DE19831705A1 - Preparation of symmetric dialkyl ethers useful e.g. as oil component in cosmetics - Google Patents

Abstract

Phosphinic acid are used as co-catalyst in the production of symmetric dialkyl ethers by acid-catalysed condensation of alcohols. The dialkyl ethers (I) and alcohols (II) are of the formulae: R<1> - O - R<1> (I); R<1>OH (II); R<1> = linear or branched, 6-22 carbon (C) alkyl and/or alkenyl.

Description

Field of the Invention

The invention relates to a process for the preparation of symmetrical dialkyl ethers by acid catalyzed condensation of fatty alcohols using selected co-catalysts.

State of the art

Symmetrical dialkyl ethers, such as di-n-octyl ether, are used, for example, in cosmetics Preparations used as oil components. They are preferably made from Fatty alcohols in the presence of acidic catalysts, such as trifluoromethanesulfone acid, condensed with elimination of water [cf. DE-A1 195 11 668 (Henkel)]. Problematic however, the long reaction times and the resulting loss of yield due to Olefin formation.

The object of the present invention was therefore to develop a new method for Production of light colored, symmetrical dialkyl ethers available, which is characterized by a significant reduction in response times by minimizing the amount of by-products and characterized by yields above 90% of theory.

Description of the invention

The invention relates to a process for the preparation of dialkyl ethers of the formula (I),

R ¹ -OR ¹ (I)

in which R ^{1 represents} linear or branched alkyl and / or alkenyl radicals having 6 to 22 carbon atoms, by acid-catalyzed condensation of alcohols of the formula (II),

R ¹ OH (II)

in which R ^{1 has} the above meaning, which is characterized in that phosphinic acid is used as the cocatalyst.

Surprisingly, it was found that the reac tion times in the etherification of fatty alcohols to dialkyl ethers can be reduced by 25 to 50% can. Despite shorter reaction times, yields of over 90% are achieved. A Another advantage of the new process is that the olefin formation is limited and the Amount used, in particular, expensive catalysts such as trifluoromethanesulfonic acid through the clearly cheaper phosphinic acid can be replaced. The invention also includes the knowledge that the reaction products are particularly light colored.

Fatty alcohols

Suitable starting materials for the preparation of the dialkyl ethers are fatty alcohols, such as, for example, capronalcohol, caprylic alcohol, 2-ethylhexyl alcohol, capric alcohol, lauryl alcohol, isotridecyl alcohol, myristyl alcohol, cetyl alcohol, palmoleyl alcohol, stearyl alcohol, isostearyl alcohol, elaalol alcohol, oleyl alcohol, oleyl alcohol, oleyl alcohol Elaeostearyl alcohol, arachyl alcohol, gadoleyl alcohol, behenyl alcohol, erucyl alcohol and brassidyl alcohol and their technical mixtures. Alcohols of the formula (II) in which R ^{1 is} a linear alkyl radical having 6 to 18, in particular 8 to 18, carbon atoms are preferably used.

Acid catalysts

The condensation takes place in the presence of acidic catalysts, such as sulfuric acid or organic acids such as B. methanesulfonic acid, p-toluenesulfonic acid or dodecylbenzenesulfonic acid. However, halogenated acids and / or sulfonic acids, such as tri fluoromethanesulfonic acid or sulfoacetic acid used. The amount of acid catalysts used is usually 10 ppm to 5 wt .-%, preferably 0.01 to i wt .-% - based on the Feedstocks.  

Co-catalysts

The amount of phosphinic acid used is also usually from 10 ppm to 5% by weight and above preferably 0.1 to 1 wt .-% - based on the starting materials.

Condensation reaction

The condensation reaction can be carried out in a manner known per se at the boiling point, i.e. H. at temperatures in the range of 180 to 220 ° C. To shift the reaction equilibrium to the product side recommends that the condensation water is continuously added via a separator remove. The course of the reaction can be determined by sampling and gas chromatographic analysis be tracked continuously. It has proven advantageous to start the reaction in a yield Abort dialkyl ether from 93 to 95 wt .-%, since a further reaction of the fatty alcohol at this point the majority leads to the formation of undesired olefins. The response time is from the kata amount of analyzer and can be between 0.5 and 5 h. Following the condensation neutralize the catalyst mixture by adding an equimolar amount of base. The dialkyl ether can then be purified by washing and distillation.  

Examples example 1 Comparative Example V1

In a 1 liter four-necked flask with cooler and water separator 520.9 g (4 mol) of n-octanol, 0.52 g (0.0035 mol) of trifluoromethanesulfonic acid and 1.04 g (0.0079 mol) of phosphinic acid (50% by weight aqueous solution) and under nitrogen blanket for Boiling heated. Water separation started at a temperature of 192 ° C. In regular Samples were taken at a distance and analyzed by gas chromatography. In Table 1 are as Function of the reaction time is the water separation, as well as the increase in ether formed Decrease in alcohol and the formation of n-octene as a by-product. After graduation the reaction became new by adding an equimolar amount of sodium hydroxide The raw ether was washed with water and purified by distillation. For comparison purposes Example 1 was repeated, but the addition of phosphinic acid as cocatalyst was omitted.

Example 2

Example 1 was carried out using 520.9 g (4 mol) of n-octanol, 0.16 g (0.0011 mol) Trifluoromethanesulfonic acid and 5.21 g (0.039 mol) of phosphinic acid repeated.

Example 3

Example 1 was carried out using 520.9 g (4 mol) of n-octanol, 15.6 g (0.111 mol) Repeated sulfoacetic acid and 1.04 g (0.0079 mol) of phosphinic acid.

Example 4 Comparative Example 4

Example 1 was made using 608.6 g (2.25 mol) Stearyl alcohol, 0.608 g (0.004 mol) trifluoromethanesulfonic acid and 0.61 g (0.009 mol) phosphinic acid repeated. Water separation started at a temperature of 219 ° C. For comparison purposes Example 4 was repeated, but the addition of phosphinic acid as cocatalyst was omitted.  

Table 1

Composition of the reaction mixture

Claims (6)

1. Process for the preparation of dialkyl ethers of the formula (I),
R ¹ -OR ¹ (I)
in which R ^{1 represents} linear or branched alkyl and / or alkenyl radicals having 6 to 22 carbon atoms, by acid-catalyzed condensation of alcohols of the formula (II),
R ¹ OH (II)
in which R ^{1 has} the above meaning, characterized in that phosphinic acid is used as co-catalyst. 2. The method according to claim 1, characterized in that alcohols of the formula (II) are used in which R ^{1 is} a linear alkyl radical having 6 to 18 carbon atoms. 3. Process according to claims 1 and 2, characterized in that as an acidic catalyst Trifluoromethanesulfonic acid or sulfoacetic acid. 4. Process according to claims 1 to 3, characterized in that the acid Catalysts in amounts of 10 ppm to 5 wt .-% - based on the starting materials - used. 5. Process according to claims 1 to 4, characterized in that the phosphinic acid in amounts of 10 ppm to 5% by weight, based on the starting materials. 6. Process according to claims 1 to 5, characterized in that the reaction at Performs temperatures in the range of 180 to 220 ° C.