxides or alkali metal alcoholates
• the invention is therefore based on the object of providing a heterogeneously catalyzed process for the transesterification of fat and / or oil of biological origin, in which the catalyst used is stable and the products formed are not contaminated by catalyst material.
• the new process is also intended to convert the free fatty acids present in the starting material into esters in order to save the deacidification that was previously required.
• the new process should be easy to carry out and should give good yields.
• a monohydric alcohol is preferably used as the alcohol.
• Zinc salt of arginine is insoluble in methanol and, moreover, in mixtures of glycerides, glycerin, methyl esters and methanol, such as occur in methanolysis. After extracting with methanol in a Soxhlet apparatus for 4 hours, no weight loss was found. This compound is therefore well suited as a catalyst for heterogeneously catalyzed transesterification. In the case of methanolysis with zinc arginate as catalyst, a yield of 45% of methyl esters was obtained in the course of 180 minutes at 85 ° C. and with the addition of 6 molaguiquet methanol to deacidified palm oil.
• Zinc arginate can be pressed into relatively stable pills and installed in this form as a package in a tubular reactor.
• a further procedure consists in suspending the powdery, finely crystalline metal arginate in a mixture of oil and alkanol. After passing through a cascade of stirred tanks, the catalyst is filtered off or separated off with a centrifuge and recirculated. The mixture of excess methanol, glycerol and, if appropriate, water (in the case of larger concentrations of free fatty acids in the feed) is then decanted from the methyl ester phase. The esters formed are freed from unsaponifiable and unreacted residues and purified by distillation.
• Preferred metals are: zinc, lanthanum, cadmium, iron, etc.
• the fats and oils produced for the transesterification can contain large amounts of free fatty acids. Even at free fatty acid concentrations of around 10% by weight, the rate of the transesterification reaction with the catalysts of this invention at temperatures above 100 ° C is sufficient for commercial use.
• Preferred alkanols for the process according to this invention are primary and secondary alkanols with 1 to 6 carbon atoms.
• reaction rate is somewhat reduced compared to the reaction with fat-free neutral oils.
• the heavy metal salts of betaine, carnitine and taurine which contain quaternary nitrogen, are also suitable as catalysts for the transesterification of glycerides with alkanols. They show good catalytic activity at temperatures above 100 ° C.
• the lanthanum salt of taurine is attractive because of its stability against thermal stress and its insolubility in the reaction media in question.
• the catalysts according to this invention do not form soaps with the free fatty acids, which make it difficult to separate the glycerol due to an emulsifier action. After a 93-hour contact time, no decrease in the catalytic activity of the zinc arginate was observed at 135 ° C. A reduction in the concentration of by-products such as tocopherols, tocotrienols and carotenes was not observed at the relatively high temperature of 135 ° C. even with reaction times of more than 4 hours.
• the water formed in addition to glycerol precipitates in a mixture with glycerol as a separate, heavy phase.
• the mixture of glycerin and water is decanted. Because when using a solid catalyst Formation of soaps is excluded, the combined formation of glycerin and water does not cause an increase in the tendency to form emulsions.
• the reaction mixture is separated into two liquid phases quickly and completely at temperatures above 100 ° C. There are two coexisting clear liquid phases. At lower temperatures, the use of a centrifuge is recommended.
• the advantages of a heterogeneous procedure can be used.
• the two liquid phases formed during the alcoholysis contain no catalyst, which considerably simplifies their work-up.
• the catalysts of this invention are temperature resistant up to about 200 ° C, it is possible to carry out the alcoholysis in the temperature range up to 180 ° C without any side reaction occurring.
• the reaction rate at temperatures above 120 ° C is so high that continuous process control is possible.
• amino acids which are suitable for the process according to this invention are listed below by way of example: arginine, asparagine, carnitine, creatine, betaine, dimethylglycine, glycine, lysine, ornithine, taurine etc.
• the heavy metal salts of these amino acids which are insoluble in the alkanols are as Catalysts suitable for the heterogeneous transesterification of fats and oils with alkanols.
• Example 5 60 g of deacidified sunflower oil were mixed with 20 ml of methanol and
• Example 7 100 g of damper condensate with a free fatty acid content of 90% by weight were mixed with 30 ml of methanol and 6 g of powdered zinc arginate and heated to 80.degree. After 120 minutes, 4% by weight of the damper condensate had been converted to methyl esters, the zinc arginate remained unchanged.
• Example 11 100 g of a palm oil, which contained 4.4% by weight of free fatty acids, were mixed with 25 g of zinc arginate powder and 20 ml of ethanol and the suspension formed was heated to 135.degree. A pressure of about 5 bar developed in the reaction vessel. After 120 minutes, 36% by weight of ethyl ester were present in the oil phase. The zinc arginate remained unchanged.
• Example 20 100 g of sunflower oil was mixed with 6 equivalents of methanol (83 ml) and the mixture was pumped through a packing of coarse-grained catalyst at 125 ° C.
• the catalyst was prepared by precipitating a zinc salt with carnitine (3-hydroxy-4-trimethylammonio-butyrate). A pressure of approx. 4 bar was established in the autoclave. After a contact time of 17
• Example 21 50 g of deacidified palm oil were mixed with 40 ml of methanol. 3 g of powdered cadmium arginate were suspended in the mixture. The suspension was heated to 85 ° C. on a reflux condenser with gentle boiling. After 120 minutes, 19% of the palm oil had been converted to methyl esters. The cadmium salt of arginine is stable and remains unchanged in the course of the reaction.
• Example 23 100 g of a mixture of 85% methyl esters and 15% glycerides were mixed with 46 ml of 2-propanol and the mixture was pumped at 150 ° C. through a packing made of fine-grain zinc arginate. After a contact time of 15 minutes, the reaction mixture minus alkanols contained 5% isopropyl ester.
• Example 24 100 g of a mixture of 85% methyl esters and 15% glycerides were mixed with 46 ml of 2-propanol and the mixture was pumped at 150 ° C. through a packing made of fine-grain zinc arginate. After a contact time of 15 minutes, the reaction mixture minus alkanols contained 5% isopropyl ester.
• Example 24 100 g of a mixture of 85% methyl esters and 15% glycerides were mixed with 46 ml of 2-propanol and the mixture was pumped at 150 ° C. through a packing made of fine-grain zinc arginate. After

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• 1999
  • 1999-10-20 DE DE19950593A patent/DE19950593A1/de not_active Withdrawn
• 2000
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