EP1308498B1 - 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 invention

The invention is in the field of basic oleochemicals 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 oleochemicals 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, are dropped usually of a quality that requires refining prior to chemical conversion. This includes processes such as degumming, filtration or deodorization. It also occurs as a result of enzymatic processes during transport and storage a partial saponification of the triglycerides, so that they usually have acid numbers between 10 and 50 have. It is obvious that fats and oils with a low acid number and therefore high quality are preferred as raw materials. On the other hand, their availability is limited, resulting in high prices leads. There is therefore considerable interest in their use on the part of the manufacturers of oleochemicals of inexpensive, high-acid number raw materials and of processes that process them, especially allow their transesterification with high yields.

Transesterifications are usually carried out with base catalysis. Are triglycerides with high acid numbers used, it comes to the partial neutralization of the catalyst. This doesn't just have that Disadvantage that valuable catalyst is lost, the soaps that are created also stand for the Transesterification is no longer available and remains in the residue. This way you can neither Achieve high sales yet minimize the amount of residue. One tries to solve the problem by using heavy metal catalysts, such as zinc soaps, instead of alkali hydroxides begins, which increases the reaction rate and reduces the formation of soaps can. Heavy metals are, however, rather undesirable as catalysts for ecotoxicological reasons.

Certain Lewis acids are in EP-A-0184740 for esterification of free fatty acids contained in triglycerides.

The object of the invention was therefore to find a new process for the transesterification of fats and oils using non-heavy metal catalysts to provide 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 are possible without catalyst losses and soaps are formed. At the same time, high conversions should be achieved, acid numbers can be reached below 1 and the amount of residue reduced.

Description of the invention

(a) technische Triglyceride mit Säurezahlen im Bereich von 1 bis 50 in Gegenwart der Lewis-Säuren , welche ausgewählt sind aus der Gruppe der Alkalisalze organischer Carbonsäuren mit 1-4 Kohlenstoffatomen, Alkalicarbonaten, Alkalihydrogen carbonaten sowie lösungen der Katalysatoren in Fettsäuren oder Partial glyceriden 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 abtrenn, wobei die Fettsäureniedrig-alkylester die Formel (I) aufweisen, R ¹ CO-OR ²    (I) in der R¹CO für einen linearen oder verzweigten, gesättigten oder ungesättigten Acylrest mit 6 bis 22, vorzugsweise 12 bis 18 Kohlenstoffatomen und R² für einen linearen oder verzweigten Alkylrest mit 1 bis 4 Kohlenstoffatomen steht Die Erfindung macht sich die Erkenntnis zu Nutze, dass säurekatalysierte Veresterungen schneller als Umesterungen ablaufen. Durch Einsatz von Lewis-Säuren kann daher in der ersten Stufe eine rasche Erniedrigung der Säurezahl erzielt werden, ohne dass es zur unerwünschten Bildung von Seifen kommt. Die nachfolgende Umesterung erlaubt durch die Kombination von mittelstarken und starken konventionellen Basen besonders hohe Ausbeuten und eine Reduzierung des Rückstands, so dass auf die sonst erforderlichen teuren Schwermetallkatalysatoren verzichtet werden kann. Dies führt natürlich zu einer weiteren Verbesserung der Ökonomie des Verfahrens. Zudem werden in den Reaktionsprodukten Säurezahlen von kleiner 1 erreicht.

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

(A) technical triglycerides with acid numbers in the range from 1 to 50 in the presence of the Lewis acids, which are selected from the group of alkali salts of organic carboxylic acids with 1-4 carbon atoms, alkali carbonates, alkali hydrogen carbonates and solutions of the catalysts in fatty acids or partial glycerides with esterifies lower alcohols and thereby lowers 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 and in the process separating off water and released glycerol, and optionally

(c) subjecting the transesterification mixture obtained in this way to a further transesterification in the presence of alkali metal alcoholates and also separating released glycerol, the fatty acid lower alkyl esters having the formula (I), R ¹ CO-OR ² (I) in which R ¹ CO is a linear or branched, saturated or unsaturated acyl radical having 6 to 22, preferably 12 to 18 carbon atoms and R ^{2 is} a linear or branched alkyl radical having 1 to 4 carbon atoms acid-catalyzed esterifications proceed faster than transesterifications. By using Lewis acids, a rapid lowering of the acid number can therefore be achieved in the first stage without the undesired formation of soaps occurring. The subsequent transesterification, through the combination of medium-strength and strong conventional bases, allows particularly high yields and a reduction in the residue, so that the expensive heavy-metal catalysts otherwise required can be dispensed with. This of course leads to a further improvement in the economy of the process. In addition, acid numbers of less than 1 are achieved in the reaction products.

Starting materials and transesterification products

Typical examples for fatty acid alkyl esters of the formula (I) are lauric, myristic, palmitic and stearic acid ethyl, propyl or butyl ester and technical mixtures thereof; however, be preferred Fatty acid methyl ester produced. Basically, synthetic materials are also used as starting materials Triglycerides are in question, since they usually do not have any particular acid numbers Problem described at the beginning not or only in a subordinate way. In the case of natural triglycerides, So the vegetable or animal fats or oils, the selection is not critical. Typical examples suitable ingredients are palm oil, palm kernel oil, coconut oil, beef tallow, sunflower oil or Rapeseed oil as well as their mixtures.

Esterification / transesterification

The first step in the process takes advantage of the fact that esterification is only acid-catalyzed run and thereby faster than transesterification reactions, which in turn both through Acids as can be catalyzed by bases. So while in usual procedures the humiliation the acid number through neutralization with the basic transesterification catalyst and soap formation takes place, takes place within the meaning of the invention, an esterification of the free fatty acids with the formation of alkyl esters instead, which are preferably directly identical to the target product. As catalysts for this first Lewis acids come into question, which are selected from the stage of the process 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 is optionally in fatty acids or monoglycerides solved. The amount of catalyst is generally 0.1 to 2, preferably 0.5 to 1% by weight 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 pressure 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. based on the amount of available fatty acids. Usually alcohol, preferably methanol and triglyceride in a weight ratio of 1: 2 to 2: 1.

Transesterifications

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

After the water formed in the second stage together with the methanol and the Glycerol released from transesterification 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, ethoxide 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. Here too, the amount of catalyst is generally from 0.1 to 2, preferably 0.5 to 1% by weight based on the starting materials. For the reasons mentioned, the second stage of transesterification typically at milder temperatures in the range of 20 to 200, preferably 70 to 150 ° C and lower pressures in the range from 1 to 10, preferably 1 to 5 bar. As a rule, it is not necessary to add fresh alcohol, although this is of course possible consists. After removal of unreacted alcohol, preferably by separation in one Rectification column, and the removal of the liberated 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

Manufacture of 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 releasing the vacuum, 40 g of potassium acetate were added in portions. A rise in temperature to 145 ° C. was observed here. When the addition was complete, the mixture was heated to 160 ° C. and the water-jet vacuum was applied again. The fatty acid turned clear and dark at 160 ° C. No more crystalline solid could be detected. 12 g of distillate, which had a pH of 4.5 and smelled of acetic acid, could be distilled off.

Manufacture of the methanolic KOH. 200 g of potassium hydroxide pellets were carefully added to 200 ml of methanol with stirring (evolution of heat). The sediment that 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 placed in the autoclave and heated to 230.degree. A pressure of 48 bar was established. Once the temperature was reached, the mixture was stirred for 30 minutes. Thereafter, the reaction was cooled and terminated. A sample was taken from the cooled, homogenized mixture for GC analysis. Then 0.32 g of methanolic KOH were added. The mixture was heated to 230 ° C. with stirring. A pressure of 33 bar was established. Once the temperature was reached, stirring was continued for 30 minutes. The reaction mixture was then cooled. A list of the reaction components in percent by weight without methanol content is given in Table 1: Composition (data as percentage of area) composition TG DG MG Methyl ester fatty acid Glycerin raw coconut oil 92.8 2.3 --- --- 4.9 --- Start-up mixture 91.3 2.5 --- --- 6.2 --- Interim rehearsal 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 sample upper phase --- 3.6 14.1 75.7 1.5 5.1 Final rehearsal 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 placed in the autoclave and heated to 230.degree. A pressure of 48 bar was established. Once the temperature was reached, the mixture was stirred for 30 minutes. Thereafter, the reaction was cooled and terminated. A sample was taken from the cooled, homogenized mixture for GC analysis. Then 0.32 g of methanolic KOH were added. The mixture was heated to 230 ° C. with stirring. A pressure of 33 bar was established. Once the temperature was reached, stirring was continued for 30 minutes. The reaction mixture was then cooled. A list of the reaction components in percent by weight without the proportion of methanol is given in Table 2: Composition (data as percentage of area) composition TG DG MG Methyl ester fatty acid Glycerin raw coconut oil 92.8 2.3 --- --- 4.9 --- Start-up mixture 91.5 2.8 --- --- 5.7 --- Interim rehearsal 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 sample upper phase --- 2.2 15.4 75.1 1.5 5.8 Final rehearsal sub-phase --- 0.9 7.7 17.6 2.6 71.2

Example 3. As in Example 3, 722 g of crude coconut oil, 373 g of methanol and 7.3 g of potassium soap were added to the autoclave and heated to 230.degree. A maximum pressure of 43 bar was established. Once the temperature was reached, the mixture was stirred for 30 minutes. Thereafter, the reaction was cooled and terminated. A sample was taken from the cooled, homogenized mixture for GC analysis. 3.9 g of methanolic KOH were then added. The mixture was heated to 230 ° C. with stirring. A pressure of 33 bar was established. Once the temperature was reached, stirring was continued for 30 minutes. The reaction mixture was then cooled. The methanol / water was removed from 1057 g of the reaction mixture obtained in this way in a rotary evaporator between 90 ° C.-135 ° C. and a water jet vacuum. At 135 ° C., no more distillate was obtained. A total of 242.5 g of a methanol / water mixture (1.5% water content) and 808 g of organic phase could be obtained. A phase separation then took place in a separating funnel at 110 ° C. It was possible to obtain 73.5 g of the lower phase (glycerol phase) and 734.1 g of the upper phase (methyl ester phase). A list of the reaction components in percent by weight without the proportion of methanol is given in Table 3: Composition (data as percentage of area) composition TG DG MG Methyl ester fatty acid Glycerin raw coconut oil 92.8 2.3 --- --- 4.9 --- Start-up mixture 91.5 2.8 --- --- 5.7 --- Total final sample --- 2.1 10.8 75.8 1.5 10.3 Final sample upper phase after
Separation of methanol --- 1.0 12.2 85.1 1.1 1.6 Final sample sub-phase after
Separation of methanol --- 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. Once the temperature was reached, the mixture was stirred for 10 minutes. The reaction mixture was then cooled and the mixture was sampled for GC analysis. A list of the reaction components in percent by weight without the proportion of methanol is given in Table 4: Composition (data as percentage of area) composition TG DG MG Methyl ester fatty acid Glycerin Final rehearsal --- 0.5 1.0 93.4 1.1 4th

Example 5. 60 g of crude coconut oil, 31 g of methanol and 0.6 g of potassium soaps were placed in an autoclave and heated to 200 ° C., a pressure of 20 bar being established. The reaction mixture was stirred for 1 hour and the course of the reaction was followed by taking samples. A list of the reaction components in percentages by weight without the proportion of methanol is given in Table 5: Composition (data as percentage of area) composition TG DG MG Methyl ester 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 (13)

1. A process for the production of fatty acid lower alkyl esters from non-deacidified fats and oils, in which

   (a) technical triglycerides with acid values of 1 to 50 are esterified with lower alcohols in the presence of Lewis acids, the acid value being reduced to values below 2 in the process,

   (b) the deacidified mixture thus obtained is transesterified in the presence of alkali metal hydroxides and lower alcohols, water and glycerol released being removed at the same time and, optionally,

   (c) the transesterification mixture thus obtained is further transesterified in the presence of alkali metal alcoholates, glycerol released again being removed,

   with the proviso that the Lewis acids used in the first step (step a) are selected from the group of alkali metal salts of C_1-4 carboxylic acids, alkali metal carbonates, alkali metal hydrogen carbonates and solutions of the catalysts in fatty acids or partial glycerides,
   and with the further proviso that the fatty acid lower alkyl esters correspond to formula (I): R ¹ CO-OR ²    (I) in which R¹CO is a linear or branched, saturated or unsaturated C_6-22 acyl group and R² is a linear or branched C_1-4 alkyl group.
2. A process as claimed in claim 1, characterized in that fatty acid methyl esters are produced.
3. A process as claimed in claim 1 or 2, characterized in that natural fats and/or oils selected from the group consisting of palm oil, palm kernel oil, coconut oil, bovine tallow, sunflower oil or rapeseed oil and mixtures thereof are used.
4. A process as claimed in at least one of claims 1 to 3, characterized in that potassium acetate or solutions of potassium acetate in fatty acids is/are used as the Lewis acid.
5. A process as claimed in any of claims 1 to 4, characterized in that potassium salts are used as the Lewis acids.
6. A process as claimed in at least one of claims 1 to 5, characterized in that the esterification in the first step is carried out at temperatures in the range from 100 to 300°C.
7. A process as claimed in at least one of claims 1 to 6, characterized in that the esterification in the first step is carried out under pressures in the range from 5 to 100 bar.
8. A process as claimed in at least one of claims 1 to 7, characterized in that the transesterification in the second stage is carried out in the presence of water-free, optionally alcoholic solutions of sodium or potassium hydroxide.
9. A process as claimed in at least one of claims 1 to 8, characterized in that the transesterification in the second stage is carried out at temperatures in the range from 100 to 250°C.
10. A process as claimed in at least one of claims 1 to 9, characterized in that the transesterification in the second stage is carried out under pressures in the range from 5 to 100 bar.
11. A process as claimed in at least one of claims 1 to 10, characterized in that the transesterification in the third stage is carried out in the presence of alkali metal alcoholates.
12. A process as claimed in at least one of claims 1 to 11, characterized in that the transesterification in the third stage is carried out at temperatures in the range from 20 to 200°C.
13. A process as claimed in at least one of claims 1 to 12, characterized in that the transesterification in the third stage is carried out under pressures in the range from 1 to 10 bar.