EP1075459A1

EP1075459A1 - Method for producing fatty acid esters from triglycerides

Info

Publication number: EP1075459A1
Application number: EP99920749A
Authority: EP
Inventors: Alfred Westfechtel; Elke Grundt
Original assignee: Cognis Deutschland GmbH and Co KG
Current assignee: BASF Personal Care and Nutrition GmbH
Priority date: 1998-05-02
Filing date: 1999-04-23
Publication date: 2001-02-14
Also published as: WO1999057091A1; DE19819655A1

Abstract

The invention relates to a method for producing fatty acid esters with an acid value of less than 1 and an OH value of less than 15. According to said method, triglycerides of native origin are reacted in the presence of a monovalent fatty alcohol with 10 to 24 C-atoms or a corresponding ethoxylate or propoxylate and a catalyst, at temperatures of 180 to 240 °C and at a pressure of 100 to 0.01 kPa. The glycerol formed during the reaction is removed by distillation through pressure reduction and the optionally separated fatty alcohol is recycled.

Description

_» Process for the production of fatty acid esters from triglycerides"

The present invention relates to a process for the preparation of esters from monohydric fatty alcohols of the C chain length 10 to 24 with triglycerides of native origin.

Fatty alcohol esters, which contain esters from branched and unbranched C _{6- 4} alcohols with fatty acids, are important raw materials for the lubricant industry. They are used as a base oil in lubricants for a wide variety of applications or for hydraulic oils. However, such esters are also suitable for metal treatment, for example as rolling oil additives. The esters are usually biodegradable and non-toxic. Esters with a low acid number are preferred because a) experience has shown that they cause minor corrosion problems b) are less prone to hydrolytic cleavage, because hydrolysis is catalyzed by free acid, and c) with a high acid number in the ester, the undesirable emulsifying properties of the esters with water are available.

In particular, esters with acid numbers of less than 1 are desired.

The esters are usually produced by direct esterification of the fatty acids with the alcohols. The fatty acids to be used are usually obtained from native fats and oils by large-scale cleavage processes (hydrolysis). Through a complex reaction procedure, the lowest possible residual acid number must be achieved in the esterification starting from a high starting acid number. The object of the present application was therefore to provide a simplified process for the preparation of fatty acid esters with a low acid number.

It has now been found that the desired ester can be obtained by a special reaction in the direct transesterification of triglycerides of native origin with monovalent fatty alcohols of chain length Cio to _C24 in a simple manner. -2-

It was surprising here that esters with a low residual OH number can also be obtained by this reaction procedure.

The present application is therefore a process for the preparation of fatty acid esters with an acid number of less than 1 and OH number less than 15, in which triglycerides of native origin in the presence of a monohydric fatty alcohol having 10 to 24 carbon atoms or a fatty alcohol ethoxylate or propoxylate and one Catalyst are reacted at temperatures of 180 to 240 ° C at a pressure of 100 to 0.01 kPa, the glycerol formed during the reaction is removed by pressure reduction by distillation and the fatty alcohol which may be separated is recycled.

In principle, all linear or branched monohydric fatty alcohols having 10 to 24 carbon atoms and their ethoxylates or propoxylates, such as, for example, lauryl, myristyl, palmityl or stearyl alcohol or their ethoxlyates or propoxylates, are suitable as starting materials for the process according to the invention. Branched or linear, monounsaturated alcohols of chain length 12 to 24 are preferably used, preferably the oleyl alcohol. Suitable branched fatty alcohols are oxo alcohols (e.g. isotridecyl alcohol) and Guerbet alcohols with more than 12 carbon atoms and their ethoxylates and / or propoxylates as starting materials for the process according to the invention. These alcohols are made by known methods, for example by the Guerbet reaction. synthesized by oxosynthesis or aldol reaction. If ethoxylates or propoxylates are used, they contain between 1 and 10 moles of ethylene oxide and / or propyl oxide groups per mole of the alkoxylate.

Practically all fats and oils known to those skilled in the art of fatty acid production can be used as triglycerides of native origin, for example soybean, palm and palm kernel, sunflower, turnip, rapeseed, coconut, peanut, olive or tall oil. Highly oleic acid-containing triglycerides such as sunflower, soybean or rape oil from new breeds are used. Particularly preferred is the use of high oleic sunflower oil of new breed, which contains less than 5% by weight, preferably less than 2.5% by weight, of stearic acid. Esters based on this -3-

Triglycerides show excellent oxidation stability and good cold behavior. The triglycerides of native origin always contain mixtures of fatty acids of different chain lengths. Depending on the fats or oils selected, esters with different fatty acid residues can therefore be produced, which encompass the C chain range from 6 to 24. Any mixtures of the native fats and oils can also be used in the process according to the invention. However, the process according to the invention is preferably suitable for the production of esters whose fatty acid residues are in the C chain range from 8 to 22 and in particular 16 to 18. Esters of oleic acid are preferably prepared with the fatty alcohols mentioned.

The raw materials are mixed according to the invention in a suitable reactor and then heated to a temperature between 180 and 240 ° C. The reaction is preferably carried out in the temperature range from 200 to 240 ° C. It has proven advantageous to carry out the reaction under an inert gas atmosphere, for example nitrogen or argon. This is especially true in the presence of water sensitive catalysts. The transesterification takes place in the presence of suitable catalysts, for example lithium compounds, such as LiOH or lithium soaps, and zinc or tin salts, for example Sn (II) oxalate. After the reaction temperature is reached. the pressure in the reactor is set to a value between 100 and 0.01 kPa. Depending on the fatty alcohols used, pressures in the range between 80 and 1 kPa are preferably selected. The pressure is reduced during the reaction so that the glycerol formed boils and can be removed by distillation. The person skilled in the art adjusts the type and scope of the pressure reduction in relation to the amount of distillate based on the reaction mixture present in each case. If fatty alcohols are used whose boiling temperature is equal to or lower than that of glycerol (eg isotridecyl alcohol), the alcohol distills off together with the glycerin in the form of an azeotrope. This mixture is separated and the fatty alcohol is returned to the reaction mixture. Finally, a final pressure in the range from 0.1 to 0.01 kPa is preferably set in order to distill off the excess unreacted alcohol. The reaction times range from 3 to 12 hours, but vary depending on the raw materials used. After cooling and venting the reaction mixture, the catalyst is filtered off. The desired ester can -4-

then, if appropriate, without further workup or, if necessary, freed from residual amounts of catalyst by known processes. To achieve the fullest possible esterification, the triglycerides and fatty alcohols are preferably reacted in a molar ratio of 1: 3 (stoichiometric) to 1:10.

The process according to the invention makes it possible to produce fatty acid esters with a very low acid number and low OH number in a simple, one-step reaction. The esters themselves are light colored and can also be used without further refining steps, eg bleaching. The use of these esters as lubricants is also claimed. They are preferably used as base oils for turbine or hydraulic oils. It can also be used in greases.

Examples

1. Preparation of oleyl oleate:

1.05 mol of oleyl alcohol (282 g) in the presence of 0.3 g of LiOH with 0.33 mol of sunflower oil of new breed (300 g, fatty acid pattern: C-16 4%, C18 4%, C-18: l 85%, C-18: 2 6%) mixed and heated to a temperature of 240 ° C under a nitrogen atmosphere. The pressure was slowly reduced as glycerol formation decreased to a final pressure of 0.01 kPa. The glycerol formed during the reaction was removed from the reaction space by distillation. A phase separation separated distilled glycerin from distilled oleyl alcohol, the oleyl alcohol flowing back into the reaction mixture. At the end of the reaction, the rest of the unreacted alcohol was distilled off at a pressure of 0.01 kPa. According to the high-temperature GC, the end product remaining in the reaction vessel contained 96% by weight of the desired ester. Characteristic data: acid number 0.2; OH number 4. Saponification number 105. Acid numbers were determined by DGF method C-V 2 (88), the OH numbers by DGF method C-V 2 17a (94).

According to GC, the glycerol released in the reaction has a purity of 99%.

2. Preparation of isotridecyl oleate:

1.05 mol of isotridecyl alcohol (210 g) were mixed with 0.33 mol of new sunflower oil (300 g) in the presence of 0.26 g of LiOH and heated to a temperature of 240 ° C. at 20 to 25 kPa. The pressure was gradually reduced to 8 kPa, with isotridecyl alcohol / glycerol distilling off in the form of an azeotrope. After phase separation, the isotridecyl alcohol runs back to the reaction mixture. After a reaction time of 4 hours, the pressure was reduced to a final value of 0.01 kPa until no more alcohol distilled off. According to the high-temperature GC, the end product remaining in the reaction vessel contained 98% of the desired isotridecyl oleate.

Claims

-6 claims

1. A process for the preparation of fatty acid esters with an acid number of less than 1 and an OH number of less than 15 by using triglycerides of native origin in the presence of a monohydric fatty alcohol having 10 to 24 carbon atoms or a corresponding ethoxylate or propoxylate and a catalyst at temperatures of 180 up to 240 ° C and at a pressure of 100 to 0.01 kPa, characterized in that the glycerol formed during the reaction is removed by pressure reduction by distillation and the fatty alcohol which may be separated is recycled.

2. The method according to claim 1, characterized in that sunflower oil, in particular high oleic sunflower oil of new breed, is used as the triglyceride of native origin.

3. The method according to any one of claims 1 or 2, characterized in that the monohydric fatty alcohol is selected from the group of monounsaturated linear or branched alcohols having 12 to 24 carbon atoms.

4. Use of esters, which were prepared by the method according to any one of claims 1 to 3, as lubricants and base oils for hydraulic or turbine oils.