DE3040732A1 - METHOD FOR PURIFYING N, N-DIALLKYLAMINOAETHANOLS - Google Patents

Description

PATENT ADVOCATE DR. HANS-GUNTHER EGGERT, DIPLOMA CHEMIST

5 COLOGNE 51, OBERLÄNDER UFER 90 _ 2 -

Description ;

The invention relates to a method for purifying Alkanolamines of the general formula

N - CH ₂ - CH ₂ OH, in which R and R _{1 are} alkyl radicals of the same type

or unequal, linear or branched structure, preferably methyl residues, ethyl residues, propyl residues, isopropyl residues, Butyl residues, isobutyl residues, tert-butyl residues, etc. are.

In the generally used manufacturing processes, ethylene oxide is under pressure in the liquid phase at 100 to 150 ⁰ C with dialkylamines of the formula R-NH-R ₁ , in which R and R _{1 are} identical or different, linear alkyl radicals, e.g. methyl radicals, ethyl radicals, propyl radicals, etc., or branched alkyl radicals, for example isopropyl radicals, isobutyl radicals, tert-butyl radicals, etc. are implemented. The reaction leads to addition compounds of the structure

N -

where η is a number of 1, 2, 3 or higher.

The products obtained, which are most interesting because of their applications, include the N, N-dialkylaminoethanols the formula

n - CH ₉ - CH ₉ OH by their higher homologues

Distillation are easily separated. A certain number of these monoethoxylated products are converted into esters of unsaturated ones

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Carboxylic acids converted for the production of cationic Flocculants are used for the treatment of wastewater. This is especially true of the esters of Acrylic acid and methacrylic acid, which are used as monomers for the production of homopolymers or with other acrylic or Methacrylic compounds are used for the production of copolymers.

In the course of this homopolymerization or copolymerization, the presence of impurities has a disadvantageous crosslinking result, which leads to gel formation of the medium, which in the final application of these products for the preparation of sewage is very annoying.

The appearance of the gel has been linked to the presence of impurities originally found in the alkanolamines used to make these esters of unsaturated acids. Of the various by-products found in the Ν, Ν-dialkylaminoethanols, a combination of gas chromatography, mass spectrometry and infrared analysis identified a compound which has a vinyl double bond, the structure of which is that of 2-vinyloxy-1-ethanol CH ₂ = Corresponds to CH-O-CH ₂ -CH _{2 OH.} This 2-vinyloxy-1-ethanol present in the Ν, Ν-dialkylaminoethanols is esterified to give 2-vinyloxyethyl acrylate or methacrylate in the production of dialkylaminoethyl acrylate or methacrylate. This impurity, which contains two double bonds, is the cause of the crosslinks that were observed during the polymerizations. It has been found that very small proportions of 2-vinyloxy-1-ethanol above 20 ppm are sufficient to make the dialkylaminoethanols contaminated in this way unsuitable for the production of cationic flocculants.

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In an attempt to eliminate this disadvantage, the classic purification processes, in particular distillation, turned out to be either as insufficient to reduce the 2-vinyloxy-1-ethanol content initially at 500 to 1,500 ppm for their application to bring admissible value, or as technically too difficult to be economically viable on an industrial scale feasible to be.

The invention is based on the finding that by pretreating the Ν, Ν-dialkylaminoethanols with suitable chemical reagents, the content of 2-vinyloxy-1-ethanol is reduced to a value that is so low that a distillation in a rectification column with 8 Up to 10 practical trays makes it possible to obtain an amino alcohol with a purity that is completely sufficient for its application, while without this treatment a distillation column with 50 to 60 trays is hardly sufficient in the case of N, N-dimethylaminoethanol, since the difference in boiling points is only ⁴⁰ C is.

The effectiveness of the cleaning process is determined by monitoring it the removal of 2-vinyloxy-1-ethanol by gas chromatography ensured on a capillary column.

The process for the purification of N, N-dialkylaminoethanols is through a heat treatment to remove the 2-vinyloxy-1-ethanol characterized with the help of inorganic or organic compounds, in particular from ammonium salts of organic or inorganic acids, halogenated aliphatic or aromatic carbon derivatives, hydrochlorides, Hydrobromides and phosphates of amino alcohol as well as anhydrides and halides of acids consist. All inorganic compounds do not react with 2-vinyloxy-1-ethanol, and of these compounds are the salts of alkali metals with inorganic acids, e.g. To mention chlorides, nitrates, sulfates and permanganates of sodium or potassium.

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Examples of compounds that are suitable for the purposes of the invention include:

- ammonium salts e.g. the acetates, oxalates, chlorides, bromides, iodides, sulfates and phosphates,

- the halogenated carbon derivatives, e.g. carbon tetrachloride, Chloroform, bromoform, iodoform, chlorobromoform, carbon tetrabromide, carbon tetraiodine, 2-chloro-2-methylpropane, 2-bromo-2-methylpropane, benzyl chloride and benzyl bromide,

- the hydrochlorides and hydrobromides of amino alcohols, e.g. the hydrochlorides of mono-, di- or triethanolamine, N, N-dimethylaminoethanol hydrochloride, Ν, Ν-diethylaminoethanol hydrochloride, N, N-dimethylaminoethanol phosphate, N, N-diethylaminoethanol phosphate, Hydroxylamine hydrochloride, hydrazine hydrochloride and phenylhydrazine hydrochloride,

- and the anhydrides and halides of acids, e.g. acetic anhydride, Acetyl chloride, acetyl bromide, thionyl chloride and chlorosulfonic acid.

According to the invention, the treatment agent is used in a mass concentration of 0.1 to 10%, preferably 0.2 to 2%, based on the alkanolamine. The treatment takes place at a temperature of 90-210 ⁰ C, preferably 120 to 15O ⁰ C, at atmospheric pressure or under a pressure up to 10 bar instead. The duration of the treatment can be between 2 and 40 hours and is preferably 6 to 24 hours. The content of 2-vinyloxy-1-ethanol is greatly reduced and in practice reduced to 100 to 150 ppm, although it can be reduced to only a few ppm if the concentration of the chemical reagents, the temperature and the treatment time are chosen accordingly. A residual content of 100 to 150 ppm 2-vinyloxy-1-ethanol can be accepted, since the distillation of the crude reaction mixture following the treatment in a distillation column with 8 to 10 or more practical trays then enables the content to be adjusted to the desired level Bring value. The treatment takes place in the reboiler of the column

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continued. This distillation is also used to separate the monoalkanolamines, especially Ν, Ν-dimethylaminoethanol and Ν, Ν-diethylaminoethanol from their higher ones Homologues formed during the synthesis reaction are indispensable. When the previous cleaning treatment is carried out is, this distillation also enables the separation of the excess' of the chemical reagents and ■ the by-products that occur in the course of the treatment to remove the 2-vinyloxy-1-ethanol.

The invention is further illustrated by the following examples. Examples 1 to 6 are comparative examples.

example 1

A solution of dimethylaminoethanol, the 1500 ppm 2-vinyloxy-1-ethanol contains and 3 hours at 200 ⁰ C under a nitrogen pressure of 5 has been heated bar, shows, after cooling, no change in the content of 2-vinyloxy-1-ethanol .

The distillation at normal pressure in a metal packed column with 8 practical trays in one The reflux ratio of 10 to 1 gives a distillate which, starting from a solution of Ν, Ν-dimethylaminoethanol containing 500 ppm of impurities, or 75 ppm of vinyloxyethanol contains.

Example 2

In a 250 ml flask with an attached condenser, 150 g of dimethylaminoethanol containing 540 ppm 2-vinyloxy-1-ethanol, heated for 24 hours at 135 ⁰ C in the presence of 0.2 weight percent sodium chloride at reflux. The vinyloxyethanol content remains unchanged, with the slight fluctuations observed being within the accuracy limits of the analytical method.

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Examples 3 to 5

No significant change in the vinyloxyethanol content is observed when among those mentioned in Example 2 Conditions with 0.3 percent by weight of potassium nitrate or 0.5 percent by weight of sodium sulfate, based on dimethylaminoethanol, which contains 540 ppm vinyloxyethanol, is worked.

Example 6

Treating the solution which is Example 3 was used in the experiments according to 5, comprising 0.6 weight percent potassium permanganate at 135 ⁰ C proves after 6 hours of heating at reflux as negative.

Examples 7 to 9

In the apparatus that was used in the experiments described above, 2 00 g of Ν, Ν-dimethylaminoethanol, which contains 350 to 650 ppm vinyloxyethanol, treated at 135 ° C and normal pressure. The respondents and the Conversions of 2-vinyloxy-1-ethanol are given in the table below. The distillation in a with metal packing provided distillation column with 8 practical trays at a reflux ratio of 10 to 1 results in a Distillate that contains less than 10 ppm vinyloxyethanol (V.O.E.).

Example reagent no.

7 ammonium chloride

8 ammonium bromide

9 ammonium iodide

Concentration VOE-Con- Conversion of the reagents concentration of (% mass) before the treatment. VOE, 'treatment ppm

0.35 500 76

0.23 500 66

0.35 640 74

1 3 0 C 2 2 / G 7 0 5

Example 10

If under the conditions mentioned in the examples above, however, working in water will result after 8 hours of heating at 125 ° C as the result of the following obtained sales of 2-vinyloxy-1-ethanol mentioned. The post-treatment distillation in the above described column enables the achievement of less than 10 ppm V.O.E, in the distillate.

Reagent concentration% H ₂ O VOE content Conversion of the reagent,% before loading VOE,% mass treatment, ppm

Amtnoniumchlorid 0.7 2.1 525 76.5

Example 11

When in the manner described in Example 10, but with a heating period of 24 hours at 125 ° C. is carried out, 88% of the vinyloxyethanol is converted.

Example 12

When operating in the manner described in Example 10 at a concentration of the reagent of 4% and 4% water, 99% of the 2-vinyloxy-1-ethanol is converted after 24 hours of heating at 125 ⁰ C.

Example 13

4 kg of dimethylaminoethanol are treated with 9 g of carbon tetrachloride ^{at 120 ° C. in a 5 liter flask.} After 10 hours the vinyloxyethanol content has fallen from 300 ppm to 120 ppm. The distillation in a column provided with metal packing and having 8 practical trays gives a distillate which contains less than 10 ppm of vinyloxyethanol.

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304Q732

Example 14

By heating of 3 kg of dimethylaminoethanol, the 1780 ppm 2-vinyloxy-1-ethanol containing 0.5 percent by weight of carbon tetrachloride at 110 ⁰ C it is possible to have a content of Vinyloxyäthanol of 50 ppm, corresponding to a conversion of 98% after 18 hours of heating to achieve. The distillation in a column provided with metal packing and having 10 practical trays gives a distillate which contains less than 10 ppm of vinyloxyethanol.

Examples 15 and 16

If N, N-Dimethylamxnoäthanol, the 640 ppm 2-vinyloxy-1-ethanol containing 6 hours at 130 ⁰ C with bromoform or iodoform is heated, the results mentioned below are obtained.

Example reagent no.

Concentration of the conversion of reagents,% Mass V.O.E.,%

20th
21

Bromoform iodoform

0.6
0.95

91.6 80

By subsequent distillation with a column with metal packing and 8 practical trays, a distillate is obtained which contains less than 10 ppm vinyloxyethanol.

Examples 17 to 24

200 g of N, N-dimethylaminoethanol, which comes from the synthesis reactor and contains 500 ppm of vinyloxyethanol, are ^{treated at 130 °} C. for 6 hours in a 500 ml flask. The reagents and the conversion of vinyloxyethanol are given in the table below. By distillation with a packed column with 8 practical trays, a distillate is obtained which contains less than 10 ppm of vinyloxyethanol.

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Examples
No. Reagents 25th Concentration of
Reagents,% mass Sales of
VOE,% 17th 2-ΒΓθΐη-2-πιβΙΙιγ1ρΓοραη 0.5 68 18th Acetyl bromide 0.3 76.5 19th Acetyl chloride 0.4 74.6 20th Thionyl chloride 0.3 91.5 21st Acetic anhydride 0.6 75 22nd Triethanolamine phosphate 1 66 23 Hydroxyamine hydrochloride 0.4 78 24 Dimethylaminoethanol
hydrochloride 3 91.3 example

200 g Ν, Ν-dimethylaminoethanol, 2-vinyloxy ethanol-1 contains 500 ppm, for 5 hours under stirring, heated at 120 ⁰ C in the presence of 18 g Diraethylaminoäthanolhydrochlorid, wherein 98.1% of the impurity to be converted. The subsequent distillation with a metal packed column with 8 practical trays gives a distillate which contains less than 10 ppm vinyloxyethanol.

Example 26

By heating 2 kg of Ν, Ν-dimethylaminoethanol, which comes from the synthesis reactor, for 2 hours to 200 ^° C. in a 10 1 autoclave in the presence of 40 g of ammonium chloride, the content of vinyloxyethanol falls from 540 to 130 ppm. During the heating process, the pressure in the autoclave reached 6.5 bar. The distillation in a column with 10 practical trays after this treatment makes it possible to achieve a content of 10 ppm vinyloxyethanol in the N, N-dimethylaminoethanol obtained.

Example 27

In flask into 200 g of crude Ν, Ν-diethylaminoethanol, coming from the synthesis reactor, and 350 ppm 2-vinyloxy-1-ethanol will contain, g in the presence of 3 g of water and 7 N, N-

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Diäthylaminoäthanolhydrochlorid heated for 6 hours at 138 to 140 ⁰ C to reflux. After this treatment, the content of CH ₂ = CH-O-CH _{2 -CH 2} OH determined by gas chromatography on a capillary column is only 3 ppm, ie 99.1% of the amount of impurities has been removed.

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Claims (5)

PATENT ADVERTISER DR.HANS-GUNTHER EGGERT, DIPLOMCHEMIKER 5 COLOGNE 51. OBERLÄNDER UFER 90 Cologne, October 24, 1980 No. 51 PCUK Produits Chimiques Ugine Kuhlmann, TOUR MANHATTAN - LA DEFENSE 2, 5 & 6, Place de L'Iris, 92400 COURBEVOIE ( France) Process for the purification of Ν, Ν-dialkylaminoethanols claims 1. ) Process for the purification of Ν, Ν-dialkylaminoethanols, characterized by a heat treatment in the presence of a compound selected from ammonium salts, halogenated carbon derivatives, amino alcohol hydrochlorides, hydrobromides, phosphates, acid anhydrides and acid halides, and subsequent distillation in a column with 10 or more practical shelves. 2. The method according to claim 1, characterized in that the treatment at a temperature between 90 ° and 200 ⁰ C is carried out. 3. The method according to claim 1 and 2, characterized in that mart the treatment under a pressure between normal pressure and 10 bar. 4. The method according to claim 1 to 3, characterized in that there is a mass concentration of the compound of 0.1 to 10%, based on the Ν, Ν-dialkylaminoethanol, applies. 130022/0705