DE1129467B - Process for the production of pentaerythritol from the mother liquor obtained during production - Google Patents

Description

The invention relates to a process for the recovery of pentaerythritol from the mother liquors, those involved in the production of pentaerythritol by condensation of formaldehyde with acetaldehyde Use sodium hydroxide as a condensing agent.

In addition to pentaerythritol and formate, polypentaerythritol and secondary are also used in the production process Reaction products, so-called polyoses, are formed.

In the usual industrial production, the majority of the pentaerythritol formed and the Polypentaerythrites by concentrating and crystallizing from that obtained by the reaction Separated solution.

Nevertheless, some of the pentaerythritol and the polypentaerythrite remain after the crystals have been separated off along with small amounts of polyose and almost all of the alkali formate in the mother liquor.

There have already been numerous processes for the recovery of pentaerythritol and formate from the Elaborated mother liquor.

According to some of these processes, the mother liquor is first concentrated and then fractionated crystallized to separate the formate from the pentaerythritol. These procedures are complicated and it can thus only a small amount of pentaerythritol and formate with a degree of purity, which for their direct reuse is not sufficient to be gained. According to other procedures this will be Formate deposited with the help of alcohols, which contain two or more carbon atoms, whereupon from the alcoholic solution obtained after Removal of the water by azeotropic distillation, the pentaerythritol is crystallized out.

However, this gives a pentaerythritol which has a high formate content and therefore it is unsuitable for many purposes. According to other methods, the pentaerythritol is made with the help of Alcohols with 4 to 6 carbon atoms are extracted after the mother liquor is almost completely removed of the water had been concentrated. The pentaerythritol is then concentrated and Separated crystallization of the alcoholic solution.

In this case, very large amounts of alcohol are used, which are 5 to 10 times the weight of the correspond to the dry residue obtainable from the mother liquor, and it becomes a pentaerythritol of low purity which cannot be used directly.

This differs from this in a very simple way according to the invention pentaerythritol and sodium processes for extraction

of pentaerythritol from the manufacture

resulting mother liquor

Applicant:

Montecatini, Societä Generale per l'Industria Mineraria e Chimica, Milan (Italy)

Representative:

Dipl.-Ing. Dipl.-Chem. Dr. phil. Dr.techn. J. Reitstötter, Patent attorney, Munich 15, Haydnstr. 5

Claimed priority:
Italy of April 30, 1958 (No. 6728)

Angelo De Michell and Alessandro Pistoni,

Milan (Italy),
have been named as inventors

Obtained formate, which can be used directly and using only small amounts of alcohol will.

This is made possible according to the invention that the formate from the mother liquor by means of a corresponding organic liquid, preferably methanol, is precipitated, and that the pentaerythritol crystallized from the aqueous solution obtained after recovery of the organic filler liquid will.

According to the new invention, the sodium formate is removed to make a mother liquor with a low formate content, from which the pentaerythritol either directly or after reuse the mother liquor can be separated.

With direct separation, the separation of the pentaerythritol from the purified formate is carried out Mother liquor understood by crystallization at a suitable temperature.

With separation after reuse of the mother liquor, the separation of the pentaerythritol, which is present in the mother liquor at the same time as freshly formed pentaerythritol, by crystallization understood at a suitable temperature. The pentaerythritol formed is recycled all or part of the formate

209 580/439

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Purified mother liquor is used as a condensation agent in the manufacturing process. In obtained, and the pentaerythritol is then from that of the final liquor is not an alkali formate, but rather this reaction coming solution containing calcium formate. This is the case with the divorced. Treatment of the final liquor with organic solution methanol is used according to scheme 1 to average out, such as methanol, together with the crude penta Precipitation of alkali formate added. I like the formate. So there is a mixture that is based on the is then separated off, and the methanol is made up of compounds contained therein, namely the CaI-der resulting liquid distilled off. cium formate and the pentaerythritol are further processed The aqueous solution thus obtained becomes, if necessary. The work-up of the mixture is wishes, first cleaned and then again the io very complicated.

Process for the production of pentaerythritol trains- The process according to the invention, however, represents leads. That in the recycled mother liquor already provides a very simple way of working. Here succeeds Pentaerythritol contained in it is practically in the same stage as the one through it, namely through the Zudie Synthesis of newly formed pentaerythritol removed. rate of the organic solvent, the pentaerythritol The sequence of the aforementioned process to separate 15 from the alkali metal formate with the success that steps can be varied, as very pure products are obtained after separation, the format and the recovery of the The further processing of the solutions that follow Methanol, the aqueous solution to remove a precipitate of the alkali metal form the pentaerythritol ent part Keeping the water it contains concentrated can be done in a number of ways, such as will; by crystallization at a suitable temperature is described in more detail below, temperature, pentaerythritol is precipitated and separated. . The filtrate obtained can, if desired, according to Example 1 partial evaporation again to produce formaldehyde and acetaldehyde are in aqueous Pentaerythritol can be used. Solution and condensed in the presence of NaOH. 25 After the condensation reaction, the solution, The pentaerythritol retained is combined with the newly formed which pentaerythritol, polypentaerythritol, sodium pentaerythritol severed. formate and small amounts of by-products ent-According Scheme 2 in which one preferably holds, concentrates and crystallizes. It will be the Embodiment of the process according to the invention Main content of pentaerythritol and polypentaerythrites is shown, the mother liquor is first separated into 30, and the mother liquor thus obtained is Removal of 50 to 80% of the contained therein treated as follows: 1000 parts of the mother liquor, Water at temperatures at which pentaerythritol which contains the following proportions by weight, 500 parts essentially can not fail, concentrated. Water, 400 parts of sodium formate, 70 parts of pen-on sodium formate is made by adding taerythritol, 30 parts polypentaerythritol and ancillary methanol precipitated and by filtration od. The like. 35 products are concentrated under vacuum until separated. 350 parts of water are removed.

The formate obtained in this way is very pure (97 to this point, 400 g of methanol are precipitated

100%) and the sodium formate can be used for numerous purposes. The formate is

will. filtered. There are 280 g of formate with a pure

The filtrate is then heated in order to obtain the methanol 40 units of 99%,

to regain. The filtrate is heated and methanol is removed

On cooling, the pentaerythritol crystallized and distilled and recovered.

is separated by filtration or the like. The remaining aqueous solution is on

The pentaerythritol obtained is also cooled to a very pure 15 ° C., as a result of which pentaerythritol crystallizes

(85 to 95 ° / o) and contains small amounts of 45 and is separated off. There are 50 g of crystals with

Formate. It can therefore have a pentaerythritol content of 90% for most purposes,

be turned. The pentaerythritol obtained is for various

The filtrate obtained, which small amounts are suitable for purposes.

Contains pentaerythritol and formate, can, if BeisDiel 2

wishes, after partial evaporation, a subsequent 50 ■ 'P

The following process step for separating 1000 g of mother liquor is, as in Example 1, be-pentaerythritol supplied from the reaction solution wrote, treated. After separating the format, will. With this method it is possible to recover the methanol and separate the up to 99% of the pentaerythritol formed and the poly-pentaerythritol is the resulting filtrate, which pentaerythrite and 90 to 95% of the secondary 55 25 parts of pentaerythritol, 120 parts of sodium formate and product obtained in the reaction formate contains in small amounts of by-products, according to Form of crystals, which account for the habitual drain of 25% of its original total Uses suitable to separate. weight to a renewed production of As an organic liquid for the precipitation of the pentaerythritol at the time at which the Formate methanol is preferably used, 60 separation of the pentaerythritol crystals precedes, which has proven to be particularly suitable. subject. That in the reused product he-It but similar results can also be obtained with other pentaerythritol being held simultaneously with the after organic liquids are obtained. pentaerythritol produced by the usual method It is already known to separate organic solvents. The mother liquors obtained are like such as methanol, treated for the recovery of pentaerythritol from 65 described above and also further verden To use mother liquors. This proposal is being processed.

meets a process for the production of pure The scheme 2 illustrates the in the two

Pentaerythritol, for the production of calcium hypers 1 and 2 described process sequence, which

can be used for both continuous and batch work.

Using this workflow it is possible to do 96 to 99% of that in the condensation reaction pentaerythritol formed between acetaldehyde and formaldehyde and 90 to 95% of the formate formed separated in the form of crystals with high purity.

Claims (5)

PATENT CLAIMS: 1Q 1. A process for the production of pentaerythritol from the mother liquors obtained in the production of pentaerythritol by treatment with an organic solvent, characterized in that the alkali metal formate is precipitated from the mother liquor with the aid of an appropriate organic solvent, preferably methanol, and after the solvent has been distilled off the resulting aqueous solution, which still contains pentaerythritol, is used for the renewed production of pentaerythritol by condensation of formaldehyde and acetaldehyde. 2. The method according to claim 1, characterized in that after separation of the formate and distilling off the methanol, the aqueous solution thus obtained concentrated and part of the Pentaerythritol contained therein before being returned to the condensation by crystallization is separated. 3. The method according to claim 1, characterized in that the prior to extraction for removal some of the water it contains is concentrated. 4. The method according to claim 1 to 3, characterized in that after separating the formate and recovering the methanol from the resulting filtrate of the solution for further preparation of pentaerythritol added and the pentaerythritol contained in the reused Fütrat is separated off at the same time as the freshly prepared pentaerythritol. 5. The method according to claim 1 to 4, characterized in that the various process steps be carried out continuously. Considered publications:
Swiss Patent No. 218 638;
U.S. Patent No. 2,270,839. For this purpose, 1 sheet of drawings © 209 580/439 5.62