EP1308498A1 - Method for the production of fatty acid esters from non-deacidified fats and oils - Google Patents

Abstract

Fatty acid lower alkyl ester production from undeacidified fats and oils comprises: esterifying triglyceride with lower alcohol in presence of Lewis acid and ester exchange of the deacidified mixture in presence of alkali hydroxide and lower alcohol and separating water and glycerol. <??>Fatty acid lower alkyl ester (I) production from undeacidified fats and oils comprises (a) esterifying technical triglyceride having acid number 1-50 with lower alcohol in presence of Lewis acid to reduce the acid number to less than 2; (b) ester exchange of the deacidified mixture in presence of alkali hydroxide and lower alcohol and separating water and glycerol; and optionally ( c) further ester exchange in presence of alkali alcoholate and separating glycerol.

Description

Field of the Invention

The invention is in the field of oleochemical raw materials and relates to an improved one Process for the production of fatty acid esters from unrefined natural raw materials.

State of the art

One of the most important processes in the field of oleochemistry is the production of fatty acid alkyl esters by transesterification of natural fats and oils with lower alcohols, especially methanol. However, natural triglycerides, such as palm oil, coconut oil or beef tallow, fall usually in a quality that requires refining before chemical conversion. This includes processes such as degumming, filtration or deodorization. As a result of enzymatic processes during transport and storage, it also happens partial saponification of the triglycerides, so that these generally have acid numbers between 10 and 50 have. It is obvious that fats and oils with a low acid number and thus high quality are preferred as raw materials. On the other hand, their availability is limited, resulting in high prices leads. Therefore, the manufacturers of oleochemicals have a considerable interest in their use of inexpensive, highly acidic raw materials and processes that process them, especially allow their transesterification with high yields.

Transesterifications are usually carried out with base catalysis. Become triglycerides with high acid numbers used, the catalyst is partially neutralized. This doesn't just have that Disadvantage that valuable catalyst is lost, the resulting soaps also stand for Transesterification is no longer available and remains in the residue. This way, neither high sales still minimize the residues. You try the problem too by using heavy metal catalysts such as e.g. zinc soaps is used, which increases the reaction rate and reduces the formation of soaps can. However, heavy metals are rather undesirable as catalysts for ecotoxicological reasons.

The object of the invention was therefore a new process for the transesterification of fats and to provide oils using non-heavy metal catalysts that meet the above reliably avoids the disadvantages described. In particular, the use of non-deacidified, Non-degummed fats and oils with acid numbers up to approx. 50 can be possible without causing catalyst losses and soap is formed. At the same time, high sales should be achieved, acid numbers reached below 1 and the residue amount can be reduced.

Description of the invention

(a) technische Triglyceride mit Säurezahlen im Bereich von 1 bis 50 in Gegenwart von Lewis-Säuren mit niederen Alkoholen verestert und dabei die Säurezahl auf Werte unterhalb von 2 absenkt,

(b) die auf diese Weise erhaltene entsäuerte Mischung in Gegenwart von Alkalihydroxiden und niederen Alkoholen einer Umesterung unterwirft und dabei Wasser sowie freigesetztes Glycerin abtrennt, und gegebenenfalls

(c) das auf diese Weise erhaltene Umesterungsgemisch in Gegenwart von Alkalialkoholaten einer weiteren Umesterung unterwirft und dabei ebenfalls freigesetztes Glycerin abtrennt.

The invention relates to a process for the preparation of fatty acid lower alkyl esters from non-deacidified fats and oils, in which

(a) esterifying technical triglycerides with acid numbers in the range from 1 to 50 in the presence of Lewis acids with lower alcohols and thereby reducing the acid number to values below 2,

(b) the deacidified mixture obtained in this way is subjected to a transesterification in the presence of alkali metal hydroxides and lower alcohols, thereby separating water and released glycerol, and if appropriate

(c) subjecting the transesterification mixture obtained in this way to a further transesterification in the presence of alkali alcoholates and likewise separating released glycerol.

The invention takes advantage of the knowledge that acid-catalyzed esterifications are faster than Transesterifications take place. The use of Lewis acids can therefore be rapid in the first stage Lowering the acid number can be achieved without causing unwanted soap formation comes. The subsequent transesterification allows a combination of medium and strong conventional bases particularly high yields and a reduction in the residue, so that on the otherwise necessary expensive heavy metal catalysts can be dispensed with. Of course, this leads to further improve the economics of the process. In addition, in the reaction products Acid numbers less than 1 reached.

Starting materials and transesterification products

In a more precise form, the invention relates to the preparation of fatty acid lower alkyl esters of the formula (I) R ¹ CO-OR ² (I) in which R ¹ CO represents a linear or branched, saturated or unsaturated acyl radical having 6 to 22, preferably 12 to 18 carbon atoms and R ^{2 represents} a linear or branched alkyl radical having 1 to 4 carbon atoms. Typical examples are lauric, myristic, palmitic and stearic acid ethyl, propyl or butyl esters and their technical mixtures; however, fatty acid methyl esters are preferably prepared. In principle, synthetic triglycerides are also possible as starting materials, since these generally do not have any particular acid numbers, the problem described at the outset does not arise or only to a minor extent. With natural triglycerides, i.e. vegetable or animal fats or oils, the selection is not critical. Typical examples of suitable feedstocks are palm oil, palm kernel oil, coconut oil, beef tallow, sunflower oil or rapeseed oil and also their mixtures.

Esterification / transesterification

The first step in the process takes advantage of the fact that esterifications are only acid-catalyzed run and are faster than transesterification reactions, which in turn both by Acids as can be catalyzed by bases. So while in usual procedures the humiliation the acid number by neutralization with the basic transesterification catalyst and soap formation takes place, according to the invention, an esterification of the free fatty acids takes place with the formation of alkyl esters instead, which are preferably directly identical to the target product. As catalysts for this first In particular, Lewis acids which are selected from the Group formed by alkali salts of organic carboxylic acids with 1 to 4 carbon atoms, Alkali carbonates, alkali hydrogen carbonates and solutions of the catalysts in fatty acids or Partial glycerides. Typical examples are alkali acetates, alkali propionates, alkali butyrates, sodium carbonate, Sodium hydrogen carbonate, potassium carbonate and potassium hydrogen carbonate. Particularly preferred are potassium salts, especially potassium acetate, which may be present in fatty acids or monoglycerides is solved. The amount of catalyst is generally 0.1 to 2, preferably 0.5 to 1 wt .-% based on the starting materials. The reaction is usually carried out at temperatures in the range of 100 to 300, preferably 150 to 240 ° C carried out. The print range can be between 5 and 100 bar and is preferably 60 to 90 bar. The amount of methanol is calculated according to the Acid number, i.e. according to the amount of available fatty acids. Usually alcohol, preferably methanol, and triglyceride in a weight ratio of 1: 2 to 2: 1.

transesterification

Condensation water is released during the esterification. In the first stage of the transesterification it is therefore necessary to use such catalysts that are not due to the presence of water be deactivated. For this reason, the use of water-free, if necessary, is recommended alcoholic solutions of lithium, sodium or potassium hydroxide. The amount of catalyst is in generally 0.1 to 2, preferably 0.5 to 1 wt .-% based on the starting materials. The transesterification in the second stage is preferably also at temperatures in the range of 100 to 250, preferably 150 to 240 ° C and pressures in the range of 5 to 100, preferably 60 to 90 bar. Again, one usually works with one based on that available in the triglycerides standing fatty acid residues a clear excess of alcohol.

After the water formed in the second stage together with the methanol and in the Transesterification released glycerol has been separated, can also be water sensitive in the third stage Catalysts are used. Sodium alcoholates are particularly suitable for this purpose, such as sodium or potassium methoxide, ethanolate or butoxide. These have the advantage to be particularly active, so that it is now possible to work in milder conditions and thus saving manufacturing costs. The amount of catalyst here is usually 0.1 to 2, preferably 0.5 to 1 wt .-% based on the starting materials. For the reasons mentioned, the second stage of the transesterification, typically at milder temperatures in the range from 20 to 200, preferably 70 to 150 ° C and lower pressures in the range of 1 to 10, preferably 1 to 5 bar. It is usually not necessary to add fresh alcohol, although this is of course possible consists. After separation of unreacted alcohol, preferably by separation in a Rectification column, and the removal of the released glycerol preferably by gravity separation the transesterification is complete.

The third stage is optional. However, their introduction can result in a significant increase in sales be achieved.

Examples

Production of the potassium soap. 1 L Canola split fatty acid was heated to 140 ° C in a 2 L round bottom flask. A water jet vacuum was applied to dry the fatty acid. After the vacuum was released, 40 g of potassium acetate were added in portions. A temperature rise to 145 ° C was observed. When the addition was complete, the mixture was heated to 160 ° C. and the water jet vacuum was again applied. The fatty acid became clear and dark at 160 ° C. No more crystalline solid could be found. 12 g of distillate, which had a pH of 4.5 and smelled of acetic acid, could be distilled off.

Production of the methanolic KOH. 200 g of potassium hydroxide biscuits were carefully added to 200 ml of methanol with stirring (development of heat). The sediment which formed was not separated from the supernatant solution in order to obtain a saturated methanolic KOH.

Example 1. 60 g of raw coconut oil (SZ = 13, FFA = 4.9), 31 g of methanol and 1 g of potassium soap were added to the autoclave and heated to 230 ° C. This resulted in a pressure of 48 bar. When the temperature was reached, the mixture was stirred for 30 minutes. The reaction was then cooled and stopped. A sample was taken from the cooled, homogenized mixture for GC analysis. Then 0.32 g of methanolic KOH was added. The mixture was heated to 230 ° C. with stirring. This resulted in a pressure of 33 bar. When the temperature was reached, stirring was continued for 30 min. The reaction mixture was then cooled. Table 1 shows a list of the reaction components in percent by weight without methanol: Composition (expressed as area percent) composition TG DG MG Methylester fatty acid glycerin raw coconut oil 92.8 2.3 --- --- 4.9 --- Anfahrgemisch 91.3 2.5 --- --- 6.2 --- between sample 25.8 13.4 12.4 41.5 3.0 3.9 Total final sample --- 2.4 13.7 70.4 1.8 11.7 Final trial upper phase --- 3.6 14.1 75.7 1.5 5.1 Final test sub-phase --- 1.3 9.9 18.9 2.9 67.0

Example 2. 60 g of raw coconut oil, 31 g of methanol and 0.6 g of potassium soap were added to the autoclave and heated to 230 ° C. This resulted in a pressure of 48 bar. When the temperature was reached, the mixture was stirred for 30 minutes. The reaction was then cooled and stopped. A sample was taken from the cooled, homogenized mixture for GC analysis. Then 0.32 g of methanolic KOH was added. The mixture was heated to 230 ° C. with stirring. This resulted in a pressure of 33 bar. When the temperature was reached, stirring was continued for 30 min. The reaction mixture was then cooled. Table 2 shows a list of the reaction components in percent by weight without methanol: Composition (expressed as area percent) composition TG DG MG Methylester fatty acid glycerin raw coconut oil 92.8 2.3 --- --- 4.9 --- Anfahrgemisch 91.5 2.8 --- --- 5.7 --- between sample 24.9 18.3 14.6 36.3 1.6 4.3 Total final sample --- 1.9 14.0 70.5 1.7 11.9 Final trial upper phase --- 2.2 15.4 75.1 1.5 5.8 Final test sub-phase --- 0.9 7.7 17.6 2.6 71.2

Example 3. Analogously to Example 3, 722 g of raw coconut oil, 373 g of methanol and 7.3 g of potassium soap are added to the autoclave and heated to 230 ° C. A maximum pressure of 43 bar was set. When the temperature was reached, the mixture was stirred for 30 minutes. The reaction was then cooled and stopped. A sample was taken from the cooled, homogenized mixture for GC analysis. Then 3.9 g of methanolic KOH were added. The mixture was heated to 230 ° C. with stirring. This resulted in a pressure of 33 bar. When the temperature was reached, stirring was continued for 30 min. The reaction mixture was then cooled. The methanol / water was separated off from 1057 g of the reaction mixture thus obtained in a rotary evaporator between 90 ° C.-135 ° C. and water jet vacuum. At 135 ° C no more distillate was obtained. A total of 242.5 g of methanol / water mixture (1.5% water content) and 808 g of organic phase could be obtained. A phase separation then took place in the separating funnel at 110 ° C. 73.5 g lower phase (glycerol phase) and 734.1 g upper phase (methyl ester phase) could be obtained. Table 3 shows a list of the reaction components in percent by weight without methanol: Composition (expressed as area percent) composition TG DG MG Methylester fatty acid glycerin raw coconut oil 92.8 2.3 --- --- 4.9 --- Anfahrgemisch 91.5 2.8 --- --- 5.7 --- Total final sample --- 2.1 10.8 75.8 1.5 10.3 Final test upper phase after
methanol separation --- 1.0 12.2 85.1 1.1 1.6 Final test sub-phase after
methanol separation --- 0.1 0.4 1.2 2.0 96.7

Example 4. 734 g of methyl ester mixture were mixed with 51 g of methanol and 4 g of sodium methylate in an autoclave. The mixture was heated to 130 ° C. with stirring. This created a pressure of about 4 bar. When the temperature was reached, the mixture was stirred for 10 min. The reaction mixture was then cooled and the mixture was sampled for GC analysis. Table 4 shows a list of the reaction components in percent by weight without methanol: Composition (expressed as area percent) composition TG DG MG Methylester fatty acid glycerin final sample --- 0.5 1.0 93.4 1.1 4

Example 5. 60 g of raw coconut oil, 31 g of methanol and 0.6 g of potassium soap were placed in an autoclave and heated to 200 ° C., a pressure of 20 bar being established. The reaction mixture was stirred for 1 h and the course of the reaction was followed by sampling. Table 5 shows a list of the reaction components in percent by weight without methanol: Composition (expressed as area percent) composition TG DG MG Methylester fatty acid glycerin Sample after 30 min 17.5 15.7 15.6 45.6 1.2 4.4 Sample after 1 h - 2.1 10.2 76.2 1.0 10.5

Claims (15)

Process for the preparation of fatty acid lower alkyl esters from non-deacidified fats and oils, in which (a) esterifying technical triglycerides with acid numbers in the range from 1 to 50 in the presence of Lewis acids with lower alcohols and thereby reducing the acid number to values below 2, (b) the deacidified mixture obtained in this way is subjected to a transesterification in the presence of alkali metal hydroxides and lower alcohols, thereby separating water and released glycerol, and if appropriate (c) subjecting the transesterification mixture obtained in this way to a further transesterification in the presence of alkali alcoholates and likewise separating released glycerol. A method according to claim 1, characterized in that fatty acid lower alkyl esters are prepared which follow the formula (I) , R ¹ CO-OR ² (I) in which R ¹ CO represents a linear or branched, saturated or unsaturated acyl radical having 6 to 22 carbon atoms and R ^{2 represents} a linear or branched alkyl radical having 1 to 4 carbon atoms. A method according to claim 2, characterized in that one produces fatty acid methyl esters. Method according to at least one of claims 1 to 3, characterized in that natural fats and / or oils are used which are selected from the group consisting of palm oil, palm kernel oil, coconut oil, beef tallow, sunflower oil or rapeseed oil and mixtures thereof. Process according to at least one of claims 1 to 4, characterized in that in the first stage Lewis acids are used which are selected from the group of the alkali metal salts of organic carboxylic acids with 1 to 4 carbon atoms, alkali metal carbonates, alkali metal bicarbonates and solutions of the catalysts in fatty acids or partial glycerides. A method according to claim 5, characterized in that one uses potassium salts. Process according to claims 5 and / or 6, characterized in that one uses potassium acetate and solutions of potassium acetate in fatty acids. Process according to at least one of Claims 1 to 7, characterized in that the esterification in the first stage is carried out at temperatures in the range from 100 to 300 ° C. Process according to at least one of Claims 1 to 8, characterized in that the esterification is carried out in the first stage at pressures in the range from 5 to 100 bar. Process according to at least one of Claims 1 to 9, characterized in that the transesterification is carried out in the second stage in the presence of anhydrous, optionally alcoholic solutions of sodium or potassium hydroxide. Process according to at least one of Claims 1 to 10, characterized in that the transesterification is carried out in the second stage at temperatures in the range from 100 to 250 ° C. Process according to at least one of Claims 1 to 11, characterized in that the transesterification is carried out in the second stage at pressures in the range from 5 to 100 bar. Process according to at least one of Claims 1 to 12, characterized in that the transesterification is carried out in the third stage in the presence of alkali metal alcoholates. Process according to at least one of Claims 1 to 13, characterized in that the transesterification is carried out in the third stage at temperatures in the range from 20 to 200 ° C. Process according to at least one of Claims 1 to 14, characterized in that the transesterification is carried out in the third stage at pressures in the range from 1 to 10 bar.