DE19517049B4 - Process for the preparation of dialkyl ethers - Google Patents

Abstract

in der
R¹ und R² unabhängig voneinander für einen geraden, verzweigten oder cyclischen Alkylrest mit 4 bis 22 Kohlenstoffatomen stehen,
R³ und R⁴ unabhängig voneinander für Wasserstoff oder eine Methylgruppe stehen,
m und n unabhängig voneinander für Zahlen von 0 bis 5 stehen, worin man Alkohole mit der Formel (II)

in der R¹, R³ und m die oben angegebene Bedeutung haben, oder mit der Formel (III)

in der R², R⁴ und n die oben angegebene Bedeutung haben, oder Gemische der voranstehenden Verbindungen in Gegenwart eines sauren Katalysators bei erhöhter Temperatur dehydratisiert, das Kondensationswasser kontinuierlich aus dem Reaktionsgleichgewicht entfernt, dadurch gekennzeichnet, daß man das rohe Reaktionsprodukt mit einer wäßrig/methanolischen Lösung von Natriummethanolat wäscht, die wässrig/methanolische Phase abtrennt und die gereinigten Dialkylether in an sich bekannter Weise weiterbehandelt.Process for the preparation of dialkyl ethers having the general formula (I)

in the
R ¹ and R ² independently of one another represent a straight, branched or cyclic alkyl radical having 4 to 22 carbon atoms,
R ³ and R ⁴ independently of one another represent hydrogen or a methyl group,
m and n independently of one another represent numbers from 0 to 5, in which alcohols having the formula (II)

in which R ¹ , R ³ and m have the abovementioned meaning, or of the formula (III)

in which R ² , R ⁴ and n have the abovementioned meaning, or dehydrated mixtures of the above compounds in the presence of an acid catalyst at elevated temperature, the condensation water continuously removed from the reaction equilibrium, characterized in that the crude reaction product with an aqueous / washes methanolic solution of sodium methoxide, the aqueous / methanolic phase is separated and the treated dialkyl ethers further treated in a conventional manner.

Description

Territory of invention

The The invention relates to a process for the preparation of dialkyl ethers, in which alcohols in the presence of acidic catalysts at elevated temperature dehydrated and the condensation water continuously from the Reaction equilibrium removed.

dialkyl represent important products of the chemical industry Production is usually done from alcohols which are present in the presence of acidic catalysts, for example Sulfuric acid, dehydrated (R. T. Morrison, R. N. Boyd, Lehrbuch der Organischen Chemistry, Verlag Chemie, Weinheim / New York, 2nd edition, 1978, p.608). However, a major disadvantage of this method is that that the acidic catalysts after completion of the reaction by treatment must be neutralized with alkalis and so in the sewage reach.

In the Soviet patent application SU 170 047, in contrast, a process for the preparation of symmetrical dialkyl ethers is described in which aliphatic C ₄ -C ₁₀ alcohols dehydrati at 123 to 147 ° C in the presence of cation exchangers and separates the condensation water formed via a water separator. However, after the reaction, the acid catalyst must be separated and regenerated at great expense, which precludes a technical utilization of the process.

In the German patent application DE-A-41 27 230 is a method for the semi-continuous preparation of symmetrical dialkyl ethers described, which are used as catalysts sulfonic acids. These sulfonic acids can be in the distillative purification of the dialkyl ethers obtained and in pure form or in the form of their esters as catalysts win back.

This However, the process requires a specific selection of the catalyst, which considerably reduced will that ever after starting alcohol, in particular depending on the boiling point of Alcohol and the ester, only specific sulfuric acid catalysts can be used. This has the consequence that the Advantages to be able to recycle the catalyst, by significantly higher costs the corresponding specific catalysts repealed become.

The US 1,067,709 describes a device for producing ethers, in which one condenses gaseous alcohol with sulfuric acid as a catalyst and the Raktionsprodukt over soda leads.

The DE 41 03 489 describes a process for preparing branched dialkyl ethers in which the crude product is treated with sodium hydroxide solution.

The WO 94/21581 describes inter alia. a process for the preparation of alkylene-bridged polyol ethers, without special purification steps involving the acidic catalysts subsequently neutralized by adding sodium hydroxide solution.

The DE 29 00 030 refers to a process for preparing ether alcohols by reacting epoxides with specific alcohols in excess, the acidic catalysts then being neutralized with sodium methoxide.

The DE 195 11 668 describes a process for preparing dialky ethers using haloalkanesulfonic acids as catalyst without special purification steps.

by virtue of their properties are the dialkyl ethers as emulsifiers and anti-foaming agents for example as a component in cosmetic preparations suitable. For such preparations However, very high quality requirements, in particular in terms of purity, stability, Odor and color posed.

at However, the production of dialkyl ethers occur unpleasant odors and discolored the reaction mixture increasingly dark, since the catalysts used, for. B. sulfonic acids or their esters, decompose at the reaction temperatures. It has turned out to be extraordinary difficult and kostenin tensively proven, both the smell and to improve the color of the products so that they meet very high quality requirements, z. For example the use in cosmetic preparations, suffice.

The The object of the invention was therefore a process for the preparation to develop from dialkyl ethers, which initially with any, inexpensive Catalysts can be produced, and which makes it possible the O product through a simple and inexpensive cleaning process to work up which products can be obtained the high quality requirements for cosmetic Products match.

description the invention

in der
R¹ und R² unabhängig voneinander für einen geraden, verzweigten oder cyclischen Alkylrest mit 4 bis 22 Kohlenstoffatomen stehen,
R³ und R⁴ unabhängig voneinander für Wasserstoff oder eine Methylgruppe stehen,
m und n unabhängig voneinander für Zahlen von 0 bis 5 stehen, worin man Alkohole mit der Formel (II)

in der R¹, R³ und m die oben angegebene Bedeutung haben, oder mit der Formel (III)

in der R², R⁴ und n die oben angegebene Bedeutung haben, oder Gemische der voranstehenden Verbindungen in Gegenwart eines sauren Katalysators bei erhöhter Temperatur dehydratisiert, das Kondensationswasser kontinuierlich aus dem Reaktionsgleichgewicht entfernt, dadurch gekennzeichnet, daß man das rohe Reaktionsprodukt mit einer wäßrig/methanolischen Lösung von Natriummethanolat wäscht, die wässrig/methanolische Phase abtrennt und die gereinigten Dialkylether in an sich bekannter Weise weiterbehandelt.The invention relates to a process for the preparation of dialkyl ethers having the general formula (2)

in the
R ¹ and R ² independently of one another represent a straight, branched or cyclic alkyl radical having 4 to 22 carbon atoms,
R ³ and R ⁴ independently of one another represent hydrogen or a methyl group,
m and n independently of one another represent numbers from 0 to 5, in which alcohols having the formula (II)

in which R ¹ , R ³ and m have the abovementioned meaning, or of the formula (III)

in which R ² , R ⁴ and n have the abovementioned meaning, or dehydrated mixtures of the above compounds in the presence of an acid catalyst at elevated temperature, the condensation water continuously removed from the reaction equilibrium, characterized in that the crude reaction product with an aqueous / washes methanolic solution of sodium methoxide, the aqueous / methanolic phase is separated and the treated dialkyl ethers further treated in a conventional manner.

Surprisingly was found that at the implementation the method according to the invention Products made with any sulfuric acid catalysts could be obtained, the in terms of color, odor and purity, i. Sulfur content, and stability very high quality requirements, especially those for cosmetic preparations, correspond.

alcohols

in denen R¹ und R² gleich oder verschieden sein können und für einen geraden, verzweigten oder cyclischen Alkylrest mit 4 bis 12 Kohlenstoffatomen stehen und m und n gleich oder verschieden sein können und eine Zahl von 0 bis bedeuten.As starting materials for the preparation of the dialkyl ethers having the general formula (I) it is possible to use alcohols or ethoxylated and / or propoxylated alcohols having the general formulas II or III,

in which R ¹ and R ^{2 may be the} same or different and for a straight, branched or cyclic Alkyl radical having 4 to 12 carbon atoms and m and n may be the same or different and represent a number from 0 to.

typical examples for Alcohols in which m and n are 0 are butanol, pentanol, caproic alcohol, eananthalcohol, 2-ethylhexyl alcohol, capryl alcohol, pelargon alcohol, capric alcohol, Stearyl alcohol, oleyl alcohol or lauryl alcohol. Preferably, the Use of aliphatic, linear or branched alcohols with 6 to 12 carbon atoms, especially caproic alcohol and 2-ethylhexanol.

The ethoxylated alcohols can obtained in a conventional manner by ethoxylation of the alcohols become. The degrees of ethoxylation m and n represent statistical averages that is for a particular product represents an integer or a fractional number can. Preferred ethoxylated alcohols have a narrow homolog distribution on (Narrow Range Ethoxylates, NRE). For application reasons are Ethoxylierungsgrade from 0 to 5 particularly preferred.

catalysts

When Catalysts have especially acid catalysts such as KHSO4, sulfuric acid or alkyl sulfuric acid half ester and sulfonic acids or their esters proved to be suitable. Heteropolytungstic acids can also be used as Catalysts are used. The acidic catalysts react in the course of etherification with the alcohols partially or completely under Ester formation from.

Particularly preferred are sulfonic acids having the following formula IV, R ⁵ SO ₃ H (IV) in which R ^{5 is} an alkyl radical having 1 to 4 carbon atoms or an optionally alkyl-substituted aryl radical.

typical examples for suitable sulfonic acids are methanesulfonic acid, ethanesulfonic, propane sulfonic acid, butane sulfonic acid, Sulfoic acid or p-toluenesulfonic acid, trifluoromethanesulfonic, especially methanesulfonic acid, alkyl benzene sulfonic acid and naphthalenesulfonic acid. For the preparation of these substances known per se, for example to the German patent application DE-A-39 29 985.

When other suitable sulfonic acids have over it Addition products of sodium hydrogen sulfite to olefinic Systems, in particular maleic acid, proved. A typical example of this is sulfosuccinic acid.

The Dehydration of the alcohols of formula I can in the presence of 0.05 to 10 wt .-%, preferably 1 to 3 wt .-% - based on the alcohols - carried the sulfonic acids.

reaction conditions

to execution the method according to the invention the starting compounds, i. the alcohols or alkoxylated Alcohols having the general formulas II and / or III mixed and brought to reaction temperature. Heating to reaction temperature can be so fast as possible carried out become.

The Reaction is preferred at a temperature of 170 to 260 ° C, especially preferably 180 to 250 ° C, carried out.

advantageously, the reaction is carried out under inert gas atmosphere, e.g. under a nitrogen atmosphere. The Reaction can be carried out at atmospheric pressure or elevated pressure to about 4 bar. Increased pressure is particularly desirable then when alcohols are used whose boiling point is below that Reaction temperature is.

The Etherification reaction usually starts at a temperature of 170 ° C, which can be recognized by the formation of condensation water. During the Reaction, the condensation water is continuously from the reaction equilibrium removed the reaction equilibrium to the side of the products to relocate. The condensation water can, for example, with the help a gravity separator are removed.

in the Connection to the dehydration is the reaction mixture according to the invention with a aqueous / methanol solution treated by sodium methoxide. The amount and concentration of Base becomes dependent the catalyst used, the amount of catalyst and to be produced Dialkyl ethers selected. Usually the base is in a concentration of 2 to 60 wt .-%, based to the solution used, used. The base may be in an amount of 4 to 30 wt .-%, based on the weight of the reaction product used. The treatment of the crude product with the base can be obtained by stirring or shaking the Reaction mixture with the base done. Treating with the Base is carried out until the pH of the reaction mixture does not change anymore. After that Both the base and the base precipitated catalyst are in turn separated in a known manner. Particularly preferably, this is allowed Reaction mixture after treating with base for some time and separates the aqueous phase from the organic phase containing the reaction product.

The Reaction product can subsequently, depending on the intended use, subjected to a distillative purification become.

The according to the inventive method prepared dialkyl ethers can as cooling lubricant, fiber spinning or lubricant, heat transfer fluid and spreading oil or as moisturizing Component in cosmetic preparations be used.

The The following examples are intended to form the subject of the present invention explain in more detail, without to restrict him to it.

Example 1 Distearyl ether (Approach 1-0)

In a 2 l three-necked flask equipped with stirrer, gas inlet tube, intensive condenser and water separator, a mixture of
1625 g of stearyl alcohol (Lorol ^(R) C 18, Fa. Henkel) and
32.5 g of methanesulfonic acid (FLUKA 64285) submitted.

The Reaction mixture was charged with nitrogen with stirring Heated to 220 ° C. and 7 h at 220 ° C held. 51 g of water (94% of theory) condensed.

The raw brown product was cooled to 100 ° C and mixed with aliquots After-treatment of alkalis.

Example 2: Dioctyl ether (Approach 2-0)

In the same apparatus as Example 1-0 and same temperature / time conditions were
1950 g n-octanol, Lorol (R) C-8 98% with
65 g techn. Naphthalene sulfonic acid (FL 70290) reacted.

On the In the course of the reaction, water separators yielded 120 g of water (90 % of theory).

In a GC analysis (FID detection), the following relative proportions were found:
2% olefins, 8% unreacted alcohol C8, 87% dioctyl ether and 2% catalyst ester.

Example 3: dioctyl ether (Approach 3-0)

In the same apparatus as Example 1-0 were
1950 g n-octanol, Lorol ^(R) C-8 98% with
100 g potassium hydrogen sulfate (FLUKA 60363)
reacted at 200 - 220 ° C in 14 h.

On the Wasserabscheider could be separated 115 g of water (85% of theory).

In a GC analysis (FID detection), the following relative proportions were found:
3% olefins, 15% unreacted alcohol C8 and 80% dioctyl ether.

Example 4: Ditala 2EO ether (Approach 4-0)

• 1240 g with talc * 2EO (Henkel) and
• 190 g 70% sulfosuccinic acid (FLUKA 86136) were 10 h at 220 ° C implemented.

Initial characteristics: hydroxyl number 162

Of the Sales was over controlled the OHZ waste and up to OHZ 44 (75% conversion) were 100 g cloudy Obtained distillate water.

The in the end black oil solidified at about 50 ° C to a foul-smelling dark brown wax.

The crude ethers of Examples 1-4 were placed in a 500 ml refining vessel with stirrer, heating mantle, thermometer and vacuum connection at different residence times and temperatures with different alkalis stirred and let settle for different periods of time to phase separation to effect.

The in all cases across from the ether phase specific heavier lye phase was removed below. If enough long residence time, clear ether phases were obtained. In some make After a short time, the lye phase was separated and the remaining ether phase for 1 h vacuum dried and either via a Seitz filter K7 (SF) clearly filtered off or in a laboratory centrifuge (LF) centrifuged and the supernatant decanted organic phase.

Of the Degree of saponification of the catalyst was by means of saponification number (DGF method C-V 3) tested.

Of the Degree of catalyst separation was determined by means of S content determination traced.

The Colors were used as iodine color numbers with a Dr. med. Long LICO 100 spectrometer measured (in too dark solutions these were diluted in diethyl ether and concentrated on conc. Solution recalculated).

The odor of the samples was classified according to the following schedule:

The results of various experiments are summarized in the following Table 1:

Claims (5)

Process for the preparation of dialkyl ethers having the general formula (I)

in which R ¹ and R ² independently of one another represent a straight, branched or cyclic alkyl radical having 4 to 22 carbon atoms, R ³ and R ⁴ independently of one another represent hydrogen or a methyl group, m and n independently represent numbers from 0 to 5 in which alcohols having the formula (II)

in which R ¹ , R ³ and m have the abovementioned meaning, or of the formula (III)

in which R ² , R ⁴ and n have the abovementioned meaning, or dehydrated mixtures of the above compounds in the presence of an acid catalyst at elevated temperature, the condensation water continuously removed from the reaction equilibrium, characterized in that the crude reaction product with an aqueous / washes methanolic solution of sodium methoxide, the aqueous / methanolic phase is separated and the treated dialkyl ethers further treated in a conventional manner. Method according to claim 1, characterized in that that he as catalyst sulfuric acid, Alkylschwefelsäurehalbester, sulfonic acids or their esters. Process according to claim 2, characterized in that sulphonic acids having the following formula IV, R ⁵ SO ₃ H (IV) in which R ^{5 is} an alkyl radical having 1 to 4 carbon atoms or an optionally alkyl-substituted aryl radical used. Method according to one of claims 1 to 3, characterized that the Catalyst in an amount of 0.05 to 10 wt .-%, in particular 1 to 3 wt .-% - related on the alcohols - used becomes. Method according to one of claims 1 to 4, characterized that he the reaction is carried out at temperatures of 170 ° C to 260 ° C.