DE1215121B - Process for the purification of formaldehyde-containing aliphatic alcohols - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. α .:

C07c

German KL: 12 ο -5/03

Number: 1215121

File number: V 24410IV b / 12 ο

Filing date: August 3, 1963

Opening day: April 28, 1966

In a number of technical processes, such as the production of monomeric! Formaldehyde Decomposition of semi-formals or the production of condensation products according to the Mannich reaction, there are alcohols which, in addition to various impurities, also contain formaldehyde. A distillative purification of these alcohols causes considerable difficulties, however, that large amounts of non-volatile resins are obtained as the distillation residue, for which there is no possibility of use consists. The alcohol losses that result from the formation of these worthless resins, are 25% and more. This increases the cost of performing procedures in which contaminated formaldehyde-containing alcohols accumulate so much that their economic viability is in question is posed. There is a further disadvantage of the purification of such contaminated alcohols by distillation in that considerable amounts of formaldehyde gas escape from the alcohols during the heating. Due to the great tendency of formaldehyde to polymerize, it occurs in the cooler and the pipes due to the deposition of low molecular weight formaldehyde polymers to blockages.

It is already known to use higher aldehydes contaminated with alcohols, such as those used, for example, in the Oxo synthesis incurred to be purified by either acetalizing the contaminated aldehyde mixtures Subjected to conditions and then fractionated, distilled or initially a distillation Alcohol-rich fraction wins, this acetalysed and then separates the aldehydes. These procedures however, cannot be applied to contaminated formaldehyde-containing alcohols because formaldehyde gas cannot be completely separated from alcohols by distillation and in a distillation the difficulties mentioned above occur.

It is also known to purify higher alcohols or to separate alcohol mixtures a total acetalization of the alcohols or a selective acetalization of an alcohol with make higher aldehydes and then carry out the distillation of the mixture. After these However, only the purification of aliphatic, monohydric alcohols is possible, whereby Soluble organic or inorganic acids can be used as acetalysis catalysts.

Surprisingly, a process for the purification of formaldehyde-containing aliphatic Alcohols with 2 to 10 carbon atoms and two to four hydroxyl groups and cycloaliphatic Process for purifying formaldehyde-containing aliphatic alcohols

Applicant:

VEB Leuna-Werke "Walter Ulbricht", Leuna

Named as inventor:
Dr. Robert Kaufhold,
Dr. Wolfgang Knothe,
Dipl.-Chem. Lothar Ratz, Leuna;
Dipl.-Chem. Rolf Kloss, Merseburg

Alcohols with 6 to 10 carbon atoms and a or two hydroxyl groups next to different

ao impurities contain more than 2% formaldehyde, which is characterized is that the formaldehyde contained in the alcohols first in the presence of known methods acidic catalysts converted to the formal and then a distillation of the contaminated, formal alcohol is made.

If the formaldehyde content is below 2%, the conversion of the formaldehyde to the corresponding formal is as follows low that the work-up cannot be carried out economically.

Furthermore, the contaminated alcohols to be worked up should expediently only be proportionate have a low water content, as the formal formation reaction leads to equilibrium its location, d. H. the degree of conversion to the formal, in addition to the water temperature, has a very large influence Has. Such alcohols can advantageously be worked up by the process according to the invention, whose water content does not exceed 15%. With water contents of more than 15% it is therefore recommended to the water before or during the conversion to the formal, by distillation or drying remove.

It was not foreseeable that in the distillation of such alcohols, in addition to various Impurities still contain formaldehyde, the high incidence of resinous distillation residues the inventive measure of the formal formation could be eliminated, since the formaldehyde in Alcohols is present as a semi-formal, which under the distillation conditions of the alcohols in question

609 560/488

decomposes into gaseous aldehyde and alcohol, so that in the present case it had to be assumed that the formaldehyde has no influence on the formation of the resinous residues.

For formal formation in the process according to the invention, acidic catalysts are used in a known manner used, which are insoluble in the alcohols concerned. Use is advantageous of acidic ion exchangers, as these are prior to the distillation of the alcohols e.g. by filtration quem separated or the alcohols treated in an exchange column with the catalysts can. Another advantage of using acidic ion exchangers is that from the exchanger impurities of a cationic nature, such as. B. metal ions or amines, simultaneously be bound. Should the alcohols to be worked up by the process according to the invention Contain amines as impurities, as z. B. with alcohols, 'as solvents Mannich condensation reactions are used were, is the case, the amines can be enriched in the resin with suitable Electrolyte solutions are eluted and recovered.

The reaction temperature can be wide according to the known processes for the preparation of formals Limits can be varied. In the case of using acidic ion exchangers as catalysts it is the upper temperature limit is given by their thermal resistance.

The distillation of the contaminated, formal-containing alcohol can be carried out in a simple manner and depends on the boiling behavior of the alcohol in question and its formal. After Distillation of the contaminated, formal alcohol formed remains as a distillation residue less than 2% of a resinous product, based on the amount of contaminated used Alcohol, while in the immediate distillation of the contaminated, formaldehyde-containing alcohols up to 30% residue occur.

The completely colorless alcohols purified by the process according to the invention can for example for the production of semi-formals or as a solvent in the production of Condensation products are used again after the Mannich reaction.

The formals obtained in the distillation can be converted into alcohol again in a known manner Formaldehyde can be split. However, they also provide for further processing, for example by polymerization in the case of cyclic formals, products valuable as solvents and plasticizers represent.

The parts and percentages given in the following examples are parts by weight and percentages by weight, respectively.

example 1

60

200 parts of contaminated ethylene glycol, which also contains 15.2% formaldehyde and 1.3% water, are passed over 350 ml emes strongly acidic ion exchanger within one hour, which the Has structure of a polystyrene sulfonic acid resin and is located in an exchanger column. the The column is heated to 70 ° C. by jacket heating. After treatment with the exchanger 86% of the formaldehyde has been converted to formal. This is followed by a distillation under Normal pressure carried out in such a way that first the formal and the water are driven off and then the ethylene glycol is distilled off. There are 84.6 parts of a water-formal mixture and 113.7 parts of pure ethylene glycol. 0.7 parts of a yellowish residue remain in the distillation bottom high-boiling resin. After the water has been separated from the water-formal mixture 61 parts of pure formal obtained by distillation.

For comparison, 200 parts of the same ethylene glycol, without prior treatment with an acidic ion exchanger, distilled immediately. At first, 14.4 parts of a formal-water mixture fall containing 17.4% formaldehyde. The second fraction can be 127.5 parts of Glycol distill off with a formaldehyde content of 0.5%. Remain as distillation residue

38.5 parts of a deep brown colored product. There will be a thick deposit in the cooler and the pipes of formaldehyde polymers. This results in a loss of

19.6 parts, based on the starting product.

Example 2

350 parts of contaminated butanediol- (1,4) with a formaldehyde content of 12.1% and a water content of 2.1% are within one hour, as described in Example 1, over 400 ml of the same Ion exchanger passed. The temperature is 80 ° C. The formaldehyde content drops to 0.9%, i. H. 93% of the formaldehyde has been converted. The distillation is initially carried out under normal pressure 171.2 parts of a water-formal mixture obtained from the 131 parts of tetramethylene formal from Bp 117 ° C can be obtained. From the distillation residue can be under reduced pressure 173 parts of pure butanediol (1,4) distill off, while 2.2 parts in the form of a resinous product lag behind.

Example 3

As described in Example 1, 200 parts of contaminated cyclohexanol containing 6.7% formaldehyde and contains 0.2% water, passed over 200 ml of the same ion exchanger at 90 ° C. The flow rate is 800 ml of alcohol per liter of resin per hour. 91% of the formaldehyde is converted into formal. By a distillation carried out under normal pressure are from the mixture after a forerun of 7.1 parts of water 106 parts of pure cyclohexanol distilled off. 84.8 parts of cyclohexanol formal remain in the residue, which can be purified by distillation in vacuo. Practically no distillation residue remains.

Claims (3)

Patent claims: 1. Process for the purification of formaldehyde-containing alcohols with 2 to 10 carbon atoms and two to four hydroxyl groups and cycloaliphatic alcohols having 6 to 10 carbon atoms and one or two hydroxyl groups which, in addition to various impurities, contain more than 2% formaldehyde, characterized in that the formaldehyde contained in the alcohols initially converted to formal by known processes in the presence of acidic catalysts and then a distillation of the contaminated, formal-containing alcohol thus obtained is carried out will. 2. The method according to claim 1, characterized in that as catalysts for Formal formation acidic ion exchangers can be used. 3. Process according to Claims 1 and 2, characterized in that the water content the contaminated alcohols, if appropriate by distillation or drying before or during the implementation of the formalities is reduced to at least 15%. Considered publications:
German Patent No. 897 846;
German Auslegeschrift No. 1078107;
U.S. Patent Nos. 2673 222, 2841618.